Investigation on Forming Behaviour of Sheet Metal by Test Using Cylindrical Cup with Hole

Abstract

Nowadays, there are several grades of sheet metal used in the automotive industry. Highstrength steel sheets, particularly, have been widely used in order to reduce the weight of vehicles,which is strongly related to their fuel consumption rate. However, it is generally known that thestrength of the sheets, which is relatively higher than that of the conventional carbon steel sheets,results in their low formability. In this work, the limiting drawing ratio and forming behavior of sheetmetal that is conventionally used for automobile parts were evaluated by test using cylindrical cupwith hole. The feasibility to use limiting cup height for comparing formability of sheet metal was alsoincluded in the investigation. The sheet materials used in the experiments are aluminium, cold rolledsteel, high strength steel and advanced high strength steel. The process parameters for this study weredie corner radius and blank holder force. Workpiece materials were prepared with a circular shapeand with a diameter of 80 millimetres. In the center of the circular workpiece, a 12-millimetrediameter hole was drilled to observe the formability of each of the materials. The advantage of usingan initial blank with a hole in the center by the cylindrical cup drawing test is that the cup does notfail from changes of the thickness of material near the punch radius at the bottom of the cup. Thelimiting cup height of the investigated materials were evaluated by test using the cylindrical cup withhole. The results show that the limiting cup height values have a relationship to the limiting drawingratio values of the investigated materials. Testing using cylindrical cup with hole by evaluating thelimiting cup height value is feasible for comparing the formability of sheet metals.