Simplified Formability Analysis for Die Development and Production Troubleshooting

Formability analysis of automotive body stampings has typically employed use of circle grid analysis (CGA) techniques. These methods are widely accepted by users and suppliers throughout the industry. Although a proven means of measuring sheet metal deformation, the CGA methodology is not without drawbacks. Utilization of thickness strains to determine formability both compliments CGA and simplifies strain analysis. Using the constant volume equation, a four-step approach to thickness strain analysis (TSA) is provided. Differences between original and final thickness can be readily converted to strain readings and plotted on developed thickness strain diagrams (TSD). Also presented is a case study which illustrates effective TSA techniques during tooling development to ensure an adequate part safety margin.

This alternative technique to formability analysis offers many benefits over traditional CGA methods. Some of these include: ease of understanding, improved reproducibility, less time consumed, and less labor intensive. The advantages of using thickness strains have the potential to directly impact sheet metal formability and design via increased acceptance and understanding by tool and die makers and engineers.