CoulombFriction

The CoulombFriction is a 1D viscous material that shall be used with for example Damper01 element.

Syntax

material CoulombFriction (1) (2) (3)
# (1) int, unique material tag
# (2) double, C
# (3) double, alpha

Theory

The stress is constant as long as the velocity is not zero.

$$\sigma =C\cdot \text{sign}\left(\dot{\epsilon }\right)\text{if~}\dot{\epsilon }\ne 0.$$

In order to avoid discontinuity, the sigmoid function is used.

$$\sigma ={\displaystyle \frac{2C}{\pi }}\cdot \arctan (\alpha \cdot \dot{\epsilon }).$$

The factor $\alpha$ is used to control the steepness of the transition region.