Learning Forum

[JWagoner]

I am an user of APDL. I am working with an anisotropic plate (using material properties of silicon), which is fixed at four sides. The plate has some thickness and subjected to pressure. Basically, I am trying to do bending simulation of an anisotropic plate. I would like to use 2D PLANE element. What could be a suitable 2D PLANE element, which can offer transverse deflection Uz? For example, I checked with element type PLANE13 and PLANE223. But, the DOF is only Ux and Uy -- NOT Uz. Any suggestion please? 

[peteroznewman]

JW,

Applying pressure to a plate in the XY plane to see transverse deflection Uz is a 3D problem so you want a 3D element.

For a thin structure, use SHELL181 for a linear element or the preferred SHELL281 quadratic element.

Regards,
Peter

[JWagoner]

Are there any 3D elements that can use the plane stress assumption such that the stress in the z direction, xz direction, and yz direction are equal to zero? This was ultimately my reason for trying to use the 2D plane element. Also, I believe using the command “DOF,UZ” should add the z direction to the 2D element, is this true?

[peteroznewman]

JW,

If you apply pressure on one side of a plate normal to Z, and zero pressure on the other side of the plate, by definition, that creates a Z axis stress gradient through the thickness of the plate, right?

I don't know what the DOF,UZ command does, but I doubt it adds a z degree of freedom to a 2D element.

Regards,
Peter

[Sandeep Medikonda]

Indeed, the way FEA works from a constitutive response perspective is that the strains are input for the valid tensorial directions of that particular element (element formulation) and the stresses are then calculated based on the constitutive law specified (Elastic, Plastic etc.). Now, if the element doesn't even have those degrees of freedom (transverse in your case), you can't get a stress response in those degrees of freedom.

Coming to this command, typically some DOFs are not active even if the element can support it. So if you do a thermo-mechanical problem you may need to switch it ON. So, in short, you can't add degrees of freedom to an element if it doesn't support it in the first place.

Regards,
Sandeep