Thank you so much for sharing this video. This random vibration tutorial is excellent, concise in theory and operation.I have a question. The EXPLANATION for random vibration analysis in the ANSYS help is as the following: "The excitation is applied in the specified direction to all entities that have a Fixed Support boundary Condition. Other support points in a structure such as Frictionless Surface are not excited by the PSD ". I'm not sure if all entities mean the whole model or just nodes with fixed boundaries. In other words, random excitations only exist at fixed boundaries and affect the whole model, or the whole model node is applied with random excitations but some face boundaries are fixed. For example, the top and bottom surfaces of a cylinder are fixed, and the side face have random excitation due to fluid action. Can the model be analyzed using the method in the video? I'm actually analyzing a compressor blade. The blade shroud and hub face are fixed boundaries, and random loads of airflow on the pressure surface and suction surface. I am not sure whether this model can be analyzed in this way.
Thank you sir good and explanation... It's more helpful,. Sir i have one doubt .. Sir we are calculating Grms value by entering psd values and frequencys using some online calculatot so that we are getting grms value.. So we are comparing the obtained grms value with grms value which we are getting in the ansys if it is +-2 then we concluding that frame is ok.. Is it correct methode
Welcome. ANSYS Does not calculate GRMS value, we need to enter the grms vs accn/displ values as load. You hvae to calcute grms before entering in ansys. you will get grms either by testing or else you need to calcualte GRMS . Root mean square (rms) value of this signal will get by squaring the magnitude of the signal at every point, finding the average (mean) value of the squared magnitude, then taking the square root of the average value.
Thank you sir for giving u r valuble repley.... I am working as testing fixtures design engineer.. To qualift the fixture design in the ansys, I am doing same process what your said,we are calculating the grms value before going to ansys.. By using psd and frequency values of component.. After that we doing ansys by entering psd and frequency values.. Then after we verifying ansys results wethere we are getting the calculated grms value r not... Is this process correct r not,,... Can u please your mail id or contact details..
Hi! Thank you for your neat and clean explanation. I was wondering what if physical test is done for 10 mins, then how to set the 10 mins physical test in simulation?
the work is to analyze the engine vibration effect on the flow through a pipe of uniform diameter. The output data analyses the flow characteristics in terms of pressure, velocity and turbulence. We have experimental data for vibration in terms of 'time vs acceleration' and 'frequency vs acceleration'. This data we need to give it as input in the simulation as per our objective. We tried to explore the option to import vibration data in the Fluent, but couldn't. Can we do it in Random vibration and Fluent combine ?
Hello, Thanks for explaining this in such a good and Understanding way. I have a question. When performing modal analysis we obtain the necessary results for the frequencies (XYZ Displacement, stress etc). How do you calculate the PSD values for these modal results ? Are the predetermined or are calculated for eg. in your case you have the values of G-acceleration to plug into PSD analysis. How did you find those values of accelerations ? thanks in advance
Sir, thanks for your highly informative explanations. Question: I have a rather large steel structure with a long boom (hollow tube) cantelever mounted on top of the structure. The end of the tube have a limited deflection that is required. There is a fan installed on the structure that runs at a certain frequency. I have no PSD data of the fan. If I do a modal analysis on the structure, could one purpose be to make sure that the calculated modal frequencies are not close to the fan frequency to limit boom end vibration?
That is amazing tutorial, you have doing a great explanation. one of my question. Could you show me the detail load that u input on point mass to present the actual load during centrifugal pump operation? thank you so much ;)
Thank you for appreciation ! Regarding CG pump: Only point mass for Centrifugal pump and motor weight are assumed and applied at the center of gravity. Their is no any operational load is considered, Only static weight are assumed.
Sir I have a doubt about one parameter in this tutorial that Mechanical >Random vibration >Analysis setting >Damping controls > "stiffness coefficient define by" That what is stiffness coefficient ? Sir Please explain.
Hello Bala, In random vibration or harmonic simulation, structural damping matrix is calculated by material damping or global damping (in analysis setting), The constant alpha, geta and Ggma are used to calculate the damping matrix and this constant will get from analysis setting, damping controls stiffness coefficients define by options.
You should get from seat manufacturer, if not check ISO standards ..like ISO 8608 (Mechanical vibration_ Road surface profiles _Reporting of measured data).
Hi sir, thank you for the video, it was awesome. Question : i have obtain some experiment result from my the researcher and they have input 1G, 2G ,3G and so on, up to 20G at the frequency of 920. can i know how am i suppose to do ? and can i say that 1G is equal to 9.81 ?
Thank you for appreciation ! There are two types of loads if you have inputs in G format then use PSD G Acceleration loading format or else use PSD Acceleration format and converts 1g - 9.81 m/s2.
@@graspengineering9249 Thank you sir for you replied so mean to say that 1G=9.81m/s2 and e.g. 20G = 20x9.81 ? just another question sir, In Ansys i obtained the 6 mode shapes natural frequency and their displacement. I square the displacement and divided by their frequency and input them under the random vibration PSD Displacement so my question is by getting the response of PSD: what do i obtain? as in whats the reading is for ? and as for my questions from previous, how can i input 1G,2G,10G etc. under the same frequency 920 cause as i tried to do that, Ansys wasnt allow me to do so?
@@dsxf I think you mis-understood random vibration simulation. Random vibration is vibration at many frequencies simultaneously and hence ANSYS will not allow you to load at single frequency. First you need to think what kind of simulation or response or purpose you are looking for ? Also the modal analysis displacement are virtual displacements, You can not do square and put as inputs in random. If you are looking for random response of the structure, you should ask your designer to provide PSD or accen vs frequency graphs. Eg. Testing of Compressor will provide you PSD as outputs, which u can use for FEA inputs. You can also think other vibration simulations like harmonic analysis where you can apply acceleration loads for frequency range.
@@graspengineering9249 thank you for your correction. can i request to have your email or something to certify some of my doubt with you ? cause i tried to ask around but none of them given me a specific answer.
For ductile material, you should consider yield stress for brittle material you can consider ultimate stress as allowable limit and compare FEA stresses with allowable limits.
@@digambarkilledar003 For random vibration, you can use 1 sigma which is also used to determine fatigue life. But you should also write conclusion based on 2 sigma and 3 sigma.
Hello Kaustubh, You might have done testing for 12 hrs and looking to perform the random vibration analysis. From testing you will load input in the form of power spectral density. Use that PSD acceleration curve and loads in random vibration and do the simulation. Other way is to perform random vibration for your PSD data and determine the fatigue life.
@@muhammadasadullahkhan1053 You have to make link between MODAL & RANDOM after seeing the connection made in this video for these two analysis @8:58 (timeline of the video)