Numerical simulation of formability of tailor welded blanks for auto door inner panel

Abstract: Tailor welded blanks (TWBs) based on modern technology are widely applied in the production of auto body components, which can reduce the weight of auto body effectively, but the overall formability of the TWBs is different from single blank, the fracture and welded seam movement usually appear in the forming process. To find out the formability of TWBs, the test and numerical simulation should be carried out, which has been a main problem of weld modeling for TWBs in simulation.The application od auto door inner panel made of TWBs can not only optimize the structure of the workpiece, but also effectively reduce the weight of the inner door panel. The fracture and welded seam movement usually appear in the forming process of Auto door inner panel made of TWBs. In order to avoid the quality problems, and at the same time to improve the efficiency of process planning, a simulation model on forming was developed using software Dynaform.In this paper, a new simulation method for weld-line is worked out. Generally the weld modeling uses a rigid way in the weld-line, but for large component such as automobile panel, it makes lower efficiency and even can't finish the calculation. Experience shows that, the fracture will not appear on the weld-line in forming process as long as the weld is qualified. And, in the phase of the component design, what we are concerning more about is the overall formability of the component, therefore a new simulation method for weld-line was brought out: to simplify the handling of the common nodes, which are taken as the common nodes of both sides of weld material. Using this calculation method, grid can be encrypted automatically in the simulation, so that the initial blank does not need to partitioned very small, and the calculation efficiency and stability can be improved.Through adjusting the simulation parameters, the appropriate blank holder force, draw bead and lubrication state were determined. The optimization and selected conditions for the forming simulation are that the blank holder force is 1 050 kN, the height of draw bead is 6.5 mm and the friction coefficient is 0.05 for the effective lubrication. The experimental result was well coincident with the numerical simulation results at thickness, the predicting movement value of weld-line is 6.61 mm, and the test value is 7.31 mm, the error is 0.7 mm, this verified the validity of numerical simulation. The amount of welded seam movement can be predicted accurately with the method, so the forming quality can be estimated. The method can shorten the time to adjust parameter in stamping repeatedly, and improve the efficiency from design to production for new automobile body cover made of TWBs. The analysis method based on numerical simulation technology is helpful for process planning of automobile body cover made of TWBs, and can provide a reference for its mould design.