基于循环阻力曲线的7075铝合金缺口件疲劳强度评估  

Fatigue Strength Assessment of 7075 Aluminum Alloy Notched Plate Specimens Using Cyclic Resistance Curve

作　　者：齐嘉诚 邓彩艳[1] 龚宝明[1] 何银铜 张涛 牛得田 Qi Jiacheng;Deng Caiyan;Gong Baoming;He Yintong;Zhang Tao;Niu Detian(School of Materials Science and Engineering,Tianjin University,Tianjin 300354,China;Innovation&Research Institute of Hiwing Technology,Beijing 100074,China;National Innovation Center of High Speed Train,Qingdao 266111,China)

机构地区：[1]天津大学材料科学与工程学院,天津300354 [2]中国航天科工飞航技术研究院,北京100074 [3]国家高速列车青岛技术创新中心,山东青岛266111

出　　处：《稀有金属》2025年第1期1-9,共9页Chinese Journal of Rare Metals

基　　金：国家自然科学基金项目(51875402);国家高速列车技术创新中心研发计划项目(CXKY-02-06(2020))资助。

摘　　要：7075铝合金由于优秀的力学性能被广泛用于工程结构件,但是在服役环境中结构易出现疲劳问题而失去承载能力。本文以7075铝合金为研究对象,提出了不同应力比下预测带缺口7075平板试样疲劳强度的方法。首先基于Chapetti模型通过光滑试样高周疲劳试验、疲劳裂纹扩展速率试验获得了0.1应力比下的7075铝合金循环阻力曲线,考虑平均应力效应预测了不同应力比的7075铝合金循环阻力曲线。在此基础之上,结合修正的缺口处疲劳裂纹尖端应力强度因子预测了不同应力比下缺口平板试样的疲劳强度。结果表明,提出的方法能够较准确地预测缺口平板试样的疲劳强度,在4个应力比下,该方法预测的结果和缺口平板试样高周疲劳试验结果都保持在20%之内,同时给出了疲劳强度由裂纹萌生确定时的评估公式。Aluminum alloys were widely used in aerospace,transportation and other engineering fields due to their advantages of high specific strength,low density,and good corrosion resistance.Among them,7075 aluminum alloy of Al-Zn-Mg-Cu series had high strength and good fatigue resistance,and was often used as various structural components.In practical engineering applications,due to the complexity of the service environment,structural parts were prone to fatigue problems and lost their load capacity.In view of the fact that fatigue damage tended to take place at stress raisers,for example,shoulder fillets,cavities,grooves,welded joints,etc.,the investigation on notch fatigue problem for 7075 aluminum alloy had become more and more important in engineering.In fatigue design,common design philosophies were conventional fatigue limit and S-N curves.The fatigue limit deduced from S-N curve was considered to be the stress threshold below which no fatigue cracks would initiate for a long period.With the development of fracture mechanics,it was well known that fatigue limit was the stress threshold below which fatigue cracks would not propagate rather than not form,which meant the fatigue limit was associated with a maximum non-propagating fatigue crack.For notched specimens,especially those with high stress concentration factor,fatigue cracks were easier to initiate at the notch tip.However,these fatigue cracks might arrest somewhere after propagation beyond the vicinity of the notch as the local stress decreased rapidly.It was commonly recognized that short fatigue cracks shorter than 1 mm behaved differently with long fatigue cracks.In the range of short cracks,the fatigue crack propagation threshold of stress intensity factor range ΔKth increased with crack extension up to the long crack threshold ΔKth,lc,which was independent of fatigue crack length.The lower threshold ΔKth of short fatigue cracks explains their characteristics distinguished from long fatigue cracks.Based on fracture mechanics,the concept of cyclic resi

关 键 词：7075铝合金 疲劳强度 缺口 循环阻力曲线 

分 类 号：TG174.3[金属学及工艺—金属表面处理]