The Construction Of Forming Limit Diagram For The High Strength Steel Plate Of H340LAD_Z

In recent years, Numerical simulation in sheet metal stamping technology mature gradually, the finite element software has entered the stage of actual production use, it has been widely used in the production of cars in many countries, but as a result of cell division, iteration parameters selected, the establishment of the material model, selected the right initial value and boundary conditions and the rule of appropriate criterion, will be the result of the simulation precision and produce certain effect, so the numerical simulation on the forming limit of study the existence of inevitable errors. Therefore, carrying out a research into the accuracy of finite element software simulation, to promote the sheet metal stamping technology and the development of auto industry in China has important theoretical significance and application value.This paper has carried out H340LAD_Z niobium alloy FLD experiment and numerical simulation, studied the friction condition and the strain rate on the influence of FLD, base on the material performance parameters hardening exponent n, the yield function index m, thick anisotropic index r simulation experiment of single factor analysis and orthogonal experimental simulation optimization analysis, so as to reveal the material parameters of FLD on law and material with optimized parameters, the influence of the final through uniaxial tensile experiments and simulation is verified. The main research content:1.Using XJTUDIC analysis of 3d digital speckle strain measurement system to the national standard design the nine different width of specimen, forming limit test, gather on the last picture before the burst point, solving the limit strain, finally get the maximum and minimum principal strain, and using Matlab fitting H340LAD_Z niobium hsla steel forming limit diagram.2.Using finite element software Dynaform for numerical simulation of forming limit test. Comprehensive two criteria: pull on the left of the pressure area by means of the criterion of maximum load judgment, on the right side of the pull- region strain path judgment criterion, can accurately obtain ultimate strain data.3.Using single factor method to study the influence of FLD for yield function index parameter m, strain hardening index n, thick anisotropic index r ’s influence on the forming limit diagram. The forming limit curve falling With the increase of the yield function index parameter m and anisotropic index r, rise with the increase of the strain hardening index n. With three kinds of material parameters for the test factors, doing orthogonal experiment design, researching the level of various factors on the influence of the sheet metal forming limit curve of significance. Obtained from the analysis results: hardening index n> the yield function index parameter m > thick anisotropic index r, hardening index n=0.18, the yield function index parameter m=4, thick anisotropic index r=0.9.4.Using Dynaform respectively before and after optimization in the material performance parameter values for numerical simulation of uniaxial tensile sample limit strain and limit load, and compared with uniaxial tensile test to obtain the corresponding results, the material parameters optimized by the draw closer to the test result. Limiting strain of the relative error is 6.2% and 2.5%, limiting displacement of relative error is 15% and 6%, it is concluded that a set of material performance parameters are optimized to improve the Dynaform finite element numerical simulation accuracy.