Evaluation and study of formability characteristics of sheet metals through stretch-bend test

Abstract

Manufacturing is the lifeline of all industrial societies. As manufacturing processes are varied understanding of competitive nature of processes is essential. A necessary requirement in this respect is appropriate measure of performance. Some of the common operations which come under Sheet metal Forming are bending, roll bending, contour forming, stretch forming, creep forming, straight stretch forming, spinning, deep drawing, explosive forming etc. The concept of formability provides us with one such measure. Formability is not easily quantified as it depends on several interacting factors. It is conceivable that a given sheet metal could be formed successfully into a particular component or lead to failure depending upon the process conditions and the tooling used. Stretch-bend formability test a sheet metal is deformed in centre by a wedge shaped punch into the sheet (clamped fully) the test is continued until fracture takes place. Punch to die throat diameter clearance is high. The depth of penetration at the instant when load reaches its maximum is used as the formability Index. The test was conducted dry without use of any lubricant. The features of the test are it measures the capability of sheet materials to be stretched before fracture, It has good consistency, easy to perform, ability to simulate desired forming mode is good. In this test aluminum and steel alloys are used with different thickness and formability index is evaluated. The study on effect of punch nose radius on maximum load and depth of deformation is used for study of formability characteristics.