Mathematical Model Describing the Hardening and Failure Behaviour of Aluminium Alloys: Application in Metal Shear Cutting Process

Abstract

Recent research has focused on sheet shear cutting operations. However, little research has been conducted on bar shear cutting. The main objective of the present investigation is to study bar shear cutting with numerical and experimental analysis. Bar shear cutting is an important operation because it precedes bulk metalworking processes for instance machining, extrusion and hot forging. In comparison to sheet shear cutting, bar shear cutting needs thermomechanical modelling. The variational formulation of the model is presented to predict damage mechanics in the bar shear cutting of aluminium alloys. Coupled thermomechanical modelling is required to analyse the mechanical behaviour of bulk workpieces, in which the combined effect of strain and temperature fields is considered in the shear cutting process. For this purpose, modified hardening and damage Johnson–Cook laws are developed. Numerical results for sheet and bar shear cutting operations are presented. The comparison between numerical and experimental results of shearing force/tool displacement during sheet and bar shear cutting operations proves that the use of a thermomechanical model in the case of the bar shear cutting process is crucial to accurately predict the mechanical behaviour of aluminium alloys. The analysis of the temperature field in the metal bar shows that the temperature can reach T = 388 °C on the sheared surface. The current model accurately predicts the shear cutting process and shows a strong correlation with experimental tests. Two values of clearance (c1 = 0.2 mm) and (c2 = 1.2 mm) are assumed for modeling the bar shear cutting operation. It is observed that for the low shear clearance, the burr is small, the quality of the sheared surface is better, and the fractured zone is negligible.