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.

Displacement gradient in axisymmetric model

Please login with a confirmed email address before reporting spam

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!

2 Replies Last Post 2016年9月9日 GMT-4 12:57
Edgar J. Kaiser Certified Consultant

Please login with a confirmed email address before reporting spam

Posted: 8 years ago 2016年9月9日 GMT-4 10:19
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
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 http://www.emphys.com

Please login with a confirmed email address before reporting spam

Posted: 8 years ago 2016年9月9日 GMT-4 12:57
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.
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.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.