Common Problems in Interfaces TYPE3 and TYPE5

Interfaces TYPE3 and TYPE5 have some common problems.

• Energy jumps
• Bad contact treatment
• Limited search algorithm

The gap used in interface TYPE5 (and TYPE3) is one sided and does not take into account the edges. This can lead to energy jumps in cases of a large gap (Figure 1).

Figure 1. Jump in Energy

Moreover, as the interface stiffness is constant, node penetration is allowed. This point can lead to a huge error, especially if sliding occurs during the penetration. Figure 2 illustrates how secondary nodes are allowed to go through the shell mid-surface because of bad contact treatment.

Figure 2. Bad Contact Treatment

With interface TYPE5 (and TYPE3), the detection of the closest main node is limited to the segments topologically close to the previous one (topologically limited search algorithm). The first search is done by Radioss Starter to determine the closest initial main node, then the Engine determines the closest main node, taking into account only the segments topologically close to the previous one. This method is rather slow in CPU time, and it does not work very well, especially if high curvatures are involved (Figure 3).

Figure 3. Bad Detection of the Closest Main Segment