On The Experimental Verification Of The Numerical Simulation Based Inferences From Strain Distribution In Axisymmetric Drawn Sheet Metal Parts

Studies based on numerical simulations of axisymmetric parts showed that the scaleability of strain distribution as described above was limited to only about 60% geometric upscaling in conventional forming of a cylindrical part and to about 90% upscaling in hydroforming. These findings may be criticized as they amount to verification of the scaleability of the differential equations being solved. In this context experiments were performed on cylindrical sheet metal cups drawn to three different diameters keeping the draw ratio as well as the R/t ratio at the die entry and the punch nose constant. The meridional strain distribution was determined using GOM automatic strain measuring system. The strain distribution was fitted into a Fourier series and the variation of the Fourier coefficients with punch travel plotted for the three sizes investigated. This variation in the major Fourier coefficients was found to run parallel indicating scaleability of the strain distribution. An attempt was made to predict the strain distribution in the larger cup based on that in the smallest one. During the course of the simulation based studies, it was noticed that the sine coefficients show a sudden increase at imminent failure. This was borne out by the measured strain distribution using a uniaxial tensile sample and that from the deep drawn cups that failed during the experimentation.