The influence of a proof load, or an initial overload, on the fatigue resistance of welded structures is investigated in this study. Arc welded stiffeners made of S355 steel are considered and fatigue-tested in as-welded and proof-loaded conditions. X-ray diffraction analyses are carried out to evaluate the influence of a proof load on the residual stress field. To better understand the role of a proof load on the mechanical fields in the stress concentration zones, a numerical approach based on elasto-plastic finite element analyses is proposed. The methodology includes a non-local multiaxial fatigue criterion, which integrates a strain hardening contribution, that makes it possible to estimate the number of cycles to failure. The comparison between experimental and numerical results indicates that the beneficial effect of a proof load on the fatigue resistance can be mainly attributed to residual stress and strain hardening effects. The final result is a master SN curve adapted to the fatigue design of stiffener structures, tested under different loading conditions.

本研究调查了保证载荷或初始过载对焊接结构的抗疲劳性的影响。考虑采用 S355 钢制成的电弧焊加强筋，并在焊接和验证加载条件下进行疲劳测试。进行 X 射线衍射分析以评估验证载荷对残余应力场的影响。为了更好地理解验证载荷对应力集中区机械场的作用，提出了一种基于弹塑性有限元分析的数值方法。该方法包括一个非局部多轴疲劳准则，它集成了应变硬化贡献，这使得估计失效循环次数成为可能。实验结果与数值结果的比较表明，验证载荷对疲劳强度的有益影响主要归因于残余应力和应变硬化效应。最终结果是一条主 SN 曲线，适用于加强筋结构的疲劳设计，并在不同的加载条件下进行了测试。