Noise-insensitive contour method for residual stress measurement in laser butt welding: Fid-Bau Portal

Noise-insensitive contour method for residual stress measurement in laser butt welding

Jiang, Hao / Liu, Junjun / Lei, Zhenkun / Bai, Ruixiang / Guo, Zhenfei / Zou, Jianchao / Dong, Honggang / Feng, Wenwen

Abstract The residual stress distribution of laser welding greatly affects the overall mechanical response of the welded structure. In this study, a new residual stress measurement method is proposed, using the finite element method (FEM) to optimize and modify the contour method. The distribution of the welding residual stress is simulated via B-spline interpolation and by solving an unconstrained weighted least-square problem in parallel, using the Levenberg–Marquardt algorithm. The control points of the B-spline are obtained to determine the residual stress distribution. For numerical verification, the residual stress dataset is generated by simulating the laser welding process, and the calculation efficiency of the FE-modified contour method is tested on this prior dataset. It is verified that the proposed method does not depend on the initial value of the residual stress distribution. This residual stress measurement method is an improvement over the traditional contour method and can achieve satisfactory accuracy, even under the influence of Gaussian noise and signal-to-noise ratio noise. In the experiments, the contour data of the laser welding seam cutting surface are obtained by employing electrical discharge cutting and three-dimensional displacement scanning technology. The traditional and FE-modified contour methods are used to identify the residual stress in the welding direction. The results show that the proposed method can adapt to contour measurement data under actual complex working conditions.

Highlights • A novel contour method obtains residual stress by iteratively solving B-spline control points. • Least-square solution obtains noise resistance of the contour method. • Thermal–structural analysis solves the evolution of residual stress in laser welding process.