A gap between faces set for surface contact can exist in the initial configuration. The gap can be caused by modeling tolerance or by specifying local contact between faces.
This check box gives you the option to specify that faces set for No penetration contact behave as if a rigid body is inserted between them.
Option Unchecked. If the clearance between faces set for surface contact is less than 0.5% of the global element size, the software automatically assumes that the faces are initially in contact. Contact forces develop at points where the faces move closer to each other. If you specify a local contact between two faces that are initially more than 0.5% of the element size apart, contact forces develop only if the faces actually come into contact with each other. The flag should not be turned on when the two faces set for contact have large curvature differences.
Option Checked. The software ignores the 0.5% of the element size threshold. There is no limitation on the initial gap between faces set for surface contact. The faces can move away from each other but they cannot get any closer to each other than in the initial configuration. The faces behave as if a rigid object is inserted between each source and target.
This flag should be unchecked (default) for most applications. It is designed to take care of special situations where meshing causes part interference, even though a clearance exists between the parts as shown in the figure.
The red element generated by meshing the inner disc interferes with the blue element generated by meshing the outer plate.
To minimize the possibility of this situation, use mesh control to specify a finer mesh in contact regions with this condition. High quality meshes (parabolic elements) are recommended for all contact problems.
In the Contact Set
PropertyManager you can set a maximum value for the clearance to be ignored
when defining a contact set. This
local setting overrides the global setting in the Static dialog box.
For models containing contact sets with large
curvature differences as well as contact faces with tolerance, clear the
Ignore clearance for surface contact
check box and use mesh control to specify a finer mesh in contact regions.