In order for loads to be transferred between elements, the nodes must be connected together. For example, if two bodies begin an analysis separated, no interaction will occur during the analysis. The bodies will pass through each other.
Use Surface-to-surface contact in Mechanical Event Simulation and nonlinear stress analysis (but not natural frequency analysis) to create pairs of surfaces that may come into contact with each other during the analysis thereby connecting the nodes on the surfaces together. The processor will determine the distance between the nodes on these surfaces at each time step of the analysis. When the nodes are sufficiently close to each other, a force will be applied to prevent penetration.
Before the user starts a contact analysis, he or she must clearly identify where the contact interaction might occur during the analysis. (Although possible, it would be very inefficient to define every part, every surface as contacting every other part, every surface.) Not only could multiple target surfaces interact with one master surface, but self contact is also possible in a large deformation problem such as a rubber elasticity analysis. In such cases, the user must define multiple contact pairs that cover all potential contact interaction.
The contact pairs can consist of any two arbitrary surfaces. Surface-to-surface contact will connect the nodes on one surface to the faces of the other surface (and optionally vice versa). However, to speed up the contact search, the user should only specify the contact pairs that will definitely interact within the given event duration. Especially in problems that involve small amounts of sliding contact, the analysis will converge more rapidly if the number of contact elements is minimized. This can be achieved by specifying a contact radius, which will ensure that all generated contact elements have a length that is initially shorter than the contact radius. Provided the contact radius is larger than the distance the parts move relative to each other, contact will be maintained over the entire range of motion.
To define where contact can occur, put the surfaces to come into contact on a unique surface number, namely, the highest surface number of any of the lines making the elements that come into contact. To determine which of the six possible sides of a brick element are in contact, the solver checks the surface number of each line making an element. Each face that has a majority of these lines (3 of 4 sides, or 2 of 3 sides) on the highest surface number can participate in contact. Faces whose lines are not on the highest surface number on the element cannot participate in contact.
For cases where it is difficult for the user to predict the relative motion of contact pairs, the processor provides an automatic updating scheme to help the user set up the contact pairs efficiently with only a few contact surfaces covering the entire contact area. However, this may require a large amount of memory in a 3D analysis. If the necessary memory is not available, the user must split the large contact surface into several smaller contact surfaces.
Apply Surface-to-Surface Contacts
Since it may not be possible to calculate the contact between some element types and others, the Element Type and Element Definition headings of the tree view should be completed before applying surface-to-surface contact.
Surface-surface contact pairs can be defined using any of these methods.
- Select two parts or two surfaces in the display area and right-click. Select Contact
Surface Contact. The details of the contact can be set by selecting the contact pair just created in the tree view, right-click, and choosing Settings. The settings are described in the Surface-to-Surface Contact Options section. Note that the first part or surface selected becomes the primary surface, and the second selection becomes the secondary surface. This may be important when defining the Contact type as Point to Surface. (See the page Surface-to-Surface Contact Options for details on the Contact Type.) - Right-click the Contact (Default:) heading in the tree view and select the General Surface-to-Surface Contact command.
- With nothing selected, right-click in the display area and select the General Surface-to-Surface Contact command.