How to reduce the affects of Volumetric Locking?
I am developing a 3D model of a tyre in ANSYS mechanical. I believe that my model is undergoing volumetric locking as the model is able to accurately predict the two scenarios that I am running, but then at a point (in both cases) the model becomes overly stiff and the sumilation results unrealistically deviate. My results are as follows:
The dotted lines are the simulated results for a 2Bar and 0.8Bar (0 camber) case, and the solid lines are the 2Bar and 0.8Bar case for a 0 and 5 camber angle setting
My full model is described in the dicussion found on: https://forum.ansys.com/discussion/21555/recommendations-on-the-behaviour-of-my-simulated-data#latest.
I found a discussion on: http://engineeringdesignanalysis.blogspot.com/2011/03/volumetric-locking-in-finite-elements.html, which points out that the following alterations can be made to reduce the affect of volumetric locking:
- Use Reduced Integration: It has fewer volumetric constrains [I have tried this and the results barely differed]
- Use of Selective Reduced Integration: It treats the volumetric and deviatoric parts of stiffness matrix separately.
- Use of B-Bar method: Similar to selective reduced integration. But instead of separating volume integral into two parts, the definition of strain is modified.
- Use of Hybrid Elements: They work by including the hydrostatic stress distribution as an additional unknown variable, which must be computed at the same time as the displacement field. This allows the stiff terms to be removed from the system of finite element equations.
- Reduced Integration with Hourglass Control: Artificial stiffness is added to the element which constrains the hourglass mode.
The following are the chnages to my model that I have made to get attempt to get rid of the strange behaviour occuring in my simulated results.
- Changed the integration method to "Reduced" to adjust for volumetric locking as well as shear locking - minor differences found in simulation results
- Changed the integration method to "Full" to adjust for Hourglass mode - minor differences found in simulation results
- Visually checked for the Hourglass mode (shown as jaggered contours in the total deformation results file) - I did not find these marking and thus assumed that the Hourglass mode is not present in my model
- Changed the origionally generated "Bonded" connections which had relative motion between the two objects to "Frictional" contacts - minor differences found in simulation results
- Refined the mesh of some parts of the tyre - despite the increase in solving time, minor differences found in simulation results
- Material adjustments to parts of the tyre - the accuracy of the behaviour prediction was lessened and thus concluded that the material properties of the bodies are correct
- In the model design, to ensure that the tyre rim is treated as static the displacement [x, y, z] = [0, 0, 0]mm as follows is applied to the faces of the sidewalls which come in contact with the rim (inage below). This contact was converted to a remote dispalcement as well as attempted to be changed to a cylindrical support - the remote dispalcement adjuestment led to the model not solving and the cylindrical support could not be applied due to the geometry of the rim-sidewall region (highlighted in yellow in the figure below) not being a cylinder.
Is there a way in which the five previosuly mentioned volumetric locking resolutions can be implemented in ANSYS Mechanical? And if so how is this done?
In addition to this are there any other recommendations that anyone can make, as I am not sure what else I can try to reduce this affect.