Hello everybody, I am glad that I found this subreddit!
I am trying to run a non-linear FSI simulation of a steel tank filled with water under seismic loads using Simcenter 3D. I've been told that the multiphysics solver would be the best for this sim but I always end up with errors that I cannot find answers for. My professor can't help because he doesn't use Simcenter. I am really desperate with this project, if anyone of you thinks that he could help me please reach out.

The title. I will DM with more details and my exact questions. Thank you in advance 🙏🏻

Hello everyone. Im currently finishing my MSc in aeronautical engineering and I want to do my thesis using finite element analysis.

I have already done several thermal-structural non linear analysis. I have played with modal analysis and harmonic response and I have started to learn explicit dynamics by myself (which seems pretty cool no?). I even worked with composite Shell elements.

My tutor gave me the OK to do analysis for my thesis but he told me that I have to choose the subject.

I want to do something challenging, worth of a really good MSc thesis, but I couldnt find anything that clicked for me. Some thoughts were performing shape optimization or a full turbomachinery analysis.

I want to ask you guys (that probably have worked with fea for some years, and maybe in a profesional environment) what are the most challenging analysis or something that is going to help me in the future. Where is FEA going in the future? AI? Machine learning? Dynamics?

Every opinion is highly appreciated!! Bonus points if its for something Aerospace related, but I am looking for things to achieve, which analysis to perform more than a specific subject.

Thanks for reading this and sorry for the typos, English is not my first language.

I am running a VUMAT which models progressive fracture, but I cannot use an automatic time incrementation since the damage model is custom and abaqus would have no way to know what stable dt to use. As the damage is building up, I think the stiffness is experiencing rapid degradation which causes very low wave speed because off which I am getting the error that deformation speed exceeds wave speed. Since I am using fixed time incrementation, it is very time consuming to run the simulation again and again and subsequently reducing the time increment. Is there a faster way to do it? Can I calculate the wave speed or the stable time increment inside the vumat to find out how slow I should run the simulation? What is formula that abaqus uses to calculate the stable time incrementation?

I've seen sometimes some lines like these in a NASTRAN input file:

NASTRAN b243nm

...

ENDDATA ea87ko9

With random letters at the beginning and at the end of the program. What are those for?

Hi Everyone,

I'm trying to do a "Random Vibration Fatigue Analysis" on a bracket assembly that is mounted on the headboard of a pickup truck.

BACKGROUND:

The bracket assembly is mounted on the headboard of the truck using 2xbolts (1 per each mount). The truck regularly travels on a rough rocky terrain that causes a lot of vibrations. The bracket assembly has been failing before its expected life.

I'm trying to simulate this in FEA to identify the weak spots, compare the life suggested by FEA to what we're actually getting, modify the design accordingly, and then re-do the analysis.

HERE'S WHAT I'VE DONE SO FAR:

We bought a couple of tri-axial accelerometers and fixed them at the two(and only) mounts of the bracket assembly. Drove the truck through the rough terrain and recorded the vibration time-history data of both mounts in x, y and z directions.

After that, I converted each of the six 85-minute long time histories into FFTs and then converted FFTs to PSDs using DewesoftX.

Then using Abaqus, in the first step I ran a frequency analysis and extracted natural frequencies and mode shapes of the bracket assy. In steps 2-4 I ran 3x steady-state dynamic(modal) analyses in x, y and z directions with a "Unit Load Curve" of 9.81 amplitude to represent gravity.

I also selected the outputs for "Generalised Displacements and Phase Angles" which are used by Fe-safe.

I then imported the odb file in Fe-safe using the option of "Open Finite Element Model for PSD Analysis", imported the PSD file, and selected Polar(degrees).

After defining the materials to the groups, you get an option to define "length per repeat in seconds".

QUESTIONS:

1. Should I put 85x60= 5100 seconds in length per repeat?

2. If yes, then how do I relate or extrapolate that to get the actual(total) life of the bracket assembly if the truck travels through that terrain(represented by the 85-minute time history) 5 times a day, every day of the year?

3. Am I doing everything correctly?

4. Is there an easier/ better alternative to what I'm trying to achieve?

I would really appreciate elaborate and easy-to-understand answers without jargon.

Thanks. :)

Hey guys, im trying to self learn FEA but I have never heard anything about it until two days ago. I have done my fair share of research but I don't think that is enough for me to start on the software.

Although the software doesn't seem that hard, i want to be able to understand the mathematics and theory behind FEA in general. So that way I can apply what i learn to a personal project that I can put on my resume. But where do I start?

What kind of personal project is there to do with FEA ?

Any book recommendations for learning the basics of FEA?

Also what software is FEA usually used on? and is it anything related to CAD????

Hello I am in my final year of university and for a project i have to conduct a flatwise compression test on a honeycomb structure made out of nylon. It is elastic plastic material.

I have the material properties attached in the image.

I have calculated plastic strain at yield stress to be 0.4441348 MPa. I am confused as it is telling me the first plastic strain value must be 0 but i don't know what the yield stress value at plastic strain 0 is. Can i consider the yield stress to be 31.451 MPa?

I need 5mm load to be applied till complete deformation. How should I arrange the step time?

The top plate has one degree of motion in the Y direction and the bottom plate is fixed.

And finally to plot the Stress vs Strain graph what value do i request from the history field output?

Help will be greatly appreciated. Thank you.

Hi I want to stimulate a shock test in abaqus. Defining the simulation was not hard. I can either use abaqus/explicit to stimulate the whole process or use abaqus/standard and use gravity load since I only need to show if the structure can withstand the max acceleration.

My part is lattice structure. A simple cubic structure with 2 plates on top and bottom of it. I designed lattice in ntopology and had exported fea shell mesh to abaqus then added plates in abaqus itself. Problem started with abaqsu/explicit not accepting shell mesh elements that is created by ntoplogy(it says they are S8R and STRI65; a mix of quad and tri). So I decided to simulate it in abaqus/standard using gravity load but abaqus/standard also does not accept "shell to solid coupling" altogether with gravity load

What can I do in this situation? I know I can remesh it using hypermesh but I want to keep that as my last option

Thanks in advance

I am doing Abaqus dynamic explicit project in SI mm units and I am defining density in tonne/mm3. However when I try to set density for stainless steel (8e-9 tonne/mm3), solving takes a lot of time like a hour. When I increase density to something like 8e-3 it is solved instantly. I am setting units as table below. Do you have any idea why does this happen?

https://preview.redd.it/upl1rddvqhrc1.png?width=399&format=png&auto=webp&s=e0d8abec91dbfdfeadd0b1a93f14bf591e35007b

Dear Viewer,

I am currently engaged in an overall analysis and evaluation of the chassis design of an experimental tractor. I have conducted some modeling for this design and simplified it to evaluate the general components: motor engine, battery pack, and suspension into distributed and point loads. However, I am in need of assistance to confirm the simulations and estimations I have conducted thus far. The general static FEA simulations appear to be satisfactory, but I encountered some confusion while attempting to perform a modal analysis to determine the resonant frequencies of the chassis in relation to the motors. I aimed to keep the dynamic simulation simple with only the modal, but I am uncertain about the information available online regarding such an analysis—whether it should be conducted with load, without load, with constraints, or without. I would greatly appreciate some insight into this matter. I have included some general mesh pictures of the model below. If someone could kindly point me in the right direction, it would be greatly appreciated.

https://preview.redd.it/68a1hazxe5rc1.png?width=741&format=png&auto=webp&s=b80ee49e99e53231e912ccf007e2e2eef7f9956a

https://preview.redd.it/g3nlkrrye5rc1.png?width=1005&format=png&auto=webp&s=e00b20e9aa1f04ce70ebac442c07ce7763959373

During an analysis, I am getting an error for PGAP. It says "Errors with missing, incorrect, or duplicate IDs found 660 times". Before this, I get several messages saying "Error 14: Missing property # referenced by CGAPG #

Im trying to model a spring, I’ve used for now a spring element with elements type CBUSH and property with CARD IMAGE PBUSH with K1,2 and 3 containing the stiffness value I desire and K4,5 and 6 as rigid. The element was placed on 2 nodes with one of them being in free space constrained in all direction and the other node connected to a mesh with a force going upward. Is this a good method? And how can I check if it is. When I see it deform in hyper view it moves up but the element is not connected at the node and doesn’t move with the meshed shape so I don’t know if it is working or if it’s the material stopping it.

I am using Hypermesh (version 2022.3) for my pre processing and OptiStruct solvers. I have an issue implementing different beam diameters in my tubular chassis, as it cannot take two or more properties while meshing, therefore even if I create the different beam sections, different properties for each beam sections, I cannot mesh without the whole part to take one properties and therefore get one beam section. Any solutions to this issue?

Hello everyone. I recall a few years ago in abaqus CAE that when on the loads module and displaying load vectors that they’d display the magnitude next to the arrow. With my current installation, this is no longer the case. Been searching for this option for a while, anyone know where it is?

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Hi, I work on a plate in Pcomp, MAT8 with different loads using Hypermesh Nastran/optistruct solver

But when I do a static analysis, I have pivot ratio due to a rigid body mode. Do you know where it can come from ?

​

https://preview.redd.it/wa3ztfvcqrqc1.png?width=263&format=png&auto=webp&s=2359279d92a4df57928f9843411a0a972f704e21

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I am currently working on a FE simulation project where a tensile test of DP800 steel is subjected to cyclic loading. The reference we are using is: https://www.researchgate.net/publication/257779252...

It utilizes Yoshida Uemori model (YUM) to formulate the modulus of elasticity (E) to simulate the hysteresis caused by cyclic loading.

We are using a USDFLD subroutine in ABAQUS CAE to formulate the E according to the cyclic loading i.e. using a FORTRAN code, we save the ratio of 'current E' (using YUM) to 'initial E' as a state variable to simulate the process using this ratio. The code recognizes the loading and unloading stages in the curve correctly after checking the PRINT statements in it.

To check the FORTRAN code, we used a RVE (a simple cube element). Original YUM formula mentioned in the research paper works correctly. The modified YUM formula gives incorrect result.

Please refer the Eng-Tips thread for detailed explanation: https://www.eng-tips.com/viewthread.cfm?qid=517720

I would highly appreciate any tips or suggestions as how to simulate this process correctly. Or how I can test/check the various parameters to ensure the correct simulation of the process.

Thank you.

https://preview.redd.it/tzjiokk0qjqc1.png?width=956&format=png&auto=webp&s=dfac012e31a287665024453b31f0589744a7a1a6

Hello I have this problem shown in a picture that I want to simulate in Abaqus to find deflection of a beam under point 3. Points 1 and 2 are rigid and does not move. Point 3 can only rotate around point 2, moves down with certain force and deflects beam. Distance between points is constant and points are rigid. How would you model this in Abaqus? I cant really came to some solution. Thanks!

I have been using *LOAD_RIGID_BODY (RB) to apply a load onto an indenter in an indentation simulation. However, I now want to model the indenter as not rigid. I have tried *LOAD_NODE, selecting the indenter's CoM as the force application node, but the force application was less stable than with *LOAD_RB and in fact produced different results despite the simulation being otherwise identical. This was done while keeping the part rigid (tested this before I move over to a non-rigid material)

If it matters, I am applying a compressive load indenting a material with an indenter with a linear ramp of 4kN.

EDIT: I'm familiar with doing this sort of this in ABAQUS where I can define a kinematic coupling between a my part and a reference point at which the load is applied. If this is doable in dyna, please let me know.

I have also played around with seeing if I can have a 3rd part that is rigid that is like a force platen that will compress the other two parts, transferring forces through the indenter to the material being indented. However, I'm having a tough time working out the tied contact in dyna, which I find comparatively very easy in abaqus.

Hi, I have a model here which is part of a heavy duty gimbal type assembly.
Boss has asked me to simplify by using Load vs Load rather than Load vs Constraint (which is how I learned to do things at first).
In reality the two cylindrical faces are supported by bearings and are allowed to rotate once static friction is overcome. The load is generated by a 'master load' through the component into the image, hence the reactions at the bearings.
I obviously can't run this with just two loads, and some constraints are required, but what, and where do I need to apply constraints?

Please help!

https://preview.redd.it/c29ud7h5biqc1.png?width=660&format=png&auto=webp&s=02679ea0163fcd43c1cfc6f451a4d7915e6de89f

Hi Everyone,

I'm trying to read the stress change with the depth of a shell element.

For example, the stress at the surface of the element, the stress at the middle of the element, and the stress at the bottom of the element.

I tried looking into the documentation and other posts but had no luck.

Could anyone tell me if there is a way to do that? (I'm sure there is but I'm pretty new to ABAQUS and I can't seem to find it)

Why am I getting this weird bulge when I apply a displacement?

• Both my parts are shells.
• I used (find contact pairs) to define interactions.
  • Frictionless: Reference point about 3 units down from contact surface.
  • Rigid Body
  • Displacement BC applied to reference point

https://preview.redd.it/nvevxmmk9bqc1.png?width=662&format=png&auto=webp&s=a4094b94831cd7969f8cb8774a443208cb017562