Studies on in-situ full-field measurement for in-plane welding deformation using digital camera

Abstract

The technique that can measure the transient welding deformation directly is very important for investigating the mechanism of welding deformation. In this study, an in-situ displacement measurement method using digital camera is self developed. This system is non-contact type and it does not need any complicated optical systems but it can measure the in situ displacement over the full field high accuracy using digital image correlation technique. Therefore, it is considered to be useful and easy to apply to practical problems. The number of measuring points that can be obtained at a time is more than 10 million. It is the same as the available pixels of the digital camera. Furthermore, since the active light source is not necessary in this system, the influence of the fluctuation of the atmosphere caused by the high temperature area is small. In this study, the detail of the proposed system is given and it is applied to the transient in-plane deformation problem under very high brightness lightened by welding arc. Through the comparison between the experiment and thermal elastic–plastic finite element analysis, the validity of the transient transverse shrinkage distribution which is measured by the proposed system is verified. The residual deformation is also investigated to check the accuracy and usefulness of the proposed system.

Keywords:

• in-situ measurement
• digital image processing
• digital image correlation
• full-field measurement
• normalized correlation
• sub-pixel matching
• welding deformation
• transient deformation

Acknowledgements

We would like to express our appreciation of the support given to part of this research through a Science Research Grant-in-Aid by the Japan Society for the Promotion of Science (Young Researcher (B); Topic 16760655).