Research On Lifetime Of Advanced High Strength Steel Stamping Die Based On Dynamic Friction And Wear Coefficient

In order to meet the needs of energy conservation and emission reduction,the lightweight of automobiles is an inevitable trend in the development of the automotive industry,and the choice of materials is one of the important ways to solve the problem of vehicle weight reduction.Advanced high-strength steel is a widely used sheet metal material,because of its strength relative to traditional steel is large,so it can meet the needs of lightweight.However,advanced high-strength steels,as a kind of high-strength material,have strong anti-deformation ability.Therefore,the force required by the punching press in the actual stamping process is greater,resulting in greater stress on the stamping die face.The larger interface pressure will inevitably lead to increased die wear,which will affect the life of the mold and increase the cost of automobile development.Therefore,this paper studies the wear of advanced high-strength steel stamping dies,and proposes a relatively more accurate method for calculating the wear of advanced high-strength steel molds,so as to predict the mold life.Die wear is a highly dynamic nonlinear process,which is affected by magnitude of load,geometrical morphology,surface quality and material properties,especially during the stamping process of high strength steel.Due to the complex dynamic nonlinear conditions such as friction and wear,the simulation is very difficult and the accuracy is not high.Aiming at the above problems,a new method of life evaluation of high strength steel stamping die based on dynamic friction and wear coefficient and thickness change is proposed.First considering the real-time changes in the process of high strength steel stamping node pressure and relative sliding velocity on the friction coefficient and wear coefficient,the influence of the real time pressure and sliding speed as a variable parameter,through orthogonal friction and wear experiment,putting forward a surface wear calculation model which is based on dynamic friction coefficient and dynamic coefficient wear.The thickness of the mold changes with the heat treatment and the thickness of the surface coating,so the wear condition is obviously affected.Therefore,a metabolic mold hardness and coefficient of wear coupling mold surface wear equation is established through hardness experiments and theoretical derivation,and the dynamic friction coefficient in the model will be stamped to numerical simulation to substitute coulomb friction model.Then the wear equation is obtained by coupling the die wear calculation.In addition,because the wear of the mold during the stamping process changes the moldgeometry,which affects the subsequent stamping and mold wear.Therefore,this paper continuously updates the worn die profile through the node movement,obtains the new parameters in the current wear state,uses the new parameter to calculate the current wear amount of the stamping,and ensures that the wear parameter is continuously updated as the wear increases,thus making the wear prediction more in line with actual physical wear and tear.Comparing the calculated results with wear facial scan data arrives at the result that using this method to calculate the wear position is exact and the wear trend is very close to the results.What's more,the accuracy of the calculation comparing with the traditional constant coefficient of friction and wear increase by 21.36%.Based on this method,the life expectancy of the left front longitudinal beam stiffener drawing die with DP780 is predicted.The results show that,about 59,000 times of the stamping,partial area of the surface of the mold coating serious wear and tear,and need to be repaired.