【摘要】：有限元方法和計(jì)算機(jī)輔助仿真分析軟件(CAE)廣泛應(yīng)用于汽車(chē)研發(fā)領(lǐng)域,有助于縮短研發(fā)周期和節(jié)約研發(fā)資金。涉及材料大變形的汽車(chē)碰撞安全仿真分析和金屬板料成形過(guò)程的仿真需要定義材料在大應(yīng)變處對(duì)應(yīng)的流動(dòng)曲線,即真應(yīng)力-應(yīng)變曲線。材料的應(yīng)力應(yīng)變曲線通常使用單向拉伸實(shí)驗(yàn)獲得,而在實(shí)驗(yàn)過(guò)程中常用的普通接觸式引伸計(jì)法無(wú)法準(zhǔn)確給出材料在大變形階段的真應(yīng)力應(yīng)變曲線。本篇研究?jī)?nèi)容主要展示了一種逆向識(shí)別方法,聯(lián)合有限元仿真和普通拉伸實(shí)驗(yàn)獲取金屬板料在大變形階段的流動(dòng)曲線。主要研究?jī)?nèi)容包括以下幾個(gè)方面：(1)鋼板是汽車(chē)車(chē)身常用的金屬材料。隨著汽車(chē)輕量化技術(shù)的推廣,高強(qiáng)鋼和鋁合金材料在汽車(chē)制造中的使用量越來(lái)越大。本文選擇低碳鋼Q195、鋁合金AL6061和高強(qiáng)鋼HSLA350三種典型板料作為研究對(duì)象。首先按照國(guó)標(biāo)設(shè)計(jì)并加工標(biāo)準(zhǔn)試樣。使用引伸計(jì)初步得到三種材料試件的拉伸力-伸長(zhǎng)量曲線。經(jīng)過(guò)數(shù)據(jù)處理后得到工程應(yīng)力-應(yīng)變曲線、真應(yīng)力-應(yīng)變曲線和真應(yīng)力-塑性應(yīng)變曲線�？紤]到板料各向異性的影響,沿軋制方向、橫向和45°方向截取試件并在拉伸過(guò)程中測(cè)量厚向異性系數(shù)。(2)仿真軟件采用的是有良好非線性仿真性能的通用有限元仿真軟件ABAQUS(?)。仿真過(guò)程中構(gòu)建了合適的有限元模型,能正確仿真分散性失穩(wěn)期間的各向異性塑性變形。在驗(yàn)證階段嘗試比較了多種單元尺寸和ABAQUS中包含的單元類(lèi)型。最終確定的拉伸試件有限元仿真模型包括合理的結(jié)構(gòu)模型、考慮各向異性屈服的材料模型、兼顧仿真精度和效率的單元參數(shù)和為了與實(shí)驗(yàn)力-伸長(zhǎng)量曲線作比較而對(duì)應(yīng)設(shè)置的輸出項(xiàng)。(3)結(jié)合實(shí)驗(yàn)與仿真,給出一種逆向識(shí)別方法。以實(shí)驗(yàn)力-伸長(zhǎng)量曲線為標(biāo)桿,不斷外推修正流動(dòng)曲線直至仿真力-伸長(zhǎng)量曲線收斂到實(shí)驗(yàn)力-伸長(zhǎng)量曲線。最終得出三種板料直至集中性失穩(wěn)前的全流動(dòng)曲線。(4)在得出材料完整的直至頸縮階段的流動(dòng)應(yīng)力曲線后,建立多個(gè)不同的硬化函數(shù)描述該曲線,并比較擬合結(jié)果,發(fā)現(xiàn)一種改進(jìn)的Hockett-Sherby函數(shù)效果最好并展示了其結(jié)果。此外,結(jié)合Q195拉伸試件的仿真結(jié)果,簡(jiǎn)要分析了試件在頸縮階段的應(yīng)力三軸性行為。
[Abstract]:Finite element method (FEM) and computer aided simulation analysis (CAE) are widely used in the field of automobile research and development, which is helpful to shorten the research and development cycle and save the R & D funds. The simulation analysis of automobile collision safety involving large deformation of materials and the simulation of sheet metal forming process need to define the flow curve corresponding to the material at large strain, that is, the true stress-strain curve. The stress-strain curves of materials are usually obtained by uniaxial tensile tests, but the common contact extensometer can not accurately give the true stress-strain curves of materials in large deformation stage. In this paper, a reverse recognition method, combined with finite element simulation and general tensile experiment, is presented to obtain the flow curves of sheet metal in large deformation stage. The main research contents are as follows: (1) Steel plate is a common metal material used in automobile body. With the popularization of lightweight technology, high-strength steel and aluminum alloy are used more and more in automobile manufacturing. In this paper, three typical sheets of low carbon steel Q195, aluminum alloy AL6061 and high strength steel HSLA350 are selected as research objects. First according to the national standard design and processing of standard samples. The tensile force-elongation curves of three kinds of material specimens were obtained by extensometer. After data processing, engineering stress-strain curves, true stress-strain curves and true stress-plastic strain curves are obtained. Considering the effect of anisotropy of sheet metal, along the rolling direction, The transverse and 45 擄directions are used to intercept the specimen and measure the thickness anisotropy coefficient in the tensile process. (2) the general finite element simulation software ABAQUS (?), which has good nonlinear simulation performance, is used in the simulation software. An appropriate finite element model is constructed to simulate the anisotropic plastic deformation during the dispersion instability. During the verification phase, a variety of cell sizes were attempted to compare with the cell types contained in the ABAQUS. The final finite element simulation model of tensile specimen consists of a reasonable structure model and a material model with anisotropic yield. The element parameters which take into account the accuracy and efficiency of the simulation and the output terms set for comparison with the experimental force-elongation curve are given. (3) combining the experiment and simulation, a reverse recognition method is presented. Taking the experimental force-elongation curve as the benchmark, the flow curve is continuously extrapolated and revised until the simulation force-elongation curve converges to the experimental force-elongation curve. Finally, the total flow curves of three kinds of sheet materials are obtained until the concentrated instability. (4) after the flow stress curves are obtained, several different hardening functions are established to describe the curves, and the fitting results are compared. An improved Hockett-Sherby function is found to work best and the results are shown. In addition, combined with the simulation results of Q195 tensile specimen, the stress triaxial behavior of the specimen at necking stage is analyzed briefly.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：U467.14;U466

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