FRF
Hi All,
Please Help with the answers for frequency response analysis of impeller assembly.
In the image you can see that impeller is directly coupled to the motor. Motor is fixed to the sheet metal structure in green. The edges of sheet metal bolted to main frame.
1. My doubt is how to do the FRF for rotating structures ?
2. Generally we apply unit force as excitation for a range of frequency in case of structures, what about rotating structures ?
3. How to specify the excitation for rotating structure?
4. Is it possible to give rotary excitation ?
5. what should be my excitation location and response location ?
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Answers
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Hi Karthic,
You can use RFORCE to apply rotational velocity and you can extend the same card to FRF analysis.
You can also apply unit load with load type set to velocity or acceleration on RLOAD card around the preferred axis.
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Thank you Prakash, Should i use both or either one of it?
If possible share me related tutorial using RFORCE and rotational velocity or acceleration on RLOAD card around the preferred axis.
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HI @Karthic
You can use any of one.
Here is an example file for RFORCE which uses transient load case. But you can extend RFORCE to FRF
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Thank you Prakash,
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My impeller operating medium is air, What damping i need to consider for FRF.
structural damping,
material/hysteresis damping,
Rayleigh damping ,
viscous damping ? Please put up me with some idea how to consider damping
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Hi @Karthic
For most of the practical applications, only material damping is considered.
If at all, air is a critical medium, you can use viscous damping for air.
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Structural damping is PARAM,G
How to give viscous damping and material damping ?
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Please check KDAMP
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Altair Employee