Abstract
Nearly all forming operations have some amount of bending. Bending can cause a multitude of effect, but raising the formability is the most relevant. In a situation of bending combined with tension the occurrence of compressive fibres at the concave side creates additional stability, therefore raising the formability. This also lowers the tension force. A normal stress at the tool contact has a similar effect, albeit of smaller magnitude. Bending can also create shear, or cause inter-crystalline fracture in some materials at the convex side that obviously lowers the formability.
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Notes
- 1.
This statement is based on the general accepted assumption that in a situation of combined bending and tension indeed the mid-plane strain describes the material behaviour, but this is doubted by some authors.
- 2.
The Erichsen test, dating from 1914, is probably the oldest standardized, pure formability test. It applies equi-biaxial stretching with a punch of 10Â mm radius. The outcome has to be corrected for thickness, see for example DIN 1623 and similar specifications.
References
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© 2011 Springer-Verlag Berlin Heidelberg
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Emmens, W.C. (2011). Bending. In: Formability. SpringerBriefs in Applied Sciences and Technology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-21904-7_6
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DOI: https://doi.org/10.1007/978-3-642-21904-7_6
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