Hertz-Mindlin Nassauer-Kuna model

The Hertz-Mindlin Nassauer-Kuna model is a modification of the Hertz-Mindlin model.

The effective radius is calculated using the Nassuaer-Kuna formula:
RNK=Vπd2
Where V is the overlap volume and d is the penetration depth. The effective radius, RNK is used to determine the equivalent radius, R* which is substituted into the Hertz-Mindlin formula as follows:
Fn=43E*R*1/2d3/2

All forces are multiplied by the correction factor of 0.62/0.752 specified in Nassauer, B., 2013, and is defined as:

fn=(0.620.752)(43)E*RNKd3/2