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Boundary Conditions for Z-Axis in a 2D Simulation (Solid Mechanics)
Posted Dec 4, 2013, 2:00 p.m. EST Geometry, Structural Mechanics Version 4.3b 1 Reply
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Hi,
I'm having difficulty figuring out how to set desired boundary conditions for the Z-axis in a 2D solid mechanics simulation. I would like my model to be infinite along the Z-axis with a fixed strain, but when I simulate such a structure, I get no strain along the Z-axis. I believe this is because the simulator treats the Z-axis as a free surface, but instead, I'd like to impose Neumann boundary conditions such that strain is maintained along the Z-axis.
Essentially, I'm modeling a substrate with 2.5% compressive strain along the X and Z directions, and I want to see the impact of this strain upon a thin rod on the top of the substrate. The substrate and rod are infinite in the Z direction, so a 2D simulation is used.
Note: I've been able to get the correct results with cylindrical coordinates using 2D axisymmetric geometry (a pseudo 3D simulation), but I would like to model the device using 2D geometry instead of 3D due to computation and memory considerations.
Attached is the model file.
Thanks for your help!
Jamie
I'm having difficulty figuring out how to set desired boundary conditions for the Z-axis in a 2D solid mechanics simulation. I would like my model to be infinite along the Z-axis with a fixed strain, but when I simulate such a structure, I get no strain along the Z-axis. I believe this is because the simulator treats the Z-axis as a free surface, but instead, I'd like to impose Neumann boundary conditions such that strain is maintained along the Z-axis.
Essentially, I'm modeling a substrate with 2.5% compressive strain along the X and Z directions, and I want to see the impact of this strain upon a thin rod on the top of the substrate. The substrate and rod are infinite in the Z direction, so a 2D simulation is used.
Note: I've been able to get the correct results with cylindrical coordinates using 2D axisymmetric geometry (a pseudo 3D simulation), but I would like to model the device using 2D geometry instead of 3D due to computation and memory considerations.
Attached is the model file.
Thanks for your help!
Jamie
Attachments:
1 Reply Last Post Dec 6, 2013, 2:24 a.m. EST
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Posted:
1 decade ago
Hi,
As you have observed, the Plane Strain formulation enforces that the out-of-plane strain solid.eZZ=0. What you are looking for is a condition which sometimes is called 'Generalized Plane Strain', where the out-of-plane strain is fixed to a non-zero value.
It is not so that the structure is free in the Z-direction, that would be Plane Stress. (You choose between Plane Strain and Plane Stress in the 2D Approximation Section of the Solid Mechanics interface).
The probably easiest way to do what you want to do is to create a thin slice in a 3D model. Use a swept mesh with only one element in the Z direction. Put a Roller condition on one face and a Prescribed Displacement on the opposite face. Prescribe the displacement so that w/thickness = intended strain.
Regards,
Henrik
As you have observed, the Plane Strain formulation enforces that the out-of-plane strain solid.eZZ=0. What you are looking for is a condition which sometimes is called 'Generalized Plane Strain', where the out-of-plane strain is fixed to a non-zero value.
It is not so that the structure is free in the Z-direction, that would be Plane Stress. (You choose between Plane Strain and Plane Stress in the 2D Approximation Section of the Solid Mechanics interface).
The probably easiest way to do what you want to do is to create a thin slice in a 3D model. Use a swept mesh with only one element in the Z direction. Put a Roller condition on one face and a Prescribed Displacement on the opposite face. Prescribe the displacement so that w/thickness = intended strain.
Regards,
Henrik