Sheet metal formability analysis by accessible and reliable digital image correlation system

The automotive industry is characterized by being a large consumer of stamped parts and by always looking for improvements in this process, aiming for more efficient products. This is since the vehicle body, basically made up of stamped parts, is highly representative of the total mass of the car, its safety, and drivability. Better results in stamping processes, however, can be achieved through better knowledge of the variables that affect the process, whose information base is still quite deficient in industries in general. Another important way to improve the processing of stamped parts is the development of more efficient materials, which have been evolving since the emergence of advanced high-strength steels (AHSS). Therefore, studies that make the effects of stamping tool parameters on the formability of metal sheets more understandable are of great relevance and are being carried out. However, more sophisticated techniques for monitoring the plastic deformation limit of sheets and the generation of more technological data are also essential. An existing technological resource for this is digital image correlation (DIC) systems, which are highly accurate and expensive. Thus, the present work aimed to develop a DIC system, initially implemented in a Nakazima stamping testing tool, to improve the analysis of the stampability of sheet metal, with possible application to tools in the industry. For this, high-resolution commercial cameras and open-source software were used, since, in addition to precision, the low cost of the system was also one of the objectives of the work. Thus, a sequence of stamping tests was carried out with BH220 steel, 1.5 mm thick, to capture images, which were later processed in software to graphically represent the deformations on the image of the stamped test piece. According to the results achieved, it was possible to attest to the efficiency of the developed DIC system, which proved to be very effective and practical for analyzing the deformations of metal sheets subjected to the Nakazima test.