XANSYS Message: 84575 [Go back to message list]
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Subject: Funny error with *MOPER MAP operation
Author: Wong Chee How
Date: 2006-10-05 09:45:41Dear Group,
Good day. As before, I am trying to model the thermal-structural effect of a head/slider of a harddisk. I have completed the modeling and after solving the results look good. The next step is to find out the displacement values of points not defiined by any nodes. I have read through the archive of Xansys and understand that I have to make use of *MOPER MAP command to get the interpolated displacments. At the same time, I have also seen the mapme.mac macro as well as its accompanying input file (mapme.inp) available in www.ansys.net.
I tried not to jump straight using the macro, hence I get my hands dirty by playing around with the macro. In the macro, both the input mesh size and the output mesh size has exactly the same volume as the model. However, that is not feasible in my research as I only need the displacement values of a small part of the model. Additionally I realised that both the input mesh and output mesh volumes are solved together albeit the output mesh volume is constrained in all directions * which effectively means it is not affecting the final results. Again that is something I thought I can skip by:
1. Solve the model as usual but without the output mesh volume
2. After solving, activate /PREP7 and model a small area at the top of the input volume
3. Mesh the area with MESH200 elements
After the above steps, I start to *VGET the coordinates as well as displacments before the *MOPER MAP operation. To my gladness, it works! I am able to get interpolated displacement values on the small area I had defined with MESH200 elements. Not satisfied, I continued to make the MESH200 elements finer and coarser and everytime I am able to get the results fine.
With that in mind, I applied the same methodology on my head/slider model. Initially, I started using a 11 x 11 mesh with MESH200 elements to obtain the displacement. The results were fine. However, I thought 11 x 11 is too coarse. Hence I increase the mesh to 50 x 50. Alas, this time Ansys, though still able to give me interpolated values, indicates that there are a few output points that are outside of the input region. It simply assigns the values from the nearest nodes to those output points with errors. Of course, I indicated ANSYS to do that by issuing the '0' at the end of the *MOPER command but I don't really expect Ansys to use it since all the output points are within the input region. Ansys should be able to interpolate all points successfully without having to use the '0' option.
That really puzzle me because I have not changed anything other than the mesh of the small area that I want to obtain the interpolated values for. I have also made a nodal plot and verified those output points ANSYS indicated out of region are certainly within the boundaries I set for the input region.
I then try and error with different mesh size and find that as far as my model is concerned, ANSYS will start reporting output points outside of the input region as long as the mesh is 25 x 25 and above.
The puzzling thing is I am able to use the same methodology on the mapme.mac macro as well as the mapme.inp file found in www.ansys.net without any errors despite how small the mesh size is. However, why is it that when I transfer the same method to my model, ANSYS starts reporting error?
I am, therefore, wondering if any ANSYS user here has faced the same problem as me before and is there any solutions to it? I hope I am not missing something crucial to the *MOPER MAP command.
Thank you very much and any suggestions will be deeply appreciated.
Regards,
CH WONG
Research Fellow
DSI
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