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  • Articles  (159)
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  • Blackwell Publishing Ltd  (159)
  • American Physical Society
  • Springer Nature
  • 1980-1984  (159)
  • 1970-1974
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (159)
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  • Articles  (159)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: This paper puts forward a new method for analysing the behaviour of very short fatigue cracks. A probability function is introduced into the definition of the growth threshold, which rationalises the scatter in experimental data produced using an aluminium bronze alloy. This probability function can be visualised in terms of the microstructure of the material.It is shown that, in this material as in mild steels, fatigue crack initiation is not the critical stage. Initiation occurs relatively easily, but the cracks so formed may grow to only a few grain diameters in length before being arrested; thus it is the behaviour of cracks of this length which is critical in determining the fatigue strength of the material.These observations, when combined with the probability functions, allow estimation of the probability of failure of a component or structure in service with greater confidence than the methods used at present.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The high temperature low cycle fatigue properties of modified 9Cr-1Mo ferritic steel in a hot forged and a hot rolled condition have been evaluated. The hot forged material exhibited inferior fatigue properties as compared to the finer grained hot rolled material. Analysis of the data indicates that a larger grain size adversely affects the initiation stage but has little effect on the propagation stage. A steeper slope on the Coffin-Manson plot results when the number of cycles to initiation is reduced.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The overload induced fatigue crack propagation behavior of several aluminum and steel alloys was examined as a function of the baseline stress intensity factor range (δKb). In order to gain a clearer understanding of the parameters which influence the cyclic delay phenomenon, under both plane strain and plane stress conditions, tests were conducted at δKb values ranging from the near threshold regime to high δK levels approaching fast fracture. Large amounts of overload induced cyclic delay (˜100,000 cycles) were observed at both high and low δK levels (provided the plastic zone size/thickness ratio and plastic zone size/grain size ratio approached unity, respectively) with significantly less delay occurring at intermediate δK values. All alloys examined exhibited this type of delay behavior which can be described by a “U-shaped” plot. The delay phenomenon at high δKb levels under plane stress conditions was attributed to increased crack closure associated with large tensile displacements in the wake of the advancing crack. At low δKb levels increasing cyclic delay was attributed to an increased effective overload ratio as δK approached δKth.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: Changes in the crack growth behavior of 7075-T651 aluminum specimens which had been exposed to temperatures between 121 and 179°C were evaluated. Specimens were fatigue tested at room temperature under flight-by-flight loading conditions. Results from these tests were then compared with data from the as-received material. Exposure to 141°C or more produced a definite increase in specimen life, apparently due to a decrease in crack growth rate. In contrast, preliminary experiments using constant amplitude loading did not show noticeable effects of these thermal treatments on fatigue lifetime. The thermal treatments were found to cause overaging of the metastable precipitate microstructure, which was thought to be responsible for the changes in fatigue response.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The initiation stage and short crack behaviour in torsional fatigue of a 0.4% C steel was investigated by a replication technique.The fatigue cracks initiated and propagated in the ferrite phase which is located at the prior austenite grain boundaries in the form of long allotriomorphs. At this stage of crack development it is proposed that crack growth rate depends on the extent and intensity of plasticity at the tip of the crack. Crack growth per cycle is correspondingly proportional to the strength of the slip band. The ferrite-pearlite boundaries are strong barriers to crack propagation, which is manifested by a deceleration of growth and possible arrest. On raising the stress level the previously non-propagating cracks may continue to grow by branching or joining with other cracks in the ferrite phase. This process is repeated until the stress fields of one or more dominant cracks attain a critical value to sustain continued growth that leads to failure.
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  • 6
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: CT type specimens containing two layers of 309L and 308L cladding stainless steels welded to A508 carbon steel and 316 stainless steel were specially devised to test the influence of R ratio and environment on the crack propagation rate behaviour of cladding materials at 300°C. Large effects are shown. The crack growth rate under vacuum can be smaller by more than one order of magnitude as compared to air. Large differences are also shown on the fracture surfaces, where it is observed than vacuum promotes the formation of large crystallographic {111} facets. The effect of environment is briefly discussed on the basis of existing gas adsorption models.
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  • 7
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The monitoring of fatigue crack initiation mechanisms and short fatigue crack growth usually involves interrupting otherwise continuous load cycling for examination of the test-piece. This permits attainment of high resolution over a large area of surface where the fatigue cracks could initiate. However, breaks in the fatigue cycling can affect the fatigue endurance of the test-piece and in the present study of Ti-6A1-4V this has been shown to depend on the duration of the rests, the number of cycles between rests, the type of examination employed and the hydrogen content of the material. The results of the work are discussed in terms of the possible influence of the monitoring technique on the fatigue process.
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  • 8
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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 crack tip opening displacements and strains in the material very close to the crack tip have been determined from measured displacements for cracks grown in both vacuum and humid air environments. The environment alters both the relations between crack tip opening displacement and crack tip strain, and the effect of cyclic stress intensity on these factors. Results of dynamic observation of intermittent crack growth are correlated with fractographic evidence. The relationships between crack tip parameters are used in a previously developed mathematical model. The effect of wet air on fatigue crack growth is found to be a reduction in crack tip plasticity.
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  • 9
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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— Unexpected arrest of long fatigue cracks was observed in mild steel single edge notch three-point bend specimens tested under constant amplitude loading. Arrest was associated with a low, but still positive, slope of the crack length against stress intensity factor curve, and can be explained using the R -curve concept for fatigue-crack growth. At a stress ratio of 0.1, the fatigue threshold was 6.6, 7.3 or 8.0 MN/m3/2 depending on the definition of threshold used. This has obvious implications for both the development of a standard test method for the fatigue threshold and the application of data to practical problems.
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  • 10
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: Fatigue crack growth rates have been determined on standard specimens containing long cracks (∼5–10mm) and on specimens containing two-dimensional short cracks (∼0.10–0.50mm). Large differences have been observed indicating that at a given stress intensity factor short cracks propagate much faster than long cracks. Mouth opening displacement measurements for both specimen geometries have shown that the crack closure effect is largely responsible for the observed effect. These results are used to rationalize the behaviour of short cracks initiated from natural sites which were either graphite nodules or microshrinkage pores. The three-dimensional aspect of these natural small cracks is analysed and discussed in detail.
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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: For ultra-high strength steels and aluminium alloys, a fatigue crack could initiate from a notch tip under cyclic compressive load. The threshold value for fatigue crack initiation under compressive load can be as great as four times that under tensile load. The crack grew at a decreasing rate until eventually it stopped growing altogether under cyclic compressive load with a maximum length of 0.2-0.5 mm. If the minimum compressive load was near zero, i.e. compression to zero load cycling, the threshold value was near that under tensile loading and the compressive fatigue crack could continue to grow; however, the crack growth rate under compression to zero load fatigue was 10–100 times less than that under the tensile fatigue loading.
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  • 12
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: An investigation has been carried out on austenitic stainless steel 0Kh16N15M3B under normal conditions and also to neutron irradiation of 6.8 × 1016nm-2s-1 (E 〉 0.1 MeV) intensity. Thin-walled torsion cylindrical specimens were tested in strain-controlled fully reversed loading mode at 923 K. Various ranges of strain, pre-loading fluences and half-cycle hold times (1, 5 and 30min) were applied. Neutron irradiation was found to result in hardening of the steel, stimulating cyclic stress relaxation and a reduction in cyclic life. When acting together, neutron irradiation and static loads cause a more significant reduction in the number of cycles to failure than if summed up as independent factors. Application of a kinetic failure criterion based on a damage parameter enables an estimation to be made of the limiting state of the steel under high-temperature cyclic loading with hold periods.
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  • 13
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: Fatigue crack propagation tests have been made on 150 mm wide panels of 1.6 mm thick 7475-T761 clad aluminium alloy sheet with and without adhesively bonded patches of pre-formed carbon fibre reinforced plastic (CFRP). The test frequency was 10 Hz, the minimum stress: maximum stress ratio, R, was 0.1 and the peak applied fatigue stress was 60 MPa.The tests were undertaken to assess the possibility of preventing the growth of fatigue cracks, or reducing their rate of growth, by the application of CFRP patches to one face only of pre-cracked aluminium alloy sheet. The variables examined included the type of patch and adhesive; the size, shape and thickness of the patch; and the effect of chamfering the edges of the patch and the removal of the cladding prior to patching.Results indicated that correctly designed and bonded CFRP patches substantially decreased the subsequent crack growth rate. The size and thickness of the patch had significant effects upon the reduction of fatigue crack growth rate whereas the shape of the patch, chamfering and the removal of the cladding prior to patching had little influence.
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  • 14
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: An experimental investigation is reported of the possible effects of adiabatic shear bands, caused by projectile impact, on the fatigue strength of a titanium alloy (Ti-6%A1-4%V). No significant reduction in fatigue strength due to the presence of adiabatic shear bands was found, nor did the fatigue cracks initiate from the bands. The results are relevant to the problem of foreign object impact damage to compressor blades in gas turbine aeroengines.
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  • 15
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: In order to study creep-fatigue interactions under multiaxial stress states, both push-pull and reversed torsion low-cycle fatigue tests were carried out using an austenitic stainless steel, SUS 304, at 923 K in air. From the tests, it is concluded that the hold-times introduced at the peak strain reduce low-cycle fatigue lives in the push-pull mode, but in the torsional mode they were not so harmful. This difference in the hold-time effect is discussed from considerations of crack formation and propagation and the stress amplitude applied to the specimen.Both maximum principal strain range, Δε1, and the von Mises' equivalent strain range, Δεeq, provide a nearly adequate comparison base for the assessment of biaxial low-cycle fatigue lives in tests without strain hold-time but are inadequate for hold-time tests. An equivalent stress range, Δσ*, which includes the effect of the stress parallel to the fatigue crack and which was previously proposed by the authors for no hold-time tests, is applied to the hold-time tests in the biaxial stress state. It is found that Δσ* is a good parameter for the correlation of biaxial low-cycle fatigue data in both no hold-time and hold-time tests.
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  • 16
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: Small fatigue crack growth behaviour in a low alloy steel was investigated under two stress step multiple loading in which the secondary stress was below the fatigue limit. Crack growth rates were presented in terms of a stress intensity factor and compared with data obtained under constant amplitude loading. In the higher ΔK region, crack growth rates increased monotonously with increasing ΔK even though the stress level was below the fatigue limit, and tended to be lower than those for constant amplitude loading. In the lower ΔK region, cracks showed a complicated behaviour, that is, an initial high growth rate was observed followed by an arrest or a drop to a minimum value and then a gradual increase. The average crack growth rates per cycle at both primary and secondary stresses in each block were approximately consistent with the da/dn-ΔK relation for constant amplitude loading. A suggestion for the prediction of crack growth life is given.
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  • 17
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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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  • 18
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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— Tests for fatigue crack initiation were carried out on two different aluminium alloys. Results and analysis of initiation under constant amplitude loading are presented; elastic and elastoplastic analyses are applied. Initiation under programmed block loading is investigated and damage accumulation is discussed. Tests were performed on two notch root radii:5 and 0.5mm. The electric potential method was used to detect fatigue crack initiation. Three point bending tests on smooth specimens were carried out to follow the evolution of damage during the crack initiation phase.
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  • 19
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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— High strain fatigue properties of AISI 316, AISI 316N and Sandvik 253MA have been investigated at 600°C. The two latter alloys, which contain significant amounts of N, exhibit a higher resistance to fatigue than 316. This effect is accompanied by a planar dislocation slip mode in 316N and 253MA as opposed to a wavy slip mode in 316. The results provide strong evidence that N improves fatigue strength in austenitic stainless steels, by inhibiting cross-slip of screw dislocations.
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  • 20
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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 phenomenological model of cumulative creep damage combining simulated grain boundary cavitation with internal redistribution of stress is developed and matched to constant load tensile creep data for an AISI 316 stainless steel tested at 550°C. The model is shown to predict the creep life of the material when it is subjected to single step changes in load provided the strain rates subsequent to the change are imposed in the model. It is inferred that this supports current suggestions that cavitation failure may be strain controlled.
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  • 21
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: A fatigue crack growth damage accumulation model is used to derive laws for the fatigue crack growth rates of brittle and ductile materials. The damage accumulated during cyclic loading is assumed to be proportional to the cyclic change in the plastic displacement in the crack tip yielded zone. The static mode contribution to the fatigue damage is assumed to be proportional to some power of the crack tip displacement. The laws are applicable in either the small or large scale yielding regimes provided that the stress ratio remains positive. Static modes are assumed to be controlled by the fracture toughness value in brittle materials, and by the gradient of the crack growth resistance curve in ductile materials. In the analysis of ductile materials it is assumed that the crack growth resistance of the material is not significantly altered by fatigue crack growth.The growth rate equations are expressed in terms of the near field value of the J-integral, i.e. the value which would be calculated from assuming the material deformed in a non-linear elastic manner during the increasing load part of the fatigue cycle. Examples are given of the predictions of the growth law for ductile materials. It is predicted that after the initiation of stable tearing the crack growth rate, when expressed in terms of the cyclic change in the stress intensity factor, depends on both the structural geometry and the degree of crack tip plastic deformation. In both brittle and ductile materials the fatigue crack growth rate is predicted to accelerate as the failure criteria relevant to static crack instability are approached.
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  • 22
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The effect of cycle ratio R on the crack propagation rate for two aluminium alloys is analysed. Fatigue crack growth under programmed block loading is presented, linear damage accumulation is established for some flight simulation tests. Aspects covered include microscopic and fractographic observations. The incidence of crack closure is examined and the concept of equivalent constant amplitude is applied. The agreement between predictions and test results is very promising.
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  • 23
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The progressive nature of fatigue damage under multiaxial stress states has been investigated. Experiments were performed on thin-wall tubular specimens of 1045 steel in tension, torsion and combined tension-torsion loading. Two equivalent strain amplitudes, one in the high cycle fatigue (HCF) region and one in low cycle fatigue (LCF) region were employed in this study. Four recently proposed damage theories were evaluated. Crack depth was used as a damage parameter in comparing damage curves under different loading modes.Different types of crack systems were observed in the HCF and LCF regions. The damage curve obtained in tension loading can be used to evaluate the damage behavior under combined tension—torsion loading. The results of torsion loading show that torsional damage behavior is different from the above two loading modes.
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  • 24
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The fatigue strength of 7075-T6 aluminium alloy under combined axial loading and torsion was examined. The S-N relations were correlated with the von Mises criterion for the high cycle region (Nf≥ 104 cycles) and with the Tresca criterion for the low cycle region (Nf 〈 104 cycles), where Nf is the cycles to failure. This transition at Nr= 104 cycles was related to the occurrence of macroscopic plastic straining and a change in fracture modes. The results are discussed in comparison with those for a high strength steel (SNCM8) in a previous study. Particular attention is given to differences in cyclic deformation behaviour, fracture modes and fatigue crack growth rates between the two materials.
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  • 25
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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: S-N curves have been determined for continuous cycling and for interrupted cycling using commercial purity titanium, and also a Ti-6Al-4V alloy in four different states of heat treatment. The incorporation of rest periods during the fatigue tests resulted in increased lives to fracture to an extent which appeared to be independent of specimen composition or microstructure, and hence primarily a function of the titanium itself. Failures from internal crack origins were found at longer lives from some specimens for both continuous and interrupted tests. It is suggested that the observed effects are due to localised hardening and strain ageing as a consequence of oxygen and/or nitrogen pick-up from the testing environment, and also as a result of oxygen and/or nitrogen present in the starting material.
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  • 26
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The fatigue behavior of a hot-rolled, control-cooled, plain carbon eutectoid rail steel has been characterized. The data include monotonic and cyclic stress-strain curves, low cycle fatigue data and near-threshold fatigue crack growth rate behavior in air and in vacuo. The effects of environment and mean stress on the near-threshold fatigue crack growth rates of rail steel are significant. At a low stress ratio (R), ΔKo is lower in vacuum (7 MPa √m) than in moist air (10 MPa √m). At high R, ΔKo is higher in vacuum (6 MPa √m) than in air (4 MPa √m). The beneficial effect of moist air on FCGR at low ΔK and low R is attributed to an increase in closure due to fracture surface roughness and oxide film.
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  • 27
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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: The cyclic deformation of polycrystalline A1-4%Cu alloy containing θ precipitates was investigated by strain controlled tests, and compared to monocrystalline cyclic behavior. The cyclic deformation of the polycrystals was found to depend on the grain size, and in coarse-grained material (grain diameter = 1 mm) a definite plateau was observed in the cyclic stress-strain (CSS) curve. In order to explore the relationship of cyclic behavior between single crystals and polycrystals, three available orientation factors were examined. This relationship can be interpreted by selection from the different types of orientation factors (Taylor factor, Sachs factor and Maximum Schmid factor), which operate to different degrees depending on the magnitude of the strain amplitude and the grain size.
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  • 28
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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— An analysis is presented of factors causing fatigue crack resistance in metals exposed to liquid corrosive environments. A new approach involving invariant diagrams is proposed that takes simultaneous account of the stress-strain state and the electrochemical conditions at the tip of a crack. Variations in electrochemical conditions at the tip of a stationary crack and the relationship between the electrochemical conditions at the crack tip and the fatigue crack growth rate in aqueous corrosive environments are discussed with the aid of these diagrams.
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  • 29
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    Fatigue & fracture of engineering materials & structures 7 (1984), 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 model is proposed for calculating the fatigue crack opening load based on the concept of residual strain in the overload plastic zone. An equation relating the fatigue crack opening load to loading parameters is given. The model is used to evaluate the retardation effect due to overload under various loading conditions. It is found that the calculated results agree with test data.
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    Fatigue & fracture of engineering materials & structures 6 (1983), 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 influence of age-hardening on the middle and low crack growth rates of a 7075 Al alloy is studied in vacuum. A transition in fracture surfaces morphology and crack growth curves is observed with the T 651 and T 7351 treatments in the near-threshold regime. Measurements of crack closure show its dependance on surfaces roughness and explain the lack of dependance of ΔKth with load ratio, except for the T 7351 alloy. An equation of crack growth rate to the fourth power of ΔKeff is in good agreement only with the crack propagation curves obtained for microstructure with an homogeneous deformation mode.
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  • 31
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    Fatigue & fracture of engineering materials & structures 6 (1983), 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 crack growth measurements are usually made on standard specimens containing long cracks (∼10 mm) although in most practical situations, a large part of the fatigue life is spent with much shorter dimensions. The purpose of the present study is a comparison of crack growth behaviour for long cracks (∼13–16 mm) in CT specimens and smaller ones (∼0.3–0.5 mm) in four point bend specimens. Large effects are noticed indicating that, at a given stress intensity factor amplitude, the crack growth rate is significantly higher in specimens with short cracks. Mouth displacement measurements for both specimen configurations show that the crack closure phenomenon accounts for the observed effect. Crack closure is likely to be associated with fracture surface roughness as shown by partly machining the material left behind the crack tip in CT specimens.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The fatigue crack closure response was investigated for a surface crack in BS4360 50B structural steel, subjected to (1) constant amplitude loading and (2) constant amplitude loading interrupted by a single peak overload. A variety of compliance techniques was employed to determine closure behaviour. The crack mouth gauge measured the bulk, plane strain closure load, while the near tip strain gauge indicated the surface, plane stress closure response. For constant amplitude loading it was found that the surface regions of a surface crack are closed for a greater portion of the load cycle than the maximum depth point. A single peak overload caused different closure and growth rate transients at the surface of the thumbnail crack and at the maximum depth point. For growth rates above 10-6 mm/cycle, such behaviour agrees with the response of a through crack when subjected to constant amplitude loading, and a single peak overload.
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  • 34
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue cracking of complex structure often involves several interacting cracks developing in a sequence of crack growth, arrest and reinitiation. A “combined” method of damage tolerance analysis is presented which employs fracture mechanics concepts to calculate crack growth and fatigue data from notched coupons with the appropriate notch radius for the crack initiation phase. The notched coupon data, plotted as peak elastic notch stress vs cycles to crack initiation, are shown to be applicable even when limited yielding occurs at the notch root. For several practical reasons it is recommended to select the initial crack size, ai, for the crack growth phase to be as large as possible, but in accord with two selection criteria. First, ai, must be within a notch-root region wherein the elastic stress distributions near a variety of notches are virtually identical. Secondly, ai must be small enough not to significantly influence the stress distributions for other cracks. The Combined Method is illustrated by means of an example involving fatigue crack growth along a widthwise row of holes in 305 mm wide test panels.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Sharply notched specimens of a structural low-carbon steel were fatigued under several ratios of the maximum to minimum loads. The growth behavior of a short fatigue crack near the notch tip was analyzed based on crack closure measurements. A fatigue crack first decelerates with increasing crack length, and then accelerates or becomes non-propagating depending on the applied stress. A similar deceleration is seen when the rate is correlated to the stress intensity range. The effective stress intensity range is a unique parameter in correlating the growth rate of a short crack for all the stress levels examined, and the relation is identical to that obtained for a long crack. By considering the increase in crack closure with crack length, a quantitative method is proposed for predicting the non-propagating crack length and the fatigue limit of notched specimens as a function of the applied stress and the notch geometry.
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Segmented fitting of fatigue crack growth rate data is shown to give a more accurate prediction of fatigue life with less statistical scatter than by a single fitting using the straight line of a Paris-type plot. Changes in the slope of the log (da/dN) vs log ΔK data are seen to correlate well with changes in the mode and mechanism of fracture.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Strains very near a growing fatigue crack have been computed from measured material displacements, both for a very dry environment and for humid air. Significant differences in crack tip strains arid crack tip opening displacements occur in these environments, with crack tip deformation in water vapor evidencing less plasticity than the dry environment. These quantitative results are incorporated into a previously developed mathematical model which is based, in part, on dynamic observations of intermittent crack growth. Fractography is shown to support the concepts of intermittent crack advance and decreased crack tip plasticity due to environmental water vapor.
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    Fatigue & fracture of engineering materials & structures 6 (1983), 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 model for fatigue threshold has been proposed based on the dislocation subgrain cell structure that evolves at the crack tip in steels during the fatigue deformation process. The stabilized subgrain cells that develop in the material act as impenetrable barriers to dislocations in slip band pile-ups that emanate from the fatigue crack tip. The blocking of these dislocations tends to limit crack growth that occurs by crack tip emission of dislocations, thereby leading ultimately to the fatigue threshold condition. The grain size effect on threshold is deduced to be an indirect effect as it is proposed that the subgrain cell size is the controlling substructural parameter at the threshold stress intensity level. The subgrain cell size is shown to be proportional to the one-third power of the initial grain size.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The fatigue strength of notched specimens of a rotor steel was examined under variable torsional loading which simulates turbine-generator oscillations resulting from the high speed reclosing of transmission-line circuit breakers. The local stress-strain response at a notch root was analysed using Neuber's rule and the resulting complex strain sequences applied to smooth specimens. Using the rain flow analysis and the linear summation rule, fatigue lives of the smooth specimens were successfully predicted from constant amplitude fatigue life data in association with the cyclic stress-strain curve obtained by the incremental step method. Experimental crack initiation lives for notched specimens subjected to variable torsional loading were in excellent agreement with the theoretical curves derived from results on smooth specimens. According to the view that fatigue damage is equated to crack length, the propagation life of a mode II crack along the notch root was predicted to be actually coincident with the life to crack initiation at the notch root denned in this study, i.e. the life at the stage of finding a continuous circumferential crack.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A crack-tip-zone interaction model for creep-fatigue crack growth is proposed. The basic details of the model are described. Experimental evidence in support of this model is presented. Existing data on creep-fatigue crack growth interaction agree qualitatively with the model. Some quantitative evidence for the model is presented and more is being developed in current work.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue crack propagation behaviour in a cast Mg-Al-Zn alloy was examined. The fatigue crack growth rate of the alloy under constant amplitude loading and the threshold resulting from a number of tests are given. Delayed retardation after the application of a single tension overload is explored in detail and described by using the model proposed by Matsuoka and Tanaka. From these observations, it may be seen that the Matsuoka model can be applied to the cast magnesium alloy as well as steels and aluminium alloys. Changes in the extent of retadation and the overload affected zone size with respect to the ratio of peak-to-baseline stress intensity factor range are discussed. Two phenomena, delayed arrest and acceleration in the later stages of retardation are reported.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue crack growth in the intermediate range can be described by the Paris law of linear elastic fracture mechanics. However, if gross plastic deformation is involved, the crack growth rate is often underestimated by LEFM. In the present study the increased crack growth rate due to plastic deformation is determined by using the J–R curve. This model was found to give very good results over a wide range of high crack growth rates for three different geometries of two different steels. A way to predict instability under controlled cyclic load is discussed and is proved to work well in practice. Instability under displacement control is also discussed.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A method of combining long term creep data with relatively short term mechanical behaviour to provide an estimate of creep-fatigue endurance is presented. It is proposed that the creep-fatigue effect in high temperature cyclic deformation is governed by a difference in strain rate around the cycle and the associated variation in ductility with strain rate.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The threshold value for fatigue crack growth of a medium carbon steel was increased when the test-environment was changed from air to an aggressive H2S-containing brine. This increase in fatique threshold was shown to be caused by corrosion product-induced crack closure. Further, the fatigue threshold and crack closure level were shown to be dependent on the growth rate history in approaching threshold. The differences in fatigue crack growth rate and fatigue threshold resulting from test procedure and growth rate history were significantly reduced by employing the effective stress intensity concept.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Four particularly pronounced beachmarks have been identified on the fracture surface of a cracked rotor. A correlation has been made between these beachmarks and events in the operational record. Fatigue crack growth calculations have been performed for a chordally cracked shaft subject to alternating self-weight bend stresses. The shaft dimensions and loading used correspond to the position of the crack in the rotor and growth rates were calculated over a range of crack depths spanning the positions of the major beachmarks. The results of the calculations agree with the beachmark correlation if allowance is made for the effect of the torsional loading of the shaft.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Crack closure in the near-crack-tip region has been considered to be an important contribution to the development of a crack-growth threshold for macroscopic cracks. Recent analytical work, however, has suggested that closure well back of the tip may be the controlling factor. In order to check on this possibility, material has been machined away far behind the crack tip in order to eliminate long-range closure. Removal of this material did not eliminate the threshold, but did lower the threshold level by approx. 10% for tests conducted on 6.3 mm-thick X7090-T6 powder metallurgy aluminum alloy.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Experimental studies aimed at understanding the fatigue process in metals and polymers have usually been performed under uniaxial stress. Only in the last two decades or so has much experimentation been carried out on fatigue crack propagation under biaxial stress. This paper reviews the available published data. Crack propagation behaviour under biaxial stress is dictated by 3 parameters: stress biaxiality itself, which is defined here as the ratio of the in-plane principal stresses, crack angle with respect to the applied principal stress directions and stress intensity factor range. Depending on the first two parameters, cracks may grow in Mode I, Mode II or Mixed-Mode. Crack growth data have been presented using these three divisions. Two short sections have been included on initiation and cyclic stress/strain behaviour under biaxial stress to emphasise the fact that crack growth cannot be fully understood without knowing something of them. The accumulated data do not lead to adequate conclusions on either the qualitative or quantitative behaviour of cracks subject to cyclic in-plane biaxial stress. Reasons for the confusion and even contradiction of independent results are put forward and some discussion given to the possible directions of future experimental work.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Evidence is presented that the cyclic stress intensity threshold for fatigue crack growth in A1 2219-T851 is associated with a critical maximum value of stress intensity, Kc. This relationship is discovered by measuring the local value of stress intensity at the crack tip which is less than the applied stress intensity because of fatigue induced compressive residual stresses in the plastic zone. Crack growth rates and values of the crack tip residual stress are measured as functions of load ratio. For local stress intensities greater than Kc, the growth rate follows a power-law relationship, increasing monotonically with δK. For local stress intensities below Kc, growth rates are also sensitive to the cyclic stress range, δσ. If the stress range is small, a threshold to growth, typical of long cracks, is seen. When the cracks are short and δσ exceeds a critical value, growth rates are a complex function of both δσ and δK. This behavior is attributed to the effect of δσ on the propagation of the crack front past obstacles such as grain boundaries.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Crack growth under cyclic loading has been studied by the finite element method. The calculation was made for plane stress conditions. The crack tip zone was modelled as a cohesive zone.The displacement of the free crack surface during unloading was found to be governed by the surrounding continuum and was independent of the details in the fracture zone. This means that crack closure upon unloading is directly related to the ultimate separation, of the cohesive zone, which in turn controls the residual plastic deformation left in the wake of the growing crack.If the distance over which closure takes place is rather small, closure may be very difficult to detect by the compliance technique.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue data required for estimates of cracked component lifetimes are conventionally obtained by cyclic loading of specimens manufactured to a specific geometry. Crack growth in the specimen results in an increase in the stress intensity factor range and crack growth curves are calculated from the variation of crack length with time. An environmental fatigue study of the effect of high pressure hydrogen on the low cycle fatigue of a medium strength steel has shown that, due to effects of elapsed time in the environment and effects of specimen size, in certain circumstances this procedure may not yield geometry-independent results which can be applied with confidence to cracked components. It is concluded that to obtain useful crack growth data in cases where fracture is influenced by diffusion or other strongly time dependent processes might require a modified approach to fracture mechanics testing procedures.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— This study is concerned with the influence of a single-peak overload and the overload ratio on the subsequent rate of growth of a fatigue crack in steels. Retardation increases with increasing overload ratio.The crack opening load was also measured during all tests. It is shown that the Elber's crack closure concept is not able to explain the effect of overloads. The importance of the material yield stress was evaluated by testing steels of different strength. It seems that the residual stress state induced by the overload is the major factor causing retardation. Two models are analyzed.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The fatigue growth of short cracks in coarse grained IMI 685, having an aligned a microstructure, has been monitored using a two stage replication technique. Crack growth rates are presented in terms of the failure mechanism and compared with standard data obtained from through cracked, compact tension specimens. The maximum difference, of up to four orders of magnitude, between long and short crack growth rates is associated with separation along specific crystallographic planes resulting in a cleavage-like fracture appearance. The rate of short crack growth is also shown to be dependent on applied stress and a dwell at maximum load during the fatigue cycle.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Computer optimization techniques were applied to the strain range partitioning method for lifetime prediction under high temperature low cycle fatigue loading. The experimental data were evaluated using a simultaneous parameter fit determination of the baseline coefficients. This approach gave good predictions whereas a more conventional method did not work. The significance of the linear damage rule and the interaction damage rule is discussed on the basis of a generalised rule containing both as special cases. This formalism was applied to a ferritic steel and a cast nickelbase-super-alloy. In both cases a very good agreement between calculated and measured lifetimes was found.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— An anisotropic form of the Von Mises yield criteria is presented which includes linear terms and therefore enables Bauschinger effects to be considered when constructing yield or loading surfaces.The coefficients representing the state of anisotropy are expressed in terms of the uni-axial and shear yield stress of the material. It is suggested that this form of the yield or loading surface can be used to determine the plastic strains for a range of multi-axial and cyclic plasticity problems and results are presented for the particular case of a tube subjected to cyclic plastic torsion with an axial stress.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The stress intensity factors at the tip of an edge crack in a round bar embedded in the tension zone of a concrete beam are found for several conditions of bond failure between the steel reinforcing bar and the concrete. A two-dimensional finite element technique is modified to represent the third dimension, the steel-concrete interface and debonding. The integrated form of the Paris crack growth law is used with the calculated stress intensity factors to compute the propagating fatigue lives for embedded bar and bar in air. The results indicate that embedded bars appear to have shorter fatigue propagation lives than bars in air if the crack initiators are less than 0.05 of the bar diameter, while for deeper crack initiators, the opposite is true. It has also been shown that the propagating fatigue life of the bar increases with the degree of bond.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Near threshold, mixed mode (I and II), fatigue crack growth occurs mainly by two mechanisms, coplanar (or shear) mode and branch (or tensile) mode. For a constant ratio of ΔKI/ΔKII the shear mode growth shows a self-arrest character and it would only start again when ΔKI and ΔKII are increased. Both shear crack growth and the early stages of tensile crack growth, are of a crystallographic nature; the fatigue crack proceeds along slip planes or grain boundaries. The appearance of the fracture surfaces suggest that the mechanism of crack extension is by developing slip band microcracks which join up to form a macrocrack. This process is thought to be assisted by the nature of the plastic deformation within the reversed plastic zone where high back stresses are set up by dislocation pile-ups against grain boundaries. The interaction of the crack tip stress field with that of the dislocation pile-ups leads to the formation of slip band microcracks and subsequent crack extension. The change from shear mode to tensile mode growth probably occurs when the maximum tensile stress and the microcrack density in the maximum tensile plane direction attain critical values.
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    Fatigue & fracture of engineering materials & structures 6 (1983), 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 results of an experimental program conducted to determine the influence of deep side-grooves on fatigue crack retardation. The results indicate that side-grooves significantly reduce the delay in fatigue crack growth caused by single peak overloads. It is suggested that the decreased retardation is due to simulation of plane strain conditions in the “thin” test sections by the stress field at the root of the side-groove.
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    Fatigue & fracture of engineering materials & structures 6 (1983), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The growth of “large” and “small” cracks in 7075–T6 aluminum is characterized in moist air and dry nitrogen. It is found that in both environments, the small cracks grow faster than large ones, but unlike large cracks, which grow much faster in air than in nitrogen, the small cracks extend in each environment at about the same average rate. The absence of environmental effect is found to be only apparent, a change to an inherently slower mode of growth in air offsetting the crack-accelerating influence of moisture. Subsurface grain boundaries apparently retard microcrack growth in both environments. Possible rationales for the rapid growth of small cracks are discussed.
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    Fatigue & fracture of engineering materials & structures 6 (1983), 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 thresholds and crack growth rates up to 10−4 mm cycle −1 have been measured in β processed IMI 685. The results obtained in laboratory air for material having an aligned α microstructure and a random basketweave microstructure displayed a pronounced load ratio dependence which increased with decreasing ΔK. This sensitivity to mean load was also apparent from the threshold results determined in a vacuum of 5 ± 10−6 torr.Fractographic observations, compliance measurements, pd output and crack path replication have indicated that contacts can be made between the fracture faces at a number of points behind the crack tip during the load cycle. These contacts wedge the crack open, thus preventing the stress intensity from falling to the value associated with the minimum applied load. A critical stress intensity, Kop, has been determined which relates to the crack being fully “open” and the results are reanalysed and discussed in terms of an effective stress intensity range, ΔKeff.
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    Fatigue & fracture of engineering materials & structures 5 (1982), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Hysteresis loops of a low carbon steel measured at various temperatures and plastic strain amplitudes are analysed using the statistical theory of the hysteresis loop. It is shown that the parameters of the statistical theory characterizing the saturated hysteresis loop, i.e. the probability density function and effective saturated stress, can be obtained from experiments. The probability density function is influenced mainly by strain amplitude; the effective saturated stress mainly by temperature.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Room temperature fatigue crack propagation in a sintered tungsten alloy was studied. The fatigue crack growth rates were found to be identical for the material in the sintered and forged and as sintered conditions. The propagation rates are slower when compared with other metals due to the relatively high Young's modulus of tungsten. The value of the exponent m in Paris' power law equation was found to be 12 which is higher than for most metals. This was ascribed to the activity of a cleavage mechanism through some of the tungsten grains along with the ductile decohesion fatigue mechanism.
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    Fatigue & fracture of engineering materials & structures 5 (1982), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The present work emphasizes the need to understand the processes involved in fatigue–creep interactions before reliable life predictions may be sensibly made. In particular, the simultaneous interaction involving a strain controlled cycle with a dwell period at maximum tensile strain is analysed and the accumulation of fatigue–creep damage computed in terms of strain range, extent of dwell and microstructure. Dominant failure modes are thus identified and the findings are used to explain the apparently different failure mechanisms previously reported for a 1Cr–Mo–V alloy steel and a Type 316 stainless steel. Due to lack of data overall mapping of regimes of dominance is not possible, but in cases where a single mechanism prevails throughout the duration of dwell accurate lifetime prediction may be achieved.
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    Fatigue & fracture of engineering materials & structures 5 (1982), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Crack shape evolution has been studied in high strength, rolled thread, bolts. It has been found that, using the Crack Microgauge, it is possible to detect and size fatigue cracks, located at the thread root, from depths of less than 0.1 mm up to fracture. This work required a special probe system to be developed and also a theoretical solution for the a.c. field distribution in a thread. Some of the work and results are briefly described in this technical note.
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    Fatigue & fracture of engineering materials & structures 5 (1982), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The paper shows the practical significance of theoretical studies of fatigue crack propagation in real structures, and a comparison of the results of fracture mechanics theory with the actual failure mode of structures. It follows from these conclusions that neither the influence of the magnitude and complexity of structure, nor that of the random character of loading can be overlooked. Therefore, when applying laboratory test data the character of the structure under consideration and the loading conditions should be thoroughly appreciated.
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    Fatigue & fracture of engineering materials & structures 5 (1982), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The problem associated with short crack growth, defined as situations in which the intensity of the crack tip field is underestimated by linear elastic fracture mechanics analyses, is briefly reviewed.Two cases are identified, cracks growing in plastically strained materials, such as occurs in high strain fatigue studies and at notch roots, and small cracks growing in single grains as occurs close to the fatigue limit in plain specimens.Important mechanical and metallurgical features of short cracks are discussed with particular reference to the upper and lower bound definition of a short crack.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Stress and strain distributions and crack opening displacement characteristics of short cracks have been studied in single edge notch bend and centre cracked panel specimens using elastic–plastic finite element analyses incorporating both a non strain hardening and a power law hardening behaviour. J contour integral solutions to describe stress strain conditions at crack tips for short cracks differ from those for long cracks. The analyses show that (i) short cracks can propagate at stress levels lower than those required for long cracks and (ii) a two-parameter description of crack tip fields is necessary for crack propagation.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The alloy IMI 829 is very sensitive to fretting fatigue damage at 20°C but its fretting fatigue strength increases as the temperature is raised to 600°C due to the formation of a glaze type oxide. Failure occurs by cracking of the glaze as a result of local creep. These cracks propagate into the bulk material. Local creep results from increased stresses in the fretting contact region, frictional heating, and preferential removal of alloying elements into the oxide film leading to reduced creep properties.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The influence of steady mode III on mode I fatigue growth behavior is investigated in four materials–a plain carbon steel, a Ni–Cr–Mo–V rotor steel, and titanium alloys, TA6V and TA5E ELI. It is shown that these loading conditions give rise to two main effects: (i) a strong reduction in propagation rate and (ii) a modification in crack path, the fatigue crack adopting a characteristic “factory-roof’ aspect. In 2024 Al alloy, it is shown that the superimposition of steady mode II to cyclic mode I leads to crack bifurcation, the angle θ being a function of Ka/Ktmax. These observations are discussed in the light of a new criterion which is introduced. This criterion is based on two main assumptions: (i) Fatigue cracking is assumed to occur only under the effect of local mode I opening. (ii) It is postulated that a fatigue crack grows in a direction where the crack propagation rate is maximum. A number of limitations of this approach, associated with crack closure phenomenon, are discussed.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Two parameters describing the growth of fatigue cracks are compared. They are the cyclic J integral ΔJ and the strain intensity expressed as an equivalent stress intensity ΔKeq-. By referring to cyclic stress-strain data obtained from hysteresis loops in high strength ferritic steels at room temperature and austenitic and ferritic steels at elevated temperature it is shown that: (i) for short cracks the parameters are simply related and (ii) both parameters adequately link fatigue crack growth rates observed in the separate high strain fatigue (HSF) and linear elastic fracture mechanics (LEFM) regimes. Correction factors for thumbnail cracks and the conditions under which the relations need further modification are discussed.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The growth of ‘small’, half-penny shaped surface fatigue cracks in a precipitation hardened aluminum alloy is compared with the growth of ‘large’cracks in fracture mechanics type specimens. It is found that the small cracks grow much faster than LEFM equivalent large ones, and also experience growth rate perturbations. It is suggested that localized microplasticity in nominally elastic specimens is responsible for the rapid growth of small cracks and that grain size limitations on the microplastic regions cause transient decelerations and sometimes permanent arrest, in crack growth.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Cyclic loading of mild steels in 4 N NaNO3 produces intergranular cracking similar to that associated with stress corrosion cracking at static loads, even when the cyclic loads are below the threshold for cracking under static conditions. However, under some circumstances cyclic loading promotes transgranular crack growth, the velocity of which may increase or decrease with increasing stress intensity factor. The transition from intergranular to transgranular cracking, or vice versa, is determined by the relative velocities of the two modes of failure, that observed having the higher velocity. The suppression of transgranular cracking as the stress intensity factor increases is only observed when the loading involves a compressive component and the effect is explained in terms of corrosion products interfering with the cracking process. Tension-tension loading in nitrates produces crack growth characteristics similar to those observed in oil.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The influence of cyclic loading on diffuse light transmission of GRP laminates was investigated. Light transmission decreased due to the presence of matrix microcracks and interface debonding. The dependence of defects caused by cyclic loading on the variation of light transmission was established by methods of scattering medium optics. This dependence can be applied both in investigations of the kinetics of GRP laminate failure and in the estimation of cumulative fatigue damage.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Near threshold fatigue crack growth under mixed-mode loading and elastic plane-strain conditions has been studied in 316 stainless steel in laboratory air at room temperature. Particular emphasis was placed on the influence of the mode II component. Crack growth from the starter crack, although initially coplanar, branches to be perpendicular to the maximum normal stress. However the threshold for the branched crack growth is controlled not only by mode I displacement, but also by the mode II component. Upper and lower bound curves are obtained for the threshold condition and discussed in terms of crack tip reversed plastic deformation, crack surface rubbing and oxide-induced closure. A theoretical method for predicting the lower bound curve is proposed and compared with the maximum normal stress and strain energy density criteria. The new theory shows the best agreement with experimental results, giving a safe prediction for design purposes.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Starting from a knowledge of inhomogeneous dislocation structures observed in cyclically strained metals, a model for cyclic straining is developed. A distribution of volumes with different internal critical flow stresses is assumed characterized by a probability density function. A generalization which includes a thermally activated component of the flow stress is derived assuming that the saturated microscopic effective stress, μes, is equal in all volumes. The relations to obtain the probability density function from experimental data are derived. The theory yields the macroscopic internal stress, σe and the macroscopic effective stress, σe, along the hysteresis loop. Experimental observations on cyclically strained metals can be explained using this statistical theory.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The effects of dry hydrogen, moist air, distilled water and hydrazine environments on the fatigue crack propagation behavior of 2021 aluminum alloy have been investigated over a wide range of growth rates spanning about six orders of magnitude. Environmental interactions in the intermediate and near-threshold crack growth regions are shown to be associated with different fracture characteristics and mechanisms. Scanning Auger and X-ray photoelectron spectroscopic analysis of fracture surface corrosion deposits revealed that oxide induced crack closure phenomena, which considerably influence the near threshold corrosion fatigue behavior of low strength steels and some aluminum alloys, are not of importance for the present 2021-T6 aluminum alloy. The mechanistic aspects of environmentally influenced fatigue behavior of the alloy are discussed in the light of hydrogen embrittlement, chemical reactions and crack closure concepts.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Accurate knowledge of defect sizes and crack shape development from initiating defects is essential for a realistic application of fracture mechanic? to the fatigue life prediction of welded joints. Defects at the toes of high quality longitudinal non-load-carrying fillet welded joints have been examined using two methods, and compared with those observed in plain unwelded plate. The defects observed at the weld toe were, on average, four times deeper than the largest observed in the unwelded plate but had similar root radii. For this particular geometry the defects could be considered continuous at the expected initiation site. A simple estimate of the stress concentrating effect of a single composite defect, coupled with experimental evidence, led to the conclusion that the proportion of total life spent in initiation is negligible for all stress levels which cause fatigue failure. Subsequent growth and crack shape development was observed to depend on the initial defect distribution and the complex stress field at the weld toe.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue crack growth rate tests have been performed on Nimonic AP1, a powder formed Ni-base superalloy, in air and vacuum at room temperature. These show that threshold values are higher, and near-threshold (faceted) crack growth rates are lower, in vacuum than in air, although at high growth rates, in the “structure-insensitive” regime, R-ratio and a dilute environment have little effect. Changing the R-ratio from 0.1 to 0.5 in vacuum does not alter near-threshold crack growth rates very much, despite more extensive secondary cracking being noticeable at R= 0.5.In vacuum, rewelding occurs at contact points across the crack as ΔK falls. This leads to the production of extensive fracture surface damage and bulky fretting debris, and is thought to be a significant contributory factor to the observed increase in threshold values.
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    Notes: Abstract— Fatigue thresholds and crack growth rates were studied in the experimental alloy, Ti—5Al—4Mo, as a function of temperature, grain size and hydrogen concentration. Deformation is confined to planar slip bands along which fracture occurred at low hydrogen concentrations. Hydrogen accelerated crack growth rates at various combinations of temperature, grain size and hydrogen with a corresponding change in fracture from “cleavage’ to interface phase fracture. In addition, hydrogen was found to promote interface phase formation. It is proposed that stress-assisted hydrogen accumulation increases the interface phase hydrogen concentration which reduces the interface phase fracture stress. This process depends on the local stress and β-phase hydrogen concentrations, temperature and the time under load. At 340 K, hydrogen had a relatively small effect on crack growth due to a change in slip behavior with increased hydrogen concentration.
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    Notes: Abstract— This work proposes a crack growth equation for short cracks, defined for cracks which have yet to cross the first grain boundary. This crack growth law is used in conjunction with a Linear Elastic Fracture Mechanics formulation to describe the complete crack growth behaviour from initiation to failure.
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    Notes: Abstract— This paper presents the results of an investigation of fatigue crack initiation in pure polycrystalline α-iron as a function of testing frequency (0.01–1000 Hz). Three distinct types of fatigue crack initiation mechanisms were identified:(i) At low frequencies, 〈0.5 Hz, cracks were observed to nucleate at intrusions, extrusions and grain boundaries. However over the frequency range studied the cracks at the intrusions and extrusions were not associated with the final fatigue failure. The results suggest that in pure iron frequencies 〈0.01 Hz are required for fatigue failure to be initiated at intrusions and extrusions.(ii) At frequencies ≤0.01 Hz at high strain amplitudes, cracks nucleated at the intersection of grain boundaries with the free surface as a result of the incompatable deformation of surface grains. The subsequent propagation of these cracks resulted in fatigue failure.(iii) Tests performed at low strain amplitude at 5 Hz and 1000 Hz initiated surface grain boundary cracking without any significant associated change of grain shape.The results of the present investigation indicate that fatigue failure in pure iron alloys (at frequencies 〉0.01 Hz) is initiated not at intrusions and extrusions but at grain boundaries.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Fatigue crack retardation behavior due to an overload under different overload ratios and different crack lengths in a Ti-6A1–4V titanium alloy has been investigated. The effect of some major factors on retardation behavior is discussed as a result of an interaction between the overload and cyclic loads. It is suggested that the retardation process may be divided into five stages. From an analysis of the modes of fatigue fracture, the overload in these tests can be regarded as occurring under plane strain conditions or a mixed mode in which the plane strain condition predominates. Thus, at a given overload ratio the number of delay cycles ND caused by an overload decreases with an increase of K01 under these plane strain conditions.In this paper, the Wheeler, Willenborg, Maarse and Matsuoka models were selected for comparison with regard to engineering applications. An evaluation of their ability to predict life has been made. The Matsuoka model based on the crack closure concept was found to be in good agreement with experimental results. It is also recognized that the experimental values of the effective overload zone size are considerably greater than the calculated values suggested by the above mentioned models.
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    Notes: Abstract— Electrochemical potential at the tip of a fatigue crack was measured in a compact tension specimen, situated in demineralized, oxygen saturated water at 93°C.Results show that the crack tip region is active with respect to the external specimen surface. Passivation occurs on the crack surfaces by the formation of an oxide layer. The oxygen concentration inside the crack is likely to be lower than in the bulk solution.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The use of d.c. electrical potential methods is described for the monitoring of Mode III (anti-plane shear) fatigue cracks in circumferentially-notched cylindrical specimens subjected to cyclic torsion. Calibration of potential change with crack depth and optimization of current input and potential measurement probe locations are achieved using simple finite element procedures, and are verified experimentally. The use of the method for Mode III crack growth studies is described in the light of crack face electrical shorting problems associated with torsional crack closure.
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  • 93
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 5 (1982), 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 was found in a previous publication that stress fields around notches are quantitatively very similar, if the peak stress at the notch root (σpeak) and the notch root radius (ρ) are the same. As a consequence, small cracks (length l) should have the same stress intensity factor, if σpeak and ρ are similar. This implies that the geometry factor C in〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:8756758X:FFE77:FFE_77_mu1"/〉should primarily depend on l/ρ only, and not on other dimensions. Available data on calculated K values was analysed, which confirmed the similarity concept. An equation for C as a function of l/ρ was obtained. It was shown that K-values calculated with this equation are an accurate approximation for the stress intensity factor of small cracks at notches.
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  • 94
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 5 (1982), 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
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 5 (1982), 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 stress-dip technique for the determination of an effective stress in cyclic straining has been improved. The critical stress drop, ΔσC, for which zero strain relaxation rate is observed can be obtained from experiments. The significance of this quantity is discussed in terms of the statistical theory of the hysteresis loop. The measurements of the effective stress at different temperatures and along the hysteresis loop are reported. The observed asymmetry of stress in cyclic straining is ascribed to asymmetry of effective stress.
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  • 96
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 5 (1982), 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— Low cycle fatigue tests at 650°C on 20% Cr–25% Ni–Nb stainless steel have been carried out under conditions of equal tension/compression ramp rates (10−3 s−1) and slow tension–fast compression ramp rates (10−6 s−1/10−3 s−1). It was found that the latter cycle significantly reduced endurance. Detailed metallography revealed that life reduction is due to the accumulation of creep damage during the slow tensile ramp. It is proposed that at high strain ranges, failure is creep dominated and this changes to a creep-fatigue interaction failure mechanism at low strain ranges.Predictive models have been developed based on cavity growth mechanisms and ductility exhaustion. Both techniques provide an accurate life prediction and only limited data are required to use them.
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  • 97
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 5 (1982), 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
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 5 (1982), 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
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 4 (1981), 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: Stress intensity factors are determined for internally and externally cracked, pressurized thick cylinders with partial autofrettage (less than 100% overstrain). The solutions are based on a superposition of existing solutions which does not involve any loss of accuracy. Implications of the stress intensity factor results for the safe-life design of pressure vessels subjected to fatigue are discussed.
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  • 100
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 4 (1981), 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: Fatigue crack propagation tests were conducted under conditions of equibiaxial, uniaxial and shear loading by using a cruciform specimen in a servo hydraulic testing machine. The effect of non-singular stress cycling on the fatigue crack propagation rate was examined based on the observation of crack opening behavior. The crack propagation rate was significantly influenced by the non-singular stress parallel to the crack when it was correlated to the stress intensity range. The crack closure behavior was greatly affected by the non-singular stress. The crack propagation rate was uniquely correlated to the effective range of the stress intensity factor except for the case of completely reversed shear loading where significant plasticity was detected. The crack opening displacement range was concluded to be a parameter controlling the crack propagation rate for all the stress conditions examined in the present experiments. Some discussion is made on the effect of material anisotropy on fatigue crack propagation in a biaxial stress field.
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