Designing a strain measurement system based on circle grid analysis for sheet metal forming applications

Abstract

For characterizing formability of sheet metals, circle grid analysis is used as an experimental means of measuring forming strains in stamped sheet metal parts. This method involves etching a pattern of circle grid with known dimensions on sheet metal before forming operation, and measuring the new dimensions of the deformed circles after forming operation. The etching process is usually conducted through an electrochemical material deposition. While electrochemical marking systems are available commercially, they could be pricy depending on the specifications. For educational and research needs of the department, a team of undergraduate students is assigned to design and prototype a cost effective electrochemical marking system for strain measurement application in a senior design framework. The design project is defined with certain design requirements and design constraints, which match with the industry standards. The learning objectives of the project are articulated from the start. The design team put into practice their knowledge of circuit analysis to simulate, design and prototype the circuitry that etch circle grid on sheet metal as desired for strain measurement. The principles of electrochemical deposition are also considered for design purposes. A prototype is built and tested successfully to the specifications. A transparent ruler is designed based on definition of true strain for strain measurement. In this paper, the learning objectives and learning outcomes of the projects are discussed.