Abstract: Necking or fracture caused by the non-uniform deformation is the problem that affects the forming of laser tailor-welded blanks (LTWB), thus the formability of LTWB needs to be known urgently. Forming limit diagram (FLD), which can be established by experiment or theoretical calculation, is an important method to evaluate the formability of sheet metal. However, the FLD obtained by experiment costs much and takes more time. And the method of theoretical calculation is not yet perfect and needs further improvement. A new theoretical model is developed to compute the FLD of same gauge laser tailor-welded blank. Base on the theoretical model, the FLD of same gauge laser tailor-welded blanks made of high strength interstitial free (HS–IF) steel is calculated by using the Hosford’s yield criteria. Good correlation between the calculation result and experimental data is indicated. The FLD of laser tailor-welded blanks can be obtained conveniently through this method after the material performance parameters of welding zone are given.

Key words: Limit strain, Forming limit diagram, Laser tailor-welded blanks, Theoretical model