Law of constant volume

The law of constant volume states that the volume of a workpiece generally does not change during forming . In the case of plastic deformation of a body, there are shifts in the crystal lattice around the lattice spacing or the lattice areas are folded over into a mirror-image arrangement, but not the lattice spacing itself, so that the density of the material does not change. Accordingly, with a constant mass of the workpiece, the volume ( ) remains constant during the forming process. The following applies: ${\displaystyle V}$

${\displaystyle \!V_{0}=V_{1}=V=const.}$

When forming cast or sintered raw parts, volume changes occur due to the compression of cavities such as voids , gas bubbles or pores (see raw density ). In the metalworking industry, however, raw parts are usually made from already formed, i.e. already compressed, semi-finished products, so that here the law of constant volume can be fully applied when calculating the initial shape ( ) from the geometry of the workpiece to be manufactured ( ). ${\displaystyle V_{A}}$ ${\displaystyle V_{Wst}}$

${\displaystyle \!V_{A}=V_{Wst}}$

This formulation assumes that the total volume of the blank can be used to manufacture the workpieces. Since this is not always achievable, volume surcharges ( ) must be taken into account , for example for edge trimming on deep-drawn parts , for forging burr or for burn-off during hot forming . ${\displaystyle V_{Z}}$

${\displaystyle \!V_{A}=V_{Wst}+V_{Z}}$

literature

• Neugebauer, R. (Ed.): Forming and cutting technology. Publishing house scientific scripts, Chemnitz 2005, ISBN 3-937524-35-5