Effects of Thickness Ratio and Length of Thickness Transition Zone on the Tensile Behavior of Tailor Rolled Blanks

摘要

In the present work, tensile behavior of tailor rolled blanks (TRBs) made of DP590 was studied. The TRBs were produced by variable gauge rolling. The tensile specimens of TRB had thickness ratios (T-r) of 0.47, 0.52, 0.68, 0.78 and 0.89, whereas the lengths of thickness transition zone (TTZ) were 58, 75 and 110 mm. The results of tensile test along with SEM and EBSD observations revealed that the total elongation of TRBs is strongly dependent on the TTZ geometry. Accordingly, it was found out that the total elongation increases with increasing T-r. However, unprecedented results were obtained for variations of total percent elongation versus the length of TTZ. In case of tensile specimens with identical gauge length, the total elongation decreases with increasing the length of TTZ. To justify the results, a novel geometrical parameter called effective length ratio (ELR) was introduced. This new parameter showed a meaningful relation with the total elongation. Accordingly, the effects of TTZ position and geometry on the total elongation were studied utilizing ELR parameter. It was concluded that the total elongation increases with increasing the ELR parameter. Furthermore, a linear correlation between ELR and total elongation was established. This can be used to interpolate the tensile behavior of TRBs for any intermediate conditions which can be more applicable for prediction of tensile behavior without performing any tests. Finally, the influence of thickness ratio on the probability of fracture from a certain region was discussed.