A new approach for the inversion of residual stress based on acoustoelasticity theory and full waveform inversion

TL;DR

This paper introduces a novel method for inverting residual stress distribution using acoustoelasticity theory combined with full waveform inversion, addressing nonuniform stress profiles in materials.

Contribution

It transforms residual stress inversion into an optimization problem and applies the adjoint method for gradient calculation, enhancing stress distribution evaluation.

Findings

Increased sources and receivers improve inversion accuracy.

The method effectively evaluates nonuniform residual stress distributions.

Simulation results validate the approach's potential for practical applications.

Abstract

Acoustoelasticity theory has been widely used to evaluate the residual stress (or prestress), almost all the available ultrasonic stress detection methods are based on the relationship between the magnitude of stress and wave speed, but these measurement methods make the assumption that the stress is uniform, only one point or average stress in the direction of ultrasound propagation can be obtained. However, the real stress distribution is usually nonuniform. In order to obtain the stress distribution in the direction of ultrasound propagation, in this paper, we propose a new approach: the inversion of residual stress. In the theory part, the inversion of residual stress is transformed into an optimization problem. The objective function is established, and the gradient of the objective function to the stress is derived using the adjoint method, which has been maturely applied in full waveform inversion. In the numerical simulation part, the welding process is simulated using the finite element method to obtain a database of the residual stress field. Then the residual stress is evaluated by inversion approach and the influence of the number of sources and receivers and the frequency of the excitation wave on the inversion effect is discussed. The results show that the inversion of residual stress is still challenging with a small amount of data, but a more accurate inversion can be obtained by appropriately increasing the number of sources and receivers. This study provides an appropriate method for the evaluation of residual stress distribution and lays the theoretical and simulation foundation for the application of ultrasonic stress testing in it.