Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
weird deformation of ultra thin plate under thermal expansion
Posted 5 lug 2013, 14:20 GMT-4 Structural Mechanics Version 4.2a, Version 5.0 5 Replies
Please login with a confirmed email address before reporting spam
I am using the structural mechanical module to simulate the deformation of a ultra thin plate under the temperature change. the plate size is: length 100mm, width 5mm, height 0.1mm, the material properties are: E = 3.0e9, poisson ratio is 0.3, desity is 1000 kg/m^3 , coefficient of thermal expansion is 1.2e-4. I am using linear elastic material model and adding the thermal expansion under this model. the temperature is the only load which changes from 340 to 290 K. The Boundary conditions: the bottom plane is fixed, while all other boundaries are free. the final simulation result shows the upper portion is under the bottom plane, which is weird! It should above the bottom plane. please refer to the attached pictures.
I tested, this weird problem is possibly due to the fact that the ratio of length to height is too large. I change the height to 1mm, the length to 40mm, and the simulation results shows the deformation of the upper portion is above the bottom plane, which is reasonable.
Can anybody give an explanations and any help for simulating the ultra thin plate deformation? Thanks very much!
Wei
Please login with a confirmed email address before reporting spam
Are you including Geometric non-linearity? This is important for large strain (ie strains above ~10%) or large rotation problems.
Your structure looks pretty flimsy so I wouldn't be surprised if you are getting large strains and/or rotations. This would also explain why the problem goes away for a thicker plate (more stiffness, less deformation).
Best regards,
Josh Thomas
AltaSim Technologies
Please login with a confirmed email address before reporting spam
I tried to check the include geometric nonlinearity checkbox under the linear elastic material model, run it and got the same results.
In my example, the coefficient of thermal expansion is 1.2e-4, the temperature drop is around 50 K, so the strain is not large.
Does the large ratio of length to height matters?
Wei-
Are you including Geometric non-linearity? This is important for large strain (ie strains above ~10%) or large rotation problems.
Your structure looks pretty flimsy so I wouldn't be surprised if you are getting large strains and/or rotations. This would also explain why the problem goes away for a thicker plate (more stiffness, less deformation).
Best regards,
Josh Thomas
AltaSim Technologies
Please login with a confirmed email address before reporting spam
The problem is why the deformaiton is not reasonable when the bottom plane is fixed?
Attachments:
Please login with a confirmed email address before reporting spam
Have you made sure that this is not just a plotting scale issue? Is the the scale in the deformation plot '1'? What are the max/min values of the deformation in the Z direction 'w'?
Regards,
Henrik
Please login with a confirmed email address before reporting spam
I check the results, and it is the problem of plotting scale. the scale factor is over 900. when I set the scale factor to 1 or 10, the result seems reasonable. I wonder why comsol sets a defaut scale factor to the deformation result as it may be misleading. Thanks again.
Best,