Finite Element Analysis of Spur Gear using Ansys Workbench
Objective: Compare the Finite Element Analysis results obtained by using 3 different materials for Spur gears and write a detailed report explaining the results obtained.
Stress Intensity: The stress intensity factor describes the stress state at a crack tip, is related to the rate of crack growth, and is used to establish failure criteria due to fracture. Stress Intensity depends on type of loading and geometry.
The stress intensity factor for an assumed straight crack of length 
perpendicular to the loading direction, in an infinite plane, having a uniform stress field 
is
Case Setup and Execution:
Model:
Boundary Conditions:
Contacts: Contacts has been applied as shown below.
Joints: Revolute joints has been applied to both gears as shown below.
Mesh: Size of element- 1mm.
Analysis Settings:
Joint Loads: Joint Loads has been applied as shown below.
Case-1: CAST IRON, DUCTILE
Material: Cast Iron, Ductile
Results:
Equivalent Stress:
Equivalent Elastic Strain:
Total Deformation:
Pressure:
Stress Intensity:
Case-1: CAST STEEL
Material: Steel
Results:
Equivalent Stress:
Equivalent Elastic Strain:
Total Deformation:
Pressure:
Stress Intensity:
Case-1: CAST BRONZE
Material: Cast Bronze
Results:
Equivalent Stress:
Equivalent Elastic Strain:
Total Deformation:
Pressure:
Stress Intensity:
Status: Common for all cases
Possible Fracture Location: Common for all cases
Possible fracture Location is at inner tip of the teeth as the load applied on the tooth is gradually transferred to this location which is like a joint.
Results Comparison & Conclusion:
Material Properties comparison:
| CAST IRON (DUCTILE) | CAST STEEL | CAST BRONZE | UNITS | |
| DENSITY | 7130 | 7820 | 8810 | Kg/m3 |
| YOUNG'S MODULUS | 1.71E+05 | 2.03E+05 | 80000 | Mpa |
| POISSON'S RATIO | 0.275 | 0.3 | 0.345 | * |
| TENSILE YIELD STRENGTH | 344 | 349 | 144 | Mpa |
| ULTIMATE TENSILE STRENGTH | 548 | 505 | 267 | Mpa |
Results Comparison:
| Total Deformation | Equivalent Elastic Strain | Equivalent Stress | Pressure | Stress Intensity | ||||||
| mm | * | Mpa | Mpa | Mpa | ||||||
| Min. | Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | Max. | |
| CI (Ductile) | 0.96822 | 30 | 5.66E-14 | 0.0026523 | 7.05E-09 | 451.03 | 0 | 664.22 | 8.04E-09 | 480.33 |
| Cast Steel | 0.96822 | 30 | 5.29E-14 | 0.0024945 | 1.03E-08 | 503.63 | 0 | 735.94 | 1.16E-08 | 539.55 |
| Cast Bronze | 0.96822 | 30 | 2.55E-13 | 0.0044829 | 1.88E-08 | 357.18 | 0 | 476.89 | 2.09E-08 | 380.17 |
- Total deformation is same for all cases.
- Equivalent Elastic Strain is higher in Cast Bronze material as compared to other materials.
- Equivalent Stress is lower in Cast Bronze material as compared to other materials.
- Stress Intensity is higher in Cast Steel and lower in Cast Bronze.
- Equivalent stress generated in all the materials is higher than their respective Tensile Yield Strength.
- Equivalent Stress generated in Cast Bronze exceeds Ultimate Tensile Strength which means that the material is failed.
- Equivalent stress generated in Cast Steel almost equals to its Ultimate Tensile Strength.
- Equivalent Stress generated & Stress Intensity in Cast Iron Ductile exceeds Tensile Yield Strength but lower than Ultimate Tensile Strength.
- In comparison, Cast Iron Ductile is the best material suited for the conditions as all other materials fail during the analysis.