一种板料成形屈服准则的建立与应用

发布时间：2018-05-27 21:38

本文选题：修正函数 + 屈服准则　；参考：《北方工业大学》2015年硕士论文

【摘要】：现有的屈服准则基本上都是应力的全局变量函数,在对屈服轨迹预测时不同加载路径间会相互影响,为了提高预测的准确性现有屈服准则都是通过在原有屈服准则的基础上进行变换,或采用高次的没有物理意义的函数形式来使计算结果更加逼近试验点。本课题在八面体剪应力与加载路径有关的规律基础上对初始屈服轨迹进行分片处理,然后基于随动强化思想对Hi1148屈服准则在二维主应力空间闭合的屈服轨迹进行分片上的修正建模,以得到新的屈服轨迹,并通过常用的单向拉伸实验和双向拉伸实验来获得屈服准则的参数值,是建立各向异性屈服准则的一类新思路。针对新屈服准则中修正函数系数的求解设计了单向加载试件(单向拉伸和平面应变)、双向拉伸试件及其对应的加载方向与轧制方向成一定角度的实验方案,且所有实验方案在现有的实验条件下都可以较容易的完成。对于其他不容易得到的实验数据进行了合理假设或通过其他屈服模型计算得到。为了验证所提出的新屈服准则的可靠性和普遍适用性,本课题选取了拉压对称情况下常用的铝合金材料2024-o和5754M以及两种钢板SPEN和BH220；拉压不对称情况下的三种常见晶体金属板料：密排六方晶体(HCP)的AZ31B Mg合金、体心立方晶体(BCC)的中碳低合金钢、面心立方晶体(FCC)的2090T3铝合金,将新屈服函数计算结果与实验数据进行比较。为了研究与现有各向异性屈服准则预测结果的差异,选取了Barlat2000、Hosford针对AA6022T4、090T3、Al-2.5wt%Mg等拉压对称材料进行了计算结果的比较,选取了公认比较准确的CPB06ex02模型对AZ31B、中碳低合金钢等材料的屈服轨迹计算结果与新屈服函数计算结果进行了比较。结果表明：新屈服准则对上述材料的屈服轨迹预测结果都有较高的准确性,即满足可靠性和适用性,且与其他现有屈服准则的计算结果具有较高的一致性。在实际板料成形过程中,板料经常处于含有剪切应力的复杂应力状态中,即主应力方向与轧制方向不重合,所以在二维主应力空间中建立的屈服准则不能对该种情况进行描述,对此将所需的用于求解分片上修正函数系数的特征点实验值写成主应力方向与轧制方向所成角度的傅里叶函数,并将这种方法对各向异性参数的描述能力与Hi1148和Barlat89的计算结果进行了比较。将提出的新屈服准则编写成用户材料子程序(UMAT),嵌入到有限元仿真软件ABAQUS中,对双向加载比例分别为4：1和4：4的双拉试验进行仿真,并与实验结果进行比较,发现新屈服准则成功嵌入到有限元软件ABAQUS中,且计算结果较为准确、子程序运行稳定。
[Abstract]:The existing yield criterion is basically a global variable function of stress, and the different loading paths will affect each other in predicting the yield trajectory. In order to improve the accuracy of prediction, the existing yield criteria are based on the original yield criteria, or the higher order function without physical meaning is used to make the calculation results closer to the test point. Based on the law of octahedron shear stress and loading path, the initial yield trajectory is processed in pieces. Then, based on the following strengthening theory, the Hi1148 yield criterion is modified on the closed yield trajectory in the two-dimensional principal stress space to obtain a new yield trajectory. The parameter values of yield criterion are obtained by uniaxial and biaxial tensile tests, which is a new way to establish anisotropic yield criterion. Aiming at the solution of the modified function coefficient in the new yield criterion, the experimental scheme of unidirectional loading specimen (uniaxial tension and plane strain), biaxial tensile specimen and its corresponding loading direction and rolling direction are designed. And all the experimental schemes can be easily completed under the existing experimental conditions. Other experimental data which are not easily obtained are reasonably assumed or calculated by other yield models. In order to verify the reliability and universal applicability of the proposed new yield criterion, The AZ31B mg alloy of aluminum alloy materials 2024-o and 5754M, two kinds of steel plates SPEN and BH220, and three kinds of common crystal metal sheet: dense hexagonal crystal (HCP), are selected in this paper, which are commonly used in the case of tension and compression symmetry, such as 2024-o and 5754M, and two kinds of steel plates, such as SPEN and BH220. The new yield function calculation results of 2090T3 aluminum alloy of BCC medium carbon low alloy steel and face centered cubic crystal FCCs are compared with experimental data. In order to study the difference between the prediction results of anisotropic yield criterion and that of existing anisotropic yield criteria, Barlat200n Hosford was selected to compare the calculated results for AA6022T4090T3 / Al-2.5wtMg and other tensile and compression symmetric materials. The calculated results of yield trajectories of AZ31B and medium carbon low alloy steels are compared with the results of the new yield function. The results show that the new yield criterion has a high accuracy in predicting the yield trajectories of the materials mentioned above, that is, it satisfies the reliability and applicability, and is in good agreement with the calculated results of other existing yield criteria. In the actual sheet metal forming process, the sheet metal is often in the complex stress state with shear stress, that is, the principal stress direction does not coincide with the rolling direction, so the yield criterion established in the two-dimensional principal stress space can not describe this kind of situation. For this reason, the experimental results of the characteristic points used to solve the coefficients of the correction function on the chip are written as Fourier functions of the angle between the principal stress direction and the rolling direction. The ability of describing anisotropic parameters by this method is compared with that of Hi1148 and Barlat89. The new yield criterion is programmed into user material subprogram and embedded into the finite element simulation software ABAQUS. The double tension test with bidirectional loading ratio of 4:1 and 4:4 is simulated, and the results are compared with the experimental results. It is found that the new yield criterion is successfully embedded in the finite element software ABAQUS, and the calculation results are more accurate and the subprogram runs stably.
【学位授予单位】：北方工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG381

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