Effect of size, shape and distribution of surface defects on the forming of aluminum sheet

The research was conducted on samples of aluminum sheet with 1 mm thickness, annealed at (275 C). To examine the effect of the size of surface defects on the stretch forming by introducing defects of different sizes on the surface of the sheet before forming process .Then forming the samples using a hemispherical punch without lubrication up to the fracture point. It was found that the defects size have a big effect on the fracture initiation and its propagation. The same result was found for the defect shape. Also the defect distribution was studied, where the defects distribution shows big effect on fracture position, which gave a clear picture of the forming is concentrated. Giving the opportunity to control forming and reduce the fracture.Keywords: Aluminum, Stretch forming, Surface defects