超声疲劳试验方法及其应用

ULTRASONIC FATIGUE TESTING AND ITS APPLICATIONS

  • 摘要: 超声疲劳是一种加速的疲劳试验方法,它的测试频率(20kHz)远远超过了常规疲劳测试频率(小于200Hz). 超声疲劳试验研究表明50#车轴钢和40Cr钢直到10 10个应力循环后仍会发生疲劳断裂,并不存在常规疲劳试验曲线所示的``疲劳极限'',因此用10 7周次的疲劳试验数据进行疲劳强度设计并不安全. 50#车轴钢和40Cr钢超声疲劳性能优于常规疲劳性能. 扫描电镜分析表明,超长寿命阶段 50#车轴钢裂纹萌生于次表面夹杂. 介绍了超声疲劳试验系统、工作原理及超声疲劳试样 的设计.

     

    Abstract: Ultrasonic fatigue testing is an acceleratedtesting method with a frequency far beyond that of conventional fatigueexperiment. The experimental results show that the fatigue strength at 20\,kHz of50# axle steel and 40Cr steel will diminish continuously as faras 10 10 cycles. It is shownthat 50# axle steel and 40Cr steel have no ``fatigue limit'' as in the conventional fatigue curve. So the design of fatiguestrength based on fatigue testing at 10 7 cycles is not adequate. The SEMshows that the fatigue crack propagation initiates at the subsurfaceinclusions in the regime of N>10 7. Testing system of ultrasonicfatigue, operating principle and design of fatigue specimens aredescribed in this paper.

     

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