涉及各向异性和厚向应力的板料变形行为研究

发布时间：2018-01-19 11:37

本文关键词： 板料成形各向异性厚向应力成形极限本构方程屈服准则　出处：《北方工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：板料成形具有非常悠久的历史,在制造行业中占据着十分重要的地位,是很多加工工艺所无法替代的。板料的变形过程是一个十分复杂的过程,传统加工中的经验模式已经不能够适应发展越来越快的成形工艺,为了描述板料的复杂变形过程,需要建立起坚实的理论来指导加工中的板料成形过程,避免造成不要的损失。板料成形工艺所采用的材料,是经过多次轧制生产加工而成的,有些板料具有明显的各向异性,在研究这些板料的成形性能时,需要考虑板料的各向异性对屈服准则选择的影响。在研究板料成形过程时选用屈服准则要有针对性,针对不同的材料选用不同的屈服准则。对于适用的屈服准则在使用的时候也需要根据具体的材料对屈服准则进行修正。此外板料在成形过程中是处于复杂应力状态下的,不是简单的平面应力状态,还受到厚度方向的应力作用,因而在研究板料的变形时将厚度方向应力纳入屈服准则与成形极限的研究是迫切需要的。本文主要以钛合金为研究对象,通过单向拉伸实验、成形极限实验,对描述平面内各向异性的屈服准则进行修改。本文通过有实验获取4种不同厚度的钛合金的基本力学性能参数,进行有限元模型的仿真模拟,确认了厚度方向应力在板料成形过程中发挥着重要作用;通过进行数据的拟合处理,建立了更为合理的本构模型,并且通过有限元模拟验证了本构模型的适用性;从实验数据发现钛合金材料具有明显的平面内的各向异性,通过对Yld2000-2d屈服准则修改,更好的描述板料的平面内的各向异性;将厚向应力引入到屈服准则中,基于改进后的屈服准则和M-K失稳准则,对成形极限进行了理论推导,并且通过实验验证,考虑厚向应力时推导出的理论成形极限图与实验更相符。
[Abstract]:Sheet metal forming has a very long history, occupies a very important position in the manufacturing industry, which can not be replaced by many processing processes. The sheet metal deformation process is a very complex process. The traditional experience mode can not adapt to the rapid development of forming process. In order to describe the complex deformation process of sheet metal, it is necessary to establish a solid theory to guide the sheet metal forming process. The material used in sheet metal forming process is produced by rolling many times, some sheet metal have obvious anisotropy, when studying the forming property of these sheet metal. The influence of anisotropy of sheet metal on the selection of yield criterion should be considered. For different materials, different yield criteria should be selected. The applicable yield criteria should also be modified according to the specific materials. In addition, the sheet metal is in the complex stress state during the forming process. In a state. It is not a simple plane stress state, but also subjected to the stress in the thickness direction. Therefore, it is urgent to study the thickness direction stress into the yield criterion and forming limit when studying the deformation of sheet metal. In this paper, we mainly take titanium alloy as the research object, through uniaxial tensile test, forming limit experiment. The yield criterion describing anisotropy in plane is modified. In this paper, the basic mechanical properties of four titanium alloys with different thickness are obtained by experiments, and the simulation of finite element model is carried out. The thickness direction stress plays an important role in sheet metal forming. A more reasonable constitutive model is established by fitting the data, and the applicability of the constitutive model is verified by finite element simulation. From the experimental data, it is found that titanium alloy material has obvious anisotropy in the plane. By modifying the Yld2000-2d yield criterion, the anisotropy in the plane of the sheet metal can be better described. The thick stress is introduced into the yield criterion. Based on the improved yield criterion and M-K instability criterion, the forming limit is derived theoretically and verified by experiments. The theoretical forming limit diagram derived when considering the thick stress is in good agreement with the experiment.
【学位授予单位】：北方工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG301

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