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工程机械的疲劳强度往往较疲劳试验所得的疲劳强度低得多,如安全系数不足,会引起事故。产生上述问题的一个主要原因是,在多数情况下,工程机械的另部件虽受疲劳极限以下的交变载荷作用,但当其间作用循环次数极少、疲劳极限以上的过大应力时,疲劳极限以下的应力(称为过小应力)将对疲劳断裂破坏产生显著的影响,其结果实际使用寿命较线性累积损伤理论所估算的寿命明显地缩短。 为了探讨裂纹扩展过程中的这种影响效果,在接近实际使用的变动载荷条件下进行了疲劳裂纹扩展试验,并应用电子显微断口分析法对裂纹扩展速度加以定量的估算。本文主要论述上述研究结果及估算疲劳裂纹扩展速度的经验公式,为机械工程设计和使用提供依据。
The fatigue strength of construction machinery is often much lower than the fatigue strength of fatigue test, such as lack of safety factor can cause accidents. One of the main causes of the above problems is that in most cases, the other components of the construction machinery are subject to alternating loads below the fatigue limit, but when there are few cycles of action and excessive stress above the fatigue limit, the fatigue limit The following stresses, called under-stress, will have a significant effect on fatigue fracture failure, resulting in a significantly shorter life expectancy than the linear cumulative damage theory. In order to investigate the effect of crack propagation, the fatigue crack growth test was carried out at nearly the same dynamic load, and the crack growth rate was quantitatively estimated by electron microscopic fracture analysis. This paper mainly discusses the above research results and the empirical formula to estimate the fatigue crack growth rate, which provides the basis for the mechanical engineering design and application.