Sharif Digital Repository

Knowing the magnitude of the maximum strain before necking is of utmost importance in the processes of designing sheet metals. Thus, numerous experimental and theoretical efforts have been done to answer these questions. In order to predict allowed strains in biaxial stretching, an experimental diagram was introduced called “Forming Limit Diagram” in which major strain is plotted versus minor strain and if the corresponding point to the strain on the sheet is higher than this diagram, necking will occur. One of the most popular methods of obtaining forming limit diagrams is using a hemispherical rod for shaping sheet, which is named as “Nakazima Test” and then the critical strains are...