Numerical analysis of stress & strain and thickness variation in single point incremental forming of tailor welded steel blanks

Finite element (FE) modeling of tailor welded blanks (TWBs) is a complex phenomenon compared to FE modeling of monolithic sheets due to the change of mechanical properties caused by the welding process. This complexity involves modeling different zones generated due to the heat effect. Research on the formability of steel TWBs with dissimilar thicknesses and strength produced by manual tungsten inert gas (TIG) welding technique and formed by single point incremental forming (SPIF) involving base sheets, weld nugget (WN), and heat affected zone (HAZ) is presented, numerically. The materials selected for the study included deep drawing quality (DDQ) steel (DC06) and stainless steel (SS) (AISI 201). Variable wall angle truncated pyramid was used as test geometry, and FE software Abaqus (dynamic explicit solver) was used for the analysis. Thickness profiles and state of stress and strain in both the cases of thickness and strength differential were analyzed. A decrease in thickness was observed at the corners in both cases. However, this decrease was more prominent in the case of strength differential. The symmetry of the pattern on both sides with minimum and maximum values of stress towards the thinner side was observed in the case of thickness differential. Variation in stress was more prominent towards the side of high-strength material along maximum value in the case of strength differential. Equivalent plastic strain observed was more linear and higher towards the sides of thicker sheet and material having less strength in the case of thickness differential and strength differential, respectively. Research investigations may be applied in a similar fashion for the precise study of formability characteristics of various kinds of TWBs being used in multiple industries including automotive, vessel, and medical.