Main Screen

The input for surface-to-surface contact is entered on three dialog windows, summarized as follows and described in detail over the next pages:

  1. MES: Surface to Surface Contact is where the pairs of surfaces in contact are defined and listed (the spreadsheet). This is the same list as given in the tree view but in an expanded format. A few global contact parameters are also defined on this screen. This dialog is described below.
  2. Controls and Parameters for Contact Pair is accessed by clicking the Parameters column of the spreadsheet for the appropriate contact pair. This dialog defines more specific information for the contact pair, such as the type of contact (frictionless, frictional, tied contact, and so on) and parameters for those options. (This dialog can also be accessed directly by selecting the contact pair in the tree view, right-click, and choosing Settings.) This dialog is described on the page Surface-to-Surface Contact Options.
  3. Advanced Controls and Parameters for Contact Pair is accessed by clicking the Advanced button on the Controls and Parameters for Contact Pair dialog. This dialog defines advanced input for the contact pair, such as contact stiffness, contact distance, maximum initial distance, and so on. This dialog is described on the page Surface-to-Surface Contact Advanced Controls.

MES: Surface to Surface Contact dialog box

The MES: Surface to Surface Contact dialog is an alternative list to the tree view of the contact pairs define in the model. Access this dialog either by clicking on the Contact (Default:) entry in the tree view or by right-clicking in the display area and choosing General Surface-to-Surface Contact. You will be able to select an existing pair in the table and edit the information, or you can define a new pair of contact.

Once the Surface to Surface Contact dialog is displayed, new contact pairs can be defined in the dialog. First use the Add Row button to create a new row in the Contact Pairs spreadsheet. Note the pointer indicating that the new row is active. Then use the drop-downs at the top of the dialog to define which part number and which surface number will make up the first contact surface (also referred to as the master surface) and which part and surface numbers will make up the second contact surface (also referred to as the target surface).

Individual contact pairs can be removed from the calculation by clicking the Enabled column for the appropriate Pair (row). Doing so will toggle the enabled status from Yes to No, where yes indicates that contact elements are created for the pair, and no indicates that contact is not created for the pair. (Contact pairs can also be enabled or disabled by selecting the pair in the tree view, right-click, and choosing Enable.)

In the Contact Element Updating Parameters section, if the Automatic option is selected in the Updating drop-down box, the surface-to-surface contact process will determine which areas of a contact surface may come into contact during each time step and will only generate contact elements in this area. On a different time step, different areas may be in or near contact, so the automatic updating will add elements where needed and remove elements where not needed. For example, imagine two gears meshing. Although all teeth on the pinion are defined as contacting all teeth on the gear, at time T=1 only the teeth in contact need contact elements. The other contact elements would simply add time to the analysis to determine that those teeth are not in contact, so those contact elements are removed from the solution. At a later time T=2, different teeth are in contact, so that area is where the contact elements are created. If the Automatic option is selected, the radius and the frequency are varied according to the relative motion of the two contact surfaces. A linear acceleration assumption is used to calculate the contact radius. A frequency of 10 times per second is used as the initial frequency of updating the contact areas.

If the Never option is selected for the Updating, the contact elements will be generated for all areas and will not be updated. This method is only recommended for models that will experience very small motion relative to the mesh size. The advantage is that the processor does not use any time to decide when to add or remove contact elements from the solution, so this time is saved during the analysis.

Tip: If using Never for the updating, also consider minimizing the number of contact elements created by setting the Maximum initial distance. See the section Geometry tab on the page Surface-to-Surface Contact Advanced Controls.

If the User-defined option is selected for the Updating, you will need to specify how often the process should update the contact elements in the Frequency field. You will also have to specify the radius through which the process should look to create contact elements for each pair in the Geometry tab of the Advanced Controls and Parameters for Contact Pair dialog.