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C250钢的扭转疲劳破坏是其主要失效形式之一。为了获得航空材料C250钢的扭转疲劳特性,并消除等直圆棒试样在扭转试验中产生的弊端,依据漏斗试样完成了C250钢在3种高温(150、200、350℃)环境下的扭转低周疲劳试验,获得了在扭转低周疲劳下的扭矩-名义扭转角曲线。基于试验结果,利用FAT方法分析得到了C250钢在3种高温环境下的材料循环本构关系,利用该循环本构关系对漏斗试样进行三维扭转有限元分析,获得漏斗根部剪切应力与扭矩之间的转换公式及漏斗根部剪切应变与名义扭转角之间的转换公式。基于以上试验与分析方法,得到了材料的剪切应变幅-倍循环次数曲线、剪切应力幅-循环分数曲线以及剪切应力-剪切应变的稳定滞回线,发现材料呈现出循环软化特性,并基于Manson-Coffin模型对材料寿命进行了分析。
Torsion fatigue failure of C250 steel is one of its main failure modes. In order to obtain the torsional fatigue characteristics of aviation material C250 steel and eliminate the shortcomings of the straight round bar specimen in torsion test, C250 steel was finished in three kinds of high temperature (150,200,350 ℃) The low-cycle fatigue test was reversed to obtain the torque-nominal torsion curve under low-cycle fatigue torsional strain. Based on the test results, the constitutive relationship of C250 steel in three kinds of high temperature environments was analyzed by using the FAT method. The three-dimensional torsional finite element analysis of the funnel was carried out by using the cyclic constitutive relationship. The shear stress and torque of the funnel root The conversion formula between funnel root shear strain and nominal torsion angle is derived. Based on the above experimental and analytical methods, the shear strain-times cycle curve, the shear stress-cycle fraction curve and the steady-state hysteresis loop of the shear stress-shear strain were obtained. The results show that the material exhibits cyclic softening properties The material life was analyzed based on the Manson-Coffin model.