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Hello Greg, First thanks for stepping in. From paper attached in my previous reply i understood, limited strain gauge measurements under actual operating load is all that is required to decompose and evaluate modal responses as function of time (refer page 8 in attachment).This is exactly the...

Thanks Jason for paper and tips , I will have a closer look at them. Just few more points for clarity I actually don't want to obtain mode shapes what i want to do is to decompose strain measurements into modal response. I was able to find a Paper which exactly is dealing with the kind of...

Hello Experts , I have a structure with multiple strain gauges attached to it. It is under fluctuating load. We know the response at any point is basically linear combination of scaled mode shapes. Is it possible to accurately decouple the total strain response from each gauge into modal...

i would highly appreciate if someone could clear my doubt regarding resonance condition of a cyclic structure (say Bladed disk). Most of the articles mention two conditions to be respected: matching frequency ( excitation force and natural frequency) matching nodal diameter of the structure...

i would highly appreciate if someone could clear my doubt regarding resonance condition of a cyclic structure (say Bladed disk). Most of the articles mention two criteria to be respected: matching frequency ( excitation force and natural frequency) matching nodal diameter of the structure with...

Hi Greg first thanks for the interest.Experimental modal analysis is new area for me. So may be i was not able to provide you with adequate information. By first plot i wanted to show that by FEA modal analysis i get a set of natural frequencies whose values are very close to each other (Case...

I have a bladed disk with 21 blades. By FEA i have obtained the First family of in plane bending modes. See the attached file(FEA_results). http://files.engineering.com/getfile.aspx?folder=2720cf01-3b8b-4bfa-bb74-05a88111a23e&file=FEA_result.png After i did an experimental modal analysis using...

Thanks amanuensis for showing interest. May be i did not made my problem clear. I built 1/3rd sector of model and applied cyclic symmetry.Hence results should follow ideally: Harmonic Index Nodal diameter set 0 : 0,3,3,6,6,9,9,12,12...... 1 ...

Is any additional information required GregLocock?

Can someone provide a bit insight into the problem.

Thanks Greg for clarification. I have attached the picture below in word format , i hope this should help. Also is it likely that as i have displacement constraint not symmetrical (that is i don't have them on both sides) , i am missing nodal diameter 1 and 2? Please...

Sorry Greg but i couldn't pickup your hint.

Hi all , I am doing modal analysis of a rotating machine.In my first run i used a sector and applied cyclic symmetry analysis in ansys code. i tried to extract first 10 nodal diameters of bending modes. I was able to identify bending modes for nodal diameter = 0,3,4,5,6,7,8,9,10. However nodal...

Dear GregLocock , From the testing team i got the input that maximum variation for nozzle to nozzle excitation can't go beyond 1%. For damping ratio values we have done hammer test on the bucket to get the individual values for each natural frequency. Now i have to use these damping ratio...

Thanks Greglocock for your reply,I am new to vibrations and will go with your experience. Now when i take all the modes into consideration, what are the potential points i look into my Campbell diagram (from FEA) in addition to resonance frequencies? In other words i am not sure what impact...

can anybody give some insight into the above posted question: considering force from all 6 jets is same [highlight #EF2929](considering only bending modes) : Is it possible to ignore some bending modes on the basis of things like it is excited by 6 jets in one revolution or had it been one...

Thanks GregLocock for your reply. few clarifications: Just for my understanding for a moment if i ignore my axial and lateral modes and focus only on the bending dominated modes. I will separate a set of bending dominated natural frequencies from the full output of modal analysis , ranging...

Dear all , I have done modal analysis of a turbine using Finite element analysis and as output i have obtained a set of natural frequencies. Now regarding excitation frequency , i have this turbine rotating at a fixed rpm while the water jet will be acting on it at different positions as...

Forgot to attach the picture of the model , the same is attached here. With reference to the above problem if we are not sure which direction the surfaces are going to come in contact , how to decide the direction to impose the displacement. Rajesh Alstom...

Problem description: I have a test model which has a radial clearance (initial gap)of 0.005 mm around two pins which are holding a mass rotating at some angular velocity(Centrifugal force).The model is created taking advantage of cyclic symmetry and symmetry plane. I used Ansys workbench 13.0...