PREDICTION OF LIMITING DRAW RATIO (LDR) BY USING FINITE ELEMENT METHOD (FEM) BASED SOFTWARE SIMULATIONS

Deep drawing process of sheet metal is mostly used for cup shape forming. For cup shape forming a limiting value of blank diameter, for which value we can successfully draw a cup. If the punch diameter, efficiency factor and all the process parameters are fixed, and we increase that value of blank diameter, then the limit value of failure can be obtained. The ratio of maximum blank diameter which is successfully drawn to the punch diameter is called LDR (Limiting Drawing Ratio). Analytically we can find out the value of LDR. We can find out the value of LDR also from Experiments. But there is a big difference between the analytical value and experimental value. The value of LDR is also find out by the software simulation of deep drawing process and this value is very close to the experimental value of LDR. So with the help of simulation we can predict the value of LDR, which can reduce the experimental set up cost. We are using RADIOSS software for FEM simulation of deep drawing process. The work presented in this paper focuses on the concept of deep drawing. All the materials considered are elastic. The material used is AE_J2340_CR_210A_Dent_Resist. The software used for the simulation and analysis is RADIOSS software. For the analysis, constant process parameters like punch speed; blank holding force, punch travel and friction co-efficient have been considered. On these parameters different blank diameters, within 0.5 mm interval, have been considered in order to find out various safe, marginal and failure conditions for different materials respectively. In this simulation, the displacement of material under deep drawing of cup shape, plastic strain on different sections of the cup and % age thinning have been analyzed. Safe value, marginal value and the failure limit of various materials with different diameters taking into consideration have been observed. It has also been observed that the zone of minimum displacement (dark blue color of the displacement diagram) varies from higher to lower progressively safe condition towards failure condition. And this dark blue zone goes on decreasing progressively. With the help of this paper, it has been shown that the value of LDR by simulation is very close to value obtained of LDR by experimental value (published data). With the value of LDR, the failure condition of different materials in deep drawing process has been predicted.