Week 1 Spur Gear Challenge
Objective: To conduct the Static structural analysis for the spur gear assembly operation with 3 different materials, and to recommend the best performing material based on the analysis report.
Case setup: The boundary conditions are set up as per the video, and all 3 cases are solved with 3 different materials. The results are discussed next.
Results:
Case 1: The results for Cast Iron (Ductile) are attached. Following is the summary:
Equivalent stress (Max): 463 MPa
Total deformation (Max): 30 mm (Outermost point in rotation)
Stress intensity (Max): 525.24 MPa
(NOTE: The fatigue analysis couldn't be conducted in Case 1, because the SN curve was unavailable in Granta design material samples)
Case 2: The results for Cast Steel are attached. Following is the summary:
Equivalent stress (Max): 457.58 MPa
Total deformation (Max): 30 mm (Outermost point in rotation)
Stress intensity (Max): 517.65 MPa
Case 3: The results for Cast Bronze are attached. Following is the summary:
Equivalent stress (Max): 439.01 MPa
Total deformation (Max): 30 mm (Outermost point in rotation)
Stress intensity (Max): 493.68 MPa
Summary:
Equivalent Stress comparison:
Total Deformation comparison:
Stress Intensity comparison:
(Definition of Stress Intensity: Stress Intensity is studied under the Linear Elastic Fracture Mechanics design approach. This approach considers that the structure, instead of being crack-free, has a crack. The governing structural mechanics parameter when a crack is present is an entity called the stress-intensity factor. The essential difference from the strength-of-materials approach is that the fracture mechanics approach explicitly introduces a new physical parameter: the size of a cracklike flaw. Stress intensity is the controlling factor in crack growth propagation rates and the identification of the critical crack size for the onset of rapid overload)
Following table summarizes all the parameters as below:
| Case 1 | Case 2 | Case 3 | |
| Equivalent Stress (MPa) | 463 | 457.58 | 439.01 |
| Total Deformation** (mm) | 30 | 30 | 30 |
| Stress Intensity (MPa) | 525.24 | 517.65 | 493.68 |
** Outermost point in the rotation
Conclusion: From the above-shown images and tables, it can be concluded that with Cast Bronze the stresses are minimum, and hence the fatigue will be the least in case 3. Therefore, Case 3, Cast Bronze should be the material of choice.