The determination of the optimum autofrettage pressure enables a clear improvement of the fatigue life for an internally highly pressurized component. The autofrettage process induces residual compressive stress after the release of a single static overload pressure, leading to plastic deformation at the inner wall whereas the outer part is only elastically stressed. This autofrettage pressure is clearly above the subsequent pulsating operating pressure range. Due to the complex geometry of the aluminium valve body, a detailed elastic–plastic finite element analysis is used to determine the critical area and the optimum autofrettage pressure. Based on an experimental stress–strain curve, three important load steps are simulated in a non‐linear way. The FKM guideline is used to assess fatigue life and crack initiation with detailed subsequent experimental verification. Even if small cracks occur, residual compressive stresses prohibit crack growth (nonpropagating crack), which can be analytically verified by fracture mechanical considerations (crack closure effect).

中文翻译：

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复杂铝高压阀门促进裂纹闭合的最佳自动强化压力的数值确定和实验验证

最佳自动玻璃钢压力的确定可以明显提高内部高压组件的疲劳寿命。自增强过程在释放单个静态过载压力后会引起残余压应力，从而导致内壁发生塑性变形，而外部仅受到弹性应力。该自紧压力明显高于随后的脉动工作压力范围。由于铝制阀体的几何形状复杂，因此使用了详细的弹塑性有限元分析来确定临界面积和最佳的自紧压力。根据实验应力-应变曲线，以非线性方式模拟了三个重要的载荷阶跃。FKM指南用于评估疲劳寿命和裂纹萌生，并进行详细的后续实验验证。即使出现小裂纹，残余压缩应力也会阻止裂纹扩展（非扩展裂纹），这可以通过断裂力学考虑因素（裂纹闭合效应）进行分析验证。