Simulation of Spur Gear using ANSYS Workbench
OBJECTIVE:
To perform spur gear simulation using three different materials given in the problem using ANSYS Workbench. The equivalent stress, total deformation, and stress intensity have to be compared between all the materials and possible fracture location must be identified.
PROCEDURE FOR CASE SETUP:
1. Open ANSYS>>Drag and drop static structural model in the project schematic window.
2. Go to the engineering data. Select gray cast iron material. For the remaining two materials, they are defined using the above properties. New material is selected from the Engineering Data and after which desired properties are selected from the Toolbox and the values are inputted. The materials necessary for the challenge is shown below.
For the initial simulation, the grey cast iron material is chosen.
3. Go to the model tab for meshing and doing the case setup.
4. In the geometry rename the gear using a convenient name so that while assigning the boundary conditions it is easier to identify. In this case, the gears are renamed as right gear and left gear respectively.
5. Go to contacts>>Define a frictional contact between the two gears. This is shown in the figure below.
6. The next important step is to define the joints for the gears. The revolute joint is defined for the two gears using the body to ground option in the joint option. This is shown below.
7. A mesh size of 0.75 mm is chosen for the simulation so that it does not exceed the maximum nodes/elements constraint in the academic version. The total number of nodes is 28900 and elements is 5270 which are well within the accepted range. The final meshed model is shown below.
8. The following analysis settings are defined for the simulation.
9. The joint load definitions are explained in the figure below. For the left gear, rotation is defined. For the right gear, the moment is defined.
10. From the solution option the results for total deformation, equivalent stress, and stress intensity are requested.
11. From the analysis settings, hit on solve to start the simulation.
12. The simulation has to be carried out for all the materials simply by changing the materials in the geometry tab.
RESULTS AND DISCUSSION:
1. The results for grey cast iron material are shown below.
2. The results for the cast steel material are shown below.
3. The results for the cast bronze material are shown below.
ANIMATION FILES:
1. The animation results for gray cast iron are shown below.
2. The animation results for cast steel are shown below.
3. The animation results for the cast bronze are shown below.
GRAPHS AND CHARTS OBTAINED:
1. The graphs obtained for gray cast iron are shown in the figure below.
The plot shown given below shows the total deformation.
The plot shown below shows the equivalent stress plot.
The stress intensity plot is given below.
2. The graphs obtained for cast steel are shown in the figure below.
The plot shown given below shows the total deformation.
The plot shown below shows the equivalent stress plot.
The stress intensity plot is given below.
3. The graphs obtained for the cast bronze are shown in the figure below.
The plot shown given below shows the total deformation.
The plot shown below shows the equivalent stress plot.
The stress intensity plot is given below.
Note: The values of all the solutions obtained are exported as excel and saved.
COMPARISON OF RESULTS:
For the comparison of the results, the maximum values of all the output requests are taken for convenience.
| Material | Total Deformation (in mm) | Equivalent Stress (in MPa) | Stress Intensity (in MPa) |
| Gray Cast Iron | 30 | 389.88 | 417.13 |
| Cast Steel | 30 | 384.82 | 426.02 |
| Cast Bronze | 30 | 392.59 | 425.3 |
From the above table, it can be inferred that the total deformation for all the cases remains the same (i.e., 30mm). The maximum equivalent stress is higher for cast bronze which is 392.59 MPa followed by grey cast iron and cast steel with values 389.88 MPa and 384.82 MPa respectively. The stress intensity is highest for cast steel with a value of 426.02 MPa followed by cast bronze and gray cast iron with values 425.3 MPa and 417.13 MPa respectively.
Note:
The stress intensity factor in fracture mechanics is used to predict the stress state near the tip of a crack or notch caused by a remote load or residual stress. Essentially it gives the stress variation in cracks or notch or tip of the material.
There is a considerable difference between the screenshot values and gif values. This is because of dynamic values obtained during the gif values. For convenience, the screenshot values are taken for comparison.
CONCLUSION:
From the above results, it can be seen that cast bronze fails more quickly than other materials since it has more stress intensity and also has higher equivalent stress. The crack formation or failure for the same number of cycles is quicker in the case of cast bronze since it has higher stress intensity values. So, it is the least preferred material
Between gray cast iron and cast steel, the equivalent stress is higher for gray cast iron but the value of stress intensity is less. The machinability of gray cast iron is better than that of cast steel. Also, as discussed above the crack formation or failure for the same number of cycles is quicked for cast steel when compared to gray cast iron since the value of stress intensity is higher for cast steel. The other properties which include compressive strength, castability, and cost are better for gray cast iron in comparison with cast steel.
Therefore, going by the above trade-off gray cast iron is the most preferred material in spite of having higher equivalent stress than others.
Drive Link: https://drive.google.com/file/d/1ehTt4XkxmwKxPsnMif52VlLYlCCpUxVA/view?usp=sharing