The “Guideline non-linear” of the German Research Association for Mechanical Engineering provides a fatigue strength assessment for machine components based on the local strain approach. Currently, this assessment is limited to homogeneous components and without the possibility to consider residual stresses. The methods are thus inadequate for surface-hardened components, where the presence of material inhomogeneity and the introduced residual stresses significantly impacts fatigue life and the potential failure origin. In the following paper, an adaptation of the proof of structural durability of the guideline is shown, that firstly includes a two-point assessment and the estimation of load cycles to crack initiation at two failure-relevant points simultaneously. This enables the consideration of inhomogeneous material states, since the failure of surface-hardened components may initiate from the notch root as well as from the transition area between the low-strength core material and the high-strength surface layer. Secondly, the consideration of the residual stress state for both failure-relevant points is also introduced as part of the adapted fatigue strength assessment.

中文翻译：

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基于局部应变法考虑残余应力的表面硬化缺口部件的两点疲劳强度评估

德国机械工程研究协会的“非线性指南”提供了基于局部应变方法的机器部件疲劳强度评估。目前，这种评估仅限于均质部件，无法考虑残余应力。因此，这些方法不适用于表面硬化部件，因为材料不均匀性的存在和引入的残余应力会显着影响疲劳寿命和潜在的失效根源。在下面的论文中，展示了该指南的结构耐久性证明的改编，首先包括两点评估和同时估计两个失效相关点处裂纹萌生的载荷循环。这使得能够考虑不均匀的材料状态，因为表面硬化部件的失效可能从凹口根部以及低强度芯材和高强度表面层之间的过渡区域开始。其次，还引入了对两个失效相关点的残余应力状态的考虑，作为适应性疲劳强度评估的一部分。