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# Solid elements only support translation DOF but not rotation3

## Solid elements only support translation DOF but not rotation

(OP)
Solid elements do not support rotation at nodes. The question is that if we have bending in our problem, using solid element would Ok? Why?
Thanks

### RE: Solid elements only support translation DOF but not rotation

It only means that you can’t apply the rotation or moment directly to nodes of these elements (and read these quantities from the nodes). There are workarounds though - usually moment or rotation is applied via special rigid links. There’s no impact on the accuracy of bending calculations.

### RE: Solid elements only support translation DOF but not rotation

Ah, no. Some solid elements are awful in bending; some are ok when used with sufficient mesh density. Some FE codes have solid (3D) shell elements. See the theoretical manual for what ever FE code you are using for bending test cases for each element type.

### RE: Solid elements only support translation DOF but not rotation

Solid elements may exhibit accuracy issues in bending due to phenomena like shear locking. It’s important whether the element is of first or second order and if it uses full or reduced integration. But in addition to standard solid elements, advanced FEA software offers elements with special formulations to better handle, among others, bending problems. For thin parts, shells are often a better choice but again - it depends. That’s why there are plenty of benchmarks that compare the accuracy of various element types in particular problems. Many of them focus on bending.

### RE: Solid elements only support translation DOF but not rotation

Consider a solid rectangular cube (like your mobile phone or Rubik's cube) and just try to twist/bend it with hand. Its not easy, right. Same thing happens with rectangular, or for that matter any, solid elements. Try bending or twisting the steel sheet or scale or steel wire which seems to be easy. The rotational stiffness of solid elements is higher than shell/beam elements and keeping this in mind these elements are formulated with only 3 translational DoF's.

Even if there are three DOF's, bending is till possible since we can bend the Rubik's cube by some means if not by hand. As its already pointed out by FEA way that there are means to achieve that.

Regarding the shear locking/volumetric locking/hourglassing effects in simulation using solid elements, I suggest to search the discussions on this forum like this - Link

### RE: Solid elements only support translation DOF but not rotation

Hi
I think you are asking the wrong question. Instad of thinking in terms of if a particular element supports for example bending, ask what element should be used for a specific analysis.

My choice is usually based on the dimensions for the analyzed object and what results I need. In some cases beams (1D) suffice, I seldom need to go beyond plates (2D) but if I need solids (3D), I use them. But I don't use solids if I don't have to. The answer to your question can probably be found in the software manual and also run som tests to check how it works.

Thomas

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