Study And Application Of Fatigue Life Prediction Method For Aluminum Profile Extrusion Die Based On Simulation

The structure of the extrusion die is complex,and under the harsh working environment of high temperature,high pressure,and high friction,fatigue fracture failures at local dangerous locations are extremely easy to occur.At the same time,mold design and manufacturing are costly and time-consuming,so the uncertainty of mold life also seriously affects the production schedule and costs of enterprises.There are many life prediction methods for different failure modes of mechanical parts,but there are not many studies on the life prediction model of aluminum extrusion die.With the popularization and development of computer technology,finite element simulation technology has been widely used in aluminum extrusion production,but the application of current simulation technology in die is mainly limited to the analysis of stress distribution and elastic deformation.This paper intends to develop an extrusion die life prediction model based on the total strain amplitude,combined with the total strain amplitude obtained by simulation,to quickly complete the life prediction of the extrusion die in the design stage,and help companies arrange mold trials and production plan according to the life prediction value,so as to achieve the purpose of improving mold life and production efficiency.In this paper,theoretical research,simulation analysis,experimental research and other methods are used to systematically study the fatigue life prediction methods of extrusion dies.The linear elasticity and elastoplastic stress-strain characteristics of aluminum extrusion die are studied by finite element simulation technology;Considering the fatigue parameter estimation method and the average stress correction method,different fatigue life prediction models of aluminum hot extrusion die based on the local stress-strain method have been established;Through the comparative analysis of the fatigue life prediction value and the actual service life data of the factory die,the optimal fatigue life prediction model of the extrusion die based on the total strain amplitude is determined;Finally,based on the established life prediction model,the life prediction of the three optimized structures of an aluminum extrusion die is carried out,and the optimal die structure is determined based on the analysis and test results.The main research work of this paper is as follows:(1)Research on linear elastic strain and fatigue failure of extrusion die based on simulation.For the H13 steel material used in extrusion die,carry out hot tensile test at working temperature to obtain its static strength performance parameters and stress-strain constitutive relationship;Use the Inspire Extrude platform to perform linear elastic finite element simulation analysis of the steady state extrusion process of a certain profile die,analyze the die stress and strain distribution law and fatigue failure characteristics and locations,and compare with the actual die test results;The research results show that the analysis results of the established finite element simulation model are consistent with the actual test results.The fatigue cracks of the extrusion die generally occur at the maximum stress and strain position of the die.(2)Research on the prediction method of die life based on elastic strain amplitude.Based on the local stress-strain method,the elastic strain amplitude is used as the damage parameter,combined with different methods to estimate the fatigue parameters of H13 steel,and on this basis,four life prediction models based on the elastic strain amplitude are established;Taking16 different size square tube profile molds as an example,the life prediction model established was used to predict the life,and the results were compared with the actual test mold results;The results show that the prediction model established based on the general slope method and the four-point correlation method to estimate the fatigue parameters is more suitable for the life prediction of the extrusion die,However,because only the elastic strain amplitude is considered in the model,and the plastic strain amplitude is not considered,there is a certain error between the predicted life value and the actual life value of the mold.(3)Research on die life prediction method based on total strain amplitude.Combined with H13 steel material hot tensile test results,reconstruct the H13 steel material elasto-plastic model,use simulation to analyze the elasto-plastic stress and strain characteristics of the extrusion die,and calculate the total strain amplitude;Taking the total strain amplitude as the damage parameter,and using the fatigue parameter values of H13 steel estimated by different methods,four extrusion die life prediction models based on the total strain amplitude are established,use these models to predict the life of 7 groups of extrusion dies and compare them with the actual life of the production,determined that the life prediction model based on the general slope method fatigue parameter estimation is more suitable for the estimation of the fatigue life of the extrusion die;Three average stress correction methods are used to revise the life prediction model based on the fatigue parameter estimation of the general slope method,and the revised model prediction results are again compared and analyzed with the actual life of the mold.The results show that the life prediction model modified by the M-H model method further improves the accuracy of life prediction.(4)Research on the application of extrusion die life prediction model.Taking a certain profile mold as an example,based on the original design,three mold structure optimization schemes are proposed: Increase the sinking structure of the upper die splitter bridge,Increase the number of shunt holes,Adding a diversion die.Use the finite element simulation results to analyze the maximum stress and strain characteristics of the dangerous point of the mold,and calculate the total strain amplitude;Use the mold life prediction model established in this article to predict the life,and compare it with the actual extrusion test results;The results show that:the life prediction model built in this paper can predict the fatigue life of the extrusion die more accurately.Based on the prediction value of die life and the simulation analysis results of profile quality,it is finally determined that adding a diversion die is the best structural design plan.