*SURFACE BEHAVIOR

Keyword type: model definition, surface interaction

With this option the surface behavior of a surface interaction can be defined. The surface behavior is required for a contact analysis. There is one required parameter PRESSURE-OVERCLOSURE. It can take the value EXPONENTIAL, LINEAR, TABULAR or TIED.

The exponential pressure-overclosure behavior takes the form in Figure 117. The parameters and define the kind of contact. is the contact pressure at zero distance, is the distance from the master surface at which the pressure is decreased to 1 % of . The behavior in between is exponential. A large value of leads to soft contact, a small value to hard contact.

The linear pressure-overclosure behavior (Figure 118) simulates a linear relationship between the pressure and the overclosure. At zero overclosure the pressure is zero as well. For node-to-face penalty contact the user has to specify the slope of the pressure-overclosure curve and the tension value for large clearances (should be small, typically 0.25 % of the maximum stress expected). The value of , which relates to the maximum clearance for which a spring contact element is generated can be specified too (default value ). For face-to-face contact only the slope of the pressure-overclosure relationship is needed.

The tabular pressure-overclosure relationsship is a piecewise linear curve. The user enters (pressure,overclosure) pairs. Outside the interval specified by the user the pressure stays constant. The value of , which relates to the maximum clearance for which a spring contact element is generated takes the value and cannot be changed by the user.

The tied pressure-overclosure behavior simulates a truly linear relationship between the pressure and the overclosure for positive and negative pressures. At zero overclosure the pressure is zero. It can only be used for face-to-face contact and similates tied contact between the slave and master face. The only parameter is the slope of the pressure-overclosure relationship.

First line:

- *SURFACE BEHAVIOR
- Enter the parameter PRESSURE-OVERCLOSURE and its value.

Following line if PRESSURE-OVERCLOSURE=EXPONENTIAL:

- .
- .

Following line if PRESSURE-OVERCLOSURE=LINEAR:

- slope of the pressure-overclosure curve ().
- (, irrelevant vor face-to-face contact).
- (, irrelevant for face-to-face contact, optional for node-to-face contact)

Following line if PRESSURE-OVERCLOSURE=TABULAR:

- pressure.
- overclosure.

Following line if PRESSURE-OVERCLOSURE=TIED:

- slope of the pressure-overclosure curve ().

Example: *SURFACE BEHAVIOR,PRESSURE-OVERCLOSURE=EXPONENTIAL 1.e-4,.1

defines a distance of length units at which the contact pressure is .001 pressure units, whereas the contact pressure at loose contact is 0.1 pressure units.

Example files: contact1, contact2.