H340LAD_Z高强度钢板成形极限图的构建

发布时间：2018-08-10 20:00

【摘要】：近些年板料有限元模拟技术快速发展,有限元分析技术已经进入实际生产运用阶段,在越来越多国家的汽车生产中都得到了广泛的应用,但由于单元划分、迭代参数的选择、板料建模、初值、边界条件和判段准则的设置,均对模拟的精度和结果有一定的影响,因此,开展对有限元软件模拟精度的研究,对推进板料冲压成形技术和我国汽车业的发展具有重要的理论意义和应用价值。本文开展了H340LAD_Z铌微合金钢成形极限试验和数值模拟,在此基础上开展了材料性能参数硬化指数n、屈服函数指数参数m、厚向异性指数r的单因素模拟试验分析和正交模拟试验优化分析,从而揭示材料参数的对成形极限图的影响规律并获得优化材料参数,最后通过单向拉伸实验验证结果的准确性。主要研究内容:1、运用XJTUDIC三维数字散斑应变测量分析系统对国标设计的9个不同宽度试样进行成形极限试验,在破裂前采集的最后一张图片上取点,求解极限应变,最终获得最大、最小主应变,并运用Matlab拟合得到H340LAD_Z铌微合金钢的成形极限图。2、运用Dynaform软件进行成形极限试验数值模拟。综合两种判据:左侧拉-压区运用最大载荷判据,右侧拉-拉区运用应变路径判据,能较准确地获得板料的极限应变数据。3、采用单因素法研究屈服函数指数参数m、硬化指数n以及板料的厚向异性指数r对成形极限图的影响。成形极限曲线会随着板料的硬化指数n的增大而上升,但会因为厚向异性指数r和屈服函数指数m的增大而下降。以三种材料参数为试验因素,进行正交试验设计,研究各因素水平对于板料成形极限曲线的影响显著性。由分析结果得出因素影响顺序:硬化指数n屈服函数指数参数m厚向异性指数r,最优材料参数组合为:硬化指数n=0.18,屈服函数指数参数m=4,厚向异性指数r=0.9。4、运用Dynaform分别采用优化前、后的材料性能参数值进行单向拉伸数值模拟,获取试样的极限应变图和极限载荷,并与单向拉伸试验获得的相应结果对比,得出优化得到的材料参数更接近于试验结果。单向拉伸实验和采用优化前、优化后材料参数模拟获得的极限应变的相对误差为6.2%和2.5%,极限位移的相对误差为15%和6.3%,得出优化后的一组材料性能参数提高了Dynaform软件模拟精度。
[Abstract]:In recent years, with the rapid development of sheet metal finite element simulation technology, finite element analysis technology has entered the stage of practical production and has been widely used in automobile production in more and more countries, but due to the division of elements, the choice of iterative parameters. The modeling of sheet metal, initial value, boundary condition and the setting of the criterion have certain influence on the accuracy and result of simulation. Therefore, the research on the simulation accuracy of finite element software is carried out. It has important theoretical significance and application value to promote sheet metal stamping forming technology and the development of automobile industry in China. In this paper, the forming limit test and numerical simulation of H340LAD_Z niobium microalloyed steel are carried out. On this basis, single factor simulation test analysis and orthogonal simulation test optimization analysis of material properties parameter hardening index (n), yield function index parameter (m) and thickness anisotropy index (r) are carried out. In order to reveal the influence of material parameters on the forming limit diagram and obtain the optimized material parameters, the accuracy of the results is verified by uniaxial tensile experiments. The main research content is: 1, using XJTUDIC three-dimensional digital speckle strain measurement and analysis system to test the forming limit of 9 specimens with different widths designed by GB, taking points from the last picture taken before rupture, and solving the limit strain. Finally, the maximum and minimum principal strain were obtained, and the forming limit diagram of H340LAD_Z niobium microalloyed steel was obtained by Matlab fitting. The forming limit test was simulated by Dynaform software. Two criteria are synthesized: the maximum load criterion is used in the left tension and compression zone, and the strain path criterion is used in the right tension and tension zone. The limit strain data of sheet metal. 3 can be obtained accurately. The influence of yield function exponent parameter m, hardening index n and thickness anisotropy index of sheet metal on forming limit diagram is studied by single factor method. The forming limit curve increases with the increase of the hardening index n, but decreases with the increase of the thickness anisotropy index r and the yield function exponent m. Taking three material parameters as experimental factors, orthogonal experimental design was carried out to study the significance of the influence of each factor level on sheet metal forming limit curve. The results show that the order of influencing factors is as follows: hardening exponent n yield function parameter m thickness anisotropy index r, the optimal material parameter combination is hardening index n 0. 18, yield function exponent parameter m 0. 4, thick anisotropy index r = 0. 9 4. The optimum material parameters are adopted before optimization using Dynaform, respectively. The ultimate strain diagram and ultimate load of the specimen were obtained by numerical simulation of the parameters of the material properties after uniaxial tensile test. Compared with the corresponding results obtained from the uniaxial tensile test, the optimized material parameters are more close to the experimental results. Before uniaxial tensile test and optimization, the relative error of limit strain is 6.2% and 2.5%, and the relative error of limit displacement is 15% and 6.3 respectively. It is concluded that the simulation accuracy of Dynaform software is improved by the optimized set of material performance parameters.
【学位授予单位】：天津职业技术师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG386

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