Overlap Removal Methods

Problem Description

This example demonstrates the process of removing overlap from two rings using two different methods: overlap removal and artificial stain coupled with general contact.

In the first case, the two rings have a small overlap due to the inner ring being slightly larger than the inner radius of the outer ring. This overlap removal block will be placed directly into the contact block. In Fig. 20 the left side is showing the model before the overlap is removed while the right is showing the resulting model after the removal.

Fig. 20 Small overlap and results after overlap removal

In the second case, a large overlap will be removed from the rings using an artificial strain in the radial direction for the first time period as shown in Fig. 21. Then contact is activated and the artificial strain is removed as you can see on the right side of the plot in Fig. 21. In Fig. 22 the left side is showing the model before anything is done and the right is showing how the model will look after the removal method.

Fig. 21 Rings under strain with strain vs time plot

Fig. 22 Large overlap and results after overlap removal method

Boundary Conditions

No boundary conditions where applied to these models.

Material Model

In both of these cases an elastic orthotropic material model with isotropic properties was used. The elastic orthotropic model allows specification of a cylindrical coordinate system, so that strain can be applied in the radial direction.

The following material properties were used during analysis:

Metric units are used
Displacement: meters
Mass: kilograms
Time: seconds
Force: \(kgm/s^2\)
Temperature: Kelvin

Table 5 Ring Material

Overlapping Rings
Young’s Modulus: Block and Bolt	E	\(64\times10^9\)
Poisson’s Ratio	\(\nu\)	0.20
Density	\(\rho\)	0.5

Finite Element Model

For the small overlap case the inside ring was made to have an outside radius of 0.205 while the outer ring has an inner radius of 0.20. For the larger overlap the case the inside ring has an outer radius of 0.2125 while the outer ring has the same inner radius. Both of these cases were created using a simple hex mesh.

Results and Discussion

Results obtained from the overlap removal case showed that no stress or strain was applied to the system in order to remove the overlap; however, this method could handle a larger overlap than 50 percent of the smallest element size. In the case where strain was applied larger amounts of overlap could be removed, however a resulting stress and strain value is added to the system causing the rings to change from their original configurations. In Fig. 23 the max principle stress of the resulting model is zero, while in Fig. 24 both of the rings are experiencing large values of stress.

Table 6 Use Case Summary

Overlap Removal	Simple to use for small amounts of overlap. Straightforward set up.
Artificial Strain and General contact	Works for large overlap but leaves a stress and deformation of original setup. Moderate set up.

Fig. 23 Stresses experienced after overlap removal

Fig. 24 Stresses experienced after strain and contact is applied

Files

Small overlap

• Overlap Removal Mesh

• Overlap Removal Input Deck

Large overlap

• Overlap Removal Strain Mesh

• Overlap Removal Strain Input Deck