摘要:

AbstractThe cylindrical specimen is a common configuration adopted for biaxial fatigue testing. A rigorous yet practical analysis is presented here under the framework of incremental plasticity. The cyclic stress‐strain curve is obtained from four different plasticity models, and correlated with twenty‐six in‐phase biaxial tests on En15R steel. Stabilized hysteresis loops can also be derived based on the cyclic stress‐strain curve under aJ2‐kinematic hardening formulation with special consideration of the rounding transition at the instant of yielding. A correlation for the hysteretic strain hardening exponentNis required for materials that exhibit non‐Masing behaviour; i.e. do not allow a full description of hysteresis loops from knowledge of the cyclic stress‐strain curve. The solution is further generalized to out‐of‐phase loading, where the rotation of the active stress state around the yield surface is illustrated. This compares favourably with ten out‐of‐phase

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper presents the results of fatigue crack growth and fatigue fracture toughness studies of a high‐pressure vessel steel with particular emphasis on the influence of heat treatment, low temperatures, plastic prestraining, the stress ratio and specimen dimensions.It has been shown that steels in an embrittled state, caused primarily by thermal treatment and low‐temperatures, exhibit unstable fatigue crack growth which is characterized by alternate crack jumps (cleavage zones) and zones of fatigue crack growth. The fatigue fracture toughness, which corresponds to the first crack jump, and final fracture can be appreciably lower (i.e. up to 50%) than the static fracture toughness under plane strain conditions at the corresponding temperature.An analysis has been performed of unstable and stable fatigue crack growth and a model of unstable crack propagation is proposed which accounts for the observed experimental behavi

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAn analysis is made of shear lip measurements as observed on fatigue crack surfaces of an aluminium alloy sheet material. It is shown that, for biaxial cyclic loads at stress ratios 1 and various R‐ratios, shear lips were controlled by an equivalent intensity factorKe=K1F(λ,R).For crack growth in air the shear lip widthtswas approximately proportional toK2eattst*swheret*sis the critical value of the shear lip dimension. The initiation of shear lips and the orientation of crack growth for different parameters of the loading cycle are briefly considered in the discu

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAs is well known, the fatigue strength reduction factor due to a notch (Kf) in the modified Neuber's rule should not be considered a constant since it varies with different stress levels. In this paper, the definition and the variation of Kfare discussed on the basis of theoretical and experimental analyses, leading to the presentation of a variable Kf‐Neuber's rule. Comparing the results of experimental stress analyses and the fatigue life tests of specimens, the variable Kf‐Neuber's rule gives good predictions and is applied to the life prediction of an aircraft compon

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Both high‐cycle and low‐cycle fatigue properties of hot‐extruded powders of a Ni3Al‐based alloy, IC218, have been evaluated. High cycle fatigue measurements were performed under stress controlled conditions at temperatures ranging from 25°C to 850°C. Tests were made in both laboratory air and vacuum environments. Low cycle fatigue tests were conducted under total strain control in a laboratory air environment at 650°C. In high cycle fatigue, high ratios of the fatigue limit (Δσ at 106cycles) to monotonic yield strength (σys), of approximately Δσ/σys∼1, were obtained in the powder extruded IC218 alloy for temperatures ranging from 25°C to 650°C. In low cycle fatigue, a substantial decrease in fatigue life occurred at 650°C, compared to results obtained previously at 25°C. High cycle fatigue performance at low stress/strain amplitudes is better than expected when compared to precipitation strengthened superalloys. The improved performance is explained in terms of the cyclic hardeni

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Fatigue crack growth behaviour under intermittent overstressing was investigated in dry air with a low carbon steel under tension‐compression and tension‐tension loading with different mean stress levels. A very small number of cycles of overstress applied intermittently during a very large number of cycles of understress below threshold caused, in all cases, a significant acceleration in crack growth rate as compared to the case of steady cyclic stress. The acceleration for the case with tensile mean stresses was a little smaller than in the case without mean stress and it was related to a little higher crack closure level in the former case. Stress history in the precracking process had some effect on crack closure and, consequently, on the acceleration. A fairly good correlation was obtained between the acceleration and the effective stress intensity range. The acceleration under multi‐level intermittent overstresses with different mean stresses could be predicted by linear summation from two‐level intermittent overstress test data. No difference was recognized in the fracture surface morphology between the cases with different mean stress level including the cases of multi‐level stresses, indicating that the micromechanism of crack growth acceleration would be the same i

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—A theoretical study of the conditions for coalescence of two fatigue cracks in a multi‐crack system is presented. As both cracks grow, the near‐side plastic zone sizes of the interacting cracks increase more rapidly than the off‐side zone sizes which results in higher overall crack propagation rates for an interacting crack growth system than the simple addition of individual crack growth rates. The use of a single crack growth model to predict failure in the presence of two or more cracks may therefore underestimate the interaction between cracks and lead to un‐conservative predictions. Some of the theoretical predictions were confirmed by published results of experimental measurements of crack interaction distances in multi‐cr

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Improvements in acoustic emission (AE) test techniques have lead to developments whereby reliable acoustic emission measurements as a fatigue damage indicator were made at room temperature on Incoloy 901 smooth specimens, over a stress‐ratio range of −1.0≤R≤0.2. Fatigue damage accumulation was evaluated in terms of an AE damage definition and a damage function was developed. Thus, various damage phases in the cumulative damage process were identified by their AE signature, and then formulated and analyzed in terms of cumulative AE ringdo

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—Hydrogen induced cracking (HIC) initiation sites and their correlation with the critical stress intensity factors of hydrogen charged specimens were studied under combined I/II mode loading. Two series of tests, is. constant load (CL) tests and slow strain rate (SSR) tests, were carried out. Experimental results showed that in CL tests, irrespective of the ratio KIJKl, the HIC initiation sites always correspond to the point of maximum hydrostatic stress; which is located some distance ahead of the notch tip. However, for SSRT tests, when K11/K1>1, HIC started at the notch tip which corresponds to the point of maximum equivalent plastic strain. When K11/K1<1 in SSR tests, HIC occurred initially some distance ahead of the notch tip.The relationship between the critical stress intensity factor for HIC and K11/K1was shown to be different for the two types of test. Multiple effects of stress and strain on hydrogen redistribution and hence on HIC initiation sites, as well as critical stress intensity factors, are discusse

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract—In this paper the Rousselier ductile damage model is used to simulate the softening behaviour of notched bars and crack growth in a pre‐cracked specimen of an A508 pressure vessel steel. The effect of the internal parameters needed to represent the damage on the calculated results is studied. The interactions between these parameters and their effects on the calibration process are discussed. The effect of the cell size on the values of the damage parameters obtained during calibration and on the response of the specimens is briefly revie

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1994.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY