| Author | Message | |||
     Mehdi Naderi (mnader4) Member Username: mnader4 Post Number: 50 Registered: 12-2006 |
Dear Mr. Nelson, I will appreciate if you help me in my problem. A crack exits in the edge of a plate (attached file) with length a0. As time passes crack moves from left to right and the motion of the crack tip is known (a(t)=a0/(1-t)^2). I am trying to use moving mesh to solve heat conduction while crck tip moves. I am wondering if you give me your hints.  | |||
| Marek Nelson (mgnelson) Moderator Username: mgnelson Post Number: 61 Registered: 07-2007 |
Attached is a script that does something close to what you want. This is just the mesh, so you will have to add your heat equations. You will probably want to adjust some of the mesh related values too. I defined two variables : 'a' for the surrogate X variable and 'v' for the internal node velocity diffusion. The velocity of 'a' and the value of 'v' for the nodes on the edge of the crack are defined as 2*a/(1-t). I also defined a feature from the tip of the crack to the opposite side of the plate and defined a velocity for the nodes on this feature. This was to keep the cells evenly spaced as the crack deepens and to avoid having the tip of the crack penetrate into the cells there.
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| Mehdi Naderi (mnader4) Member Username: mnader4 Post Number: 51 Registered: 12-2006 |
Dear Mr. Nelson, I really appreciateyour help. I defined heat conduction equation. A heat source exits at the tip of the crack. As crack propagates the heat source generates heat at the crack tip and moves with crack. In flexPDE how can I impose a point source at the crack tip? for example; source=10000*a0/(1-t)^4 | |||
| Marek Nelson (mgnelson) Moderator Username: mgnelson Post Number: 62 Registered: 07-2007 |
You can do this with POINT LOAD. It is stated in the same fashion as any other BC, but it applies to the point preceeding the statement. So LINE TO (x,y) POINT LOAD (u)=... where (x,y) is the tip of the crack and u is your temp variable. See "Point Load" in the Help index. | |||
| Mehdi Naderi (mnader4) Member Username: mnader4 Post Number: 52 Registered: 12-2006 |
Dear Mr. Nelson, Thank you so much. I applied the point load, but temperature result is not reasonable. Is it because of course mesh or FEM problem in sharp corner? I will appreciate if you answer my question
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| Mehdi Naderi (mnader4) Member Username: mnader4 Post Number: 53 Registered: 12-2006 |
I'm sorry, here it is the modified file
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| Marek Nelson (mgnelson) Moderator Username: mgnelson Post Number: 64 Registered: 07-2007 |
I suspect that there is a discrepancy of units. It looks like you have KMS (Kg-m-sec) units for your conductivity etc. I started this model with arbitrary dimensions of 20x30. That means this script is modeling a block 20 meters wide by 30 meters high. Try dividing all your dimensions by 100 or 1000 (i.e. cm or mm). |
moving crack in a plate