Optimisation of the bending process of high strength low alloy sheet mtetal

Anchorage parts for automobile safety belts and other safety parts must resist shock loadings without breaking. They are typically made from High Strength Low Alloy sheet metal and fabricated by blanking and bending operations. The study of their behaviour during fabrication and their resulting mechanical properties has been studied experimentally and numerically. The experimental results were used to validate the numerical simulation. The resulting material damage is taken into by user subroutines in the Abaqus Standard finite element code. Damage is one of the objective functions intervening in the shape optimisation of the safety parts as well as the optimisation of the bending process. This study is based on the use of "the design of experiments technique", the approximated representation by response surfaces and the use of artificial neural networks. The objective functions represent the maximum punch loads, the maximum stresses and maximum damage during the bending operation. For unbending operations, representative of dynamic choc loadings, the objective functions are again the maximum unbending load, the maximum stresses and maximum damage. The optimisation is done by the moving least square method, evolution strategies and a global calculation method. The parameters that represent the die radius and the clearance between the sheet and tool are optimised with the objective to obtain the most resistant safety part possible.