Quasi Static Analysis in Abaqus/FEA (Mass scaling & Increase load rate), Part - 01
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- เผยแพร่เมื่อ 23 ส.ค. 2024
- In this video i talked
1. Quasi static analysis & technique associated with it i.e. Mass scaling & Increase load rate.
2. Fundamentals Difference in both approaches.
3. Different Applications of quasi static approach.
4. Mathematical relationship.
5. Relation between Quasi static and Explicit.
Implicit vs Explicit video - • Implicit and Explicit ...
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thank sir.... I just starting learning structural analysis... I got very good knowledge from you
Always welcome dear.
Dear Dr. Gajendra,
Much appreciation for this huge work that you're presenting to the Engineering Community.
I would like to ask if you can present a video on coupled thermal analysis for civil engineering problems.
Thank you.
Dear, Thanks for appreciation.
I would like to share details on thermal also..but surly it will take time.
However, you can ask your queries.
@@simtech0598 Thank you a lot Dr
agree, that’ll be precious subject..since the abaqus frequently used to analyze the thermal things
Thank you for your explanation. Spent so much time trying to get implicit solver working.
Dear,
Implicit is quite different. Used for large event structural dynamics.
You can go with implicit vs explicit video on my channel.
Also go through part - 2 of quasi static analysis.
@@simtech0598 was trying to model quasi-static state with static, general or dynamic implicit. Neither could work well as the convergence was hard to achieve. Having gone through your tutorial, I can try explicit instead to speed up the computation.
wow, realize that im doing many mislead in my analysis this whole time. thanx for your explainations
Always welcome dear. Keep knowledge sharing.
Great!!!! very useful tutorial and information. Thanks!!!!!
Always welcome dear.
Nice video man. Simple and very well explained
Very detailed and helpful video 👍
Thank you for knowledge sharing. I have two questions
1. What f used in mass scaling?
2. how to calculate excitation frequency
Dear,
1. f is Freq of system
2. You can find natural frequency by frequency analysis in Abaqus... available in linear perturbation.
Hi , in my model the kinatic energy compare to internal and extarnal energy is nearly zero. In this case can i use coupled temperature-displacement instaid dynamic ,temp-disp,explicit ?
Thank you, it is helpful
Thank you Sir for sharing your knowledge 👍
Always welcome.
Thank you so much sir, really this is very helpful video.
Always welcome dear,
I highly recommend to go with implicit Explicit video.
Keep knowledge sharing !
Thanks, Sir, it's a very informative video.
Always welcome !
Thanks for explaining!
Always welcome dear.
hello, I regret I have a question.
You said that if inertia can be neglected, we can use quasi static analysis. Do you mean by inertia the [M]*{u double dot} term ?
because you said that even if velocity or acceleration are involved, inertia can be neglect so for this case mass should be very less to neglect inertia effect and quasi static analysis can be performed only for lower mass model if we consider velocity ? did I understand well?
Dear,
If velocity involved but at very slow rate...like compression test... forming... drawing...then only inertia term is negligible up to certain mass scaling limit.
If lower value of mass moving at high velocity...then overall m(u") term will not be negligible...and we cannot ignore inertia.
Increasing the load rate essentially increases the inertia of the system, hence more kinetic energy in the plot. Doesn't that imply, load rate must be less for minimal inertia in the system? Its like going in vicious circle. Moreover, how reliable and accurate is the forced mass scaling of the elements which is also the application of the fictitious density for particular elements?
In mass scaling portion, you have mentioned, explicitly, that the mass scaling doesn't affect the result accuracy. Is it possible mathematically sir? Thanks :)
Dear,
KE will increase...with both technique.
And we have to limit the increment in KE upto certain limit...if analysis is Quasi static..
For full dynamic event don't use any of them.
Watch all videos of Abaqus dynamic analysis playlist..your concepts will be crystal clear.
2nd point
Accuracy depends on your parameters.. nothing like that one technique is good over another.
Both having advantages and disadvantages.
I never mentioned such words in my videos - "mass scaling doesn't affect results accuracy".
Couldn't thank you more sir! You're absolute master. Thanks for those videos! Love and greetings from Nepal.🙏
Welcome and love from INDIA.
How did you find the natural frequency, is it free free run or fixed at the bottom
Dear,
Model analysis performed earlier to find natural frequencies.
Thanks!
Always welcome dear.
What value of "f" did you decide in this problem for the mass scaling @27:39
Not remember exactly but sufficient high..i believe i used 256 for this example.
Thank you so much very much a detailed video,
I have a similar question Chun Yang asked.
Hi Sir, how to determine whether the result is correct when using mass scaling? Or how much maximum added mass can be acceptable? Any cross-check criteria for using mass scaling?
Dear,
You can check energy balance of simulation and can predict whether convergence is correct or not.
For mass scaling calculations I'll upload more videos.
1. Thanks for nice video. I have one question, please clarify it. For increase loading rate, we check energy plot. if kinetic energy is less then 5 %, we say , it is OK. However, what parameter, we should check for mass scaling, so that we could know about our model accuracy in one glance?
2. Also, it will be very helpful if you upload one other video and explain mass scaling and loading with one small example in Abacus.
3. Also, One video on different an-isotropic plasticity model like C-Hill48-AF,C-Hill48-KIN ,C-Hill48-ISO, Hill48-AF and Mises-AF and explain with some small example in Abacus.
Dear,
1. For all quasi static analysis you can check KE,IE,AE and can make a judgement of analysis accuracy.
2. I'll try.
3. I know few of them only.
@@simtech0598 Thanks for your reply. for question-2, i will be waiting. for part-3, if you upload any of an-isotropic, it will be helpful.
Sir, what is the amplitude for applying displacement load you have used here? Because I am using a linear amplitude variation and getting a linear curve for internal energy plot.
Dear i believe you are using only elastic material properties of material. Or your displacement is less that deform only up to elastic limit.
Energy plot always different in elastic and plastic region.
@@simtech0598 Thanks Sir for the reply! I am using both elastic and plastic properties for the material. I think the deformation applied is less. I will check with increasing the deformation load.
Hello.. this video is really helpful for me.. while calculating the natural frequency of the model what was the constraint used. The can was completely constrained on top and bottom to get the natural frequency of 795 Hz.?
Dear,
Unconstrained model's natural Frequency you have to consider.
@@simtech0598 thank you for your reply.. if the analysis involves many parts, then the first natural frequency of the loading part only has to be considered or the natural frequency in the entire assembly has to be considered for deciding the time period of the analysis..
1st minimum natural frequency in all cases.. whether it is single part or assembly
@@simtech0598 Thank you very much for quick reply.. one last question , in my static analysis the model was not converging at all.. So after watching your video I thought of running the analysis as dynamic with Quasi static application available in abaqus standard..
1.please let me know if I can use this approach.?
2. The analysis can be run for natural time period (by running modal analysis)?
3. The accuracy of the analysis will be same as static analysis?
Dear,
1. I clearly explained the applicationa of quasi-static analysis in videos. If ur static analysis not converging and for that you are using quasi-static analysis...it is not a right way.
2. With mass scaling it may possible..but it may take huge time.
3. These techniques are completely based on knowledge and problem statement. For variety of problems statement of accuracy will change. So there is no universal comment for all problems.
hai
sir
i am working on multilayer component for that how can i choose the mass scaling
Yes. If it fulfills the given condition explained in video.
Dear Dr. Gajendra,
What is the meaning of zero kinetic energy at the end of the simulation (Zero Residual KE)?
System become in static equilibrium even if velocity terms are involved. Ideally KE may not zero but small enough (within 5%) to ignore.
Nice work sir, how did you plot energy curves as in 21.21 sir.?
Energy plot already avilable in history plot..you can request different energy plots (in step module)
thanks for the explanations; but how you calculated the natural frequency (795.41)?
Dear,
By Performing frequency analysis 1st.
Sir, if I want to perform a compression test (strain rate -0.001 /s & 1 /s) on a particulate metal matrix composite which method you suggest.
Thank you
Dear,
As i explained in these 2 videos also..
For rate dependent material only mass scaling you have to use.
I think you not seen part-2 yet.
@@simtech0598 Yes I didn't find it yet. I will watch that also. Thank you 😊
Could you tell me sir if I can make a quasi static orthongonal cutting by johnson cook hardening ?
Thanks for the worth infos.
Waiting answer....
Dear,
Yes, You can utilise JC material model.
@@simtech0598 thanks for the answer but a asked if I can make a quasi statique study for orthogotnal cutting
@@simtech0598 if I can use a quasi static study for metal cutting ? ..
Best regards
Dear,
You can utilise quasi static technique for such simulation.
@@simtech0598 thanks sir
Hello sir, I ma performing quassi static analysis. I reduced mass scaling to 16 to keep KE within 5%IE. But job gets aborted stating large number of increments are required. I can not even increase mass scaling. Any suggestion from your side. Thank you in advance for your time🙌
Dear,
Somehow stable time increment is very less, so to complete simulation software demanding huge number of increment.
Check min element length.. modify it.
@@simtech0598 sir, I have cyclic loading of 150 second having 10 cycles. So for that, whether Texcitation will be 150 second or 15 second(150/10 cycles).
Tn is 0.02 second so I have to give all cyclic displacement in 0.06 second(3*0.02 sec)
Go with implicit for such cyclic load. Or may be General static.
@@simtech0598 thank you sir for your valuable suggestion. I'll look into implicit solver.
Dear Dr. Gajendra,
Thanks for your sharing. I wonder if I don't use the mass scaling, could the result ignore the 5% rule and make sense? the energy comparison from my output doesn't meet the requirement.
Dear,
If you are not using mass scaling and still KE is about 5% in your system...means system can't be considered as quasi-static.
There is no sense of 5% energy rule.
@@simtech0598 Thanks for your reply. I am doing a cylindrical turning simulation on Abaqus, and no matter how I set the mass scaling factor, the kinetic energy is always far more than 5% of the internal energy. Finally, I canceled the mass scaling, but the kinetic energy is far more than 5% of the internal energy either. So how do I tune other parameters to get an accurate result? or the result without mass scaling is the precise result?
Dear,
Mass scaling technique applicable for quasi-static problems. The turning operation that you want to simulate not a quasi-static problem, its a pure dynamic problem due to high rotation speed of component. So you cannot apply mass scaling here.
Dear @@simtech0598 , I appreciate your patient answer.
Sir,Will you please send me the .inp file of these analysis? Thanks to you I improved my knowledge about the mass scaling.
Dear,
recently i uploaded part 2 of quasi static analysis...that model i have...this model i missed.
Thank you very much for this video! One question -- how did you find the fundamental frequency f_n that you mention at 13:24?
Perform frequency analysis for the model/assembly.
@@simtech0598 means we have to perform Linear Perturbation Step in Abaqus ?? and while defining its step do we need to use 1sec time period or enter the real time required to complete the experiment ??
I don't know what you understood.
I explained the calculation of time via its natural frequency, in video.
So the question is how to calculate natural frequency... Answer is by performing frequency analysis.
How we are calculating the natural frequency here at 12:53 ?
Dear,
Using frequency analysis step.
how about hourglassing energy in quasi static analysis?should be low as posible?
Dear,
I already uploaded a video on the hourglass effect. There I discussed in-depth on the same. Please go through the video.
Thank you sir, but how to find the natural frequency of a honeycomb structure?
Dear,
Yoi can use Frequency step (model analysis).
@@simtech0598 thank for your reply sir
Welcome dear.
sir can you explain turbulence modelling in CFD??
Dear,
I am not CFD expert..just aware to CFD as much you are.
What's the meaning of 'material is rate dependent'?
Strain rate.
load rate is decreased to get the result , but why it is called increased load rate?
Dear,
Load rate increased not decreased.
Say,
0-100 mm displacement applied in 10 sec. Load Rate is 100/10 = 10
Now 0/100 mm displacement applied in 1 sec. Load rate is 100/1 = 100
Could I get this presentation please !?
Dear,
you have to do excercise..all slides i shared in video.. write it as per ur understanding..in ur way.
😑👍👍👍👍