| In order to adapt to the new challenges from energy,environment and safety,automobile lightweight is a direction of future development.Compared with other light alloys,high strength steel has more outstanding advantages in cost and performance,which can meet the characteristics of lightweight and crash safety of today’s automobiles.As one of the high strength steels,H260 YD steel is used to produce automobile panels,which represents the development direction of automobile lightweight steel.The steel is generally used in cold forming and deep drawing automobile panels,and it has been widely used to produce deep drawing and cold forming automobile panels.However,this high-strength steel,while showing its superior performance,also has certain defects when used for stamping.Therefore,it is necessary to carry out experimental research on its forming performance,especially when it is used to form automobile cover with complex structure,so as to guide the forming of specific automobile cover with the results of forming characteristics exploration.In this paper,the mechanical properties of H260 YD high-strength steel for automobile lightweight were tested by means of uniaxial tensile test to obtain the basic mechanical properties of materials.Secondly,the forming performance of the high-strength steel plate is analyzed and evaluated by the typical cupping test method,and the forming law of cupping value under different process conditions(blank holder force,stamping speed,lubrication conditions)was obtained.The numerical simulation software was used to simulate the cupping process,and the simulation results are compared with the physical cupping test results,and it is found that the forming results are consistent.On this basis,according to the mechanical properties and forming performance indexes of the high-strength steel plate,H260 YD high-strength steel plate is used to form the middle channel of the automobile front floor.By process design,the forming quality is continuously optimized and the forming defects are eliminated,and the best forming process parameters of the middle channel of the formed automobile floor are obtained.Finally,the final process parameters are used in the actual engineering verification after the simulation forming of the panel which meets the requirements of the enterprise.The main contents of this paper are as follows:(1)First of all,the forming process of steel plate is explained by using the forming mechanism of sheet metal,the plastic flow law of material in forming is analyzed,and the work hardening in forming process is explained theoretically,and the judgment criterion to evaluate the yield condition of sheet metal forming is given,and then the relevant algorithms of numerical simulation of sheet metal forming are compared,and various defects appearing during the material forming are predicted.Finally,the evaluation method of sheet metal forming performance is put forward.(2)The tensile specimen was designed,and then the uniaxial tensile test was carried out on H260 YD high strength steel plate on the electronic universal tensile testing machine to explore the mechanical properties of the material.The stress-strain correlation curve is obtained from the uniaxial tensile test results,and the mechanical properties parameters of the material were obtained from the test results,which can provide reference for the follow-up simulation forming and engineering verification of the middle channel cover.(3)In order to explore the formability of H260 YD high-strength steel plate,the typical cupping test was used to control the single variable in the test,and to explore the influence of different process parameters under each process condition(stamping speed,friction coefficient,blank holder force)on the formability of H260 YD high-strength steel plate,and to simulate the forming process and verify the accuracy of the experimental method by combining with numerical simulation.Finally,the forming law of sheet metal under different process conditions was obtained,which provided the basis for the following process parameter design and optimization of the automobile channel stamping.(4)This paper takes the middle channel of automobile front floor as the forming object,which is made of 1.2mm H260 YD high-strength steel plate.By using Dynaform simulation analysis software,numerical simulation analysis of forming process and prediction of forming defects were carried out for the middle channel of H260 YD high-strength steel automobile floor.By process design iteration and continuous optimization of forming process parameters,gradually reducing defects in the forming process and maximizing the forming characteristics of the steel plate.Therefore,the best process parameters of H260 YD high-strength steel plate in the panel were obtained,and finally obtain the qualified automobile channel simulation.(5)The channel die of the front floor of the car was trialed,the parameters corresponding to process and forming under the final simulation forming quality qualification conditions were applied.The engineering actual verification in the enterprise was carried out.The actual products formed by stamping was detected by special detection tools,and finally meet the specified forming requirements and enterprise quality requirements. |
