Discussion Forum

Hi

I am carrying out an estimation of eigenfrequencies of a multiwalled carbon nanotube of 50nm of diameter and 10um of length. This is a work that has been developed before, and can be found in the literature, however the lenght and diameter used on such work is shorter.

According to those works, a model based on Euler-beam theory can succesfully estimate the eigenfrecuencies. So, I build a model based on it. After some calculus to determine the area moment of inertia and torsional constant for a concentric geometry, we run the model, and the obtained results were very similar to reported. The eigenfrequencies obtained are in the order of THz.

However, when we want to visualize the deformed shape of the beam, this is not showed. If we only check the option for Boundary in "postprocessing>plot parameters" and also we select any obtained eigenfrecuency, we can clearly observe the zones on the beam were the crest of the "vibration modes" are located, by means of the "total displacement". (Please find attached: Image 1: The zone of total displacement at vibration mode of 3.08 THz. Image 2: a Line/extrusion plot of the beam, where is shown the displacements at "crest" of the vibration mode.)

Why cannot I visualize the deformed shape of the beam when I check the option "deformed shape" in plot parameters?.

When we performed this same model at larger scale (m), the deformed shape can visualized. Is there a constraint of COMSOL 3.5a for nanoscale concerning these issues?

I really will appreciate the answer of someone from this useful forum.

Thank you.

PSD: THE MODE OF VIBRATION AT IMAGE1 IS 3.08 THz. and not as "TPa".