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1、分类号 密级 UDC 编号 硕 士 学 位 论 文高速冷打热力耦合作用下成形机理研究学 位 申 请 人： 朱文娟 指 导 教 师： 崔凤奎 教授 学 科 专 业： 机械制造及其自动化 学 位 类 别： 工学 2013 年 5 月摘 要I论文题目： 高速冷打热力耦合作用下成形机理研究 专 业： 机械制造及其自动化 研 究 生： 朱文娟 指导教师： 崔凤奎 摘要高速冷打成形关键理论研究是冷打成形技术发展的迫切需求。高速冷打成形是一个多因素耦合作用下的复杂成形过程，目前对冷打成形进行的研究都是基于纯力学和材料学角度，没有涉及冷打过程中产生的热效应，而热效应引起的工件内部不均匀的温度场将影响工件金属的
2、流动性，进而对成形零件质量和性能产生影响。为此，本文采用理论分析、数值模拟和试验研究相结合的方法，对高速冷打热力耦合作用下成形机理进行系统的研究，以提高其成形零件的使用性能和表面质量，主要研究内容和结果如下：分析了高速冷打热力耦合形成过程，基于连续介质力学理论建立了高速冷打成形过程中工件塑性耗散的热传导能量方程式，给出了方程式的求解方法。得出冷打成形过程中产生的热量主要是由于工件不可逆塑性变形功的热耗散和工件、滚打轮截面摩擦生热；高速冷打成形过程中产生的热耗散能依赖于工件材料的塑性变形本构方程。进行了 40Cr 调质钢常温条件下、应变速率为 0.004s-1 的静态实验和温度为204000C、
3、应变速率为 6325160s-1 的动态实验，分析了温度和应变速率对流动应力的影响及动态实验中产生的绝热温升。得出 40Cr 调质钢具有较强的应变速率和温度敏感性；确立了描述 40Cr 调质钢流动应力的本构方程，拟合得到了本构方程中的相关参数；分析了 40Cr 调质钢流动应力本构方程与实验数据的相关性，得出所确立的本构方程可以较好地描述 40Cr 调质钢在不同温度和应变速率下的流动应力。建立了高速冷打热力耦合有限元分析模型，实现了冷打成形过程的可视化，分析了工件几何构形的变化、等效应力场、等效应变场和温度场的分布情况。得出工件表面两侧的突起、中间凹陷是由金属的体积不可压缩性和金属流动符合最小阻
4、力定律共同完成的；工件的温度分布和等效塑性应变分布是不均匀的：剧烈变形区的等效塑性应变高，温升高，难变形区的等效塑性应变低，温升低。对比分析了考虑热效应和不考虑热效应等效应力、等效应变和接触力的分布情况。得摘要II出高速冷打成形过程中热力耦合作用的实质是能量的转化，揭示了高速冷打成形过程中的热力耦合形成机制。分析了本构方程、滚打轮形状、工件形状、摩擦系数和滚打轮转速对冷打成形过程中等效应力场、变形场、温度场、接触力及成形尺寸的影响规律。得出材料参数是影响冷打成形件的重要因素，存在一个最佳转速，使成形件质量和性能最优，为工艺参数的优化、成形工件质量预测与控制提供了依据。关 键 词：高速冷打，热力
5、耦合，本构方程，有限元论文类型：应用基础研究 本文的研究得到了国家自然基金项目(项目编号：51075124、50975229)的资助。摘要IIISubject: Study on forming mechanism coupled thermo-mechanicsof cold rolling Specialty: Machine Manufacture and Automation Name: Zhu Wenjuan Supervisor: Cui Fengkui ABSTRACTKey theoretical study of high-speed cold rolling is of u
6、rgent need in the development of high-speed cold rolling forming technology. High-speed cold rolling is a complex plastic forming process under coupled effects of multi-factors. Current research is based on pure mechanics and material angle; thermal effects are not involved in the cold rolling formi
7、ng process. While non-uniform temperature caused by thermal effects affects metal flow of the work piece, thus the quality and performance of forming part is affected. Therefore, in this paper, in order to improve the quality and performance of forming parts, a systematic investigation on forming me
8、chanism coupled thermo-mechanics of cold rolling was carried out using numerical simulation, combined with the analytical and experimental methods. A brief introduction to the project and its main achievements are as follows:High-speed cold rolling forming process under thermal-mechanical coupling w
9、as analyzed. Based on the theory of continuum mechanics, the energy equation of heat conduction of plastic dissipation in forming process was established. Solving method of the equation was given. The heat produced in the forming process mainly due to the irreversible heat dissipation of plastic def
10、ormation and friction heat caused by the work piece and roller section. The heat dissipation of the process depends on the plastic deformation constitutive equation of work piece material.The thermo-mechanical responses of 40Cr under uniaxial compression loading were presented. The strain rates incl
11、ude quasi-static (0.004s-1) at temperature of 200C and dynamic loading regime (6325160s-1) at temperature regime (204000C). The influence of temperature and strain rate on flow stress and the adiabatic temperature rise in dynamic experiment were analyzed. Significant strain rate and temperature sens
12、itivity were measured. Constitutive model was established to predict the mechanical behavior of the 40Cr over wide ranges of strain rate and temperature. Parameters of constitutive model were obtained. Correlations with the established model were shown very close to 摘要IVthe observed responses. The e
13、stablished model can preferably describe the effect of strain hardening, strain rate and temperature of 40Cr quenched and tempered steel.High-speed cold rolling coupled thermo-mechanical finite element analysis model was established, realized the cold rolling forming process of visualization. Analys
14、is the work piece geometry configuration changes, the equivalent stress field, the distribution of equivalent strain field and temperature field. It is found that the protruding of the work piece on both side and the middle sag is due to the volume incompressibility of metal and metal flow conforms to the law of least resistance. Temperature and equivalent plastic strain distribution of work piece is uneven. Temperature rise of severe equivalent plastic strain area is high while temperature rise of difficult equivalent plastic strain zone is low
