The investigation of the effect of temperature on limit drawing ratio in angular deep drawing dies

The deep drawing process has very wide applications. For that reason, it is one of the most important metal forming process in industry. It is difficult to shape metals such as Al, Mg, and Ti alloys with features of high strength and low forming ability at especially room temperature. The deep drawing investigations have been recently accelerated in order to eliminate these problems. In addition to the temperature, such as the shape and geometry of the die, the mechanical features of the material, the dimensions and geometry of blank, the friction and lubrication between the die-blank-blank holder, the blank holder force and the die cavity have been effecting the process directly. Therefore, it's important to choose the appropriate process conditions for the productivity of the method. In this study, the effects of the forming temperatures, die/blank holder angles and blank holder force on the limit drawing ratio, the punch force, the wall thickness and hardness distribution were investigated both experimentally and numerically in angular deep drawing of cylindrical cups. For this purpose, tests were conducted by giving 0°, 5°, 10° and 15° angles to die/blank holder surfaces at room temperature, 100°C, 175°C and 250°C temperatures. The EN AW-5754 (AlMg3) sheet metal parts in 1 mm in thickness were used as the target material. MoS2 (3-4 µm) was used as a lubricant for the purpose of reducing friction between surfaces. The punching forces during deep drawing operations were recorded by a load cell conducted on the forming axis with 10-1 second intervals. A micrometer in 10-4 mm resolution was used to measure the variations in the wall thickness of the cups. The hardness of the samples was measured by applying a force of 200 g (HV 0,2 kgf) through the rolling direction. The experimental results were also modeled using finite element method. eta/Dynaform computer package program was used for this purpose. Full factorial experimental design method was used to collect the data. The eta/Dynaform results were compared with experimental findings. As a result, it was observed the positive effects on the limit drawing ratio, wall thickness, punch force, and the hardness distribution of the warm deep drawing. It was found out that when the limit drawing ratio was increased from 2,14 to 2,80; the distribution of wall thickness was became more homogeneous and the hardness value of the cup was decreased with the increasing temperature. The FEM model results were in a good agreement with the experimental results. The experimental results were statistically evaluated by analysis of variance (ANOVA) method. Keywords: Warm Deep Drawing, Hardness Distribution, Angular Deep Drawing, Limit Drawing Ratio, Finite Elements Method, ANOVA.