【摘要】：近些年板料有限元模擬技術(shù)快速發(fā)展,有限元分析技術(shù)已經(jīng)進(jìn)入實際生產(chǎn)運用階段,在越來越多國家的汽車生產(chǎn)中都得到了廣泛的應(yīng)用,但由于單元劃分、迭代參數(shù)的選擇、板料建模、初值、邊界條件和判段準(zhǔn)則的設(shè)置,均對模擬的精度和結(jié)果有一定的影響,因此,開展對有限元軟件模擬精度的研究,對推進(jìn)板料沖壓成形技術(shù)和我國汽車業(yè)的發(fā)展具有重要的理論意義和應(yīng)用價值。本文開展了H340LAD_Z鈮微合金鋼成形極限試驗和數(shù)值模擬,在此基礎(chǔ)上開展了材料性能參數(shù)硬化指數(shù)n、屈服函數(shù)指數(shù)參數(shù)m、厚向異性指數(shù)r的單因素模擬試驗分析和正交模擬試驗優(yōu)化分析,從而揭示材料參數(shù)的對成形極限圖的影響規(guī)律并獲得優(yōu)化材料參數(shù),最后通過單向拉伸實驗驗證結(jié)果的準(zhǔn)確性。主要研究內(nèi)容:1、運用XJTUDIC三維數(shù)字散斑應(yīng)變測量分析系統(tǒng)對國標(biāo)設(shè)計的9個不同寬度試樣進(jìn)行成形極限試驗,在破裂前采集的最后一張圖片上取點,求解極限應(yīng)變,最終獲得最大、最小主應(yīng)變,并運用Matlab擬合得到H340LAD_Z鈮微合金鋼的成形極限圖。2、運用Dynaform軟件進(jìn)行成形極限試驗數(shù)值模擬。綜合兩種判據(jù):左側(cè)拉-壓區(qū)運用最大載荷判據(jù),右側(cè)拉-拉區(qū)運用應(yīng)變路徑判據(jù),能較準(zhǔn)確地獲得板料的極限應(yīng)變數(shù)據(jù)。3、采用單因素法研究屈服函數(shù)指數(shù)參數(shù)m、硬化指數(shù)n以及板料的厚向異性指數(shù)r對成形極限圖的影響。成形極限曲線會隨著板料的硬化指數(shù)n的增大而上升,但會因為厚向異性指數(shù)r和屈服函數(shù)指數(shù)m的增大而下降。以三種材料參數(shù)為試驗因素,進(jìn)行正交試驗設(shè)計,研究各因素水平對于板料成形極限曲線的影響顯著性。由分析結(jié)果得出因素影響順序:硬化指數(shù)n屈服函數(shù)指數(shù)參數(shù)m厚向異性指數(shù)r,最優(yōu)材料參數(shù)組合為:硬化指數(shù)n=0.18,屈服函數(shù)指數(shù)參數(shù)m=4,厚向異性指數(shù)r=0.9。4、運用Dynaform分別采用優(yōu)化前、后的材料性能參數(shù)值進(jìn)行單向拉伸數(shù)值模擬,獲取試樣的極限應(yīng)變圖和極限載荷,并與單向拉伸試驗獲得的相應(yīng)結(jié)果對比,得出優(yōu)化得到的材料參數(shù)更接近于試驗結(jié)果。單向拉伸實驗和采用優(yōu)化前、優(yōu)化后材料參數(shù)模擬獲得的極限應(yīng)變的相對誤差為6.2%和2.5%,極限位移的相對誤差為15%和6.3%,得出優(yōu)化后的一組材料性能參數(shù)提高了Dynaform軟件模擬精度。
[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.
【學(xué)位授予單位】：天津職業(yè)技術(shù)師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TG386

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