摘要:

AbstractThe results of a round robin exercise in predicting ductile instability in two compact tension test specimens are presented and analysed. Many techniques were used, both to analyse the given raw data and to analyse the specimen behaviour, and large differences were obtained especially in definingJ‐resistance parameters. Despite these differences there was little scatter in the final result principally because the specimens failed at plastic collapse. It was concluded that all the techniques were broadly satisfactory provided a plastic collapse analysis is performed, either as part of the analysis or independentl

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00437.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractOrdinary short‐term creep fatigue tests were carried out on a servo‐hydraulic testing machine for various heat resistant steels. From these results a life prediction method in the long‐term creep‐fatigue regime is proposed using creep rupture ductility data up to 105h. To verify the predicted life the authors have developed a new type of testing machine driven by thermo‐actuator which can evaluate the long‐term creep‐fatigue behaviour of material

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00438.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractMeasurements of crack depths by newly developed sectioning techniques raise questions about the validity of the optical microscopy technique used by Cheng and Laird for measuring crack size distributions. Accordingly, these measurements have been repeated using an improved technique. The cracks have thus been found deeper than reported earlier. This result suggests that random‐walk mechanisms for crack nucleation apply to the earliest stages of fatigue life. Moreover, it is found that the crack size distribution matches the distribution of local strains in persistent slip bands, suggesting that Stage I crack propagation kinetics are controlled by the local plastic strai

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractIn the present study, the authors have focused attention on the internal stress in a material. A stress applied to a specimen does not fully act to deform the material. The effective stress which actually acts on dislocations depends on the internal stress in the material. The origin of the internal stress is attributed here to the dislocation structure. From this viewpoint, fatigue tests were carried out and the following results were obtained:(1) The origins of the internal stress and the effective stress were clarified by means of a dislocation model.(2) The behaviour of the internal stress during the fatigue process showed clear differences between over‐stressed and under‐stressed states.(3) The concept of internal and effective stresses assists in our understanding of the fatigue phenomenon.(4) The mechanism of fatigue failure in the under‐stressed fatigue state was also studied, and the concept of an internal stress was applied to instances of practical fatigue situa

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper describes an experimental investigation of fatigue‐crack growth in an ultra‐high strength maraging steel, with particular attention to the relationship between crack growth rate and microstructural element size. The occurrence of intergranular fracture is shown to be unrelated to any grain size‐plastic zone size equivalence, while inflections in the growth rate vs ΔKrelationship are discussed in terms of the interaction between the plastic zone and other microstructural dimensions. The incidence of intergranular fracture and crack surface oxide is shown to decrease with decreasing test fre

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFatigue crack growth rates have been measured at 22 kHz for two types of carbon steel, between 20 and 500°C under symmetrical push‐pull loading. The crack length was determined from the decrease in the resonant frequency of the specimen. For ČSN 412013 steel, an increased crack propagation resistance was observed between 250 and 300°C. The values of the constantsCandnin the Paris equation, andKa,thare dependent on temperature. The fatigue crack growth rate andCboth increase with temperature, whilenandKa,thdecrease with increasing temperature. Electron scanning and light microscopy have shown that intercrystalline fracture does not occur in ČSN 415313 steel at elevated temperature. Intercrystalline fracture was observed for specimens fatigued at 20°C and also in ČSN 412013 steel at temperatures of 200 and 500°C. The width of the plastic zone and the height of the surface relief around the fatigue crack increased with tem

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1986.tb00436.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY