Hydraulic components in mobile machines are subjected to varying conditions and loads, which limit their lifetime. In particular, high pressure drop rates are suspected to increase fatigue crack growth rates. Existing studies on the fluid-structure interaction inside fatigue cracks during fast pressure drops do not explain increased crack growth in hydraulic systems. A laminar flow model was developed to simulate the fluid flow inside a crack under periodic pressure loads. The viscosity restrained the oil inside the crack, and the mechanical resistance of the closing crack led to a high pressure increase. Knowledge of the pressure profiles inside fatigue cracks helps to estimate the effective fatigue damage during transient loads.

中文翻译：

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高压降率对疲劳裂纹扩展的影响

移动机械中的液压元件会受到各种条件和负载的影响，从而限制了它们的使用寿命。特别是，高压降率被怀疑会增加疲劳裂纹的增长速度。现有的关于快速压力下降过程中疲劳裂纹内部流固耦合的研究并不能解释液压系统中裂纹增长的增加。开发了层流模型来模拟周期性压力载荷下裂缝内的流体流动。粘度限制了裂缝内的油，闭合裂缝的机械阻力导致高压增加。了解疲劳裂纹内的压力分布有助于估算瞬态载荷期间的有效疲劳损伤。