Structural analysis of a Spur Gear setup with three different materials
Objective - The objective of this simulation is to perform structural analysis on a Spur gear setup with three different materials, namely Cast Iron, Cast Bronze and Cast Steel using Ansys
Model Import
The static structural ansys system is used for this simulation. The Spur gear model is imported and checked for any errors in spaceclaim.
Then the three material properties Cast iron, Cast Bronze and Cast Steel are chosen from Engineering data.
Simulation Setup
Contact definition
The auto generated contacts are deleted and manually the gear faces which will come in contact area are alone chosen as contact surfaces.
The contact properties are
Type - frictional contact
Formulation - Augumented lagrange
Interface treatment - Adjust to touch
Joint creation
For the each gear a BODY-GROUND revolute joint is created by selecting the inner face of the gears.
Mesh generation
An element size of 1mm is chosen and the entire setup is meshed
The mesh metrics are as given below
Analysis settings
The Left gear is assigned with rotation taking place in 6 steps from 0 to 180 degree.
The Right gear is assigned with constant moment value of 10 Nm (moment direction is opposite to roation of left gear) for all the 6 steps
Results
The model is solved and following results are generated Equivalent stress, Total deformation and Stress intensity
1) Cast Iron
Equivalent stress
Total Deformation
Stress Intensity
2) Cast Bronze
Equivalent stress
Total deformation
Stress intensity
3) Cast Steel
Equivalent stress
Total deformation
Stress intensity
Comparing results of all three material models
Material properties
Results of the three models
On comparing the results, the maximum stress induced in Cast Bronze model is greater than the Ultimate strength of the material, hence the material fails and cannot be used.
In the case of cast iron and cast steel the induced stress is lesser than ultimate strength but greater than yield strength. It indicates that plastic deformation has taken place.
Stress Intensity
The stress intensity factor K, is used in fracture mechanics to predict the stress state ("stress intensity") near the tip of a crack or notch caused by a remote loador residual stresses.It is a theoretical construct usually applied to a homogeneous, linear elastic material and is useful for providing a failure criterion for brittle materials, and is a critical technique in the discipline of damage tolerance. The concept can also be applied to materials that exhibit small-scale yielding at a crack tip.
The magnitude of K depends on sample geometry, the size and location of the crack or notch, and the magnitude and the distribution of loads on the material.
Possible Location of Fracture
The point where the equivalent stress is maximum will have the high probability of crack formation. Then the crack propagates and leads to fracture formation.
Conclusions
Depemding upon the application, either cast iron or cast steel can be used.
If factor of safety is considered, then cast iron maybe used because it has higher ultimate strength value than cast steel.