摘要:

AbstractFatigue crack growth tests have been carried out on pre‐cracked specimens of steel AFNOR XC 38 under rotary bending conditions. The semi‐elliptical surface crack shape evolution was determined and the results were analyzed by da/dN =f(ΔK) using a stress intensity factor solution for semi‐elliptical surface cracks in round bars subjected to a bending stress modified to take into account the rotatary bending conditions. Results show a very good correlation with fatigue crack growth data obtained in standard centre cracked tension specimens of the same steel. An application to the sensitivity of design parameters to an analysis of cracked railway axles is proposed, allowing an improvement in maintenance proc

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFatigue life and crack retardation behaviour after penetration were examined experimentally using CT specimens and surface pre‐cracked specimens of aluminium alloy 5083‐0. The fatigue crack shape before penetration is almost semicircular, and the measured aspect ratio is larger than the value obtained by calculation usingKvalues proposed by Newman‐Raju. It was found that crack growth behaviour on the back side after penetration is unique, and can be divided into three stages. The Wheeler model retardation parameter was used successfully to predict crack growth behaviour after penetration. By using a crack propagation rule, the change in crack shape after penetration can be evaluated quantitat

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe local approach method is used to calculate the fatigue crack initiation/early crack growth lives (Ni) in high strength structural steel weldments. Weld‐toe geometries, welding residual stresses and HAZ (heat affected zone) cyclic mechanical properties are taken into account in the Niestimation procedure. Fatigue crack initiation lives are calculated from either a Basquin type or a Manson‐Collin type equation. The local (HAZ) stress and strain amplitudes and the local mean stress are determined from an analysis based on the Neuber rule and the Molski‐Glinka energy approach. The accuracy of the different methods is evaluated and discussed. Finally the previous methods are used with HAZ cyclic mechanical properties estimated from hardness measure

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of prestraining by 15‐30% and ageing on the fatigue properties of a cold‐rolled high‐strength dual phase sheet steel was investigated. Prestraining was performed before machining the fatigue specimens and was carried out in uniaxial as well as biaxial tension. Fatigue testing was carried out under fully reversed strain control and both the cyclic stress‐strain behaviour and the fatigue lives were recorded.Significant fatigue strength improvements by up to 50% were noted for the prestrained material as compared to the as‐received condition. During fatigue testing in uniaxially prestrained conditions, the occurrence of mean stresses was noted. These mean stresses were persistent when testing at levels corresponding to longer fatigue lives. Taking into account an estimation of these mean stresses and the increase of monotonic strength, modelling of fatigue resistance for the prestrained materials shows fairly good correlation with experimenta

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study describes shot peening effects such as shot hardness, shot size and shot projection pressure, on the residual stress distribution and fatigue life in reversed torsion of a 60SC7 spring steel. There appears to be a correlation between the fatigue strength and the area under the residual stress distribution curve. The biggest shot shows the best fatigue lie improvement. However, for a shorter time of shot peening, small hard shot showed the best performance. Moreover, the superficial residual stresses and the amount of work hardening (characterised by the width of the X‐ray diffraction line) do not remain stable during fatigue cycling. Indeed they decrease and their reduction rate is a function of the cyclic stress level and an inverse function of the depth of the plastically deformed surface laye

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00156.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents analytical and numerical solutions to the analysis of welded specimens when loaded in three‐point bending, and compares the results with those obtained experimentally. In each case the crack is located within the weld material, and runs parallel to the weld. Two analytical models are presented for deriving limit loads using slip‐line field theory. Due to the welding process, the material behaviour in the weld‐base interface is complex, and this is described in the analytical solutions using a number of material zones. The analytical solutions also provide the η and d∞coefficients which are used to determine the J and crack tip opening displacement (CTOD) parameters. These solutions are then compared with numerical results obtained using the finite element method.Good agreement is obtained between the numerical and analytical results, and it is shown that for overmatched specimens a better analytical solution can be obtained by using a slip‐line field geometry which passes predominantly through the base material. When the analytical η solutions are applied to the experimental results it is shown that, in the case of undermatched weldments,Jcan be used as a fracture characterising parameter, but it cannot be used in the case of an overmatch

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00157.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractExperimental and numerical analyses were carried out to examine the elastic‐plastic behaviour and low cycle fatigue (LCF) life of EN15R steel notched specimens. Notch root strains were measured and compared with estimates obtained from three methods: Neuber, Glinka and hite element (FE) analyses. All methods provided fairly accurate estimates of cyclic strain up to net section yield, from which point the Neuber and Glinka predictions were greater than measured. The finite element results compared well with measured results. The estimated notch root strains were used to predict the life of the notched specimens based on LCF results from unnotched specimens. Uniaxial Coffom‐Manson and multiaxial Lohr‐Ellison approaches were used. Improved fatigue life predictions were obtained when the FE predictions of the multiaxial strains were combined with a multiaxial strain parameter. The possible influence of strain gradient is inferred by comparing LCF lives for hollow thin‐walled and solid bar sp

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00158.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFatigue crack growth is modelled by an improved step‐by‐step finite element technique for a shallow and long surface crack in a finite thickness plate under different combinations of tension and bending loads. The predicted crack shape development is presented for growth through the plate thickness and the shape compared with the widely assumed semi‐elliptical profile. The predictions of the present simulation technique for the aspect ratio and the number of crack growth cycles are compared with those obtained both by Newman and Raju's method, and experimental results for aspect ratio changes taken from the liter

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00159.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA statistical model has been developed to evaluate fatigue damage at multi‐sites in complex joints based on coupon test data and fracture mechanics methods. The model is similar to the USAF model, but modified by introducing a failure criterion and a probability of fatal crack occurrence to account for the multiple site damage phenomenon. The involvement of NDI techniques has been included in the model which can be used to evaluate the structural reliability, the detectability of fatigue damage (cracks), and the risk of failure based on NDI results taken from samples. A practical example is provided for rivet fasteners and bolted fasteners. It is shown that the model can he used even if it is based on conventionalS‐Ncoupon experiments should further fractographic inspections be made for cracks on the broken surfaces of specim

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00160.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIt is now generally agreed that the applicability of a one‐parameter J‐based ductile fracture approach is limited to so‐called high constraint crack geometries, and that the elastic‐plastic fracture toughnessJ1c, is not a material constant but strongly specimen geometry constraint‐dependent. In this paper, the constraint effect on elastic‐plastic fracture toughness is investigated by use of a continuum damage mechanics approach. Based on a new local damage theory for ductile fracture(proposed by the author) which has a clear physical meaning and can describe both deformation and constraint effects on ductile fracture, a relationship is described between the conventional elastic‐plastic fracture toughness,J1c, and crack tip constraint, characterized by crack tip stress triaxialityT. Then, a new parameterJdc(and associated criterion,Jd=Jdc) for ductile fracture is proposed. Experiments show that toughness variation with specimen geometry constraint changes can effectively be removed by use of the constraint correction procedure proposed in this paper, and that the new parameterJdcis a material constant independent of specimen geometry (constraint). This parameter can serve as a new parameter to differentiate the elastic‐plastic fracture toughness of engineering materials, which provides a new approach for fracture assessments of structures. It is not necessary to determine which laboratory specimen matches the structural constraint; rather, any specimen geometry can be tested to measure the size‐independent fracture toughnessJdc. The potential advantage is clear and the results are

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1995.tb00161.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY