This paper performed experimental and analytical investigations on the synthetical effect of material inhomogeneity and welding defects on the fatigue behavior of 2205 duplex stainless steel cruciform welded joints. A series of experiments were performed, including microstructure characterization by the electron back-scattered diffraction, fatigue mechanical tests assisted by digital image correlation technique and fracture morphology observations by scanning electron microscope. Results show that fatigue life and failure location of cruciform welded joints depended heavily on their geometric configurations for lower cyclic amplitudes. However, with the elevation of loading, material inhomogeneity played a greater roles, leading to the change of fatigue failure mode with both geometric configuration and cyclic stress amplitude. To quantize the effects of welding defects and material inhomogeneity, a modified structure strain method was proposed by considering the heterogeneous plastic properties, to accurately predict both fatigue lifetime and failure location of cruciform welded joints at both low and high cycles fatigue. Lastly, a damage tolerance-based fatigue design method was discussed to guide the highly-reliable manufacture and damage detection of duplex stainless steel cruciform welded joints in the engineering.

本文对材料不均匀性和焊接缺陷对 2205 双相不锈钢十字形焊接接头疲劳行为的综合影响进行了实验和分析研究。进行了一系列实验，包括电子背散射衍射的微观结构表征、数字图像相关技术辅助的疲劳力学测试和扫描电子显微镜的断口形貌观察。结果表明，十字形焊接接头的疲劳寿命和失效位置在很大程度上取决于其较低循环振幅的几何配置。然而，随着载荷的升高，材料的不均匀性发挥了更大的作用，导致疲劳失效模式随几何构型和循环应力幅的变化而变化。为了量化焊接缺陷​​和材料不均匀性的影响，提出了一种考虑异质塑性特性的改进结构应变方法，以准确预测十字形焊接接头在低周疲劳和高周疲劳下的疲劳寿命和失效位置。最后，探讨了一种基于损伤容限的疲劳设计方法，以指导工程中双相不锈钢十字形焊接接头的高可靠制造和损伤检测。