Fracture types and thickness distribution in superplastic sheets formed with plastic injection molding
Journal
Materials and Manufacturing Processes
Journal Volume
16
Journal Issue
4
Pages
503-518
Date Issued
2001
Author(s)
Abstract
This paper investigated the fracture types and thickness ratio distribution in superplastic Zn–22% Al sheets formed during a hybrid process combining superplastic forming with plastic injection molding. Three types of sheet fractures (edge crack, central crack, and combined crack) were observed. The effects of using this approach on sheet molding and fracture window for various parameters, including melt temperature, injection pressure, and mold temperature, were investigated. They are presented and discussed as they relate to molding area and various fracture types. Central cracks occurred when superplastic sheets were formed by injection molding at higher melt temperature, whereas edge cracks occurred at higher injection pressure. When melt flow was parallel to the sheet rolling direction, areas of edge crack were enlarged. The sheet thickness ratio distribution was obtained for various injection parameters and rib depths. Observation of sheet thickness distribution for variation parameters, and the tendency for fracture can be generalized.
Type
journal article