Development of Nakazima Test Simulation Tool for Forming Limit Diagram Generation of Aluminium Alloys

Sreenath Kumar, J Jeyasingh, Amjith
2015 unpublished
In sheet metal forming processes, plastic instability may occur, leading to defective products. In order to manufacture defect free products, the prediction of the forming limits of sheet metals is a very important issue. In this study, FLD's are predicted by simulating Nakazima test using finite element software Pam-Stamp 2G. For this purpose Finite Element Model (FEM) for Nakazima test is established. Then the credibility of Nakazima test simulation tool is established. INRODUCTION Sheet
more » ... ODUCTION Sheet metal forming is the process of converting flat sheet of metal into a part of desired shape without fracture or excessive localized thinning. The application of sheet metal forming includes automotive industry, aerospace industry, household equipment"s and many more. Forming Limit Diagram (FLD) is used during the design stage of any new sheet metal component for tooling shape & optimizing variables. It is nothing but a combination of major & minor strain. The Forming Limit Diagram (FLD) is a widely used concept to represent the formability of thin metallic sheets. To control the operation of sheet metal forming without failure, a diagram is used in which the safe, critical and failure forming regions are shown. This diagram is known as the Forming Limit Diagram (FLD) or the Forming Limit Curve (FLC). In sheet metal industry and studies, it is widely used and considered as one of the important tool to determine the formability of sheet metals. Every sheet metal has its own forming limit diagram which determines its formability, strain limit and forming regions. Forming limit diagram is a representation of the critical combination of the two principal surface strains major and minor above which localized necking instability is observed, illustrated in Fig 1. For varying strain ratios, from pure shear to equibiaxial tension, the forming limit curve is plotted. When the strain ratio is positive, in other words where minor strain is positive, it means stretching is observed. In case of negative strain ratio, in other words negative minor strain, one can conclude that drawing is observed. It should also be noticed that the strains plotted are true strains.