Week 1 Bevel Gear Challenge
##COMMENTS BY GRADER:
Hey Santhosh,
Good job on completing the challenge. I would like to point out some mistakes in your report though. I don't think you completely understood what convergence is because you kept using it wrongly. When we say solution hasn't converged, it means there is an imbalance in the forces in the system. So we won't be getting a solution. But, in this case the solution has converged for all the three cases and that is why you are actually getting results. What you mentioned about grid dependency is partially correct. So kindly check out the term and why it is used.
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1)As the mesh is kept on refined if there are drastic changes in solution then convergence hasnt taken place and the results might not be accurate i.e the solution of the present meshing wont match with the solution of the next meshing owing to dependency of the accuracy on type of mesh
The following factors affect grid dependency
a)If the time step is too large then convergence might not be achieved very soon,though fast the accuracy is very less
b)Greater the increase in size of elements greater the grid dependency
grid dependency study is hence done to find the inaccuracies in result due to changes in mesh
2,3) Grid Dependency test on Bevel Gear
The following model was unpacked using spaceclaim for analysis
All three cases use structural steel as material whose properties are given below
In order to reduce the computational power and reduce the number of nodes and elements most of the stock was removed from the small gear and larger gear.
Since our primary objective of focus is on the faces where they are meshing and observe the Stress changes,deformation changes and strain changes the meshing faces are refined with face sizing of 1.75 while the rest of the faces of gear have a coarse mesh of size 4
For grid dependency test,The anlaysis is run again with coarse mesh of size 5
For grid dependency test,The anlaysis is run again with coarse mesh of size 6
The contact surfaces are definied and a revolute joint is given
The smaller gear is given a rotation of 120 degrees and made to rotate in clockwise direction
The larger gear is given resistance moment of 100N-mm for all 6 time steps and is made to rotate in anticlockwise direction
simulations were run independently and the total deformation,elastic strain,vonmisses stresses were found
As mentioned time step was set to 6 with initial time step=0.1,mintime step=5e-2,maxtime step=0.2
Deformation plot with mesh size 4,5,6 respectively
Mesh Size=4
Mesh size=5
MeshSize=6
Conclusion from deformation plot
Plot showing variation in average deformation with three meshsizes=4,5,6mm
With increase in mesh size the max and min deformation value remained same showing convergence had happened,there was change in average deformation with the average deformation being high when mesh size was=5 and avg deformation being low when mesh size was =4
Comparison of Vonmisses stresses
With mesh size=4
With meshsize=5
With mesh size=6
Conclusion from vonmisses stress values
Plot comparing the MINIMUM value of stresses with three meshes
XAXIS-TIME
YAXIS-MINIMUM STRESS
Minimum-MESH SIZE=4
Minimum2-MESH SIZE=5
Minimum3-MESH SIZE=6
Plot comparing the MAXIMUM value of stresses with three meshes
XAXIS-TIME
YAXIS-MAXIMUM STRESS
MAXIMUM-MESH SIZE=4
Maximum2-MESH SIZE=5
Maximum4-MESH SIZE=6
Plot comparing the AVERAGE MAXIMUM value of stresses with three meshes
XAXIS-TIME
YAXIS-AVERAGESTRESS
AVERAGE MAXIMUM-MESH SIZE=4
Average2-MESH SIZE=5
Average3-MESH SIZE=6
With increase in mesh size the Maximum stress dropped by a order of 1.2MPa (with change to mesh size=5) and dropped by a order 0f 2.3Mpa(with change to mesh size=6) while the minimum stress kept increasing with increase in mesh size.The variation in average stresses over changes in meshes very small.
Comparison of elastic strains
Mesh size=4
Mesh size=5
Mesh size=6
CONCLUSION FROM ELASTIC STRAIN VALUES
PLOT COMPARING MINIMUM ELASTIC STRAIN VALUES
Minimum-MESH SIZE=4
Minimum2-MESH SIZE=5
Minimum3-MESH SIZE=6
PLOT COMPARING MAXIMUM ELASTIC STRAIN VALUES
Maximum-MESH SIZE=4
Maximum2-MESH SIZE=5
Maximum3-MESH SIZE=6
PLOT COMPARING AVERAGE ELASTIC STRAIN VALUES
Average-MESH SIZE=4
Average2-MESH SIZE=5
Average3-MESH SIZE=6
The max value of elastic strain drops with increaseing mesh size,the average value of elastic strain remains relatively constant with changes in mesh sizing