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Posted: 8 years ago 3 giu 2016, 17:53 GMT-4

Hi Hoon, It looks like you forget to define the material properties. You can specify the crystal orientation by defining anisotropic material properties (like Young's modulus). Hope that helps you!

Posted: 8 years ago 5 giu 2016, 14:19 GMT-4

[QUOTE] I would like to simulate 3D solid mechanics eigenfrequency study, with just simple rectangular waveguide. My rectangular waveguide is just 400um x 80um x 40um, I set Fixed constraints at both end, and used normal mesh. Finally material is Si - silicon(single crystal, anisotropic). Here was the problem. the material I choose was crossed with red cross. Also, there were STOP signs at Young's modulus and Poisson ratio. Ofcourse, clicking the study gives me an error, saying ------------------------- Undefined variable. - Variable: material.nu - Geometry: geom1 - Domain: 1 Failed to evaluate Jacobian of expression. - Expression: (-(2*comp1.solid.Sl12))*dvol Failed to evaluate Jacobian of expression. - Expression: (-comp1.solid.Sl11*test(comp1.solid.el11)-2*comp1.solid.Sl12*test(comp1.solid.el12)-2*comp1.solid.Sl13*test(comp1.solid.el13)-comp1.solid.Sl22*test(comp1.solid.el22)-2*comp1.solid.Sl23*test(comp1.solid.el23)-comp1.solid.Sl33*test(comp1.solid.el33))*(dvol) - Feature: Eigenvalue Solver 1 (sol1/e1) ------------------------- So, How do I implement anisotropic silicon with crystal orientation into this model? (as well as --------------------- well i found the forum, https://www.comsol.com/community/forums/general/thread/2329 but it was in 2009. where on earth is Orientation/Condition? [/QUOTE] Hello Hoon Jeong, After defining the material properties under the material section, you need to check what type of orientation you have in comsol material library. If you have 100 orientation then it is okay. But if you have some other orientation e.g. 110,111 then you will need to define a rotational frame where you will write the rotation angle according to the orientation that you want (In this case 100). Then in the physic module you are going to use the rotated frame. Best,

Posted: 8 years ago 10 giu 2016, 10:04 GMT-4

If you have added anisotropic single crystal silicon from the materials library, I think you have just not changed your material to anisotropic in your physics Is there a warning sign on your “Materials” section? If so, just click on “linear Elastic Material 1” in “solid Mechanics” physics On the settings locate “linear Elastic Material” section Change “solid model” to Anisotropic Check if everything is correct in your “Materials” section… Hope this helps Dara

Posted: 8 years ago 10 giu 2016, 11:20 GMT-4

Wow thanks This one really helps!