Temperature Increase in Forming of Advanced High-Strength Steels Effect of Ram Speed Using a Servodrive Press

Abstract

In forming of advanced high-strength steel (AHSS), the temperature increase at die/sheet interface affects the performance of lubricants and die wear. This study demonstrates that finite-element (FE) analysis, using commercially available software, can be used to estimate temperature increase in single as well as in multiple stroke operations. To obtain a reliable numerical process design, the knowledge of the thermal and mechanical properties of the sheet as well as the tools is essential. Using U-channel drawing the thermomechanical FE model has been validated by comparing predictions with experimental results. The effect of ram speed and stroking rate (stroke per minute (SPM)) upon temperature increase in real productionlike operation have been investigated. Deep drawing of CP800 and DP590 sheets in a servodrive press, using an industrial scale die, has been studied. Thinning distribution and temperatures in the drawn part have been investigated in single and multiple forming operations. It is found that temperatures may reach several 100 deg and affect the coefficient of friction (COF). The values of COF under productionlike conditions were compared to that obtained from laboratory experiments. This study illustrates that in forming AHSS, (a) the temperature increase at the die/sheet interface is relatively high and should be considered in process design stage, and (b) the lubricant performance is significantly affected by the ram speed and sheet/die interface temperature during deformation.

A combined numerical and experimental approach for determining the contact temperature in an industrial ironing operation

“…However, the developed model did only emulate single-stroke operations. Fallahiarezoodar et al (2016) have investigated the temperature increase in the tool-workpiece interface in U-channel drawing and deep drawing for single as well as multiple strokes. They found that the maximum temperature rise in the tool-workpiece interface reached 120 ˚C in only nine strokes.…”