谐振式曲轴弯曲疲劳试验系统的瞬态动力学分析

摘要

尽管谐振式曲轴弯曲疲劳试验获得了广泛的应用,但其动力学特性仍有待深入研究.首先对试验系统两自由度等效简化模型进行受迫振动响应的理论分析,得到了瞬态响应的形式,并讨论了系统阻尼比、频率比对瞬态响应的影响.进一步进行了试验系统的有限元模态计算,并利用模态测试对有限元计算的有效性进行了验证.然后根据模态计算的结果和模态测试得到的阻尼比,采用模态叠加法进行曲轴弯曲疲劳试验瞬态动力学计算,得到系统位移响应,并研究了瞬态响应的形式及其对疲劳试验结果的影响.最后通过模态扩展计算得到圆角危险截面圆弧上各点在疲劳试验过程中的弯曲正应力幅值.%Resonant tests are widely used in bending fatigue study of crankshafts, but vibration characteristics of the test system are not well known. In this paper, the forced vibration analysis of the simplified model of test system having two degrees of freedom was performed. Patterns of transient response were obtained and influence of damping ratio and fiequency ratio were discussed. Modal calculation of resonant bending system was made with the finite element method, and the results are validated by the modal test.Based on modal calculation and damping ratios from modal tests, modal superposition method was adopted to compute the dynamic response of resonant bending system during fatigue tests. The pattern of transient response and its effects on bending fatigue tests were studied. The bending normal stress amplitudes of the nodes in the critical section near crankshaft fillet were obtained by modal expanded computation.