Experimental and Analytical Study of Drawbead Restraining Force for Sheet Metal Drawing Processes 2020-01-0753
In recent years, implementation of aluminum alloys, advanced high strength steels and ultra high strength steels is quickly increasing in automotive components due to their superior structural performance and vehicle weight reduction capabilities. However, these materials often have more limited formability compared to broadly used mild steels. Design of the sheet metal drawing process requires accurate information about the restraining forces distribution usually accomplished by a set of drawbeads positioned along the perimeter of the die cavity. This study is targeting bringing together the results of analytical models, results of finite element analysis and experimental data in attempt to understand the most critical factors influencing the restraining force.
The experimental study of the restraining force was performed using drawbead simulator tool installed into Instron tensile testing machine. Based upon the experimental results, it was observed that the restraining force of the given drawbead configuration is dependent upon the depth of bead penetration, friction between the drawbead surfaces and sheet metal as well as the clearance between the upper and lower die. This clearance is often adjusted during stamping operations to increase or decrease material inflow into the die cavity without any modification in the die.
Numerical simulation results will be presented together with the results of experiments to illustrate the influence of drawbead geometry as well as the clearance between the upper and lower die. This study will be complemented with independent measurements of coefficient of friction for similar amounts of lubricant on the surface, contact pressure and velocity of sliding.