Constraining effects of weld and heat-affected zone on deformation behaviors of welded tubes in numerical control bending process

The constraining effects of the weld and heat-affected zone (HAZ) material in welded tube numerical control (NC) bending process are key problem to be solved in the research, development and application of thin-walled welded tubes. To investigate the constraining effects of the weld and HAZ material on the tube bend formability, finite element (FE) model with weld and subdivided HAZs, model with weld-only and model with parent metal alone under ABAQUS platform are employed. The results show that: (1) the weld and HAZ material have obvious constraining effects on the strain distributions in weld and HAZ as the weld line locates on the outside and inside of the bend, meanwhile, the cross-sectional deformation becomes more severe as the weld line locates on the outside; (2) as the weld line locates on the outside, the constraining effects of the weld and HAZ material make the tangent strain and thickness strain decrease, the hoop strain increase in the weld and HAZ, the cross-sectional deformation increase and the wall thinning decrease as compared with model that contains parent metal alone; (3) the constraining effects of the weld and HAZ material are minimal as the weld line locates on the middle of the bend.

► The implementation of weld and HAZ in FE model can reflect the constraining effect.
► Constraining effect of weld joint is great as weld locates in large strain region.
► Constraining effect increases with larger bending angle and bending radius.
► Constraining effect of weld joint makes the cross-sectional deformation decrease.