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Displacement gradient in axisymmetric model
Posted Sep 9, 2016, 10:02 a.m. EDT 2 Replies
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Hi there!
I am working on Weak Form PDE in an axisymmetric model and I need to implement the displacement gradient. I am facing problems because COMSOL recognizes PHI as an undefined varible, so I cannot take its derivative. In cartesian coordinates, being u and v my displacement field, I would do my gradient as:
ux uy
vx vy
So, how do I implement then?
ur 1/radius*(d(u,phi)-phi)
vr 1/radius*(d(v,phi)+r)
Idiot question, but it's taking me so long... Please help!
I am working on Weak Form PDE in an axisymmetric model and I need to implement the displacement gradient. I am facing problems because COMSOL recognizes PHI as an undefined varible, so I cannot take its derivative. In cartesian coordinates, being u and v my displacement field, I would do my gradient as:
ux uy
vx vy
So, how do I implement then?
ur 1/radius*(d(u,phi)-phi)
vr 1/radius*(d(v,phi)+r)
Idiot question, but it's taking me so long... Please help!
2 Replies Last Post Sep 9, 2016, 12:57 p.m. EDT
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Posted:
8 years ago
Ingrid,
maybe I misunderstand the issue, but in an axisymmetric model nothing depends on phi, so all derivatives regarding phi should be zero, no?
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
maybe I misunderstand the issue, but in an axisymmetric model nothing depends on phi, so all derivatives regarding phi should be zero, no?
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
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Posted:
8 years ago
Edgar, thanks for your prompt reply. I am trying to evaluate stress at the crack tip of a geometry (like a pac-man) and it depends on the radius and the angle. I have prescribed both displacement and pressure.
To implement in axisymmetric, I need to inform the gradient of the displacement field so I can get the infinitesimal strain tensor. My problem is on how to declare this gradient of the displacement.
Thank you once again.
To implement in axisymmetric, I need to inform the gradient of the displacement field so I can get the infinitesimal strain tensor. My problem is on how to declare this gradient of the displacement.
Thank you once again.