共查询到20条相似文献,搜索用时 15 毫秒
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ZHENG Yesha WANG Zhongguang AI Suhua State Key Laboratory of Fatigue Fracture for Materials Institute of Metal Research Academia Sinica Shenyang China 《金属学报(英文版)》1992,5(5):385-389
SEM microfractography of near-threshold fatigue crack propagation were carried out in thedual-phase steels of 3 martensite morphologies and 6 volume fractions of martensite (V_m).All of them are featured by cyclic cleavage characteristics in near-threshold region,i.e.,main-ly controlled by mode Ⅱ stress.In the higher ΔK regions,the fracture surfaces are character-ized by mixed modes including cyclic cleavage facets,two types of secondary cracks andstriations,etc..The roughness-induced crack closure of fracture surface is attributedprimarily to extreme high fatigue crack growth threshold values. 相似文献
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本文研究了LD10铝合金和Ti-6Al-4V合金近门槛值疲劳裂纹扩展的断口形貌。SEM观察表明:两种合金的近门槛值区域(1×10~(-7)-1×10~(-5)mm/cycle)的微观断口形貌均为循环解理刻面;在LD10铝合金中循环解理刻面多数呈锯齿型或梯田状,而在Ti-6Al-4V合金中主要为孤岛状循环解理刻面。 本文在实验观察的基础上,进一步阐明了近门槛值疲劳裂纹扩展机理。 相似文献
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GAO Hua CHEN Youxuan LI Ming Shanghai University of Engineering Science Shanghai ChinaCHEN Dehai Shanghai Dalong Machinery Shanghai China Associate Professor Dept.of Materials Shanghai University of Engineering Science Shanghai China 《金属学报(英文版)》1991,4(1):59-64
The effect of proportional and non-proportional overloading on mode l fatigue crack growthhave been studied,and the influences of crack tip plastic zone,crack tip blunting as well ascrack closure were discussed.Proportional(model I)overloading may cause more seriouscrack growth retardation than non-proportional(mixed mode)overloading.Therefore,forestimating the fatigue life of engineering structures to simplify a real overload which may of-ten be non-proportional as a proportional one is not always safe. 相似文献
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R.O.Ritchie Department of Materials Science Mineral Engineering University of California Berkeley CA U.S.A. 《中国有色金属学会会刊》1999,(Z1)
1 INTRODUCTIONFatigueinvolvesthemicrostructuraldamageandfailureofmaterialsunderalternatingloads.Structuralmaterials,however,arerarelydesignedforfatigueresistance.Metallicalloysaregenerallydesignedforstrength,intermetallicsforductility,andceramicsfor… 相似文献
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H.C.Yang Y.Tu M.M.Yu J.Zhao 《金属学报(英文版)》2004,17(4):597-600
Low cycle fatigue tests and crack growth propagations tests on P91 pipe base metal and its weld joints were conducted at three different temperatures: room temperature, 550℃ and 575℃. The strain-life was analyzed, and the changes in fatigue life behavior and fatigue growth rates with increasing temperature were discussed. The different properties of the base metal and its weld joint have been analyzed. 相似文献
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JING Xiaotian LOU Bingzhe GU Chenqing SHEN Fusan Shanxi Institute of Mechanical Engineering Xi''''an China Dept.of Materials Shanxi Institute of Mechanical Engineering Xi''''an China 《金属学报(英文版)》1990,3(4):268-275
The morphology of the retained austenite in the carburized case of 20CrNiMo steel and itstransformation during fatigue crack propagation through the case were investigated by usingX-ray and TEM analysis.In the carburized case both film and block shaped retainedaustenite were found.Due to the crystallographic orientation relationship at the interface,thefatigue crack is inclined to pass through the block shaped retained austenite and thereby stim-ulates its strain-induced martensitie transformation.During the process of the fatigue frac-ture,most of the retained austenite structures on the crack path are transformed into themartensite,and the untranaformed parts on the fracture surface remain less than 6%.Thetransformation of the retained austenite,which is restrieted mainly within the plastic zone,oc-curs only during the proeess of fracture,and is independent of the magnitudes of the externalstress,stress ratio and cyclic number.The volume expansion accompanying the transforma-tion creates an additional residual displacement of about 0.44μm on fracture surfaces,whichis equivalent to the magnitude of the plasticity-induced residual displacement.The phasetransformation induced fatigue crack closure is believed to be an important factor affectingthe fatigue crack behaviors in the high carbon laver of the carburized case. 相似文献
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EFFECTSOFTRACEZrONFATIGUECRACKGROWTHRATEOFHIGHDAMPINGZn-AlALLOY¥ZhouShanchu;LuoBinghui(DepartmentofMaterialsScienceandEnginee... 相似文献
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1.IntroductionInmetalsandalloys,thenearthresholdfatiguecrackgrowthisfrequentlytermed'microstructurallysensitive'.Thisisduebothtotheappearanceofthefracturesllrface,whichisoftenfaceted,andtotilelargevariationsincrackgrowthratewhichcanbeobtainedbyalteringparameterssllchasgrainsize,yieldstrength,ortherelativeproportionsanddistributionsofphasesinthemicrostructure[1].Thisimpliesthatsignificantimprotremelltintotalfatiguelifecouldbeachievedbychangingthemicrostructureofalloys.Therefore,itwouldbeveryadv… 相似文献
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QIAN Yourong HE Xiangdong Beijing University of Aeronautics Astronautics Beijing China QIAN Yourong Dept.of Materials Science Engineering Beijing University of Aeronautics Astronautics Beijing China 《金属学报(英文版)》1990,3(3):204-207
The fatigue crack growth rate (CGR) of ultra high strength steel 30CrMnSiNi2A in distilledwater at 18,35 and 55℃ were measured.It was confirmed that the temperature is strongly af-fected on the corrosion fatigue CGR of ultra high strength steel.An expression concerning theeffects of Δ K and temperature on the CGR was proposed.The fact that the apparentactivation energy (36.6 kJ/mol) resulted from regressive analysis of CGR data was similarto the activation energy of hydrogen diffusion in γ-Fe,strongly supporting the theory ofhydrogen-assisted crack growth.The overload retardation effect was greatly reduced in cor-rosion fatigue crack growth,especially at lower frequency,e.g.,0.1 Hz.This phenomenonmight be due to the increase of the SCC component of CGR after an overload. 相似文献