BUP sheet metal testing machines
The hole expansion test to KWI is a method for the determination of sheet metal forming properties and is used to understand the change in shape of a sheet metal edge.
For testing of thin sheets, specimens with a hole are clamped on the outer edges and deep drawn. The part of the specimen in front of the face of the drawing die is strained in a tangential direction until onset of cracking.
The percentage of hole expansion of the hole at crack onset is an indication of the ductility of a material under load, which is similar to that which occurs in a range of deep draw operations in cooperation with radial and tangential stresses.
The image shows the built-in tool for the hole expansion test to KWI. The die is in the middle. The light outer ring is the draw matrix, and in between is the metal sheet with the hole.