ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of Macroscopic and Local Strains in a Three-Dimensional Woven C/SiC Composite (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    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: Engineering tests and full-field strain measurements are used to assess the accuracy of predictions made by the Binary Model, a computational tool for textile composites. The test case is a carbon fiber/SiC matrix composite, in which the reinforcement is a three-dimensional angle-interlock weave. The test composites are thin, having been designed for heat exchanger applications. The thinness leads to strong variations in local strains and strong effects of tow waviness upon macroscopic elasticity. The model performs well in predicting both local variations in strain and macroscopic elasticity. The effect of averaging local strains over variable gauge lengths is explored. Strains averaged over an appropriate gauge length have recently been proposed as the preferred measures of strain for use in local failure criteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00156.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A STATISTICAL MODEL OF INTERMITTENT SHORT FATIGUE CRACK GROWTH (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 9 (1987), S. 0 
    Details
    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: The stochastic nature of the growth of short surface fatigue cracks under uniform cyclic loading can be attributed to their interaction with a stochastic microstructure. In this paper, a computational scheme is proposed to describe the statistical effects of the temporary arrest of short cracks by grain boundaries, and the modification of rates of propagation across grains by various effects of grain boundary constraint. The fact that a crack tip may be in one of two states, either temporarily arrested at a grain boundary or actively propagating, is treated explicitly by considering probability densities evolving in complementary state spaces corresponding to each case. The evolution of the densities during fatigue is described by conservation equations, which are solved numerically. It is shown how engineering quantities, such as the time to initiation of a macroscopic crack, can be derived from the calculated densities. The explicitness with which the characteristics of short crack growth are treated greatly enhances the potential accuracy of predictions based on this approach.The theory is constructed to allow considerable flexibility in the microstructure-related mechanisms assumed to control growth rates in any given material. However, as it is stated here, the theory is restricted to Mode I (tensile opening) transgranular crack growth under constant amplitude cyclic loading. Examples are given of the various effects that can be treated, as well as those that would require modification of the structure of the computational procedure. The theory is illustrated by an application to data for Al 2219-T851.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1987.tb00470.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    CRACK BRIDGING IN THE FATIGUE OF FIBROUS COMPOSITES (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 14 (1991), S. 0 
    Details
    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— Recent observations of fatigue cracks bridged by continuous fibers in titanium alloy and titanium aluminide composites are compared to analogous observations in fiber-reinforced ceramics under monotonic loading. Three failure modes have been identified under axial loading in each case: longitudinal failure (failure parallel to the fibers) and noncatastrophic and catastrophic mode I failure (failure normal to the fibers). The criteria for transition from one failure mode to another are reviewed. Models developed previously to describe the failure of fiber-reinforced ceramics are extended to describe the mechanics of mode I fatigue crack growth. The extension is straightforward as long as the fibers do not fail in the crack wake, i.e. the failure mode is noncatastrophic mode I failure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1991.tb00716.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    MODEL-BASED STATISTICAL ANALYSIS OF SHORT FATIGUE CRACK GROWTH IN Ti 6Al-2Sn-4Zr-6Mo (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 10 (1987), S. 0 
    Details
    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 framework of a new probabilistic model of short fatigue crack growth was laid down in the preceding paper. In this paper, the model is used to analyze growth rate statistics for surface fatigue cracks in Ti 6Al-2Sn-4Zr-6Mo. Specific models are proposed for the evolution of the stochastic growth control variable, which appears subsequently as an independent variable in a parametric law for the growth rate. Comparison with data shows that for cracks of length 10–250 μm in Ti 6–2-4–6, fluctuations in the instantaneous rate of propagation of each surface crack tip depend only on the visible surface microstructure in the tip's immediate neighborhood. They are not influenced by the microstructural environment of the subsurface crack front. Furthermore, they probably depend only on the sizes of at most the three grains nearest the crack tip, i.e. those within about 30 μm of it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1987.tb00494.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    A PROBABILISTIC MODEL OF SHORT FATIGUE CRACK GROWTH (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 10 (1987), S. 0 
    Details
    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 probabilistic model is presented that draws a direct link between stochastic microstructure and the statistics of measured growth rates. The model is formulated as a semi-Markov process. The underlying Markov process describes the evolution of a growth control variable as an explicit function of crack length. The growth control variable is open to a variety of interpretations, depending on the mechanisms known to control growth in any given application. Elapsed fatigue cycles and the distribution of times to failure are calculated by invoking an empirical or postulated law of growth rate. This law is either a deterministic or probabilistic relationship between the growth control variable and the crack velocity. It may, and usually does, contain parameters that are evaluated by calibration against available statistical data. This process guarantees a high level of robustness of the model's predictions. The computational generality of the formulation facilitates the treatment of spectral loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1987.tb00490.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Lockup, chains and the delocalization of damage (1996)
    Springer
    Journal of materials science 31 (1996), S. 4871-4881 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Whether damage is localized or delocalized in a composite, the composite's fracture toughness when localization occurs can be controlled to a much greater extent than hitherto exploited by properly choosing the composite's internal geometry. Delocalization and high toughness are both favoured by building in systematic defects and lock-up mechanisms. Widespread defects make available arbitrarily many sites at which energy may be absorbed by non-linear behaviour. Lock-up mechanisms cause local hardening following local damage, which drives subsequent damage to initiate elsewhere, possibly leading to damage delocalization. In brittle-brittle composites, these mechanisms may be the best hope for achieving toughness values similar to those of alloys. Illustrations are taken from recent research into woven composites with three-dimensional reinforcement and new work on model composites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355875
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Microscopic deformation in a heated unidirectional graphite-epoxy composite (1989)
    Springer
    Journal of materials science 24 (1989), S. 199-204 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Out-of-plane displacements caused by heating of a unidirectional P75S/1962-ERLX graphite-epoxy composite were measured on a surface cut normal to the fibres after thermal cycling. On heating to 44° C from room temperature, the epoxy confined within clusters of three fibres sank in a trough beneath the plane of the fibre ends by 50–120 nm. The sense of the deformation was the opposite of what one would expect from differential thermal expansion. The role of residual stresses in this deformation was studied by measuring the depth of the trough for several different thermal histories applied before the free surface was cut. When the maximum temperature achieved in the prior thermal cycles exceeded 100° C, the depth of the trough increased. However, if cycles exceeding 100° C were followed by thermal cycles of decreasing amplitude, chosen to induce interfacial stress relaxation, the depth of the trough decreased, as expected. The experiments illustrate the feasibility of deducing quantitative information about local deformation in the interior of a specimen from high spatial resolution strain measurements on cut surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00660954
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The determination of crack bridging forces (1991)
    Springer
    International journal of fracture 49 (1991), S. 159-176 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method is presented for determining the bridging tractions acting on the fracture surfaces of cracks from measurements of the crack opening profile. The tractions may be expressed either as a function ϕ(x) of position in the crack or a function p(u) of the crack opening displacement. The feasibility of deducing ϕ(x) or p(u) from noisy displacement data is demonstrated by numerical simulations. It is found that the most complete information is contained in profiles of cracks growing from notches. Improved estimates of p(u) can also be found by analzying data from several cracks at different stress levels simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035040
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Braided composites for energy absorption under tensile loading (2000)
    Springer
    Journal of materials science 35 (2000), S. 3467-3478 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new class of braided composites has been designed to maximise thetotal energy absorbed during tensile failure. Braided loops oflight, continuous fiber tows are configured in such a way that theymust be drawn through relatively large displacements before they comeinto direct contact with one another. Upon loop contact, thematerial hardens locally, forcing further damage to develop by thesame process elsewhere. In this way the entire gauge section absorbsenergy before ultimate failure. Levels of energy absorption per unitvolume reach 30 MJ/m3 and, per unit mass, 18 J/g. The mechanismsinvolved in damage delocalisation and failure are detailed andmodeled at a very simple level. While the current values of energyabsorption are already attractive, the simple models indicate muchhigher values for composites that have been optimised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004888824424
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A high accuracy automated strain-field mapper (1990)
    Springer
    Experimental mechanics 30 (1990), S. 60-67 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The design and capabilities of a computer-automated high-spatial-resolution displacement-measurement system are described. The system is used to determine the relative displacement fields generated by thermal or mechanical loads by comparing a pair of SEM or optical micrographs, one recorded before the load is applied and the other afterwards. The displacements are measured by cross-correlation analysis of the relative positions of visible surface texture on the micrographs. Displacement accuracy on a specimen surface is ±60 Ă for optical microscopy, and ±10 Ă for scanning electron microscopy. Both in-plane or out-of-plane deformation can be characterized depending on the angle at which the specimen is viewed. This instrument has the potential of quantifying surface deformation over submicron gage lengths and will be an invaluable tool in experimental micromechanics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02322704
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...