摘要:

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 analy

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01135.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

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

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01136.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

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 theJ–Rcurve. 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 discus

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01137.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Fatigue thresholds and crack growth rates up to 10−4mm cycle−1have 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 ± 10−6torr.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 intensi

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01138.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

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 cy

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01139.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

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

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01140.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

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 s

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01141.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1983.tb01142.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY