摘要:

AbstractThe Gough test data on fatigue under combined bending and twisting with superimposed mean bending and torsion stresses with and without stress raisers has been re‐investigated in terms of the stresses acting on the plane of maximum range of shear stress. It has been shown that the allowable amplitude of shear stress on this plane can be predicted from an equation of the formτa= [t ‐ c1(Kt×σa)1.5−c2σ2m]/Ktwhere σaand σmare the normal stress amplitude and mean normal stress respectively on the plane of maximum range of shear stress, c1and c2are defined material constants and Ktis the theoretical stress concentra

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00415.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe impact fatigue crack growth characteristics of a low carbon steel and an aluminium alloy were studied. An impact fatigue testing machine of the Hopkinson bar type was used in these experiments to conduct a series of crack growth tests under simple impact stresses.The following characteristics of impact fatigue crack growth behaviour were revealed: (1) crack growth rate is higher in impact fatigue than in non‐impact fatigue; (2) crack opening ratio in impact fatigue takes a higher value than in non‐impact fatigue; (3) crack tip plastic zone size is smaller in impact fatigue than in non‐impact fa

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00416.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractSurface crack growth has been studied in centre notched and smooth panels of low carbon steel under symmetric axial elastic‐plastic cyclic straining. The crack shape, followed by heat tinting, has been found to be approximately semi‐circular for crack radii 0.3–5 mm. Both smooth and notched specimens have been fatigued until fracture. The smallest notches of 0.1 mm in radius and depth approximately represent defects of a critical size under present loading conditions. Crack propagation rates have been measured and plotted vs ΔJ. Both present part through‐crack data and previous long through‐crack data in the elastic and the elastic‐plastic regions are compatible. A single dependence of dl/dNvs

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00417.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe low‐cycle fatigue performance of the Ni‐Cr‐base alloys IN597 and IN738 has been examined with particular reference to the creep‐fatigue interaction. Results are reported showing a systematic effect on life of IN597 of the level of tensile stress during tests involving cycles with dwell periods. For both alloys the simple life fraction rule correlates the data in a fairly satisfactory manner but some method of stress compensation is necessary for the strain range partitioning (SRP) method. Certain limitations of the SRP method in dealing with results from highly creep resistant alloys are di

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00418.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractCrack initiation and early growth of fatigue cracks in a fully annealed 0.4% carbon steel was investigated using plastic replicas and torsion loading.In a structure consisting of a 70/30 mixture of pearlite and ferrite the cracks are seen to develop and grow initially along slip bands in the ferrite phase. Energetic considerations lead to the formulation of a model which, while characterizing short crack growth rate, also considers those microstructural variables relevant to fatigue crack initiation and early crack growth. The driving force for crack growth is provided by the energy of the slip band; correspondingly crack growth per cycle is proportional to the strength of the slip band.In the short fatigue crack region, cracks grow initially at a fast rate but deceleration occurs quickly and, depending on the stress level, they either arrest or are temporarily halted at a critical length. This critical length is shown to coincide with the value of the threshold length for crack growth under LEFM conditions.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00419.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe near threshold fatigue crack growth behavior of alloy 718 was studied in air and helium environments at room temperature and at 538°C. Tests were performed at 100 Hz and at load ratios of 0.1 and 0.5. At room temperature and at 538°C, the ΔKthvalues in helium were lower than in air. The ΔKthvalues in air decreased with increasing load ratio. These results can be explained with a model that involves the accumulation of oxide in the crack which enhances crack closure. In the air tests, the oxide build‐up on the fatigue fracture surfaces at ΔKthwas of the order of magnitude as the crack tip opening displacement. In the helium tests, no significant build‐up of oxide on the fracture surface at threshold w

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIt was found that crack opening stress intensities are not constant after holding for various times in the unloaded state for iron and a sequence of Fe‐Si binary alloys. The crack opening level decreased with time first because of asperity creep and substructure relaxation, and then increased again with time due to reverse plastic zone relaxation allowing a new set of asperities to come into contact. It is demonstrated that the crack closure phenomenon is not only a result of residual plasticity, oxidation and asperities, but also is due to asperity creep and reverse plastic zone relaxation at the crack tip for low strength material

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper studies the effect of laser beam radiation on the fatigue crack growth threshold and the crack growth rate in 25CrMnSi steel plate. A comparison of radiated and unradiated specimens permits the derivation of an equation for the fatigue crack growth rate. The results show that radiation can enhance the fatigue threshold and retard crack growth rate.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb00414.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY