Energy-efficiency increase through hybridization of solid forward extrusion with electrical resistance heating - Modeling the contact between electrodes and workpiece

研究的重点是WZL开发的杂交热固正向挤压工艺。在该工艺中，工件在成形过程中通过电阻加热进行加热。由工艺的性质决定，局部加热发生在易受内部v形裂纹影响的区域。这导致了一个更高的能源效率相比，传统的温固体前挤压工艺。到目前为止，混合热固体正向挤压引起的能源效率的提高还不能在工业上使用。这有两个原因。首先，由于工件与冲床接触区域以及工件与反冲床之间复杂的叠加电热机械现象，加热时间会产生很大的波动。这些都大于典型的冷固体正挤压工艺时间。其次，对于接触区域的工具侧，以表面粗糙度变化和边际质量损失的形式观察到烧断。烧蚀降低了刀具的使用寿命。高，波动的加热时间以及烧断导致过程稳定性降低。本研究旨在广泛地解释冲床、反冲床和工件接触系统中的电热-机械相互作用。这方面的知识，使接触系统的全面推导与较短的加热时间和减少燃烧。

Focus of examination is the hybridized warm solid forward extrusion process developed at WZL. In this process the workpiece is heated during forming through resistance heating. Determined by the nature of the process local heating takes place in the area susceptible to inner chevron cracks. This results in a higher energy-efficiency compared to the conventional warm solid forward extrusion processes. As of now the effects within the hybridized warm solid forward extrusion causing increased energy-efficiency cannot be used industrially. There are two reasons for this. Firstly, due to complex superimposed electro-thermal-mechanical phenomena in the contact area between workpiece and punch as well as workpiece and counterpunch highly fluctuating heating-up times occur. These are greater than typical cold solid forward extrusion process times. Secondly, as for the tool-side of the contact area a burn-off is observed in the form of a changing surface roughness and a marginal mass loss. The burn-off reduces the tool lifetime. The high, fluctuating heating-up times as well as the burn-off result in a reduced process stability. This research aims at extensively explaining the electro-thermal-mechanical interactions within the contact system of punch, counter punch and workpiece. This knowledge enables the comprehensive derivation of a contact system with shorter heating-up times and reduced burn-off.