EXPERIMENTAL INVESTIGATION OF MAJOR AND MINOR STRAINS IN DIFFERENT REGIONS OF DEEP DRAWN CUPS

Drawing is one of the most important processes for forming sheet metal parts. It is used to manufacture parts in industries such as automobile, aerospace and home appliance, etc. The parts produced include cooking pans, kitchen sinks, automobile panels, gas tanks, fountain pen caps, etc. A deep drawn cup has different regions like, flange, corner radius, side walls and flat bottom. The values of stresses and strains vary throughout the cup (i.e in different regions). The objective of the present work is to perform an experimental investigation of major and minor strains in the different regions of deep drawn cups. In this work, the cups are drawn with different blank thickness and major strain and minor strain are measured in different regions of the cup. Also a comparison is made by drawing graphs between major strain(y axis) and minor strain (x axis) for cups drawn with different sheet thickness. By performing this study it will be possible to find out which region of the cup is strained maximum, hence where exactly fracture is likely to occur. Also, areas which are not stressed can be identified and in those areas, heat treatment is not necessary. It will also be possible to know which sheet thickness can take a maximum and minimum amount of stresses and strains. The material selected for this work is Brass. The diameter and heights of cups drawn are 200mm and 40mm respectively. The sheet thickness selected is 0.71, 0.8and 0.88mm. This work was carried out at Metal industries, Sanathnagar, New modern stone company, Hyderabad and metal forming lab of CBIT. The studies revealed that the die corner radius, region (neck) of the cup has maximum strain. Hence this region is the source for a fracture to take place