This paper analyses the applicability of a modified strain approach to predict the fatigue life of HFMI-treated transverse stiffeners under variable amplitude loading (VAL) with random load sequences of a p(1/3) and linear shaped spectrum. Local stresses are determined using linear-elastic finite element analyses. The measured weld geometry and component imperfections are considered. From the hardness of the HFMI-treated zone and the base material, the elastic–plastic material behaviour and Coffin-Manson parameters to describe the damage parameter Woehler curve are estimated. Based on a hysteresis counting method (HCM), the damage for each closed hysteresis is calculated. The applied notch strain approach includes the impact of residual stresses and the influence of surface roughness. Thus far, the application of similar approaches has only been validated for welded components with comparatively low residual stresses and HFMI-treated welds subjected to constant amplitude loading. To validate the accuracy of the approach for HFMI-treated welds under variable amplitude loading, the approximated fatigue life is compared to the number of cycles derived from experimental investigations. In this study, it is shown in conjunction with experimental results that it is essential to consider the strength of the base material near the weld when assessing the service life. This area can be more critical than the HFMI-treated weld toe.

本文分析了修正应变方法的适用性，以预测经 HFMI 处理的横向加劲肋在变幅载荷 (VAL) 下的疲劳寿命，其中随机载荷序列为 ap(1/3) 和线性形状谱。使用线弹性有限元分析确定局部应力。考虑测量的焊缝几何形状和部件缺陷。根据 HFMI 处理区域和基材的硬度，估计弹塑性材料行为和描述损伤参数 Woehler 曲线的 Coffin-Manson 参数。基于磁滞计数方法 (HCM)，计算每个闭合磁滞的损坏。所应用的缺口应变方法包括残余应力的影响和表面粗糙度的影响。迄今为止，类似方法的应用仅针对残余应力相对较低的焊接部件以及经受恒幅载荷的 HFMI 处理焊缝进行了验证。为了验证该方法在变幅载荷下经 HFMI 处理的焊缝的准确性，将近似疲劳寿命与实验研究得出的循环数进行了比较。本研究结合实验结果表明，在评估使用寿命时，必须考虑焊缝附近母材的强度。该区域比经过 HFMI 处理的焊趾更为关键。