ceyhunsozbir
Mechanical
- Jan 24, 2011
- 5
ANSYS problem: difference in /post1 and /post26 results
Hi all,
I am doing harmonic analysis in ANSYS 11.0 for a ultrasonic sonotrode we are trying to improve. The sonotrode is bounded only to the transducer that is producing +-0. 6 µm displacement at 60kHz. Tis condition is applied as 1.2 µm displacement boundary condition. (please see problem.doc)
I did modal analysis and then harmonic analysis to see the behavior around a eigen frequency close to 60kHz. I need to read some displacement and stress results at the tip of the sonotrode and on the surface.
After doing harmonic analyses in general postproc (/post1) I looked at the displacement results from results viewer. I have seen that very close to eigenfrequency (60029 Hz), there is a weird movement which is totally different from the eigenmode. But +- 4 Hz from the eigenmode frequency, the movement is similar to the modeshape.
More than that, when I open the timehist postproc (/post26) and track the displacement results at the tip of the sonotrode I saw that result is different from /post1 result. When I read the displacement results at the tip using /post1 prnsol command the tip movement gets very low (due to the weird movement I explained). And if I read displacement using /post26 nsol command the tip displacement is highest at the eigen frequency as expected. (please see frequency response graph in doc file)
My question is:
What may be the reason of the weird movement? Should I read displacement results using /post1 prnsol or /post26 nsol for the analysis I make? I am really confused with the concept and I appreciate any help.
Thanks.
Muharrem Ceyhun Sözbir
Mechanical Engineer
RWTH Aachen
Hi all,
I am doing harmonic analysis in ANSYS 11.0 for a ultrasonic sonotrode we are trying to improve. The sonotrode is bounded only to the transducer that is producing +-0. 6 µm displacement at 60kHz. Tis condition is applied as 1.2 µm displacement boundary condition. (please see problem.doc)
I did modal analysis and then harmonic analysis to see the behavior around a eigen frequency close to 60kHz. I need to read some displacement and stress results at the tip of the sonotrode and on the surface.
After doing harmonic analyses in general postproc (/post1) I looked at the displacement results from results viewer. I have seen that very close to eigenfrequency (60029 Hz), there is a weird movement which is totally different from the eigenmode. But +- 4 Hz from the eigenmode frequency, the movement is similar to the modeshape.
More than that, when I open the timehist postproc (/post26) and track the displacement results at the tip of the sonotrode I saw that result is different from /post1 result. When I read the displacement results at the tip using /post1 prnsol command the tip movement gets very low (due to the weird movement I explained). And if I read displacement using /post26 nsol command the tip displacement is highest at the eigen frequency as expected. (please see frequency response graph in doc file)
My question is:
What may be the reason of the weird movement? Should I read displacement results using /post1 prnsol or /post26 nsol for the analysis I make? I am really confused with the concept and I appreciate any help.
Thanks.
Muharrem Ceyhun Sözbir
Mechanical Engineer
RWTH Aachen
