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CQUAD4 vs CQUAD8 vs CQUADR

Pioneer
Pioneer

Hey together,

I am planning to mesh an axisymmetric "Casing", which approximately looks like a cylinder with some changing diameters as a shell model. I have already been trying to read myself into the different element types, but I was not able to extract the correct element for my case.

After the meshing, I am going to do a dynamic reduction.

 

The Quad elements are to prefer because of quality and precision reasons according to some references. But there are three main Quad elements in NX: CQUAD4, CQUAD8, CQUADR

CQUAD4 is according to the element guide the most common element, but is perhaps not perfectly fitting for my cylinder-like casing. CQUAD4 is better when meshing a doubly-curved shell (like a sphere) whereas the CQUAD8 performs better by singly-curved shells like cylinder. Is there anything I have to consider concerning the midnodes as there are 3 different possibilites to generate them?

 

Can somebody explain the advantages of the CQUADR to me please?

And which kind of element would be the best-suited for my case?

 

I already did a comparison with these three elements. The resulting eigenvalues are approximately up to 1% different. Where do these deviation come from?

 

Thank you a lot!

Best regards.

Benny

 

2 REPLIES

Re: CQUAD4 vs CQUAD8 vs CQUADR

Siemens Phenom Siemens Phenom
Siemens Phenom

CQUAD4 has a linear strain variation and 5dof stiffness. There is no in-plane rotational (drilling) stiffness in the formulation. The in-plane rotations are typically constrained automatically by AUTOSPC

 

CQUADR has a linear strain variation and 6dof stiffness. An in-plane rotational stiffness is part of the formulation

 

CQUAD8 has a parabolic strain distribution. There is no in-plane rotational (drilling) stiffness in the formulation.

Re: CQUAD4 vs CQUAD8 vs CQUADR

Pioneer
Pioneer

Thank you very much Jim!