Week 8 - Universal Joint

OBJECTIVE

To carry out a transient structural analysis on a given double universal joint model. The analysis is to be carried out in 3 cases with each case involving a different material for the spring joint in the model. The materials to be used are structural steel, stainless steel and titanium alloy. The outputs to be requested are that of equivalent stress and total deformation and are to be compared.

MODEL IMAGE

PROCEDURE

1. After opening ANSYS Workbench, we are met with the Project Schematic window. Here, we can select the 'Transient Structural' analysis system on the left. Doing so creates a new project. Here, we can rename the project and also change the material if needed. We will need to right-click 'Geometry' and select 'import'. The file provided for this project should be selected. 

Now, we can add the materials. To do that, we need to double-click Engineering Data'. This opens up the list of inserted materials. We can then pick materials we need from the repository listed in the Engineering Data Sources. Going to the 'General Materials' source, we can pick the required materials - Stainless Steel & Titanium Alloy (Structural Steel is included by default).

After that, we simply need to click the yellow '+' symbol on the material's corresponding 'add' column to add this specific material to the project. Once we are done, we can simply close the tab.

We can then exit out of the engineering data tab and return to the project schematic window, where we can right-click geometry and select 'edit'. This will bring the model up in the Mechanical interface.

2. In the mechanical interface, in the outline, under geometry, we can rename each of the components. We can assign the material for the spring joint here.

3. We then need to go to contacts under connections and delete all the available contacts. We shall be creating joints. To do that, we can right-click connections > insert > joint. The first one is a fixed body-ground joint on the free end of the spring component as shown:

Next, we need to create a revolute body-ground joint situated on the curved surface of the driver joint component as shown. Care must be taken to ensure the axis of rotation is correct.

Then, we need to create a revolute body-ground joint on the curved surface of the sprint joint component as shown. Once again, we will need to ensure that the axis of rotation is correct.

Finally, we will need to create a total of 8 body-body revolute joints for each of the hole cavities through which the universal joint is connected to each of the other components in the model. The mobile scope surface would be the inner surface of each of the whole and the reference scope surface would be the corresponding surface on the particular universal joint.

4. Next, we shall work on the analysis settings. The number of steps would be 5. Selecting all the steps, we can assign the following attributes:

All the output controls are enabled as well.

5. Next, we need to right-click Transient > Insert > Joint Load. This is for the revolute joint we created on the driver joint. The type would be 'rotation' and we can assign tabular values as shown:

6. Finally, we can assign a mesh size of 3mm with medium smoothing attribute and adaptive sizing disabled.

7. Now we can generate the outputs. To do this, we can right-click Solution > Insert > Stress > Equivalent (Von-Mises) (for stress) and right-click Solution > Insert > Deformation > Total (for total deformation).

Now, all we need to do is right-click solution again and click 'Evaluate all results'. It must be reiterated that after reaching the solution, we should save the model and go back to the components and change the material of the spring joint. After that, we will need to evaluate the results again and save it as a separate file.

Finally, when the analysis is done, we can view the results by simply clicking each of these solution entities we created, in the Outline menu.

OUTPUTS

CASE 1 - STRUCTURAL STEEL SPRING JOINT

EQUIVALENT STRESS

Maximum & Minimum Stress

TOTAL DEFORMATION

Maximum & Minimum Deformation

CASE 2 - STAINLESS STEEL SPRING JOINT

EQUIVALENT STRESS

Maximum & Minimum Stress

TOTAL DEFORMATION

Maximum & Minimum Deformation

CASE 3 - TITANIUM ALLOY SPRING JOINT

EQUIVALENT STRESS

Maximum & Minimum Stress

TOTAL DEFORMATION

Maximum & Minimum Deformation

OBSERVATIONS

As we can see, the spring joint with the titanium alloy material experiences the least stress out of the three. The reason for this can be explained through the deformation values, which are the same in each case. Therefore, it's safe to assume the strain values are largely similar. This just means that material properties like Young's Modulus and stiffness are the primary reason for the stress results. Stress is directly proportional to the Young's Modulus of the materials and as we can see, the structural steel spring joint generates the highest amount of stress, and it has the higher Young's Modulus. Conversely, titanium alloy has the least, and it generates the least amount of stress.

RESULT

Transient structural analysis was carried out on the given universal joint model and 3 cases with different materials for the spring joint were applied and outputs compared. The spring joint with titanium alloy material generated the least amount of stress out of the three.