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stress strain for heterojunctions
Posted Jan 27, 2010, 7:38 p.m. EST 2 Replies
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I have modeled a heterostructure with the epitaxial layer being very small compared to the substrate. I have modeled the epilayer as orthotropic.
For a given young's modulus within the elastic limit, the stress comes out to be around 0.4 GPa greater than what's expected.
I have changed the thermal expansion coefficient for the x and y directions(-8.4e-3 in each direction) and have kept zero expansion coefficient in the z direction. I have changed the temperature by 1 K. I have disabled thermal expansion of substrate.
The Young's modulus is 125 GPa and the strain is 0.0084, whereas the stress plotted is 1.29 or so GPa. The expected stress is 1.05 GPa. why should that happen. The strain comes out as expected but not the stress. Is there any way to correct this or am I doing something wrong?
For a given young's modulus within the elastic limit, the stress comes out to be around 0.4 GPa greater than what's expected.
I have changed the thermal expansion coefficient for the x and y directions(-8.4e-3 in each direction) and have kept zero expansion coefficient in the z direction. I have changed the temperature by 1 K. I have disabled thermal expansion of substrate.
The Young's modulus is 125 GPa and the strain is 0.0084, whereas the stress plotted is 1.29 or so GPa. The expected stress is 1.05 GPa. why should that happen. The strain comes out as expected but not the stress. Is there any way to correct this or am I doing something wrong?
2 Replies Last Post Jan 29, 2010, 5:30 p.m. EST
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Posted:
1 decade ago
Hi
Difficult question. I would start to take a look at the meshing details: turn off interpolation and use 1, as well as remove filling view to really see the mesh details.
I would first suspect a stress concentration issue. These are not necessarily just numerical "errors" stress concetration due to holes, or just some geoemtrical shapes are a serious concern in structural
Good luck
Ivar
Difficult question. I would start to take a look at the meshing details: turn off interpolation and use 1, as well as remove filling view to really see the mesh details.
I would first suspect a stress concentration issue. These are not necessarily just numerical "errors" stress concetration due to holes, or just some geoemtrical shapes are a serious concern in structural
Good luck
Ivar
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Posted:
1 decade ago
Thanks for the reply.
If i want to plot stress vs length in a graphical manner and not just as colour contours does COMSOL enable me to do that? For example in Microsoft excel one can plot X-Y scatter graph, can I do the same thing in COMSOL?
Thanks,
Salil.
If i want to plot stress vs length in a graphical manner and not just as colour contours does COMSOL enable me to do that? For example in Microsoft excel one can plot X-Y scatter graph, can I do the same thing in COMSOL?
Thanks,
Salil.