摘要:

Abstract—The alloy IMI 829 is very sensitive to fretting fatigue damage at 20°C but its fretting fatigue strength increases as the temperature is raised to 600°C due to the formation of a glaze type oxide. Failure occurs by cracking of the glaze as a result of local creep. These cracks propagate into the bulk material. Local creep results from increased stresses in the fretting contact region, frictional heating, and preferential removal of alloying elements into the oxide film leading to reduced creep propert

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01235.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Low cycle fatigue tests at 650°C on 20% Cr–25% Ni–Nb stainless steel have been carried out under conditions of equal tension/compression ramp rates (10−3s−1) and slow tension–fast compression ramp rates (10−6s−1/10−3s−1). It was found that the latter cycle significantly reduced endurance. Detailed metallography revealed that life reduction is due to the accumulation of creep damage during the slow tensile ramp. It is proposed that at high strain ranges, failure is creep dominated and this changes to a creep‐fatigue interaction failure mechanism at low strain ranges.Predictive models have been developed based on cavity growth mechanisms and ductility exhaustion. Both techniques provide an accurate life prediction and only limited data ar

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01236.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The influence of steady mode III on mode I fatigue growth behavior is investigated in four materials–a plain carbon steel, a Ni–Cr–Mo–V rotor steel, and titanium alloys, TA6V and TA5E ELI. It is shown that these loading conditions give rise to two main effects: (i) a strong reduction in propagation rate and (ii) a modification in crack path, the fatigue crack adopting a characteristic “factory‐roof’ aspect. In 2024 Al alloy, it is shown that the superimposition of steady mode II to cyclic mode I leads to crack bifurcation, the angle θ being a function ofKa/Ktmax. These observations are discussed in the light of a new criterion which is introduced. This criterion is based on two main assumptions: (i) Fatigue cracking is assumed to occur only under the effect of local mode I opening. (ii) It is postulated that a fatigue crack grows in a direction where the crack propagation rate is maximum. A number of limitations of this approach, associated with crack closure phenomeno

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01237.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01238.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01239.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—This paper presents the results of an investigation of fatigue crack initiation in pure polycrystalline α‐iron as a function of testing frequency (0.01–1000 Hz). Three distinct types of fatigue crack initiation mechanisms were identified:(i) At low frequencies,<0.5 Hz, cracks were observed to nucleate at intrusions, extrusions and grain boundaries. However over the frequency range studied the cracks at the intrusions and extrusions were not associated with the final fatigue failure. The results suggest that in pure iron frequencies0.01 Hz) is initiated not at intrusions and extrusions but at grain bo

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01240.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—This work proposes a crack growth equation for short cracks, defined for cracks which have yet to cross the first grain boundary. This crack growth law is used in conjunction with a Linear Elastic Fracture Mechanics formulation to describe the complete crack growth behaviour from initiation to failur

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01241.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractTwo parameters describing the growth of fatigue cracks are compared. They are the cyclicJintegral ΔJand the strain intensity expressed as an equivalent stress intensity ΔKeq‐. By referring to cyclic stress‐strain data obtained from hysteresis loops in high strength ferritic steels at room temperature and austenitic and ferritic steels at elevated temperature it is shown that: (i) for short cracks the parameters are simply related and (ii) both parameters adequately link fatigue crack growth rates observed in the separate high strain fatigue (HSF) and linear elastic fracture mechanics (LEFM) regimes. Correction factors for thumbnail cracks and the conditions under which the relations need further modification are disc

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01242.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01243.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Crack shape evolution has been studied in high strength, rolled thread, bolts. It has been found that, using the Crack Microgauge, it is possible to detect and size fatigue cracks, located at the thread root, from depths of less than 0.1 mm up to fracture. This work required a special probe system to be developed and also a theoretical solution for the a.c. field distribution in a thread. Some of the work and results are briefly described in this technical not

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1982.tb01244.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY