Week 2 Bevel Gear Challenge
Objective:
- Few words about Grid Dependency.
- Running the simulations at the three mesh sizes.
- Presenting your findings( Report presentation with appropriate figures and tables/charts comparing your results etc.)
- Perform all three cases as per the Question and Attach the simulated data to the assets block.
GRID DEPENDENCY TEST:
’Grid Independence Test’ and 'Grid Dependency Test', ‘Mesh Refinement Test’ are synonyms and they all mean the same. While performing Finite Element Analysis, one of the most common questions is finite element mesh quality. How can one know if the mesh is good enough for the analysis? Mesh density is a significant metric used to control accuracy (element type and shape also affect accuracy). Assuming no singularities are present, 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 the Grid dependency test, where, analysis begins with a coarse mesh and it is refined to a finer mesh for each run until the results do not change significantly and depend on 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 too coarse to produce inaccurate results, nor where it will consume a lot of computing effort and time.
There are different mesh refinement techniques are used which have advantages and disadvantages and some depend on the experience and technical expertise of the FEA analyst. These techniques include- Reducing the element size, Increasing the element order, Global Adaptive mesh refinement, local adaptive mesh refinement, manually adjusting the mesh, Time adaptive mesh refinement, wavelength adaptive mesh refinement, etc.
Procedure:
[NOTE:- the procedure for setting up the material and card is the same for all three cases, so only one case is explained here]
First i opend the ansys workbench and double click on the static structural analysis and rename it 'bevel gear'.
After that we have to double click on the engineering data and select the materail but here we have to make it default (structural steel) as it is no need to change the material.
After that we have to right click on geometry and import the mode which is given in the question.
This is the original geometry then we have to cut the un necessary part from it so again right click on geometry and click on edit in spaceclaim.
Ater the cleanup the geometry will looks like below.
After this we have to right click on model and click update again double click on model to edit and a mechanical widow will open as shown below.
Contact SET-UP
First, make contact under the connection, here the user should select the possible face that involved in the contact. Apart from that, I had defined the Type Definition- Frictional, Behavior-Symmetric, Formulation- Augmented Lagrange, Interface Treatment-Adjust to Touch.
Joint Set up (Revolute)
After contact definition it's time to add joints, Here we are using gears so we have to define the axis of rotation. Revolute joint with Body to ground contact is the best one here.
Analysis setting
here Time step for the simulation is to be set for proper execution of the Analysis.
In the "Static-structural" Deck we have to set the boundary condition. I had to given the Rotation moment to the small gear and the moment to the large one so that it can follow the Right gear rotation movement.
Parameter set
by setting the Input and output parameters in the Parameter set we can check for different conditions like grid dependency. For example, by changing the element length from the coarse level to the fine level we can obtain the result without setting up the case over and over. Also, we don't have to open the model in the model editor. we can make all changes outside in the parameter set deck.
All the parameters with the "p" remark are added to the parameter set. If you want to add a parameter to the Parameter set we just have to click the adjacent check box and when you see the p symbol there it means that a specific parameter is added to the Parameter set you define.
After that, I made an output request for the required results for Von-Mises stress, Equivalent elastic strain, and Total Deformation using the previously mentioned mesh sizes (6mm, 5mm, 4mm)
After successfully adding parameters the parameter set is getting define below the main window as per the above image.
Objective:
- Few words about Grid Dependency.
- Running the simulations at the three mesh sizes.
- Presenting your findings( Report presentation with appropriate figures and tables/charts comparing your results etc.)
- Perform all three cases as per the Question and Attach the simulated data to the assets block.
GRID DEPENDENCY TEST:
’Grid Independence Test’ and 'Grid Dependency Test', ‘Mesh Refinement Test’ are synonyms and they all mean the same. While performing Finite Element Analysis, one of the most common questions is finite element mesh quality. How can one know if the mesh is good enough for the analysis? Mesh density is a significant metric used to control accuracy (element type and shape also affect accuracy). Assuming no singularities are present, 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 the Grid dependency test, where, analysis begins with a coarse mesh and it is refined to a finer mesh for each run until the results do not change significantly and depend on 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 too coarse to produce inaccurate results, nor where it will consume a lot of computing effort and time.
There are different mesh refinement techniques are used which have advantages and disadvantages and some depend on the experience and technical expertise of the FEA analyst. These techniques include- Reducing the element size, Increasing the element order, Global Adaptive mesh refinement, local adaptive mesh refinement, manually adjusting the mesh, Time adaptive mesh refinement, wavelength adaptive mesh refinement, etc.
Procedure:
[NOTE:- the procedure for setting up the material and card is the same for all three cases, so only one case is explained here]
First i opend the ansys workbench and double click on the static structural analysis and rename it 'bevel gear'.
After that we have to double click on the engineering data and select the materail but here we have to make it default (structural steel) as it is no need to change the material.
After that we have to right click on geometry and import the mode which is given in the question.
This is the original geometry then we have to cut the un necessary part from it so again right click on geometry and click on edit in spaceclaim.
Ater the cleanup the geometry will looks like below.
After this we have to right click on model and click update again double click on model to edit and a mechanical widow will open as shown below.
Contact SET-UP
First, make contact under the connection, here the user should select the possible face that involved in the contact. Apart from that, I had defined the Type Definition- Frictional, Behavior-Symmetric, Formulation- Augmented Lagrange, Interface Treatment-Adjust to Touch.
Joint Set up (Revolute)
After contact definition it's time to add joints, Here we are using gears so we have to define the axis of rotation. Revolute joint with Body to ground contact is the best one here.
Analysis setting
here Time step for the simulation is to be set for proper execution of the Analysis.
In the "Static-structural" Deck we have to set the boundary condition. I had to given the Rotation moment to the small gear and the moment to the large one so that it can follow the Right gear rotation movement.
Parameter set
by setting the Input and output parameters in the Parameter set we can check for different conditions like grid dependency. For example, by changing the element length from the coarse level to the fine level we can obtain the result without setting up the case over and over. Also, we don't have to open the model in the model editor. we can make all changes outside in the parameter set deck.
All the parameters with the "p" remark are added to the parameter set. If you want to add a parameter to the Parameter set we just have to click the adjacent check box and when you see the p symbol there it means that a specific parameter is added to the Parameter set you define.
After that, I made an output request for the required results for Von-Mises stress, Equivalent elastic strain, and Total Deformation using the previously mentioned mesh sizes (6mm, 5mm, 4mm)
After successfully adding parameters the parameter set is getting define below the main window as per the above image.
RESULTS:
For the case 1 mesh = 6mm,
Here the equivalent stress is maximum of 345.27 MPa and the minimum of 3.0958e-005 MPa
Equivalent elastic strain:
Here the maximum of equivalent elastic strain is 2.212e-003 and minimum of 1.5479e-010.
Total deformation:
Here the max total deformation is 6.9542 mm and minimum of 6.9542 mm
Like this we got all the values of all three cases in the parametre set as sshown below.
So here from the above data we get the total deformation after changing from coarse mesh to fine mesh which is 6mm of element size to 4mm is almost same which is 6.9542mm, because we have given the face sizing to the are of contact in the bevel gear which is same for all three case is 1.75mm of element size.
And the max equivalent stress in all the three cases are having maximum value of 403.19Mpa which is of 4mm mesh size and it is increasing by decreasing the mesh size.
Lastly the max equivalent elastic strain value 0.0027693 of 4mm mesh size among all the maximum values in three cases.
So here as we decreasing the mesh size the simulation time is increasing so it can achive the best result.
Conclusion:
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.