Week 1 Spur Gear Challenge

SPUR GEAR SIMULATION

OBJECTIVE

To perform Static Structural analysis on Spur Gear in ANSYS Workbench with three different materials namely

• Cast Iron (Ductile)
• Cast Steel
• Cast Bronze

Compare the results of

1. Equivalent stress,
2. Total deformation
3. Stress intensity (The stress intensity factor is a concept in Fracture Mechanics that is used to measure the stress concentration at a crack tip)
4. The location for possible fracture

MODEL SETUP

The 3D model of the setup is imported into ANSYS Space Claim. Check for any abnormalities in the Geometry.

MATERIAL ASSINGMENT:

The materials which are assigned to both the gears for different cases are shown below

• Case 1: Cast Iron (Ductile) as the material for two Gears
• Case 2: Cast Steel as the material for two Gears
• Case 3: Cast Bronze as the material for two Gears

The properties of various materials used are shown below

• Cast Iron (Ductile)

• Cast Steel

• Cast Bronze

MODEL SETUP:

After importing the Geometry, rename the Parts and assign respective materials for different cases

CONTACTS DEFINITION:

We need to define contact regions for this model. The settings are as shown below

• Frictional Contact is selected between the faces of the Gear tooth which will be in contact throughout the simulation.

JOINT DEFINITION:

We need to define joints for the model, they are

• A Revolute joint for the Left Gear :

• A Revolute joint for the Right Gear :

Also make sure the reference co-ordinate system assigned to the joints are as shown above.

MESHING:

The meshing is done as follows,

• A Patch Confirming method with Tetrahedral elements is selected for both the gears

• A element size of 1 mm is assigned to both the Gears. The details and settings of the mesh are shown below.

MESH QUALITY:

ANALYSIS SETTINGS:

Now, the simulation is run for 6 steps. The following settings are modified

Auto Time stepping is set to ON and Time step values are assigned as shown below.

Solver Type is set to Program Controlled

Weak springs are set to OFF

The Large deflection is set to ON.

Other settings are as shown below

BOUNDARY CONDITIONS:

The boundary condition for this model are

• A Revolute Joint load of Rotation type is assigned to the Left Gear :

• A Revolute Joint load of Moment type is assigned to the Right Gear :

The values of the moment assigned are shown below

The values of the moment assigned are shown below

RESULTS:

CASE 1: Cast Iron (Ductile) as the material for two Gears

ANIMATION :

• Equivalent stress

• Total deformation

• Stress intensity

The area in red implies the location of possible fracture

CASE 2: Cast Steel as the material for two Gears

ANIMATION :

• Equivalent stress

• Total deformation

• Stress intensity

The area in red implies the location of possible fracture

CASE 3: Cast Bronze as the material for two Gears

ANIMATION :

• Equivalent stress

• Total deformation

• Stress intensity

The area in red implies the location of possible fracture

CONCLUSION:

From the results, it can be inferred that

• Total Deformation remains the same for all the three materials
• Equivalent Stress is maximum for Cast iron gear, remains almost equal to that of Cast Steel gear and lower in the case of Cast Bronze gear.
• Stress Intensity is maximum Cast Steel gear, remains almost equal to that of Cast iron gear and lower in the case of Cast Bronze gear.

Comparing all,

1. The Equivalent Stress induced and Stress Intensity is maximum and almost equal for both Cast Iron and Cast steel gears.
2. The Equivalent Stress is greater than the Tensile Yield Strength for all the three cases which implies that the gears enter into Plastic deformation zone for the three cases.
3. For Cast Bronze as the gear materials, the stress induced and stress intensity is less than those of Case1 and Case 2, but greater than the Ultimate Tensile Strength (267 MPa) and hence it has more probability of fracture, which ultimately leads to failure of the Gears.
4. Hence, considering all, it is recommended to use Cast Steel as the material for gears because it has higher Youngs Modulus (more stiffness), higher Tensile Yield strength and Ultimate Yield strength is more or less same as that of Cast Iron.

The simulation files are attached below