Bevel Gear Challenge
1) Grid lndependency Test’ and ‘Mesh Refinement Test‘ are the synonyms and they all mean the same. While performing Finite Element Analysis, one of the most common question is finite element mesh quality. How can one know if the mesh is good enough for the analysis?
Mesh density is used to control accuracy (element type and shape also affect accuracy). a high-density mesh will produce results with high accuracy. However, if a mesh is too dense, it will require a large amount of computer memory and long run times, especially for multiple-iteration runs that are typical of nonlinear and transient analyses.
The most fundamental method of checking the mesh quality is to refine a mesh until a
critical result such as Equivalent stress does not change significantly with each refinement
(i.e. it converges). This is Grid dependency test, where, analysis begins with a coarse
mesh and it is refined to finer mesh for each run until the results do not change
significantly and depend of the grid size anymore. As the grid or mesh size approaches
zero, the approximate solution is almost equal to the actual solution. The aim of this test is
to find the optimum mesh size for the solution, where it is neither to coarse to produce
inaccurate results, neither too fine, where it will consume a lot of computing effort and
time.
2) Perform a grid dependency test for the Bevel gear simulation for mesh sizes of 6,5 and 4 mm
1. Importing this cad file to ansys and edited in ansys spaceclaim, ID is incresed as it may cause more time for analysis
2. Assigning same material for both gears in All Cases.
3. In connections - contact type is set to frictional and Selecting All tooth faces from gear geometry.
Augmented Lagrange
In the analysis, a relation must be established between two surfaces to prevent them from
passing through each other. Augmented Lagrange or Pure Penalty is preferred for non-linear solid body contact faces.
3.1 connection type is body ground and revolte For Both gears
3.2 connection type is body ground and revolte For Both gears
Made Sure that they are in same ( RZ ) Plane of Rotation By changing Axis Direction.
4. Mesh value set to 4,5,6 mm, checking statistics limit wether they are in Problem size limit, and selecting only necessary area for analysis for both gear by Clicking on Face Meshing to 1.75mm.
Mesh 4mm
Mesh 5mm
Mesh 6mm
5. in Analysis setting rotation 120 degree is divide in 6 steps and moment 100N divide in 6 steps
6. Results
Simulation Images
Total Deformation
Case 1.
Case 2.
Case 3.
Equivalent elastic strain
Case 1.
Case 2.
Case 3.
Tabular Result:
Case 1.
Case 2.
Case 3.
In all cases total deformation remains same in both Min. & Max with element mesh size changing From 4 to 6mm.
Equivalent stress and Equivalent elastic strain in Minimum deformation, value is decreasing as Mesh size increasing from 4 to 6mm
Conclsion : As expected from the Grid dependency test, as the mesh was changed from coarse to fine, the accuracy in the results improved. It can be seen from the tables that there was a significant improvement in results for both Equivalent Stress and Equivalent Strain, which means that Grid lndependency has reached and further the results are not dependent on Grid size or element size anymore and further reducing element size is unnecessary.
If the mesh size is further reduced, it will only increase computational time. Therefore, it
can be said that the optimal mesh size is 4mm.