Concentrated stresses and residual ones are critical for the metal structures’ health, because they can cause microcracks that require emergency maintenance or can result in potential accidents. Therefore, an accurate approach to the measurement of stresses is key for ensuring the health of metal structures. The eddy current technique is an effective approach to detect the stress according to the piezoresistive effect. However, it is limited to detect the surface stress due to the skin effect. In engineering, the stress distribution is inhomogeneous; therefore, to predict the inhomogeneous stress distribution, this paper proposes a nondestructive approach which combines the eddy current technique and finite element (FE) method. The experimental data achieved through the eddy current technique determines the relationship between the applied force and the magnetic flux density, while numerical simulations through the FE method bridge the relationship between the magnetic flux density and the stress distribution in different directions. Therefore, we can predict the inhomogeneous stress nondestructively. As a case study, the applied stress in a three-point-bending simply supported beam was evaluated, and the relative error is less than 8% in the whole beam. This approach can be expected to predict the residual stress in metal structures, such as rail and vehicle structures, if the stress distribution pattern is known.

中文翻译：

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预测金属结构中的非均匀应力：一种结合涡流技术和有限元方法的混合方法

集中应力和残余应力对金属结构的健康至关重要，因为它们会导致需要紧急维护的微裂纹或可能导致潜在事故。因此，准确测量应力的方法是确保金属结构健康的关键。涡流技术是一种根据压阻效应检测应力的有效方法。然而，由于趋肤效应，它仅限于检测表面应力。在工程中，应力分布不均匀；因此，为了预测不均匀的应力分布，本文提出了一种结合涡流技术和有限元 (FE) 方法的无损方法。通过涡流技术获得的实验数据确定了外加力与磁通密度之间的关系，而通过有限元方法的数值模拟则桥接了磁通密度与不同方向应力分布之间的关系。因此，我们可以无损地预测非均匀应力。作为案例研究，对三点弯曲简支梁施加的应力进行了评估，整个梁的相对误差小于8%。如果应力分布模式已知，则该方法有望预测金属结构（例如轨道和车辆结构）中的残余应力。而通过有限元方法的数值模拟弥合了磁通密度与不同方向应力分布之间的关系。因此，我们可以无损地预测非均匀应力。作为案例研究，对三点弯曲简支梁施加的应力进行了评估，整个梁的相对误差小于8%。如果应力分布模式已知，则该方法有望预测金属结构（例如轨道和车辆结构）中的残余应力。而通过有限元方法的数值模拟弥合了磁通密度与不同方向应力分布之间的关系。因此，我们可以无损地预测非均匀应力。作为案例研究，对三点弯曲简支梁施加的应力进行了评估，整个梁的相对误差小于8%。如果应力分布模式已知，则该方法有望预测金属结构（例如轨道和车辆结构）中的残余应力。