Development of three-dimensional welding deformation measurement based on stereo imaging technique

Abstract

Due to the rapid improvement of digital cameras, especially the pixel resolution, digital image correlation (DIC) has been introduced to measure the deformation and strain of structures. Using digital cameras for the DIC technique is an easy and fast method for obtaining structural information, represented as all the pixel points in a photo. Because a wide range of structural deformation can be obtained with high accuracy, this method has the potential to be very useful. Currently, DIC can execute a measurement with high accuracy only when the out-of-plane displacement is small. When the out-of-plane displacement is large, the deformation causes the measurement error. Therefore, a stereo imaging method using two digital cameras is proposed in this study. The proposed method can measure not only in-plane deformation but also out-of-plane deformation with high accuracy without calibration of the errors caused by the out-of-plane displacement. In this paper, the measurement accuracy of the proposed method for in-plane deformation and out-of-plane deformation is discussed through the application of a bead-on-plate welding test. The proposed method can measure transverse shrinkage and angular distortion with high accuracy. In contrast to the vernier caliper and laser distance metre measurement methods, which can measure only a few points at a time, the proposed method using two digital cameras can measure the full field in a short time. These results confirm that the proposed method is more advantageous than other methods.

Keywords:

• 3D measurement
• digital image processing
• digital image correlation
• stereo imaging technique
• welding deformation
• angular distortion
• transverse shrinkage

Acknowledgements

This study was partially supported by a scientific research grant from the Japan Society for the Promotion of Science (Youth Research (B); Topic Number 19760579) and we should like to express our gratitude for this. We are also very grateful to Professor Shibuya Yoshiaki of the Centre of Product Technology, Osaka Prefectural University for his invaluable advice and help during this study.