某车用铝合金动态力学性能及其断裂失效行为研究

发布时间：2018-06-18 16:21

本文选题：应变率 + 流动应力　；参考：《宁波大学》2017年硕士论文

【摘要】：铝合金板材是车身轻量化最重要的材料之一,本文选用A6C16-T4铝合金作为研究对象,通过大量实验分析研究应变率对该铝合金流动应力的影响以及应力三轴度对该铝合金断裂失效行为的影响。其主要内容为:首先,本文通过准静态单轴拉伸实验和动态冲击拉伸实验分析研究了应变率对A6C16铝合金力学性的影响。结果表明:A6C16铝合金有着良好的塑性变形能力,在不同应变率范围内应变率对其力学性能有着不同的影响,当在较低应变率(0.00033~0.033s~(-1))条件下抗拉强度会随着应变率的增加有一定的减小。在中等应变率条件下该铝合金表现出正相关,随着应变率的增加,其屈服强度和抗拉强度也发生相应的增加;随着应变率的增加该合金的断裂应变会有所增加,应变率可以提高该合金的塑性变形能力,但是断裂强度随着应变率的升高不会有太大的变动。基于Johnson-Cook简化本构模型,建立该铝合金的率相关塑性变形本构模型,最后利用有限元软件LS-DYNA对动态冲击拉伸实验进行数值仿真,仿真结果与实验结果吻合良好。其次,本文通过平板实验、剪切实验、缺口实验、开孔实验得到试样断裂位置处2mm标距段的应变,分析研究了应力三轴度对A6C16铝合金断裂失效应变的影响,并利用有限元软件对以上试样进行仿真验证各个试样的应力三轴度。结果表明:试样所受应力状态对A6C16铝合金断裂失效应变有着较大的影响。剪切实验应力三轴度接近零,其剪切断裂应变可达95.17%,随着应力三轴度的增加断裂失效应变逐渐减小,当三轴度达到0.48时,降至最低约为46.32%。随后,断裂失效应变又随着三轴度的增加而增加。最后利用有限元软件LS-DYNA对上述实验进行数值仿真,仿真结果与实验结果吻合良好。最后,本文通过有限元软件LS-DYNA对穿孔实验进行有限元数值仿真计算,验证了材料模型参数。仿真结果与实验结果有着较高的吻合度,并且试样变形过程以及断裂形状类似,本文所得到的材料参数可以直接运用于整车碰撞有限元数值仿真计算中。
[Abstract]:Aluminum alloy sheet is one of the most important materials for body lightweight. In this paper, A6C16-T4 aluminum alloy is selected as the research object. The effect of strain rate on the flow stress of the aluminum alloy and the effect of stress triaxiality on the fracture failure behavior of the aluminum alloy were studied by a large number of experiments. The main contents are as follows: firstly, the effect of strain rate on mechanical properties of A6C16 aluminum alloy was studied by quasi-static uniaxial tensile test and dynamic impact tensile test. The results show that the weight A6C16 aluminum alloy has good plastic deformation ability, and the strain rate has different influence on its mechanical properties in different strain rate range. The tensile strength will decrease with the increase of strain rate when the strain rate is lower than 0.00033 ~ 0.033 s-1 ~ (-1). The yield strength and tensile strength of the alloy increase with the increase of strain rate, and the fracture strain of the alloy increases with the increase of strain rate. The strain rate can improve the plastic deformation ability of the alloy, but the fracture strength does not change greatly with the increase of the strain rate. Based on the Johnson-Cook simplified constitutive model, the rate-dependent plastic deformation constitutive model of the aluminum alloy is established. Finally, the dynamic impact tensile experiment is simulated by the finite element software LS-DYNA, and the simulation results are in good agreement with the experimental results. Secondly, the strain of 2mm distance at fracture location of A6C16 aluminum alloy is obtained by plate test, shear test, notch test and open hole test. The effect of stress triaxiality on fracture failure strain of A6C16 aluminum alloy is studied. The stress triaxiality of each specimen is verified by finite element software. The results show that the stress state of the specimen has great influence on the fracture failure strain of A6C16 aluminum alloy. When the triaxiality of shear stress is close to zero, the shear fracture strain can reach 95.17. With the increase of triaxiality of stress, the failure strain of fracture decreases gradually, and when the triaxiality reaches 0.48, the minimum is about 46.32. Subsequently, the fracture failure strain increases with the increase of triaxiality. Finally, the numerical simulation of the experiments is carried out by using the finite element software LS-DYNA, and the simulation results are in good agreement with the experimental results. Finally, the finite element simulation of the perforation experiment is carried out by the finite element software LS-DYNA, and the parameters of the material model are verified. The simulation results are in good agreement with the experimental results, and the deformation process and fracture shape of the samples are similar. The material parameters obtained in this paper can be directly applied to the finite element numerical simulation of vehicle collision.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21

【相似文献】