Erichsen cupping test
Erichsen cupping test: Sheet metal is stamped with a ball punch until a crack forms. Measures stretch formability and deep drawability.
Physical-Chemical Mechanism of Action
A punch with a spherical cap is pressed into the sheet, stretching and indenting the material. The process is continued until a crack appears. This test shows the maximum formability (stretch-formability) and the depth to which the sheet can be pressed without breaking.
Metallurgical Relevance & Welding Risks
A low Erichsen cupping test value indicates low formability and potential difficulties in deep drawing. This can lead to cracks or breakage if the sheet is stretched too much. A high test value indicates good formability and deep drawability.
Workshop Practice & Action Guidelines
• Use a punch with a spherical cap.
• Press the sheet continuously until a crack appears.
• Measure the maximum depth of the crack in millimeters (mm).
• A value above 2.5 mm is normally acceptable for many applications.