基于损伤力学高强度钢热冲压成形极限图的预测

发布时间：2018-05-27 05:41

  本文选题：高强度钢 + 热成形　； 参考：《吉林大学》2017年硕士论文

【摘要】：材料冲压成形CAE仿真模拟时通常采用成形极限图(FLD)来评价。高强度钢热成性技术的发展决定了研究高温成形极限图的必要性。国际标准所规定的获取成形极限图的方法都是针对冷成型而言的,目前尚缺乏热成形标准。热成形延用冲压形式的冷成形试验标准,模具材料润滑度均受到限制。除此之外,高温下材料的成形性能与温度和应变率均相关,一条成形极限曲线FLC是无法评价的,需要多条成形极限曲线才能进行成形性能分析。本文提出了一种获取高温成形极限图新的试验方法—双向拉伸试验方法。设计了一种可以将单向拉伸转变为双向拉伸的装置,并且提出了一种适合高温操作环境下连接处转动的绝缘方案。本文引入损伤因子作为评判失效的参数,建立自定义材料模型,利用LS-DYNA有限元模拟拉伸过程,分别设计了获取左右两侧成形极限曲线试件形状。再利用对试件关键尺寸的设计,改变拉伸时主次应变方向材料的流动状态,进而改变应变路径,最终设计出一组试件,可以获取不同应变路径下的成形极限点。通过双向拉伸试验得到了700℃和800℃两个温度下成形极限图中等轴双向拉伸应变状态、平面应变状态、过渡应变状态等5个试验点,同时验证了新试验方法的正确性。建立了基于粘塑性损伤力学22Mn B5高温双轴损伤本构模型,利用遗传算法拟合方程中材料参数,确定了FLD预测模型。并且通过与试验数据对比,验证了FLD预测模型的有效性。本文利用FLD预测模型预测了22Mn B5在应变率为0.1/s时,600℃、650℃、700℃、750℃、800℃、850℃的成形极限曲线,预测了22Mn B5在温度为800℃下,应变率分别为0.01/s,0.1/s,1/s的成形极限曲线。随着温度的升高和应变率的降低,成形极限图FLD的位置升高,即22Mn B5板料的成形性能随温度的升高和应变率的降低而提高。
[Abstract]:Forming limit Diagram (FLD) is usually used to evaluate material forming CAE simulation. The development of high strength steel thermogenicity technology determines the necessity of studying high temperature forming limit diagram. The method of obtaining forming limit diagram stipulated by international standard is for cold forming, but there is no hot forming standard at present. The cold forming test standard for hot forming, the lubrication degree of die material is limited. In addition, the formability of materials at high temperature is related to temperature and strain rate. One forming limit curve (FLC) can not be evaluated, and many forming limit curves are needed to analyze the formability. In this paper, a new test method for obtaining the high temperature forming limit diagram, the biaxial tensile test method, is presented. A device is designed to convert uniaxial tension to biaxial tension, and an insulation scheme suitable for rotation of joints under high temperature operating conditions is proposed. In this paper, the damage factor is introduced as the parameter to evaluate the failure, and the self-defined material model is established. The tensile process is simulated by LS-DYNA finite element method, and the shape of the specimen obtained from the left and right sides of the forming limit curve is designed respectively. By designing the key dimensions of the specimen, the flow state of the material in the direction of primary and secondary strain is changed, and the strain path is changed. Finally, a set of specimens are designed to obtain the forming limit points under different strain paths. Through the biaxial tensile test, five test points such as biaxial tensile strain state, plane strain state and transition strain state in the forming limit diagram at 700 鈩，

本文编号：1940702