冲击液压载荷作用下管材动态塑性本构关系的研究

发布时间：2018-01-22 00:56

本文关键词： 液压成形冲击本构关系遗传算法有限元模拟　出处：《桂林电子科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：基于轻量化和一体化特征开发的管材液压成形技术(THF),具有成本低、成形零件质量好、节约材料等优点,正获得快速发展。然而,在实际生产应用中发现,THF存在制造过程繁琐、成形难度大、成形效率较低等缺点。冲击液压成形(Liquid Impact Forming,LIF)是在液压胀形和冲压成形基础上发展起来的一种新型复合成形技术,它利用压力机上下模具闭合时的径向压管运动,使管材内部液体自发产生内压力而快速填充模具型腔,完成胀形过程,以此甩掉复杂的液压系统而大幅降低管材成形的成本和周期。高精度的管材塑性本构关系不仅对管材成形机理的分析具有重要影响,而且是有限元数值模拟的重要前提。因此,本文对冲击液压载荷作用下管材的动态塑性本构关系进行研究具有重要意义。本文研究的主要内容包括:(1)分析本构关系的基础理论和材料的应变速率响应,根据管材冲击液压成形的受力条件,选定管材冲击液压成形的动态塑性本构模型。(2)对SS304不锈钢管材进行不同速度的冲击液压成形试验,通过应变在线测量系统对管材胀形区的动态变化数据进行在线测量,根据试验数据计算轮廓上的轴向曲率半径和周向半径。(3)基于上述试验变形数据,先用一般线性回归法,求解两种本构模型的参数;然后研究根据遗传算法的收敛特点,求解管材冲击液压条件下的两种塑性本构关系。(4)基于DYNAFORM和ANSYS Workbench联合仿真,建立管材冲击液压成形的有限元模型,分别将线性回归法和遗传算法得到的管材塑性本构关系作为材料模型,对管材冲击液压成形过程分别进行有限元模拟,通过试验结果与模拟结果的对比,来检验所构建出冲击液压成形条件下管材的动态塑性本构关系的精度。研究表明:(1)本文提出的动态塑性本构关系,从应变速率角度研究冲击载荷作用下金属薄壁管准确的塑性本构关系。通过模拟结果与试验结果对比,表明本文构建的动态塑性本构关系具有较高的精度。(2)根据模拟结果的最大胀形高度与试验的结果对比,可以定量地得出J-C本构模型最大误差范围在7.43%以内,F-B本构模型最大误差范围在8.65%以内,表明J-C本构模型更适合描述管材冲击液压胀形时的塑性硬化关系。(3)根据验证结果,线型回归法确定的本构模型误差均大于遗传算法确定的本构模型的误差,表明遗传算法具有稳定且快速收敛的优点,能够在变量空间中找出包含最优解和极值的单峰值区域并搜索最优解,在拟合复杂目标函数时具有明显优势。(4)随着冲击速度的提高,仿真结果的误差逐渐减小,表明本文确定的动态塑性本构关系适应于冲击速度较大的管材液压成形。本课题研究成果提供了一种冲击液压载荷作用下管材动态塑性本构关系的构建方法,对LIF的其他研究和有限元模拟具有一定的借鉴和指导作用。
[Abstract]:The tube hydroforming technology based on lightweight and integrated features is developing rapidly, which has the advantages of low cost, good quality of forming parts and saving materials. It is found that the manufacturing process is cumbersome, the forming is difficult and the forming efficiency is low in the practical application. The impact hydroforming is liquid Impact Forming. Lif is a new compound forming technology developed on the basis of hydraulic bulging and stamping forming. It utilizes the radial pressure tube movement of the upper and lower die closure of the press. The liquid inside the tube spontaneously produces the internal pressure and fills the mold cavity quickly to complete the bulging process. In this way, the cost and cycle of tube forming can be greatly reduced by getting rid of the complicated hydraulic system. The high precision plastic constitutive relation of pipe not only has an important influence on the analysis of forming mechanism of pipe. And it is an important premise of finite element numerical simulation. In this paper, it is of great significance to study the dynamic plastic constitutive relations of pipes under hydraulic impact loading. The main contents of this paper include: 1). The basic theory of constitutive relation and the strain rate response of materials are analyzed. According to the stress condition of pipe impact hydroforming, the dynamic plastic constitutive model of pipe impact hydroforming was selected. The dynamic change data of tube bulging region are measured online by the strain on-line measurement system. Based on the experimental data, the axial curvature radius and circumferential radius on the profile are calculated. (3) based on the above experimental deformation data. First, the general linear regression method is used to solve the parameters of the two constitutive models. Then according to the convergence characteristics of genetic algorithm. The two kinds of plastic constitutive relation under hydraulic pressure condition of pipe impingement are solved. The simulation is based on DYNAFORM and ANSYS Workbench. The finite element model of tube impact hydroforming is established. The plastic constitutive relation of pipe obtained by linear regression method and genetic algorithm is taken as the material model, respectively, and the process of tube impact hydroforming is simulated by finite element method. By comparing the experimental results with the simulation results, the accuracy of the dynamic plastic constitutive relationship of the pipe under the condition of impact hydroforming is tested. The study shows that the dynamic plastic constitutive relation proposed in this paper is the first. The accurate plastic constitutive relationship of metal thin-walled tubes under impact loading is studied from the strain rate angle. The simulation results are compared with the experimental results. It is shown that the dynamic plastic constitutive relationship constructed in this paper has a high accuracy. (2) the maximum bulging height of the simulation results is compared with the experimental results. The maximum error range of J-C constitutive model is within 7.43% and the maximum error range of F-B constitutive model is 8.65%. The results show that J-C constitutive model is more suitable to describe the plastic hardening relationship of pipe under hydraulic bulging. The error of constitutive model determined by linear regression method is larger than that of constitutive model determined by genetic algorithm, which indicates that genetic algorithm has the advantages of stable and fast convergence. The region of single peak value including the optimal solution and extreme value can be found in the variable space and the optimal solution can be searched. It has obvious advantage in fitting the complex objective function with the increase of the impact velocity. The error of simulation results decreases gradually. The results show that the dynamic plastic constitutive relationship is suitable for the tube hydroforming with high impact speed. This paper provides a method to construct the dynamic plastic constitutive relationship of the pipe under the impact hydraulic load. It can be used for reference and guidance to other LIF research and finite element simulation.
【学位授予单位】：桂林电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG306

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