# Common Problems

The following sections contain examples of some common problems in the contact interfaces and solutions to overcome them.

## Nearest Main Node Found Incorrect

If the interface surface is not simply convex, the simplified main node search may find an incorrect nearest main node.

This problem occurs with interface TYPE3, TYPE6 and TYPE5 (main side only).

The solution to this problem is to use TYPE7 interface.

## Nearest Main Segment Found Incorrect: B1

In some cases the nearest main node is not connected to the nearest segment.

This problem can occur with interface TYPE3, TYPE6 and TYPE5 (main side only).

The solution is to either use TYPE7 interface or to refine the mesh.

## Nearest Main Segment Found Incorrect: B2

In some cases the nearest main node is not connected to the nearest segment.

This problem can occur with interface TYPE3, TYPE5 and TYPE6 (main side only).

The solution is to either use TYPE7 interface or change the mesh (for initial mesh problem).

## Nearest Main Segment Found Incorrect: B3

If the angle between segments is less than 90 degrees, the incorrect nearest segment may sometimes be found, as in Figure 4.

This problem can occur with interface TYPE3, TYPE5 and TYPE6.

The solution is to use a TYPE7 interface or to refine the mesh. With a finer mesh, the shape is smoother.

## Impact Side Incorrect: C1

A node can only impact on the positive side of a segment for interface TYPE3, TYPE6, and TYPE5 (main side). The solution is to use a TYPE7 interface.

## No Main Node Impact: D1

With TYPE5 interface, only secondary nodes impact main segments; main nodes cannot impact secondary segments.

This can be solved by either inverting the secondary and main sides, or by changing the type of interface. Interface TYPE3 and TYPE7 will solve this problem adequately.