Numerical Investigation On Wear Behavior Of Hot Stamping Die And Prediction Of The Die Life

High-strength steel has been used more and more widely in automobile manufacturingfield as Reducing the weight of vehicle body has become the development trend, whichwould further increase the importance of hot stamping dies. Compared with traditional die,the hot stamping die cost more because of higher cost of die materials, quite complexstructure and much higher precision. So, the life of the hot stamping die has been asignificant economic indicator of assessment of component cost. Generally, die failure ismainly due to wear. As a result, the investigation on the wear of the hot stamping die possessfundamental significance.In this paper, the research places emphasis on wear behavior and prediction of the wearloss and the life of hot stamping die during the work. It will go deep into the sliding wearbehavior, as well as the effects of key physical factors on the wear perfomance, conductedout by the finiet element analysis model at mesoscopic level. Aslo, an improved wear finiteelement model has been developed to devote to estimating wear-loss and life, and tounderstand the effects of forming parameters on the wear depth and life of hot stamping diein the proces of service. The following conclusiongs are drawn:(1) On the basis of the analysis of existing models for exporing the wear behavior, anew finite element model in mesoscopic scale has been developed to carry out the simulationof sliding wear behavior of the hot stamping die. Comparing the wear rates obstainedexperimentally with the simulated wear rate, we find that the two results are match whichprove that this finite element model is avaliable for the research of die wear performance.(2) The finite element model of sliding wear behavior has been used to investigateparametrically the influence of loadig, friction coefficient and tempering hardness on thewear rate. The results reveal that the wear rate increases with contact pressure at themacroscale level, especially when the contact pressure exceeds15MPa, the wear rateincreases exponentially. The predicted results are found that a reduction in the frictioncoefficient can considerably improve the wear resistance of hot stamping die. It is also foundthat the wear rates depends strongly on the tempering hardness of the die and better wearresistance is achieved when the tempering hardness is48HRC. The simulation results show that between20and300℃, with the increase of the temperature, the wear rate becomeshigher slightly, however, over500℃, wear rate rises sharply with the temperature.(3) A wear prediction model applicable to die has been established by combining thelaw and finite element method, while dynamic simulation of the whole wear process isrealized by compiling the user subroutine. Two key parameters are confirmed based on theresults of comparing the wear depths achieved by experiment with simulated wear depths.The wear prediction model was adopted to simulate and analyze wear process, and toestimate the life of die, and was employed in study on effects of blank holder force andinitial temperature of blank on wear depth and die life. For researching on the wear underdifferent BHF condictions, the results demostrate that the increasing BHF will conduce tothe increase maximum wear depth of die in the steady stage, and to the increase slope of thecurve that describes the approximately linear relationship between the maximum wear depthand stamping cycles, and lead to decrease of lifetime of the mould. In addition, through thesimulation reseaches on the die’s wear in condition of different initial blank temperature, it isclear that the maximum wear depth is sensitive to the initial temperature of blank and whenthe initial temperature of blank increases, the maximum wear depth will become smaller,which gives rise to a increase of the life of the hot stamping die.