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  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (548)
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  • Articles  (548)
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  • 1995-1999  (519)
  • 1980-1984  (29)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 80 (1997), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: X-ray diffraction (XRD) patterns from nominally β-SiC specimens often differ from those expected for the cubic crystal structure. These differences include the presence of additional peaks, enhanced background intensities, peak broadening, changes in relative peak heights, and shifts in peak positions. It has long been recognized that they are due to the presence of stacking faults, and models relating the experimental observations to stacking fault population have continued to evolve. The presence and relative magnitude of these features vary among different β-SiC specimens. In this work, computer simulations were used to show that the variations are closely related to differences in the type and spatial distribution of stacking faults in each specimen. In these simulations, stacking sequences were generated using a selectively activated 1-D Ising model with a Boltzmann-type probability function for specifying errors, which allows a wide variety of fault configurations to be generated. Direct correlations between different features in the XRD data to the underlying fault population are demonstrated, which are discussed in this paper. It is also shown that this computer model is general, in the sense that many of the models presented in prior work can be interpreted as limiting cases of it.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— This paper examines the application of the Jk, L and M integrals, in complex-variable form, to the Boussinesq wedge. The wedge is symmetrical and subjected to a point couple and point forces at the apex of the wedge. In the case of a point couple acting at the wedge apex the Jy, L and M integrals are found to vanish for all wedge angles whereas Jx displays a 1/r3 path-dependence; where r is a radial dimension measured from the wedge apex. When the wedge is subjected to point forces at the wedge apex then Jx and Jy are 1/r path-dependent whereas L and M are path-independent.The property that the L and M integrals are path-independent for the Boussinesq wedge is applied to the problem of determining the modes I and II stress intensity factors for a corner-loaded edge crack in a half-plane subjected to both normal and parallel point forces to the free surface of the half-plane.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue tests were performed on thin-walled tubular specimens of S45C steel under tension-compression, pure torsion, in-phase and out-of-phase axial-torsional loadings. The relationship between cracking behaviour and stress components on the crack plane was investigated. Measurement of microcrack density showed that microcracking was governed predominantly by the shear stress amplitude acting on the crack plane for all loading conditions. The failure crack was formed by coalescence of many cracks initiated near the maximum shear planes. The cracks grew turning their orientation to the direction perpendicular to the maximum normal stress. The transition of crack orientation occurred at relatively longer crack lengths at a higher stress ratio. The crack growth behaviour for all loading modes can be correlated using an equivalent strain intensity parameter based on shear and normal strains on the crack plane.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A ductile medium strength steel has been modelled by means of the Gurson model, and been used to investigate the effect of crack tip constraint in several fracture mechanics specimens. Both numerical and experimental results have been obtained, in the course of the crack extension process, for single edge notch bending specimens with different crack length-to-width ratios. The geometries with the shorter cracks always exhibited higher J values at initiation and steeper J crack growth resistance curves, and these results have been explained in terms of the stress and strain fields and damage development in the region ahead of the crack tip.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— It is shown that autofrettage at low temperatures is superior to autofrettage at room temperature in enhancing the fatigue resistance of thick-walled tubes against pulsating internal pressure. The physical reason is based on the well-known temperature dependence of the mechanical behaviour of metals and alloys which generally exhibit an enhancement of both the yield stress and strain hardening behaviour at lower temperatures. As a consequence, significantly larger compressive residual hoop stresses can be introduced during pressurization at low temperatures than at room temperature. Experimental data obtained on thick-walled tubes of the metastable austenitic stainless steel AISI 304 L which were subjected to pulsating internal pressure at room temperature after autofrettage at temperatures between-110°C and room temperature are presented. These data demonstrate convincingly the advantages offered by low-temperature autofrettage in enhancing both the fatigue life in the finite-life region and the fatigue endurance limit in comparison with autofrettage at room temperature. In conclusion, some specific materials requirements for optimum low-temperature autofrettage performance are discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A new single-specimen testing method, the normalization method with the so-called LMN calibration function, based on the load separation principle and function calibrations from an individual test record, was used to construct J-R curves directly from load versus load-line displacement records without any additional on-line crack-length monitoring equipment. The research was done on CT-specimens of a glassy polymer PVC at different crosshead speeds ranging from 0.01 to 50 mm/min. The J-R curves evaluated from the normalization method are in good agreement with those from the conventional multiple-specimen testing method in the whole range of the tested crosshead speeds. The results demonstrated the applicability of the normalization method for developing J-R curves at different crosshead speeds in PVC. The crack initiation J-integral values, J0.2, showed a two-regime dependence on the crosshead speeds in the tested crosshead speed range.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Biaxial fatigue tests were conducted on a high strength spring steel using hour-glass shaped smooth specimens. Four types of loading system were employed, i.e. (a) fully reversed cyclic torsion, (b) uniaxial push—pull, (c) fully reversed torsion with a superimposed axial static tension or compression stress, and (d) uniaxial push—pull with a superimposed static torque, to evaluate the effects of mean stress on the cyclic stress—strain response and short fatigue crack growth behaviour. Experimental results indicate that a biaxial mean stress has no apparent influence on the stress—strain response in torsion, however a superimposed tensile mean stress was detrimental to torsional fatigue strength. Similarly a superimposed static shear stress reduced the push—pull fatigue lifetime. A compressive mean stress was seen to be beneficial to torsion fatigue life. The role of mean stress on fatigue lifetime, under mixed mode loading, was investigated through experimental observations and theoretical analyses of short crack initiation and propagation. Using a plastic replication technique the effects of biaxial mean stress on both Stage I (mode II) and Stage II (mode I) short cracks were evaluated and analysed in detail. A two stage biaxial short fatigue crack growth model incorporating the influence of mean stress was subsequently developed and applied to correlate data of crack growth rate and fatigue life.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The development of fatigue damage in Co45Ni specimens during push—pull and reversed torsion tests, performed inside a scanning electron microscope, was observed and the different stress states compared. It appeared that transgranular crack initiation and development is delayed and intergranular crack initiation promoted under torsional loading. This was explained in terms of reduced surface distortion at the emergence of persistent slip bands (PSBs) and smaller compatibility stresses at the PSB-matrix interfaces. The influence of the mechanical strength of grain boundaries on the difference between tensile and torsional fatigue lives is discussed.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A Fourier series approach is proposed to calculate stress intensity factors using weight functions for semi-elliptical surface cracks in flat plates subjected to two-dimensional stress distributions. The weight functions were derived from reference stress intensity factors obtained by three-dimensional finite element analyses. The close form weight functions derived are suitable for the calculation of stress intensity factors for semi-elliptical surface cracks in flat plates under two-dimensional stress distributions with the crack aspect ratio in the range of 0.1 ≤a/c≤ 1 and relative depth in the range of 0 ≤a/t≤ 0.8. Solutions were verified using several two-dimensional non-linear stress distributions; the maximum difference being 6%.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A conventional finite element method may show a weakness when determining the hot spot stress distributions in the brace/chord intersection region of offshore tubular joints. This is because the chosen element displacement functions do not implicitly satisfy the conditions which prevail on the free surfaces. A procedure has been proposed to modify the conventional finite element method so as to allow the hot spot stresses, which occur at the free boundary of the weld toe of tubular joints, to be determined with improved accuracy. The results obtained by this modified method are compared with both an experimental and a traditional finite element solution. The comparison shows that the modified solution is in better agreement with the experimental data as compared with the traditional solution.
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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 12
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Simple extensions to the standard deep notch bend test procedure are suggested to allow the collection of data relevant to the energy dissipation rate, D, crack opening angle, COA, and J, all for arbitrarily large amounts of growth in extensive plasticity. The methods of analysis are detailed for real elastic-plastic behaviour of a high strength low-hardening type metal with a view to encouraging use on a wider range of materials. A proposal is made, and equations given, that the particular version of J used for an R-curve derived from the area under the loading diagram, should correspond to the value of the far-field integral, Jff.The relationship between the global measure of COA that emerges from D and the local crack tip opening angle, CTOA, as used in computational studies, is established. Transferability of CTOA data is examined in the light of effects of size and configuration. An explicit rule of the form CTOA √G =f (material and configuration) is proposed for the modelling of ductile growth in finite element studies. It is applied to a set of data in the literature, for the variation of CTOA with size in the deep notch bend test and for the configurations, bending, double edge and centre cracked tension.
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  • 13
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— In this investigation the Electron Channelling Contrast (ECC) technique in scanning electron microscopy (SEM) was applied to reveal the dislocation structures in the vicinity of surface fatigue cracks in comparison to those of cyclically-deformed recrystallized polycrystalline copper. The plastic zone around a fatigue crack was found to consist of an innermost region containing cells, followed by a region containing dense veins and PSBs, surrounded by a structure of loose veins, bundles and loop patches typical of the cyclically deformed matrix. A relation between plastic strain amplitude values deduced from cyclic stress-strain investigations and the dislocation structures near fatigue cracks are given. Typical regions of damage accumulation were identified and plastic strain contours for surface fatigue cracks established. The essentially non-destructive ECC technique is particularly suited to identify the changes in mesoscopic dislocation structures from surface layers to the interior of specimens over large specimen areas.
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  • 14
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 15
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The propagation behaviour of fatigue cracks emanating from pre-cracks was numerically simulated to evaluate the development of crack closure with crack growth. The crack opening stress intensity factor at the threshold was approximated as a function of the applied stress and the amount of crack extension. Pre-cracked specimens of a medium-carbon steel with a small surface crack and a single-edge crack were fatigued to investigate experimentally the initiation and propagation of cracks from pre-cracks. Crack closure was dynamically measured by using an interferometric strain/displacement gauge. The threshold condition of crack initiation from pre-cracks was given by a constant value of the effective stress intensity range which was equal to the threshold value for long cracks. The cyclic R-curve was constructed in terms of the threshold value of the maximum stress intensity factor as a function of crack extension approximated on the basis of the experimental and numerical results. The cyclic R-curve method was used to predict the fatigue thresholds of pre-cracked specimens. The predicted values of the fatigue limits for crack initiation and fracture, and the length of non-propagating cracks agreed very well with the experimental results.
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  • 16
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A basic study was performed on the evolution of three-dimensional shapes of small surface fatigue cracks during fatigue, and the effect of this evolution on small-crack growth behavior of a titanium-base alloy. Specifically, the nature and the magnitude of variations in crack aspect ratio, a/c (a is the crack depth and c is the half-surface crack length), during cyclic crack growth and its impact on growth rates have been studied. Experiments were performed on naturally initiated micro-cracks in a microstructure consisting of equiaxed primary-α2 phase in a Widmanstätten (transformed β) matrix. Several cracks under stress ratio (R) levels of 0.1 and −1, were studied. A specialized experimental system, consisting of a laser interferometer (to measure precisely the small-crack surface displacements), and a photo microscope (to automatically and continuously photograph the fatigue micro-cracks) was employed in the study. Apparent aspect ratios of surface cracks were calculated from the compliance response and the surface crack length data as a function of fatigue cycles. These data enabled accurate calculations of growth rates at the surface crack tip as well as the tip at depth in the bulk over the entire crack growth period, thus giving an insight into the crack growth process. Measurements of closure levels of small cracks were also performed and were used to partly account for the differences in growth rates. In the comparisons of small-crack growth data with the large-crack data, surface growth rates correlated relatively well with the large-crack data. Growth rates at depth exhibited large variations due to the irregularity of crack fronts at this location, and these rates deviated significantly from the large-crack behavior. Additionally, these growth rates varied between different cracks. An attempt was made to rationalize these observations in terms of the effects of inhomogeneities present in the microstructure.
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  • 17
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A new technique, known as crack modelling, is used here to predict fatigue failure in a crankshaft component. The technique uses a linear elastic finite element (FE) analysis to derive a stress intensity factor (K) for the component under load. The novel feature of the technique is that K is calculated without introducing a crack into a component; the stress field around the maximum stress point is examined and compared to that for a standard centre-cracked plate. The fatigue limit for a crankshaft was successfully predicted, when compared to experimental data. The only material parameter required for this prediction was the threshold stress intensity range, ΔKth.
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  • 18
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The effects of bluing, associated with drawing strain, on the fatigue strength of eutectoid steel wires have been investigated. The fatigue limit increases by bluing and the increase is more significant with higher drawing strain. The peak in the fatigue limit with regard to the drawing strain in the wires, at a strain of 2.5, disappears after bluing. On the other hand, in the ferritic steel wires investigated for comparison, the fatigue limit gradually increases with the drawing strain up to 7.7. Furthermore, no appreciable change in the fatigue limit due to bluing is found. Based on the results of hardness tests on fatigue specimens with- and without-bluing, it is deduced that the decrease of the fatigue limit beyond the peak drawing strain in the eutectoid steel wire can partly be attributed to insufficient locking of the high-density dislocations by solute atoms. The effect of relaxation of residual stress during bluing is also briefly discussed.
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  • 19
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— It is well known that for very short cracks the stress intensity factor K is not a suitable parameter to estimate the stress level over the small but finite Stage II process zone activation region of size rs near the crack tip, within which crack growth events take place. A critical appreciation of the reasons for the limitations on the applicability of ΔK as a fatigue crack propagation (FCP) parameter, when the crack length a is of the same order of magnitude or smaller than the size of the ‘fatigue-fracture activation region’, rs is presented. As an alternative to ΔK the range Δσs of the cyclic normal stress at a point situated at the fixed distance s=rs/2, ahead of the crack tip, inside the fatigue-fracture activation region, is proposed. It is observed that the limitation on the use of ΔK when the crack is short, is mathematical (and not physical) but this inconvenience is easily circumvented if the stress Δσs at the prescribed distance is used instead of ΔK since nowadays Δσs can be obtained numerically by using finite element methods (FEM). It follows that the parameter Δσs is not restricted by the mathematical limitations on ΔK and so it would seem that there is, a priori, no reason why the validity of the parameter Δσs cannot be extended to short cracks. It is shown that if the Paris law is expressed in terms of Δσs (πrrs)½ instead of ΔK the validity of the modified Paris law can be extended to short cracks.A coherent estimate of the value of the fatigue-fracture activation region rs is derived in terms of the fatigue limit ΔσFL obtained from S-N tests and of the threshold value ΔKth obtained from tests on long cracks where both relate to Stage II crack growth that ends in failure, namely, rs= (ΔKth/ΔσFL)2/π. An overall, threshold diagram is presented based on the simple criterion that, for sustained Stage II FCP, Δσs must be greater than ΔσFL. The study is based on a simple continuum mechanics approach and its purpose is the investigation of the suitability of both ΔK and Δσs to characterise the crack driving force that activates complex fracture processes at the microstructure's scale. The investigation pertains to conditions that lead to the ultimate failure of the component at values of Δσs 〉 ΔσFL.
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  • 20
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The boundary value problem for an arbitrarily shaped plane crack embedded in a 3D linear elastic solid can be reduced to a governing hyper-singular integral equation. A discretizing procedure based on a triangulation of the crack area has been offered in Part I of this work. The main goal of Part I is to introduce the analytical results for the 18 resulting finite-part integrals defined over a triangular mesh area. The finite-part integrals occur in those triangles where the source point coincides with one of the element nodes. Mostly the source point lies outside of the considered triangle. In these cases the occurring area integrals are regular.The aim of Part II is, therefore, the derivation of the closed form expressions for the relevant 18 regular area integrals. The resulting relations are of algebraic form which can easily be coded in compact form. Their numerical proof by two different methods shows the highest accuracy and, therefore, the correctness of the final solutions. The relevant numerical results are offered in Appendix I.With the formulae provided in Part I and Part II of the paper the determination of the coefficient matrix, necessary for the calculation of COD values from a linear equation system, is precise and needs only minimum computer time.
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  • 21
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Circumferentially notched cylindrical specimens are tested in torsion to obtain critical J values from crack resistance curves. The specimens are explosion cladded, half ferrite, half austenite, with the interface perpendicular to the cylinder axis and the circumferential notch at, or parallel to, the interface. Critical J values for crack extension in mode III were found to be a factor 1.1 to 2.1 higher than under comparable mode I loading.
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  • 22
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Strength measurements are becoming increasingly important for electroceramics. Bending of specimens small enough to be cut out of small electroceramic components may be one possibility. Therefore the miniaturisation of the 4-point bend-test for ceramic specimens is now being attempted. In this paper the errors in determining the flexural strength arising from the test principle itself, plus the geometry and measuring inaccuracies are calculated and expressed as a function of the outer span length. Contact pressure and a tolerable total measuring inaccuracy determines the dimensions of miniature specimens and fixtures. The possibilities of appropriate specimen preparation are also investigated.Ceramic materials show a volume (i.e. a specimen size) dependence of strength which is described by Weibull's statistical theory. The applicability of the miniature bend-fixtures is demonstrated by measuring this volume effect.
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  • 23
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— This paper describes a versatile technique for simulating the fatigue growth of a wide range of planar cracks of practical significance. Crack growth is predicted on a step-by-step basis from the Paris law using stress intensity factors calculated by the finite element method. The crack front is defined by a cubic spline curve from a set of nodes. Both the 1/4-node crack opening displacement and the three-dimensional J-integral (energy release rate) methods are used to calculate the stress intensity factors. Automatic remeshing of the finite element model to a new position which defines the new crack front enables the crack propagation to be followed. The accuracy and capability of this finite element simulation technique are demonstrated in this paper by the investigation of various problems of both theoretical and practical interest. These include the shape growth trend of an embedded initially penny-shaped defect and an embedded initially elliptical defect in an infinite body, the growth of a semi-elliptical surface crack in a finite thickness plate under tension and bending, the propagation of an internal crack in a round bar and the shape change of an external surface crack in a pressure vessel.
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  • 24
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Cold-expansion of fastener holes is now commonly used within the aerospace industry to increase the fatigue endurance of airframes. Although a number of methods of cold expansion are possible, the split-sleeve cold-expansion process is the most widely accepted and is frequently used in the repair and manufacture stages of both military and civil aircraft. In the present work, the redistribution of residual hoop stresses due to the application of constant amplitude fatigue loading at 4% cold-expanded holes has been studied. A modified Sachs method was adopted to evaluate the residual stress profiles and a replication technique was used to quantify crack growth. It was found that the decay of the residual hoop stress profile near the bore of the hole was due to the initiation and growth of small fatigue cracks. Cracks were found to initiate both near and below the fatigue limit, but subsequently arrested so stabilising the overall residual stress profile.
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  • 25
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    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The factors affecting the fatigue strength of nitrided titanium were clarified. The fatigue strength depended strongly on the fracture strength of the compound layer formed on the surface by nitriding. We found a Hall-Petch relationship between the fatigue strength of nitrided titanium and the grain size. The findings indicated that the reduction in the fatigue strength by nitriding results from both the formation of the compound layer possessing low fracture strength and grain growth occurring from ordinary nitriding. Furthermore, low-temperature nitriding (620°C, 24 h) was proposed to suppress grain growth. This treatment method improved not only the wear resistance and the corrosion resistance but also the fatigue strength of titanium.
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    Industrial lubrication & tribology 49 (1997), S. 5-6 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Describes the basic orbital combustion process X engine and gives the specification of the lubricant required. Sets out the objectives of a programme for the development of a lubricant for the IAPAC two-stroke engine being developed in France and Italy. Also describes ELEVATE, another development engine.
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    Industrial lubrication & tribology 49 (1997), S. 8-9 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Gives the results of trials conducted in China which show the use of top-grade, low smoke, part synthetic two-stroke oil gives better performance and four times longer engine life than the four-stroke engine oils generally used to lubricate two-stroke engines in China. Sets out existing and proposed international standards for two-stroke engine oils.
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  • 28
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    Industrial lubrication & tribology 49 (1997), S. 10-12 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Outlines the use of rubber, ceramic, metallic and plastic coatings to protect pump components from corrosion and abrasive wear. Describes in detail the products of two specialist companies in this field and gives examples of their uses.
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  • 29
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    Industrial lubrication & tribology 49 (1997), S. 13-14 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Uses the case of a continuous-flow travelling oven to illustrate the use of carbon bearings in adverse environments which preclude the use of lubricants. Gives more general information regarding the use of carbon-graphite bearing materials for a variety of applications.
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  • 30
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    Industrial lubrication & tribology 49 (1997), S. 68-70 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents the comparative surface roughness measurement data from a paper on the wear of filled PTFE lip seals in contact with a variety of different surfaces, as reported in a paper from the University of Stuttgart Institute of Machine Elements.
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    Industrial lubrication & tribology 49 (1997), S. 71-77 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The technical properties of Crambe abyssinica oil prompted the co-operation between a research institute and a lubricant producer to determine some possible industrial applications. The results confirm the special physico-chemical characteristics of crambe oil which, compared with some vegetable or synthetic oils, shows a higher heat removal capability and interesting lubrication characteristics. The research establishes that crambe oil could be a good hydraulic fluid. These findings led to the cultivation of a suitable area with Crambe abyssinica to obtain a sufficient amount of oil for lubricant formulation on a commercial scale.
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  • 32
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    Industrial lubrication & tribology 49 (1997), S. 120-126 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The more frequently an engine oil is changed, the more the overhaul life of the engine is extended but with an increase in the cost both of the oil and of the oil drain services. If engine oil is changed less frequently the associated costs will decrease. In order to find the optimum drain interval, it is necessary to establish the relationship between the cost of the oil and oil drain services and the cost of more frequent overhauls. Presents an investigation into the degradation of a proprietary lubricant marketed in Turkey, and the wear rate of a petrol engine driven in urban traffic. Lubricant samples were examined approximately every 2,000km for deterioration of the lubricant and evidence of wear of the engine components. From the experimental results, determines the optimum oil drain period of the engine.
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  • 33
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    Industrial lubrication & tribology 49 (1997), S. 176-177 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summarizes the results of a recent study of the US industrial lubricants industry. Highlights the negative effect on volume gains that inevitably will occur following the institution of fluid management programmes incorporating recirculation and recycling efforts.
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  • 34
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    Industrial lubrication & tribology 49 (1997), S. 178-180 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Defines the four main routes for reclaiming used oils - recovery as fuel; reconditioning on site; oil laundering and re-refining. Places used oil re-refining in its historical context and presents profiles of the (only) two used-oil re-refiners in the UK.
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    Industrial lubrication & tribology 49 (1997), S. 283-287 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Discusses the properties of various asbestos-free gasket materials, in particular expanded PTFE. Presents the factors which need to be taken into account when choosing a gasket. Highlights the requirements of gaskets in the automotive industry and the conditions they have to withstand.
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  • 36
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    Industrial lubrication & tribology 49 (1997), S. 288-290 
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: States that magnetic fluids, in a zero leakage, non-wearing seal, offer an innovative solution to the problems of harmful emissions from rotating process equipment. Discusses the properties and uses of the new GT series of ferrofluids from AP&T Ltd.
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  • 37
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A valve train system which could work in the absence of lubricants could reduce engine oil consumption. Routes to produce such a valve system have been explored, and composites, mostly powder metallurgy (PM) containing solid lubricants, have been tried. The expectation from utilizing these materials, keeping, at least, unchanged the life of engine components, is a reduction in oil consumption and oil fog in the cylinder head and a big environmental benefit. Various sintered materials for three different engine components - valve cap, valve seat and valve guide - have been developed and tested by disk-on-disk and fretting tests, in cold and hot conditions, respectively. Prototype components were produced, and the successful ones were then evaluated by an engine endurance test. The sintered valve cap and guide gave very interesting results in terms of friction coefficient and reduction of environmental pollution. Discusses the tribological characterization and the evaluation of these sintered materials.
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  • 38
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    Soldering & surface mount technology 9 (1997), S. 4-7 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A test procedure was developed to assess the capillary flow wettability of soldersinside a confined geometry. The test geometry comprised two parallel plates with a controlledgap of constant thickness (0.008 cm, 0.018 cm, 0.025 cm and 0.038 cm). Capillaryflow was assessed by: (1) the meniscus or capillary rise of the solder withinthe gap; (2) the extent of void formation in the gap; and (3)the time dependence of the risen solder film. Tests were performed with the lead-freesolders 95Sn-5Sb, 96.5Sn-3.5Ag, and 91.84Sn-3.33Ag-4.83Bi. The capillary rise of the lead-free solders was less than that observed with the 63Sn-37Pb control. Reducing the solder surfacetension and contact angle improved capillary flow. Void formation by the non lead soldersincreased as the gap became smaller. The extent of voiding was determined primarily by the gapsize rather than the wettability parameters (contact angle or surface tension) of theindividual alloys.
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    Soldering & surface mount technology 9 (1997), S. 4-7 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Since establishing a low volume, high reliability surface mount technology(SMT) facility, a number of problems have been overcome as part of the learningexperience. The tailoring of processes for a flexible assembly area brought to light a number ofissues that traditional SMT facilities do not face. This paper describes the many processesoptimised by the SMT facility team in becoming an on-time, high reliability producer. The topics include the development of design standards, forming, tinning, stencil printing, andcomponent placement. Several producibility enhancements are also described in acase-study of a solder mask evaluation project. The paper describes the many processimprovements implemented over the past few years.
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    Soldering & surface mount technology 9 (1997), S. 11-12 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The electronics industry seems to be under slightly less pressure, at present, to move to lead-freesolders. Nevertheless, many companies are interested in switching to comply with initiativesaimed at reducing the use of toxic materials such as lead. At the same time, these and othercompanies are hoping to use the improved properties of many lead-free solders toincrease solder joint reliability. While lead-free solders can indeed giveimproved properties in the proper system, using them with lead-containing materials canactually give poorer properties and uncertain reliability. It is important to understand thesematerials' interactions as thoroughly as possible before introducing new soldercompositions. To illustrate this point, some case histories will be presented, along with a generaldiscussion of how solders and substrates can and do interact.
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    Soldering & surface mount technology 9 (1997), S. 39-42 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The most commonly used solder for electricalinterconnects in electronic packages is the near eutectic 60Sn-40Pb alloy. This alloy hasa number of processing advantages(suitable melting point of 183°C and good wettingbehaviour). However, under conditions of cyclic strain and temperature(thermomechanical fatigue) the microstructure of this alloy undergoes aheterogeneous coarsening and failure process that makes the prediction of solder joint lifetimecomplex. A finite element simulation methodology to predict solder joint mechanical behaviour,that includes microstructural evolution, has been developed. The mechanical constitutivebehaviour was incorporated into the time-dependent internal state variable viscoplasticmodel through experimental creep tests. The microstructural evolution is incorporated through aseries of mathematical relations that describe mass flow in a temperature/strainenvironment. The model has been found to simulate observed thermomechanical fatiguebehaviour in solder joints.
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  • 42
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    Soldering & surface mount technology 9 (1997), S. 9-13 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Detailed studies to characterise the coarsening behaviour of eutecticSn-Ag and near-eutectic Sn-Pb-Ag solder joints were carriedout on samples reflow soldered and solidified at various cooling rates. Light and scanningelectron microscopy as well as EDS were used to study the microstructural evolution, whilemicrohardness measurements were used to monitor the change in the mechanical properties.Samples consisting of copper substrates and solder paste were reflow soldered about 30 °Cabove their melting points and then solidified at cooling rates ranging from furnace cooling torates associated with water quenching. Analysis of some of these samples showed that increasingthe cooling rate increased the quantity (volume fraction) of primarySn-dendrites, decreased the (EQ) intermetallic phase in the bulk solder, andresulted in finer microstructures with higher hardness. The microstructural evaluation involvedcharacterisation of bulk intermetallica and dendrite/eutectic ratios. Subsequent isothermalannealing of these reflow soldered joints at 125 °C for times between 0.25 h and 8 daysresulted in an initially fairly rapid decrease in hardness to a given level for each alloy and eachcooling rate.
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    Soldering & surface mount technology 9 (1997), S. 58-60 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The objective of this paper is to point out the limitations and ròles of DNP (distance to neutral point) on predicting the solder-joint thermal-fatigue life of area-array assemblies.
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  • 44
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    International journal of clothing science & technology 9 (1997), S. 10-22 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: To clarify the principles and mechanisms of water vapour transfer by diffusion in waterproof breathable fabrics for clothing, experiments using a simple glass dish were carried out under steady state conditions with and without a temperature gradient in the climatic chamber. It was found that both vapour pressure and natural convection within the air gap affect water vapour transfer. The rates of water vapour transfer are ranked microfibre fabrics, cotton ventiles, PTFE-laminated fabrics, poromeric polyurethane laminated fabrics, hydrophilic laminated fabrics, and polyurethane-coated fabrics. In the presence of a temperature gradient, condensation was also found to be a major factor, especially at air temperatures below 0°C. Condensation occurred the least on the inner surface of PTFE-laminated fabrics followed by cotton ventiles, microfibre fabrics, hydrophilic-laminated fabrics, poromeric polyurethane-laminated fabrics, and polyurethane coated fabrics.
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  • 45
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    International journal of clothing science & technology 9 (1997), S. 45-61 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Protective clothing should ideally provide maximum comfort and protection for the wearer. The design and fit of a garment are factors which can affect both the protective aspects of a garment as well as its comfort. Proper garment fit depends on the relationship of the size of the garment compared with the size of the wearer. Garment ease (where the garment is larger than the wearer) should allow for comfort and mobility; both too much or too little ease can result in a garment that is uncomfortable and restrictive to movement. The purpose of this study was to explore a research technique to isolate the effects of garment ease in one area of a garment while ease in all other garment areas was controlled, and to determine a design that would maximize wearer mobility. Using five male subjects, protective overalls with differing amounts and garment location of crotch ease were evaluated for their effects on mobility and wearer acceptance. Range of motion measurements for selected joints were evaluated using a Leighton Flexometer. Subjects completed a subjective evaluation scale after performing an exercise protocol while wearing the overalls. Results indicated that a specific amount of ease in the crotch length of overalls may be appropriate. Additionally, an overall design that had all needed crotch ease in the back waist area of the garment may be desirable over the more conventional method of adding ease evenly between the front and back sections of the garment. The methodology used in this study provides a means of evaluating not only the potential for design variations in protective clothing, but provides a means to evaluate the dynamic aspects of fit of clothing.
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  • 46
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 525-544 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Derives a first order perturbation algorithm for the computation of mean values and (co-) variances of the transient temperature field in conduction heated materials with random field parameters. Considers both linear as well as non-linear heat conduction problems. The algorithm is advantageous in terms of computer time compared to the Monte Carlo method. The computer time can further be reduced by appropriate transformation of the random vectors resulting from the discretization of the random fields.
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  • 47
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 548-564 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The present investigation has been carried out in the framework of the numerical studies of the wall function influence on the calculation of wall shear stress. This shear stress is generated by the action of a normal plane impinging jet on a flat plate. The Navier-Stokes, continuity and energy equations are solved for a two-dimensional turbulent compressible flow by using the finite volume method. The standard k-e turbulence model is used as a closure model. To take into account the external shape influence of the nozzle, a quasi-orthogonal curvilinear mesh is used. For a suitable calculation of the wall shear stress, the classical logarithmic wall law and its generalized form are used. The results of these calculations depend on the near wall grid. Therefore, this influence of near wall grid is studied more specifically here. A hybrid wall law is proposed, which results from the simultaneous use of the classical logarithmic wall law and the generalized one. This hybrid law gives suitable shear stress distributions with less dependence on the near wall grid. The calculations are validated through experimental data.
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  • 48
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 580-597 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Heat transfer by natural convection in a system formed by two and three cavities heated from below and covered by a cold plate is numerically studied using the Navier-Stokes equations with the Boussinesq approximation. Presents results in terms of streamlines, isotherms and heat transfer for Rayleigh numbers ranging from 103 to 106 and the Prandtl number 0.72 (air). Geometric parameters are the aspect ratio A = L'/H' = 1.5 and 2.5 respectively for two and three cavities, the relative height of the cavities B (1/8 = B = h'/H' = 1/2) and the parameter C = l'1/l'2 = 1. The inclination angle F from the horizontal was varied from 0 to 180°. The calculations reveal that the flow regime depends strongly on the Rayleigh number, the parameter B and the inclination angle F of the system; it may be stationary, oscillatory periodic or chaotic. The geometrical parameter B has a significant effect on the transition from one regime to another.
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  • 49
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 659-674 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Develops a generalized Douglas ADI method for solving three-dimensional parabolic differential equations based on the idea of the regularized difference scheme. The method is simple, unconditionally stable and well suited for either simulating fast transient phenomena or for computations on fine spatial meshes. Numerical procedures that employ the generalized Douglas ADI scheme were developed to solve three-dimensional parabolic differential equations on multilayers. In these procedures, the generalized "divide and conquer" method for solving tridiagonal linear systems is applied in order to overcome the problem with the unknown value at the interface between layers. Numerical results show that the procedure is accurate and efficient.
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  • 50
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 722-736 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents validation of the Eulerian approach for unsteady two-phase flows, whose behaviour depends on the coupling between the two phases, on the basis of the study of attentuation and dispersion of an acoustic wave propagating into a one dimensional two-phase flow. This approach and the corresponding numerical aspects are accurate enough for later applications in more complex geometries, where "vortex shedding" phenomena take place. Attenuation and dispersion of a pressure wave in a two-phase medium of rest was previously studied by Temkin and Dobbins. Present work is an extension of this theory to the case of a two-phase flow. This theoretical approach leads to a numerical solution of the problem. Compares the derived results with those obtained from a direct numerical simulation based on MacCormack scheme in a finite volume formulation. Verifies that analytical and numerical approaches are in good agreement.
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  • 51
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 794-800 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Refers to Montgomery and Fleeter (1996) who employed the finite-analytic method of Chen et al. (1980) to study steady, two-dimensional, inviscid, compressible, subsonic flow in a nozzle. Shows that, contrary to the statement made by Montgomery and Fleeter, their boundary conditions at the computational cell's boundaries are not constructed from the particular solution to their equation (10). Deduces from a simple non-linear second-order ordinary differential equation that the finite or locally analytic method of Chen et al. (1980) only yields continuous but not differentiable solutions. Suggests a finite-analytic method which provides continuous and differentiable solutions.
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  • 52
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 843-862 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Pulsatile flow of an incompressible, Newtonian fluid through a symmetric bifurcated rigid channel was numerically analysed by solving the three-dimensional Navier-Stokes equations. The upstream flow conditions were taken from an experimentally measured human arterial pulse cycle. The bifurcation was symmetrical with a branch angle of 60° and a daughter to mother area ratio of 2.0. The predicted velocity patterns were in qualitative agreement with experimental measurements available in the literature. The effect of unsteadiness on the various flow characteristics was studied. The most drastic effect observed was on the flow reversal regions. There was no flow reversal at the highest inlet Reynolds number in the pulse cycle, whereas in the case of steady flow at the same Reynolds number, the flow reversal region was the largest. The presence of secondary flow was observed at all times during the pulse cycle. Shear stress was calculated along the outer and inner walls and the low and high time averaged shear stress regions correspond to the clinically observed sites of formation of atherosclerotic plaque and lesions.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 863-879 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Describes a generalized two-cycle componentwise splitting method for solving three-dimensional parabolic differential equations with variable coefficients which has been developed based on the idea of the regularized difference scheme. The method is simple, unconditionally stable and well suited for simulating fast transient phenomena and for computations on fine spatial meshes. A numerical procedure that employs the generalized two-cycle componentwise splitting scheme was developed to solve three-dimensional parabolic differential equations with variable coefficients on multilayers. In the procedure, the generalized "divide and conquer" method for solving tridiagonal linear systems is applied in order to overcome the problem with the unknown value at the interface between layers. Numerical results show that the procedure is accurate and efficient.
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  • 54
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 880-906 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Describes a new finite element scheme for the large-scale analysis of compressible and incompressible viscous flows. The scheme is based on a combined compressible- incompressible Galerkin least-squares (GLS) space-time variational formulation. Three- dimensional unstructured meshes are employed, with piecewise-constant temporal interpolation, local time-stepping for steady flows, and linear continuous spatial interpolation in all the variables. The scheme incorporates automatic adaptive mesh refinement, with a choice of various error indicators. It is implemented on a distributed-memory parallel computer, and includes an automatic load-balancing procedure. Demonstrates the ability to solve both compressible and incompressible viscous flow problems using the parallel adaptive framework via numerical examples. These include Mach 3 flow over a flat plate, and a divergence-free buoyancy-driven flow in a cavity. The latter is a model for the steady melt flow in a Czochralski crystal growth process.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 4-23 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Describes the solution of the shallow water flow equations in strongly conservative form using a finite volume method. A SIMPLE-like scheme is developed to treat the velocity depth coupling. The method is applied to flow in a sharply curved channel and the results compared with published data. An error analysis is included which indicates that the method proposed is suitable for solving two-dimensional steady state problems in open channel flow.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 24-41 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: High-power chemical lasers operating in high repetitive rate show a decrease of the output energy laser beam. In such lasers, the characteristic time which depends on the laser output is short in comparison with those related to the flow. Consequently, shock waves, acoustic waves and thermal perturbations, induced by the strong electric energy deposition and remaining in the laser cavity between two pulses, may explain the decrease of output energy of the laser beam. For a better understanding of the flowfields, a numerical approach is carried out using flux corrected transport algorithms (FCT methods) associated with a Riemann solver on the computational domain boundaries. Under two-dimensional assumptions, the inviscid flow in the convergent-divergent laser cavity is computed to describe the creation and propagation of the wave system and the hot gas column in both single and multidischarge operating modes. Distortions of the contact surfaces are put into evidence through the study of flowfield instabilities. Finally, the limitations of the two-dimensional modelization become apparent. The numerical resolution is extended to a 3D case in order to take into account the optical direction. This allows to study the influence of shock waves travelling between optics and being generated by a side effect developing at the electrodes. These waves have an effect of long duration on the flowfield and lead to a high residual perturbation level.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 63-80 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The primitive equations of a barotropic atmosphere in isobaric co-ordinates are reformulated, in order to express the geopotential gradient as a function of the pressure at the Earth's surface. Furthermore, the free surface equation is written in conservative form. A finite difference, semi-implicit, semi-Lagrangian scheme in isobaric co-ordinates is developed. The numerical scheme is mass conservative, is proven to be stable and requires the solution of a single five-diagonal system. Numerical simulations show that the model captures the main dynamical features of large scale atmospheric motion.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 42-62 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Asymptotic methods are employed to derive the long wave equations governing the fluid dynamics of thin, time-dependent, incompressible, vertical, planar liquid sheets at low Reynolds numbers subjected to London-van der Waals body forces and gravity. Analytical solutions for steady, viscous sheets in gravitational and zero-gravity environments are obtained for large surface tension. Numerical studies of planar liquid sheets at low Reynolds numbers with no surface tension indicate that, for plane stagnation flows, the deceleration of the sheet as it approaches the solid wall decreases as the London-van der Waals forces are increased, the effects of these body forces decrease as the Froude number is increased, and, for Reynolds-to-Froude numbers greater than one, the thickening of the sheet as it approaches the solid boundary increases as the Hamaker constant is increased. Numerical experiments of film casting processes with three different flow approximations which account for or neglect inertia and/or the gravitational pull have also been performed and indicate that for high take-up speeds, a boundary layer is formed at the downstream boundary, the thickness of this layer decreases as the London-van der Waals forces are increased, and, for Reynold-to-Froude numbers larger than one, the leading-order thickness and axial velocity component are very sensitive to the value of the Hamaker constant.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 81-94 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical study is performed to investigate turbulent Couette flow and heat transfer characteristics in concentric annuli with a slightly heated inner cylinder moving in the flow direction. A two-equation k-e turbulence model is employed to determine the turbulent viscosity and the turbulent kinetic energy. The turbulent heat flux is expressed by Boussinesq approximation in which the eddy diffusivity for heat is given as functions of the temperature variance t2- and the dissipation rate of temperature fluctuations et, together with k and e. The governing boundary-layer equations are discretized by means of control volume finite-difference technique and numerically solved using a marching procedure. It is disclosed from the study that the streamwise movement of the inner core causes substantial reductions in the turbulent kinetic energy and the temperature variance, particularly near the inner wall region, resulting in the deterioration of the Nusselt number, and that an attenuation in heat transfer performance is induced by the velocity ratio of the moving inner cylinder to the fluid flow.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 120-140 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents the numerical investigations of interaction of several coaxial vortex rings in inviscid fluid. For the solution of non-linear system of ordinary differential equations chooses the method of extrapolation with variable step and order. Controls the accuracy of calculations by the conditions of conservation of the first integrals and also by the comparison of numerical results with the known analytical solutions. Discusses the problems of order and chaos, and presents examples of mixing of fluid particles by interaction of two and three vortex rings.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 95-111 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Numerical simulation of a fluid flow involves the specification of boundary conditions along all or part of the boundary. Designs a means of handling outflow boundary conditions for the incompressible Navier-Stokes equations. Addresses through-flow problems involving the specification of outflow conditions at the synthetic boundary. This outflow boundary condition is applicable to a developing flow problem. The underlying objectives behind designing the boundary condition at the truncated boundary are three-fold, namely: matching with Navier-Stokes equations inside the domain; taking both non-linear and diffusive contributions into account; and ensuring the discrete divergence-free condition. In order to meet these requirements, follows the concept of a free boundary condition by taking the outflow nodal values of u, v and p as unknowns, which are coupled with the interior unknowns through the surface integrals in the momentum equations. The computed solutions can be legitimately regarded as solutions to conservation equations under consideration when both components of the surface traction vector approach zero. With the convergent property accommodated in the present mixed finite element analysis, the task remains to simply improve the accuracy. Demonstrates the capability of the proposed non-linear outflow boundary conditions through several benchmark tests.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 141-168 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Addresses two difficulties which arise when using a compressible code with equal order interpolation (non-staggered grids in the finite-difference nomenclature) to capture a steady-state solution in the incompressible limit, i.e. at low Mach numbers. Explains that, first, numerical instabilities in the form of spurious oscillations in pressure pollute the solution and, second, the convergence to the steady state becomes extremely slow owing to bad conditioning of the different speeds of propagation. By using a stabilized method, allows the use of equal-order interpolations in a consistent (weighted-residual) formulation which stabilizes both the convection and the continuity terms at the same time. On the other hand, by using specially devised preconditioning, assures a rate of convergence independent of Mach number.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 169-180 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Reports that major advances have been achieved on computational simulations of multidimensional fluid flow, heat and mass transfer during the last 20 years. Focuses on the numerical prediction of fluid flow, combustion and gas radiation in a combustion chamber of a typical industrial glass-melting furnace. Carries out the flow simulation in a three-dimensional calculation domain by using computer models in conjunction with the standard k - e turbulence model. Tests the predictions of spectral intensity by solving the equation of radiative transfer. Employs the Goody statistical narrow band model with the Curtis-Godson approximation to calculate radiative properties for inhomogeneous gas mixtures.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 181-199 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Explains that segregation processes during the solidification of a binary alloy occur at two distinct length scales: on the microscopic length scale of the crystal interface, in the two-phase mushy zone, segregation is controlled by solid state mass diffusion; and, on the macroscopic scale of the process, segregation is controlled by the convective transport of the molten metal. Concludes that developing models that can capture both these scales is a challenge. Introduces a bi-level grid, and uses a macro grid on the scale of the process for the solution of equations describing macroscopic heat and mass transport. Details how each node point in the macro grid is associated with a micro grid on which equations describing the microscopic phenomena in the mushy region are solved. In this way, develops a dual-scale model of segregation during the solidification of a binary alloy. On investigating the unidirectional solidification of a binary alloy, demonstrates that this dual-scale model is able to capture both the macro and micro-scales in a single numerical treatment.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 200-214 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Considers the conjugate natural convection motion of a power law fluid in a vertical finite channel, taking into account the heat transfer into channel walls as well as the effect of the existence of different heat sources distributed uniformly in the walls and in the fluid. Examines the results obtained in some test cases in more detail and shows that the influence of the wall becomes significant when the thermal conductivity of the wall is small enough. Also notes that the effect of the heat source distributed in the fluid is more considerable than in the wall.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 236-249 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents four examples which were researched in a large eddy simulation (LES) of turbulence for engineering applications. Explains that, in the former two cases, developments of the advanced LES are indicated in a Smagorinsky model and in the treatments of the wall and the external boundary, and, in the later cases, the LES on the boundary fitted grids are applied using the finite different method (FDM) and the finite element method (FEM), where new numerical treatments, a composite grid technique and a modified scheme, are adopted for efficient calculations. Evaluates the results, and discusses the possible application of the LES for engineering problems.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 215-235 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Deals with the formulation and application of temporal and spatial spectral element approximations for the solution of convection-diffusion problems. Proposes a new high-order splitting space-time spectral element method which exploits space-time discontinuous Galerkin for the first hyperbolic substep and space continuous-time discontinuous Galerkin for the second parabolic substep. Analyses this method and presents its characteristics in terms of accuracy and stability. Also investigates a subcycling technique, in which several hyperbolic substeps are taken for each parabolic substep; a technique which enables fast, cost-effective time integration with little loss of accuracy. Demonstrates, by a numerical comparison with other coupled and splitting space-time spectral element methods, that the proposed method exhibits significant improvements in accuracy, stability and computational efficiency, which suggests that this method is a potential alternative to existing schemes. Describes several areas for future research.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 250-274 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Proposes a measure to stabilize the fourth(fifth)-order high resolution schemes for the compressible Navier-Stokes equations. Solves the N-S equations of the volume fluxes and the low-Reynolds number k-e turbulence model in general curvilinear co-ordinates by the delta-form implicit finite difference methods. Notes that, in order to simulate the flow containing weak discontinuities accurately, it is very effective to use some higher-order TVD upstream-difference schemes in the right-hand side of the equations of these methods; however, the higher-order correction terms of such schemes in general amplify the numerical disturbances. Therefore, restricts these terms here by operating the minmod functions to the curvatures so as to suppress the occurrence of new inflection points. Computes an unsteady transonic turbine cascade flow where vortex streets occur from the trailing edge of blades and interact with shock waves. Finds that the stabilization measure improves not only the computational results but also the convergency for such a complicated flow problem.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 280-296 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents a finite-difference solution to transient free convection flow past a semi-infinite vertical plate in which the plate temperature T¢w(x) varies as the power of the axial co-ordinate in the form T¢• + axn. Gives numerical results for fluids with Prandtl numbers Pr = 0.7 (air) and Pr = 7 (water) for three representative exponent values under non-uniform surface heating conditions. Finds that the time to reach the steady-state increases as the value of n or Pr increases. The steady-state local skin-friction falls by increasing the exponent n and Pr; however, the steady-state local Nusselt number increases with n at a distance along the plate far away from the leading edge but decreases with increasing n near the leading edge of the plate. Also, the average Nusselt number increases and the average skin-friction decreases as n increases because of enhanced heating of the plate.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 344-366 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents a quasi three-dimensional formulation for filling a thin section cavity which is derived under the assumption that no transverse flow occurs in the gap. A no-slip condition was applied on all surfaces occupied by the fluid and a slip condition on all air-filled (empty) surfaces. The formulation was developed to analyse the sections which lie in the xy-plane or may be oriented arbitrarily in three-dimensional space. Solves the discretized thickness-integrated finite element flow equations by using the implicit mixed velocity-pressure formulation, and uses the volume of fluid (VOF) method to track the free surfaces. Presents numerical examples which confirm the accuracy of the formulation and demonstrate how it can be used to model the filling of planar and three-dimensional thin section cavities of irregular shape.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 297-343 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In part I uses an iterative point successive over-relaxation (PSOR) finite difference scheme to solve the coupled unsteady Navier-Stokes and energy equations for incompressible, viscous and laminar flows in their primitive variable form. Presents the details concerning the derivation of the solution scheme, as well as details on its computer implementation. For validation purposes, includes the results of the two-dimensional and three-dimensional benchmark problem of natural convection in a cavity with differentially heated vertical walls. Benchmark computations have been performed for a Prandtl number of 0.71, and different values of the Rayleigh number ranging between 103 and 106 depending on the problem. By comparison with other approaches in the literature, the scheme has been found to be accurate even for large Rayleigh numbers.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 401-416 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Studies numerically natural convection in a saturated porous medium bounded by two horizontal, isothermal eccentric cylinders by solving the governing two-dimensional Darcy-Boussinesq equations on a very fine grid for different values of the eccentricity e. For a radius ratio of 2 and e 〈 0.5, both a bicellular and a tetracellular flow patterns remain stable for moderate Rayleigh numbers. For e = 0.5, the transition from one flow regime to the other occurs with one of the solutions losing stability. Suggests that in a real situation, insulation is more efficient if the eccentricity is set to the maximum value for which the four-cell flow pattern is physically realizable than to the value that minimizes the heat transfer when the flow pattern is bicellular. The net gain with respect to a concentric insulation can be of the order of 10 per cent.
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 367-400 
    ISSN: 0961-5539
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents a numerical study on heat transfer by natural convection in porous media in vertical enclosures with side wall heating. The model for porous media includes inertia terms and also the Brinkman extension in addition to the Darcy resistance term. A semi-implicit finite element scheme based on operator splitting method is adopted for solving the time-dependent system of equations. The first half of the investigations is confined to the low permeability regime where Darcy law holds good. Presents the results for annular and rectangular cavities and proposes correlations for two types of boundary conditions, namely constant wall temperature case and uniform wall heat flux case. In the second half of the investigations, the scheme is applied in a high permeability regime, where the validity of Darcy law becomes questionable. Employs plane rectangular cavities with the two types of boundary conditions mentioned earlier. Highlights the influence of Rayleigh number (Ra) and Darcy number (Da) as separate parameters and proposes correlations for a square cavity for the first time in terms of Ra and Da as separate parameters. Discusses a qualitative study of the effect of aspect ratio on heat transfer as the permeability changes.
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    Soldering & surface mount technology 9 (1997), S. 5-8 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: As the electronics industry moves towards the 21st century, environmentally consciousmanufacturing is becoming a very important issue for the industry. In recent years, advancedmanufacturing technologies have been developed for automotive electronics packing that notonly are environmentally friendly, but also reduce manufacturing complexity and cost, improveproduct quality, and meet the stringent reliability requirements for the automotive environment.In this paper, aspects of no-clean soldering and lead-free solderr developmentare reviewed, and some of the most critical factors for implementing no-clean solderingand for developing lead-free solders for automotive electronics are outlined.
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    Soldering & surface mount technology 9 (1997), S. 29-32 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 'Fine Pitch'and 'High speed printing' are relative terms but many solder paste users seecapability in meeting these two requirements as their major goals for process improvements. Notsurprisingly, solder paste rheology governs both, and this paper describes how the complexrelationship between resins and solvent can lead to solder pastes with optimised performance.Work on the physical behaviour of resin solutions and how this relates to solder paste rheology isreported. These results are related to user experience on volume production processes.
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    Soldering & surface mount technology 9 (1997), S. 45-54 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents a solder joint engineering reliability model —Solder Reliability Solutions** (SRS) — and its application to surface mountarea-array and chip-scale assemblies. The model is validated by failure datafrom 33 accelerated thermal cycling tests, and test vehicles covering several generations ofcomponent, assembly and circuit board technologies and a variety of test conditions. The SRSmodel has been implemented as a PC-based design-for-reliabilltytoolthat enables rapid assessment of assembly reliability in the early stages of product development.
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    International journal of clothing science & technology 9 (1997), S. 23-33 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: To assess the effect of wind speed in practice, experiments were conducted under conditions of realistic wind velocities generated in the climatic chamber. The theoretical and experimental results were compared. In the theoretical model of forced convection between the human skin and the external environment the water vapour transfer rate was found to be proportional to V0.81. The experimental results obtained when a layer of fabric was included showed that water vapour transfer is proportional to V0.5. The rates of water vapour transfer for the fabrics ranked slightly differently from that seen under steady state conditions; microfibre fabrics, cotton ventiles, PTFE-laminated fabrics, hydrophilic-laminated fabrics, and poromeric polyurethane-laminated fabrics. Condensation was reduced under windy conditions.
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    International journal of clothing science & technology 9 (1997), S. 75-87 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Plans a wear simulation of assembled textile structures by sewing, basing the study on the submission of standardized seams carried out on 40 wool fabrics and blends containing wool to a series of 20 cycles of fatigue, including: washing, drying and submission to a static mechanical load under determined characteristics and steam ironing. Seams in the warp and weft directions were performed on. Examines the following parameters: fabric strength and elongation to break; seam strength and slippage; seam efficiency; seams' opening limit and both the modulus at 1mm and at break, along the fatigue cycles. Analyses results obtained in function of the seam directions and fatigue cycles.
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    International journal of clothing science & technology 9 (1997), S. 141-153 
    ISSN: 0955-6222
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Investigates whether water vapour transfer from the local environment of the human body at a relative humidity less than 100 per cent to a rainy or wind-driven environment of relative humidity almost 100 per cent is possible. To identify whether prolonged rain has an effect on water vapour transfer in waterproof breathable fabrics, secondary experiments were carried out using a precipitator simulator covering a large area with severe rain. It was found that waterproof breathable fabrics breathe even under rainy conditions (with lower water vapour transfer rate), though encountering limitations under prolonged severe rain. The water vapour transfer rate was reduced under wind-driven rainy conditions. More condensation was observed under rainy conditions on all fabrics except PTFE laminated fabrics.
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    International journal of clothing science & technology 9 (1997), S. 241-248 
    ISSN: 0955-6222
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Demonstrates the modelling of the kinetic process when the sewing needle enters the fabric. To get an adequate mechanical model of the given problem, the function - the mathematical model - of the penetration force with respect to the fabric, the needle and the mechanism in the sewing machine must be developed. The fabric was modelled as a combination of warp and weft threads. Each thread from the fabric is modelled as an ideal elastic Hook's material. Outlines the restrictions which needed to be made to get the mathematical model of the problem.
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    International journal of clothing science & technology 9 (1997), S. 193-199 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Describes an experiment designed to investigate the influence of washing/ironing cycles and softening after sanforization on the hand grade, shrinkage and surface roughness of three selected cotton weaves for men's shirts. Constructs the ANOVA type models with or without interactions, on the basis of the experimental results.
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    International journal of clothing science & technology 9 (1997), S. 207-213 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Describes an investigation into the hand of non-wovens used for nappies under both dry and wet conditions. The mean score of the subjective hand assessments (THVsub) of dry nappy was correlated with their surface properties which are obtained using the single wire U-shape sensor.
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    International journal of clothing science & technology 9 (1997), S. 285-300 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Reports on a study for which data were generated from responses to a survey by 132 US apparel manufacturers in 1993. States that the purpose of the study was to determine the extent to which companies were investing in ergonomic equipment as a prevention strategy, and whether there was a relationship between such investments and positive results in four areas: increased productivity, increased quality, decreased workers' compensation costs and improved employee morale. Using chi-square analysis, a significant difference was found for those who invested in automatic sewing equipment in both increased productivity and increased quality. Provides justification for companies to invest in ergonomic equipment because of additional benefits.
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    International journal of clothing science & technology 9 (1997), S. 334-345 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Reports on investigations into the mechanism of sewing thread strength reduction. Results indicate that structural damage, namely, structural openness and pull-out of fibre ends from the surface are the major cause of strength reduction and that the fibre strength reduction is found to be only marginal compared to the thread strength reduction. Cotton threads exhibit higher strength loss owing to their poor abrasion resistance. Comparatively shorter fibres in cotton threads are also found to be responsible for the higher strength reduction.
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  • 85
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 438-478 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of inclination on laminar natural convection in a square cavity is studied numerically for inclination angles ranging from 40° to 160°, Rayleigh numbers between 103 and 106 and Prandtl numbers from 0.02 to 4,000. Contours of stream functions and temperature are presented in order to provide a new insight and a better understanding of the flow and heat transfer characteristics in a square cavity. Finds computed local and mean Nusselt numbers at the hot wall in satisfactory agreement with experimental and other numerical results. Finds the mean heat flux at the hot wall as well as the distribution of the local heat flux along the heated wall are found to depend on the inclination angle, the Rayleigh number and the Prandtl number. Such a dependence is significant for angles greater than 90°, while for smaller angles the effect of the inclination angle on the Nusselt-Rayleigh correlation is weaker.
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  • 86
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 497-524 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In part I of this study, a three-dimensional finite difference iterative solver capable of handling the coupled Navier-Stokes and energy equations for incompressible viscous flows was described and validated with two- and three-dimensional benchmarks. Part II describes the results of the computational study of two distinct complex geometries: 1) two-dimensional and three-dimensional natural convection in cavity whose surface is cooled while two internal blocks are heated; 2) two-dimensional and three-dimensional natural convection in the region defined by two interconnected cavities of different sizes which are differentially heated. All computations have been performed for a Prandtl number of 1.0, and different values of the Rayleigh number ranging between 103 and 106 depending on the problem. In the first problem, three-dimensional effects in the top region of the cavity trap fluid in vortices near the top of the heated blocks adversely affecting heat transfer in the region while enhancing it in the region between the two heated blocks. In the second problem, the sudden expansion of fluid as it leaves the top cavity and enters the bottom one generates three-dimensional wakes in the bottom cavity that enhance the convective heat transfer across the system walls near them. These studies tend to suggest that three-dimensional effects play a very important role in the enhancement of convective heat transfer in complex geometries, especially at higher Rayleigh numbers.
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  • 87
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 598-608 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents a non-similar boundary layer analysis for the problem of mixed convection in power-law type non-Newtonian fluids along an isothermal vertical plate with surface mass transfer. Solves the transformed governing laws numerically using a finite difference method. Presents numerical results for the details of the velocity and temperature fields. Discusses the effect of suction and injection as well as the viscosity index on the surface heat transfer rate.
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  • 88
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 675-695 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Analytical or hybrid numerical-analytical solutions of multidimensional diffusion problems involve the evaluation of nested multiple infinite summations, which require the computation of eigenvalues and related quantities, from associated auxiliary eigenvalue-type problems. A substantial reduction of the total computational effort in the construction of the final solution for the original potential can be achieved through the proper reorganization of the multiple summations into a single series representation. Such reordering of terms should be carefully accomplished, in order to account for the most significant contributions to the final numerical result, up to a truncated finite order that meets the user prescribed tolerance for the relative error. Presents an algorithm for an optimized scheme with consequent reduction on the number of eigenquantities to be evaluated. This approach is illustrated through representative two and three-dimensional transient heat conduction problems.
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  • 89
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 751-766 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Considers the filling stage of an injection moulding process for polymer melts through a transient finite element method. Presents results for a thin-walled cup-shaped mould problem. Adopts a generalized Newtonian formulation for inelastic non-isothermal incompressible flow under cooling conditions. Gives some attention to the transient aspects of the problem, including the motion of the melt front and the numerical deformation patterns that develop. Advocates a localized remeshing technique that tracks the moving front effectively.
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  • 90
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 696-710 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Solves the inverse problem of estimating the wall heat flux in a parallel plate channel, by using the conjugate gradient method with adjoint equation. The unknown heat flux is supposed to vary in time and along the channel flow direction. Examines the accuracy of the present function estimation approach, by using transient simulated measurements of several sensors located inside the channel. The inverse problem is solved for different functional forms of the unknown wall heat flux, including those containing sharp corners and discontinuities, which are the most difficult to be recovered by an inverse analysis. Addresses the effects on the inverse problem solution of the number of sensors, as well as their locations.
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  • 91
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 814-842 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Deals with the non-stationary pure convection equation in two dimensions. An attribute of the method is that the advective fluxes are approximated by taking the flow orientations into consideration. The interfacial numerical fluxes are interpolated by virtue of the rational areas which depend on the corner velocity vectors. This leads to a discrete system containing dissipative artifacts in regions normal to the local streamline. Conducts two-dimensional fundamental studies for the flux discretization developed. These analyses give insight into the order-of-accuracy, and the scheme stability. According to the underlying positivity definition, this explicit scheme is, furthermore, classified as conditionally monotonic. This scheme has been applied successfully to solve smooth, sharply varied, and discontinuous transport problems.
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  • 92
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    Soldering & surface mount technology 9 (1997), S. 8-10 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Well designed stable reflow ovens andwave machines can be operated at low rates of the inerting gas. One problem is that at the lowestflow rate settings changes in room draughts and in external venting conditions can affect theinternal oxygen levels unless the flow rates are altered. The internal oxygen levels can drift orsuddenly alter. This generally means that the ovens are operated at higher flows than necessaryin order to ensure steady operations below some desired oxygen level without excessive operatorintervention. A closed-loop control system using the output of internal oxygen metersto vary the flow rates set by mass flow meters is one way to ensure steady operation. One suchsystem — NITRAPILOT™ control system—has been developed by BOC Gases as a standalone system that can be added to existing equipment. The results of small-scale andproduction level testing on this system are described in the present paper. Reduced flow ratescan be achieved for stable set point oxygen levels at critical locations. An equally significantbenefit, particularly when used in conjunction with data logging, is that the system assists instatistical process control since it ensures, monitors and logs compliance with process recipeswithout operator intervention.
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  • 93
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    Soldering & surface mount technology 9 (1997), S. 13-16 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new product design required the addition of a secondlayer of electronics to control a base module. This product was designed with significantoverhangs of heavy leads and components which presented a significant challenge to manydifferent solder assembly processes. Only the heated gas jet process was able to solder theproduct successfully without damaging the printed wiring boards.To answer thechallenge, a new machine was developed, combining dispensing of solder paste with hot gas jetreflow technology. This provided a combination of capabilities resulting in a flexible processwhich was significantly superior to alternative technologies.Other soldering processessuch as laser, focused xenon lamp, robotic soldering iron, and focused IR soldering technologieswere evaluated. Each of these technologies causes some damage or defect to the assembly due tothe heat sinking aspect of the circuit assembled. These alternative processes would createdamage or defects to the assemblies by burning the laminate, delaminating the pads on theprinted wiring board, or not soldering the pads.Proof of concept tests before machinedesigns were initiated demonstrated the potential and capabilities of this technology forautomated assembly soldering. Testing indicated that the heated gas jet processing wouldprovide a means of soldering the assemblies at a controllable rate without damaging the circuitboards.While evaluating the machine ion its design phase, a designed experiment wasinitiated to help understand the relationships between head temperature settings versus gas flowrates, the measurable output was time to reflow.The process meets all expectations interms of solder fillet appearance, volume, and overall visual quality while maintaining processcycle time requirements.
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  • 94
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    Soldering & surface mount technology 9 (1997), S. 22-28 
    ISSN: 0954-0911
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A series of composite solders in 63/37 Sn/Pb was prepared: Cu6 Sn5 (10, 20,30 wt%); Cu3 Sn (10, 20, 30 wt%); Cu (7.6 wt%); Ag (4 wt%); and Ni (4 wt%). These composite solders were prepared by two procedures: (A) admixture with solder paste; and (B) admixture with molten solder. The original particulates and the final composite solders were analysed and characterisedby SEM (scanning electron microscopy) EDX (energy dispersive X-ray), and ESCA (electron spectroscopy for chemicalsanalysis); or XPS (X-ray photoelectron spectroscopy). A variety of morphological characterisations, intermetallics and porosities were noted. Good wetting was noted in all cases, and porosity was greater for method (A). The particulates all exhibited excellent binding to the solder matrix.
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  • 95
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    International journal of clothing science & technology 9 (1997), S. 236-240 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Considers the complexity of a problem of thread's rheological properties evaluation, and evaluates the visco-elastic properties of a thread on the basis of static tests using numerical methods. Describes a new software package VILKUS which was designed and programmed for this purpose. This program calculates parameters needed for the evaluation of visco-elastic properties on the basis of numerical values of a stress-deformation s(e) curve. The stress-deformation s(e) curve served as a starting-point for evaluation of visco-elastic properties of threads. The B-spline approximation using the least squares method was chosen as an appropriate and suitably smooth curve for construction of the average s(e) curve.
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  • 96
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    International journal of clothing science & technology 9 (1997), S. 311-325 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: States that bra design is a highly specialized process requiring a combination of design creativity, precision pattern making skills and a detailed knowledge of fabric performance. Although there is substantial published material cataloguing the historical origins of the garment, there is little information documenting the bra design and manufacture. Examines the design process, following a survey of professional designers. Describes a common framework along with the variations in individual working methods. Emphasizes the high dependence on heuristic knowledge and the reliance on physical prototyping in the design cycle.
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  • 97
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    International journal of clothing science & technology 9 (1997), S. 367-379 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Apparel pattern making creates a set of pattern pieces of fabric which are sewn into the desired garment. The pattern pieces are developed through fashion analysis, pattern design and pattern drafting. Seeks to build an object-oriented model of the apparel pattern-making process through these subprocesses. Defines the model in terms of a requirements specification and subsequently uses it in the development of a computerized pattern-making system. Uses object behaviour analysis, which is derived from object-oriented technology, as the method for defining the model.
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  • 98
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    International journal of clothing science & technology 9 (1997), S. 249-251 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents a new sewing technology developed by Moll Automatische Nähsysteme GmbH, a German company. This allows complex shapes to be sewn in three dimensions as well as providing the means to automate the manufacture of apparel and other objects.
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  • 99
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    International journal of clothing science & technology 9 (1997), S. 200-202 
    ISSN: 0955-6222
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Explains that men's suit manufacturing has been industrialized and the line production system is now popular in suit manufacturing. As a trend in the suit manufacturing industry, semi-custom-made-suit manufacturing is becoming popular instead of the ordinary ready-made-suit production system. Also the industry is shifting to higher quality suit production.
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  • 100
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    International journal of numerical methods for heat & fluid flow 7 (1997), S. 424-437 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Presents a novel theoretical approach, based on extension of ideas associated with the generalized integral transform technique, for obtaining accurate analytic solutions for fully developed steady forced convection inside circular ducts with turbulent flow and constant wall surface temperature conditions. Within the temperature field, reports the thermal response of the fluid in terms of hybrid solutions for bulk fluid temperature and Nusselt number distributions along the thermal entrance region of the duct. Further, in assessing the accuracy and validity of the theoretical work, critically examines predicated analytical solutions of thermally developed Nusselt numbers and compares them with results from reliable empirical correlations of the open literature. For the investigated cases, satisfactory agreement prevailed between the theoretically and empirically derived heat transfer parameters, exhibiting a maximum difference of 9.58 per cent for the range of system variables analysed.
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