Calculation Of In-stamping Surface Stresses Of An Automobile Panel Die And Optimization Of Laser Hardening Process

In recent years, laser hardening, as a surface processing technology, is appliedwidely on hardening the surfaces of automobile panel dies for avoiding wear.However, parameterized designing of laser hardening parameters according to die’swear is impossible for now. Laser hardening parameters designing based on the stresson die’s surface during stamping is studied in this paper.First, it is found that the zones where the tensile stress is more than the limit ofthe die’ surface can be the ones to be worn and it is explained that why laserhardening can improve wear resistance of the die’s surface. A method for calculatingstress on drawing die’s surface of automobile panel characterized by large scale andcomplexity is proposed. The possible failure zones on die’s surface are predicted aftercompare the calculated stress with failure limit of the die. The calculation includestwo parts: establish the theoretical model for calculating nodal displacements on die’spanel using central difference method and solve it with DYNAFORM; establish thetheoretical model for calculating stress on die’s surface using energy conservationmethod with obtained nodal displacements loaded upon it and solve it with ABAQUS.It is found that this method can calculate the die’s stress accurately by comparingdistribution and morphologies of predicted zones to be worn with worn zones of a realdie.Second, the three-dimensional transient temperature field calculating model oflaser surface hardening QT600-3ductile cast iron is established and solved withABAQUS. The influence to laser hardening from laser hardening parameters isanalyzed by studying the maximum temperature and the temperature gradient. Thewidths and depths of hardened zones are calculated and their variation with laserhardening parameters is researched. Laser hardening experiments are performed withthe same parameters as in simulation. It is demonstrated that the widths and depths ofhardened zones in experiments are in a good agreement with the ones in simulationafter comparisons and the errors are all less than10%.At last, it is verified that the stress calculation and the prediction of widths anddepths of the hardening zones are both of accuracy, so, plan the scanning path forlaser hardening based on the calculated distribution of zones to be worn; design thelaser hardening parameters preliminarily based on the calculated widths of zones to be worn on die’s surface and the relationship between the widths of hardened zones andlaser hardening parameters; concerning the relationship between residual stress andlaser energy density for the balance of the residual compressive stress and the tensilestress on die’s surface, design the final parameters based on the calculated stress ondie’s surface during stamping.