Analytical study on effects of strain distribution in welding start/end on welding distortion

Abstract

A welding distortion prediction method based on the inherent strain concept is presented. In the proposed method, welding distortion of large-welded structures could be estimated by elastic analysis using the result of thermal-elastic–plastic analysis and the result of smaller welded joints or components. Thermal-elastic–plastic analysis is performed to calculate residual plastic strain distribution, which is the input data for the elastic analysis of welding distortion. The obtained residual plastic strain distribution is mapped to non-deformed finite element models to calculate welding distortion by elastic analysis. The mapping procedure is done in different ways for welding start/end parts and the rest of the weld length in order to take into consideration the unsteady strain distribution at the start/end of welds. For start/end parts, strain distribution used is identical with thermal-elastic–plastic analysis. For the part except start/end parts, strain distribution obtained by thermal-elastic–plastic analysis is extracted from the centre of weld length and is extruded along the welding direction.

The proposed method was applied to the welding distortion prediction of joints with weld length of 900 and 1200 mm based on the thermal-elastic–plastic analysis result of a joint with weld length 600 mm. The estimated results were in good agreement with the thermal-elastic–plastic analysis results of models of corresponding weld length to show the validity of the proposed method.

Keywords:

• inherent strain
• welding distortion
• residual stress
• numerical simulation
• elastic analysis
• thermal-elastic–plastic analysis

Acknowledgements

We are grateful to Eiichi Murakawa, Hiroaki Kane, and Keiji Nakanaga of the Joining and Welding Research Institute, Osaka University and Toshio Terazaki of Kyushu Industrial University for their valuable advice and discussions during this study.

The study was partially supported by the Advanced Structural and Functional Materials Design, Research and Education Centre of the Global COE Programme (Research representative: Prof. Tomoyuki Kakeshita, Osaka University) of the Ministry of Education, Culture, Sports, Science and Technology.