I want to do modal analysis for finding natural frequencies should I conduct part by part giving fixed constrains or as a whole assembly with bonded contact I should conduct the analysis which is best way kindly suggest.
I think the best idea here is to describe your application and what you're trying to learn in the analysis.
Your initial question is relatively straight forward. If you have a part, analyze the part. If you have an assembly, analyze and assembly.
This thread might give you some starting ideas:
Oh, and the response of the assembly will not be the same as the part, partly because you cannot accurately model the interactions. An easy to understand, real-world example is the tuned-mass-damper on large power lines. If the little part wasn't there then the cables would vibrate and destroy themselves.
Dear James Riddell
Thanks for the reply kindly explain if I want to find the natural frequencies of thread grinding machine which condition should I consider I feel maximum vibration will be on sheet guards so assembly with sheet guard will it be fine
As long as your natural frequencies are no where near your operating frequencies then the structure should not fail due to vibration. Almost always you want to know the frequencies of the assembly. Don't forget to take into account the mounting condition of the machine to the floor.
These are the results I got In assembly Analysis is it reasonable kindly suggest
only you can tell us. what is the expected freq response?
Then I seriously doubt your answer you got with the assembly frequency analysis is actually correct as you marked it. You probably have not taken into account (correctly) the actual connections between parts (i.e. bolted joints with pre-load, gaskets, etc.) which all would contribute to damping and/or resonance.
(Of course, all Adams fans know that the correct answer is 42.)
Dear James Riddle,
kindly provide the reference for the value how 42 is arrived and quoted as right answer how it can be applicable for all structures as the natural frequencies are mainly depends on stiffness and mass either of the one varies the natural frequency of the structure varies ( for conducting modal analysis the following inputs are must in material property is Young's modulus to relate with stiffness, Poisson's ratio to relate with lateral and longitudinal strains and Density to relate with mass) and resonance occurs while forced frequencies matches with the natural frequencies of the structure
My answer of 53 HZ was arrived from the maximum forcing frequency at the maximum rpm of wheel spindle the generated frequency. since all other forcing frequencies are less than 53 Hz I didn't considered those frequencies.
I defend the structure will not fail as the first natural frequency fall at 70 Hz as my maximum forcing frequency itself 53 Hz, no forcing frequency goes beyond that
I know Damping is needed to absorb energy from the process and to prevent chatter and damage to the surface to absorb energy from structural modes excited by the servos and other sources. The damping co efficient will not affect the value of natural frequency ( if required I will provide reference)
I have considered all bolted connections and assigned material properties for gaskets etc. with out providing material properties analysis cannot be done
For your information combined damping effect on machine structures.
Dear James Riddell,
As you doubt the answer I just un mark the answer as correct answer If you feel any of the other answer is correct kindly discuss I will surely mark as correct answer.
i think 42 was a joke.
in the end, only you can tell us what the frequency should be. either from hand calcs or experiments. your note below is that you checked it against ansys. that is a good test but if you use the same conditions in both simulations, you are just checking the consistency between analysis tools.
Comparison of Solid works analysis result with ANSYS results for same boundary conditions and material properties considering machine base alone. "The results are matching but it took 3 hrs in solid works but 1.5 day in ANSYS"
Retrieving data ...