Construction of FLD using CGA

Abstract

Sheet metal deforms plastically into a desired shape and it depends upon the formability of sheet metal. Different strain values just before the localized failure can be described through principal strains shown in forming limit diagram (FLD). Shop floor problems in forming auto body door panels etc. can be investigated successfully using circle grid analysis (CGA). CGA is one of the important strain assessment methods for sheet metal formability through the construction of an FLD diagram. The circular grid pattern is etched over the surface of the blank and circles are deformed into ellipses during the forming operation. The circles at different places test the different circles’ deformation zone will be deformed into different size ellipses based on the forming severity. The grid circle method is one of the important strain measurement systems generally used in the sheet metal stamping process. This method provides clear knowledge of the formability of sheet metals and is only used as a research tool because of the slowness and tediousness involved in getting the results from each deformed circle. But in recent years, there is a considerable improvement in this method due to the advanced application of computers along with a solid-state camera is able to give fast and accurate results.