Abstract Fatigue assessment of welded assemblies is a key challenge both for industrial and academic research. This paper assesses possibilities of thermoelastic coupling quantitative analysis for the comprehension of fatigue phenomena occurring with welded structures. A test protocol has been set up to measure temperature field on cruciform as-welded specimens under cyclic loading thanks to an infrared camera. Identification of temperature variations associated to thermoelastic coupling (order of magnitude of 0.1 K) allows to map temperature which are directly correlated to stress tensor first invariant. From this result, analysis of thermoelastic coupling gradient allows to determine the part of bending stress due to specimen distortion (up to 20% higher than nominal stress). Besides, thermal conduction influence when evaluating a local stress at weld toe is evaluated thanks to a numerical thermal model. In addition, infrared images post-treatment based on image segmentation is proposed for fatigue crack monitoring at weld toes (minimal crack size detection of 1 mm). Experimental validation is performed through analysis of marked fracture surface. Finally, fatigue crack growth rates are evaluated with this approach for different load amplitudes.

中文翻译：

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使用定量热弹性应力分析进行海军焊接接头局部应力评估和疲劳裂纹监测

摘要 焊接组件的疲劳评估是工业和学术研究的关键挑战。本文评估了热弹性耦合定量分析的可能性，以了解焊接结构发生的疲劳现象。由于红外摄像机，已经建立了一个测试协议来测量循环载荷下十字形焊接试样的温度场。与热弹性耦合（0.1 K 的数量级）相关的温度变化的识别允许绘制与应力张量第一不变量直接相关的温度。根据该结果，热弹性耦合梯度分析可以确定由于试样变形（比标称应力高 20%）而导致的弯曲应力部分。除了，由于数值热模型，评估焊趾局部应力时的热传导影响被评估。此外，提出了基于图像分割的红外图像后处理，用于焊趾疲劳裂纹监测（最小裂纹尺寸检测为 1 mm）。实验验证是通过分析标记的断裂面进行的。最后，使用这种方法针对不同的载荷幅度评估疲劳裂纹扩展速率。