Nucleophobe
Bioengineer
- Sep 7, 2012
- 29
I am working on modelling the response of an orthotropic hyperelastic material (vein) to a given load. Because the local thickness of the material is unknown, shell elements with a constant thickness are used. I am able to get the simulation to run. However, I had some questions about the material properties.
The orthotropic material in Abaqus requires 11 material constants: b1111, b2222, b3333, b1122, b1133, b2233, b1212, b1313, b2323, c, and D. The parameter 'c' defines the linear response of the material, while 'D' determines the response to a thermal load and may be set to 0.
Since this is a 2D shell model, I thought all terms involving the '3' direction would drop out. Abaqus requires that b3333, b1133, b2233, b1313, and b2323 are non-zero however. I have been setting them to arbitrary values and observing the results. The solutions seem to be quite similar with widely varying properties in the '3' direction; however, the solutions do not converge when these constants differ from my b1111 and b2222 constants by an order of magnitude or more.
Needless to say I'm a little lost concerning the theory behind this material model. With a 2D orthotropic material, shouldn't I only need the modulus in the '1', '2', and '12' directions? That would leave b1111, b2222, b1122, and c.
Any comments / recommended references would be greatly appreciated. Thank you!
The orthotropic material in Abaqus requires 11 material constants: b1111, b2222, b3333, b1122, b1133, b2233, b1212, b1313, b2323, c, and D. The parameter 'c' defines the linear response of the material, while 'D' determines the response to a thermal load and may be set to 0.
Since this is a 2D shell model, I thought all terms involving the '3' direction would drop out. Abaqus requires that b3333, b1133, b2233, b1313, and b2323 are non-zero however. I have been setting them to arbitrary values and observing the results. The solutions seem to be quite similar with widely varying properties in the '3' direction; however, the solutions do not converge when these constants differ from my b1111 and b2222 constants by an order of magnitude or more.
Needless to say I'm a little lost concerning the theory behind this material model. With a 2D orthotropic material, shouldn't I only need the modulus in the '1', '2', and '12' directions? That would leave b1111, b2222, b1122, and c.
Any comments / recommended references would be greatly appreciated. Thank you!