A Preliminary Assessment Of The Applicability Of Image Processing For Large Strain Measurement

Abstract

The present understanding of formability in a forming process is based largely on the knowledge gained from the strain measurement. In sheet metal forming, strains or strain increments are evaluated from the shape change of grids marked previously on the surface of the workpiece. Conventional grid measurements are performed manually using a tool-maker’s microscope which is time- consuming and prone to errors. In this document, the development of an alternative strain measuring technique is discussed. A software comprising of digital image processing, visualization, and analysis is interfaced with image acquisition hardware and a SUN Sparc workstation. The system is many times faster and more consistent in obtaining strain values than contemporary methods, as demonstrated in this research. In the sheet metal forming process, the system has the potential of generating a real-time strain distribution of the material as it is being deformed. This strain distribution may then be used to evaluate the condition of the forming process. Therefore, on-the-spot corrections to forming parameters can be made during manufacture of sheet metal parts.