塑性加工过程的变形与传热耦合分析方法的实验验证

金属塑性加工过程的变形与传热耦合分析方法,是近代塑性加工理论中的前沿研究领域。至今,已提出了多种耦合计算方法,但由于技术上的困难,这些方法很少得到直接实验验证。作者在有关文献资料基础上,建立了一种金属塑性加工过程的变形与传热的有限元耦合分析方法,并编制了可在微机上实施的程序。对冷态镦粗过程进行耦合分析的结果表明,所建立的方法和编制的程序是可行的。为了检验所提出方法的可靠性,作者首次采用专门改制的铠装热电偶,精确地跟踪记录了镦粗过程中坯料内某些部位的温度变化情况。此外,还用光塑性方法获得了坯料内的应力-应变状态。理论预测结果与实验数据一致。作者所提出的方法可发展成为难变形材料热态成形过程的变形与传热耦合分析方法。

Experimental Verification of the Method for Deformation and Heat Transfer Coupled Analysis of Metal Forming Processes

The deformation and heat transfer coupled analysis of metal forming processes has become one of the frontiers of plastic-working theory. In order to present the new contributions of this paper logically, it is necessary to review concisely previous work done. The first coupled analysis of extrusion process was conducted by Altan and Kobayashi by using the upper bound approach and finite difference method1]. Obviously, the accuracy of this kind Of analysis is not satisfactory. Then, Rebelo and Kobayashi proposed a method for coupled analysis of viscoplastic forming processes based on the finite element method and applied it to isothermal forging and hot forging process of titanium alloy disk successfully 2-4]. Recently, Sun et al. performed a coupled analysis of upsetting process in Ref.5], which makes use of finding in Ref. 6]. It is worth noting that the methods for coupled analysis presented in the literature are rarely verified by experiments. The main contribution of this paper is believed to be its experimental findings. It is only after overcoming great difficulties that reliable experimental data can be gathered, especially data about temperature changes in the interior of billet under deformation. Considerable work was done on refitting armoured thermocouple. It is believed that the authors are the first to precisely trace the temperature variations of several locations during cold upsetting process. Another contribution of this paper is establishing a software system able to implement the coupled analysis in microcomputer. The computed results about the temperature changes and stress-strain state in the billet during upsetting process agree well with the observations obtained by means of refitted thermocouple and photo-plastic method.