Modelling the formability of various grade aluminium sheet metals

Abstract

The excellent properties of aluminium alloys such as low density, affordable cost, appropriate mechanical properties, simple fabrication process and structural integrity promote their usage in military vehicles, aeronautical industries, rail cars, marine hulls and packaging industries. In this research, the influence of tensile and formability parameters on the forming limit diagram is reported, and a model is created to predict the forming limit strains of various grades of aluminium sheet metals. The investigation is done for aluminium alloys of grades AA5052, AA6061 and AA8011 with thickness 0.8 mm, 1.0 mm and 1.2 mm in the study and experiments are conducted to construct the Forming Limit Diagram (FLD) for the above sheet metals. The study employed tensile tests to evaluate strain hardening index, strength coefficient, ductility, yield strength, ultimate tensile strength, normal anisotropy, planar anisotropy and strain rate sensitivity. The fractured surfaces of the specimen were viewed by scanning electron microscope. Using Design of Experiments (DOE), the regression modelling was done by taking the tensile properties and formability parameters as input variables and forming limit strain as the response. Regression equations were created to predict the limiting strain values in tension-tension, plane strain and tension-compression strain states. The experimentally evaluated strain values were compared with the predicted strain values which showed good agreement. Taguchiand#8223;s method of optimization was used to find the optimum values for the input variables and using these optimum values, optimum forming limit strains are found. It was found that the regression model, thus created, predicted the FLD of various grades of sheet metals by which the tedious job of experimental determination of FLD may be avoided. Further Analysis of variance newline(ANOVA) was done to find the percentage contribution of input parameters on the newlineforming limit strain. newline newline