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# Connecting a Surface Body Edge to a Rigid Body Face in ANSYS® Workbench Mechanical

Figure 1: Connection of a Rigid 3D Body to the Inside of a Hole in a Surface Body

Introduction

ANSYS Workbench Mechanical can connect the face of a flexible body to the edge of a surface body (shell) with contact elements. If the Contact side of the contact pair is on the surface body edge, and the Target is on the flexible body face, setting MPC Bonded Contact to “Target Normal, Couple U to ROT” will transmit both displacement and rotation across the contact pair, so that the edge of the surface body transmits moment and acts as if it is welded to the face of the flexible body.

If the flexible solid body is set to Rigid, the MPC bonded constraint no longer transmits rotation and moment at the node level. The connection acts like a hinge, losing the ability to act as a welded connection. Node rotation coupling could cause overconstraint if the flexible body edge nodes are set to rotate, so no such coupling takes place.

If a user wants to use a rigid solid body connected to a surface body edge as if welded, a workaround is to use a Fixed Joint to join the surface body edge to the rigid body. The edge of the surface body will act as if it is welded, transmitting node rotation and moment at the connection. This article shows setting details.

Details of Connecting a Surface Body Edge to a Rigid Body

Users can create a contact between the edge of a surface body (shell) and the face of a Flexible body. The surface body Edge is the Contact, and the solid body Face is the Target. If the contact is Bonded and set to MPC, one way to connect node rotations on the surface body is with Constraint Type set to “Target Normal, Couple U to Rot.”

Figure 2: Shell Edge to Flexible Body Face--Bonded MPC Target Normal, Couple U to Rot

In the Figure 2 example above, the surface body edge tracks the solid body translation and rotation. The surface body edge remains perpendicular to the face on the solid body, as if the surface body is welded to the cylinder.

In some models involving thin shells that connect to solid bodies, users may wish to simplify the solid body representations by setting them to be Rigid, for example:

Figure 3: Solid Body Set to Stiffness Behavior – Rigid

In Figure 4 below, the solid body has been declared to be Rigid. Rotations of the surface body edge nodes have not been coupled to the rigid body rotation. UX, UY and UZ are bonded to the rigid body movements, but not rotations:

Figure 4: Rigid Body with Surface Body Edge Connected by Bonded MPC Contact–Node Rotation Not Continuous–Not Working!

A Fixed Joint can connect the surface body edge to the rigid body to capture this effect:

Figure 5: A Fixed Joint between a Rigid Solid Body and a Surface Body (Shell) Edge

Because the surface body (shell) edge Behavior above is set to Rigid, it translates and rotates with the rigid body:

Figure 6: Fixed Joint between the Rigid Body, and the Surface Body Edge

Plots with rigid bodies do not show their movement. Figure 6 above was generated by coating the rigid body with contact and target elements that do nothing, purely for the sake of plotting:

Figure 7: A Coating of Contact and Target Elements on a Rigid Body for Visibility Only

The deflection results in Figure 6 are close to those with a flexible body... the flexible solid body has slightly larger deformations as in Figure 2.

Conclusions

Workbench can connect edges of surface bodies (shells) to faces of Flexible solid bodies with Bonded MPC contact, with Contact on the edges, and Target on the faces. Surface body edge nodes respond to translations and rotations of the solid bodies if the Contact Type is set to “Target Normal, Couple U to Rot.” If the solid bodies are set Rigid, the edge node rotations are no longer coupled. Complete coupling of translation and rotation is possible with a Fixed Joint set to Rigid on the surface body edge.

Tags: ansys, structural analysis