Prediction of Inhomogeneous Stress in Metal Structures: A Hybrid Approach Combining Eddy Current Technique and Finite Element Method

Yating Yu,Fei Yuan,Guiyun Tian,Hanchao Li,Cristian Ulianov

doi:10.1155/2021/6647093

Yating Yu, Fei Yuan + Show 3 more

Open Access

https://doi.org/10.1155/2021/6647093

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Abstract

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.

Highlights

Stress concentration, or residual stress, is the main cause of the micro cracks in metal components and structures
This paper presented a hybrid approach combining the eddy current technique and finite element (FE) method, which uses the piezoresistive effect, to predict the stress distribution in early stage damages in metal structures
The surface stress can be obtained through the eddy current technique, while the finite element method (FEM) method can describe the relationship between surface stress and in-depth stress, so that the inhomogeneous stress can be predicted

Summary

Introduction

Residual stress, is the main cause of the micro cracks in metal components and structures (such as oil/gas pipeline [1, 2], airfoil [3], steel bridge [4], hoisting equipment [5], and polycrystalline solids [6]). The experimental results indicated that the stress coefficients are generally positive and depend on the annealing (heat treatment) condition as well as the level of prior plastic work; the rectangular probe is much more sensitive when oriented normally to the tensile stress After that, they continued to study the response of the eddy current on the change of electrical conductivity due to the elastic and plastic stress. Nagy et al [30,31,32] proposed the residual stress assessment for nickel-based superalloys after the shot-peened processing by the eddy current technique While their investigation discovered that the relationship between the electrical conductivity profile and the sought residual stress profile is very sensitive to the sample’s state of precipitation hardening [33] and thermoplastic effect [34]. A prediction approach is proposed by combination the eddy current technique and finite element method (FEM) to evaluate the inhomogeneous distribution stress in metals accurately and nondestructively.

Fundamental Theory

Hybrid Approach for Inhomogeneous Distribution Stress

Case Study

Determination of Coefficient h by Finite Element Method

Findings

Conclusions