A PC-based system for automatic analysis of material flow and strains using digital image-processing

Physical modelling is an important tool for analyzing material flow and strain distributions in metal-forming processes. A common technique, utilized for plane-strain conditions, is to make use of a grid network which is printed or etched on a visible cross-section of the original workpiece. During the process the distortion of the network is studied. In this work, a PC-based system has been developed to facilitate the evaluation of the mesh and to improve the accuracy of the results. An ordinary video camera is used to record the continuous distortion of the grid. A frame-grabber, which is installed in a PC as an add-on board, is utilized to digitize the video signals. The coordinates of the network-nodes are determined automatically by a newly developed software based on image-processing techniques. By means of the so-established coordinates, the material flow and strain distributions can be followed through the whole process. Special algorithms are proposed to treat mesh images of low quality. Several methods for strain calculations are incorporated in the system, this having been done to make it possible for the user to choose the theory that is considered proper for the actual application. In order to clarify how the system works, the evaluations of two forging experiments are described in detail.