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*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 penalty contact analysis, it is not needed in a Mortar contact calculation. There is one required parameter PRESSURE-OVERCLOSURE. It can take the value EXPONENTIAL, LINEAR or TABULAR.

The exponential pressure-overclosure behavior takes the form in Figure 116. 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 117) simulates a linear relationship between the pressure and the overclosure. At zero overclosure the pressure is zero as well. 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 ).

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.

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 ().
- ().
- (, optional)

Following line if PRESSURE-OVERCLOSURE=TABULAR:

- pressure.
- overclosure.

Repeat this line as often as needed.

    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.

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