Bracket — Rigid Connector Analysis

Rigid connectors provide an alternative way for modeling geometrical parts that are of little interest in the analysis and have a negligible deformation. Such parts can be replaced with virtual rigid bodies with appropriate boundary conditions. This saves computational time and memory.

In this example, you study the stress in a bracket connected to a pin where a load is applied. The pin is simulated as a rigid connector.

It is recommended that you review the Introduction to the Structural Mechanics Module, which includes background information and discusses the bracket_basic.mph model relevant to this example.

Model Definition

This model is an extension of the example described in the section “The Fundamentals: A Static Linear Analysis” in the Introduction to the Structural Mechanics Module.

The model geometry is represented in Figure 1.

Figure 1: Bracket geometry.

A pin is connected between the bracket hole where a load is applied. The pin is assumed to be perfectly rigid and is modeled with a rigid connector. Thus, the pin is not represented in the model geometry. Figure 2 below shows the boundaries connected to the rigid connector and the position of its center of rotation.

Figure 2: Center of rotation of the rigid connector applied to the bracket geometry.

Results and Discussion

Figure 3 shows the von Mises stress in a deformed geometry. You can see the effect that the pin’s rotation and applied force has on the bracket arms.

Figure 3: Von Mises stress distribution.

Notes About the COMSOL Implementation

The rigid connector has the translational and rotational degrees of freedom of a rigid body. Options for this feature include applying an external load or moment to the rigid body, or defining mass and moments of inertia in dynamic analyses. The rigid connector can also be used to apply loads and constraints at points so that these are distributed and thereby preventing singularities.

To visualize the position of the center of rotation you need to enable the physics symbols. This is done in the settings of the physics interface.

Structural_Mechanics_Module/Tutorials/bracket_rigid_connector

Modeling Instructions

Root

From the menu, choose .

Browse to the model’s Application Libraries folder and double-click the file bracket_basic.mph.

Solid Mechanics (solid)

Rigid Connector 1

In the window, under right-click and choose .

Add a rigid connector that connects the holes in the bracket arms to simulate the presence of the pin.

In the window for , locate the section.

From the list, choose .

By default, the location of the center of rotation is computed automatically. You can also manually specify its location.

Locate the section. From the list, choose .

Specify the Xc vector as


0	x
-0.40	y
-0.10	z

To visualize its position you need to enable the physics symbols.

In the window, click .

In the window for , locate the section.

Select the check box.

The displacements of the rigid connector are constrained in the x − and z − directions at its center of rotation.

In the window, click .

In the window for , locate the section.

Select the check box.

Locate the section. From the list, choose .

Apply a prescribed rotation of the rigid body of 0.05 degrees around the y-axis.

Specify the Ω vector as


0	x
1	y
0	z

In the φ0 text field, type 0.05[deg].

Applied Force 1

In the toolbar, click

and choose .

Apply an external load of 10 kN at the center of rotation of the rigid body.

In the window for , locate the section.

Specify the F vector as


0	x
-10[kN]	y
0	z

Add Study

In the toolbar, click

to open the window.

Go to the window.

Find the subsection. In the tree, select .

Click in the window toolbar.

In the toolbar, click

to close the window.

Study 1

In the toolbar, click

Results

Stress (solid)

Click the

button in the toolbar.

The default plot shows the von Mises stress on a deformed geometry.