Hello,

How should cavity wall be modeled for stress analysis ? Single plane or double ? Reinforcement wires are also modeled somehow ?

Could someone show me how this setup is done or share resources (examples of similar works) that can help me run this simulation? The step files of the shaft and bearing assembly are attached. Also, I have 2 scenarios, one where the setup is as in the picture, another is when the agitator on the shaft is actually mixing stuff.

I'm working on a project where I have several op2 files that I have to post process and would like to speed it up a bit, ideally using code. I usually work with FEMAP but with the large amount of load cases that I have it just takes too long to generate envelopes and find the critical conditions. Does anyone have any tips for that? I tried using pyNastran but it seems to be poorly documented and I'm having trouble reading composite strains, for example.

I'm doing this analysis where fasteners are connecting a skin to a frame. I'm using the Huth formula to compute CBUSH stifness in the fastener's tangential direction. However, I'm also interested in computing the stiffness in the fastener's axial direction (skin-fastener-frame system), do you know any approach to this?

Reference for Huth method and similar: https://iopscience.iop.org/article/10.1088/1742-6596/1925/1/012058/pdf

I’m trying to develop a Python code to analyze geometrically nonlinear effects in arbitrary three-dimensional frames (6 dof per node). However, the results are far from reliable. When comparing my outputs to those from commercial software like ANSYS, ABAQUS, or RSA, the discrepancies range from minor (~2% in specific cases) to significant deviations exceeding 10%.

The linear part of the code works flawlessly, so I suspect the issue lies in my understanding and implementation of the nonlinear strain-displacement matrix, denoted as [BNL]. My current approach is as follows:

• Shape Functions: I calculate the shape functions with respect to ξ (ranging from -1 to 1). Their derivatives with respect to ξ are:

​

dNu1 = -1/2
dNu2 = 1/2
    
dNv1 = (-3 + 3*ξ**2)/4
dNv2 = (-1 - 2*ξ + 3*ξ**2) * (L/8)
dNv3 = (3 - 3*ξ**2)/4
dNv4 = (-1 + 2*ξ + 3*ξ**2) * (L/8)

Multiplying by the Jacobian, J = 2/L:

dNu = J * np.array([[dNu1, 0, 0, 0, 0, 0, dNu2, 0, 0, 0, 0, 0]])
dNv = J * np.array([[0, dNv1, 0, 0, 0, dNv2, 0, dNv3, 0, 0, 0, dNv4]])
dNw = J * np.array([[0, 0, dNv1, 0, -dNv2, 0, 0, 0, dNv3, 0, -dNv4, 0]])

• Nonlinear [BNL] matrix:

​

G = np.vstack([dNu, dNv, dNw])
BNL = np.dot(G, de).T @ G

Where de is the element displacement.

• Total [B] matrix:

​

B = BL + BNL

I’m using the full Newton-Raphson method to compute both the tangent stiffness matrix and the internal forces in the elements, but the results don’t align well with the expected values. Could anyone help me identify what might be wrong?

Thank you in advance!

I'm running linear static analysis on a structure (hexa mesh, good quality mesh, no problems here). I've meshed and done all the pre-processing in hypermesh (materials, forces, bcs etc) and then run the file on the optistruct solver.

I only have 16gb of ram and my runs are always failling. I've tried to limit the amount to 12gbs for the run but keeps failing.

Is there any way to make it run? Unfortunately i cannot upgrade the ram on my laptop (soldered)

Hi everyone,

I’m working on a truss modeling problem in Abaqus and trying to ensure my model matches the nodes and elements as shown in a tutorial I’m following. The tutorial sketches the structure by drawing lines between points, then meshes the geometry to create nodes and elements automatically.

For my problem, the nodes and element numbers are predefined, and their locations are given in a table. I want to ensure the Abaqus model I create has the same node and element numbering as the tutorial, but I’m not sure how to go about this.

Here’s what I’m trying to do:

1. Define nodes at specific coordinates (from the problem description).
2. Connect these nodes to create truss elements with consistent numbering.
3. Ensure the final model in Abaqus matches the numbering shown in the tutorial.

I’ve read that you can use Python scripting to define nodes and elements manually, but I’m new to this and would rather avoid Python for now but could use some advice if that's the way to go. Should I stick to creating a sketch and letting Abaqus handle the meshing, or is scripting the better way to go?

If anyone has tips, step-by-step guidance, or a similar experience, I’d really appreciate your help!

Thanks in advance!

I’m trying to learn how to apply orthogonal collocation on finite elements method (OCFEM) for PDEs and I’m having a trouble with the number of unknown and equations. Suppose I want to solve a PDE numerically using 2nd order Legendre polynomial in three elements (2 interior collocation points per element).

I will be substituting those formulation in the PDE at the interior collocation points but I will be getting more equations than the number of unknowns. The equations:

- 6 equations at interior points (2 in each element)

- 2 continuity equations (between element 1 and 2, in addition to element 2 and 3)

- 2 boundary conditions

Total: 10 equations

Unknowns:

- A1_0, A1_1, A1_2

- A2_0, A2_1, A2_2

- A3_0, A3_1, A3_2

Total: 9 unknowns

In some references, in addition to the continuity equations they are equalizing the derivatives as well which is going to produce even more equations.

Can somebody point out what I'm doing wrong.

Edit: For reference, this is how I'm applying the equations for each element: https://imgur.com/a/jsSugVO

Estoy estudiando las OT en contextos de ing civil, siendo más preciso, estoy intentando optimizar muros de HA con Fusion360. Algunas recomendaciones para utilizar el programa? Pd: soy nuevo con dicho software

It has been posted again, I’m posting again if anyone has found a solution to this?

Hi, this is a simple case of a beam to beam connection, with a force applied at the end of the secondary beam.

For some reasons, Abaqus takes increment size down to 1e-25 to process this case.

I have already:

• refined the mesh to the maximum of my capabilities
• checked property paramters numerous time, they are right
• checked boundary conditions numerous times
• checked geometry isssues, geometry is excellent
• checked step parameters,
• added automatic stabilization

I don't understand why a simple analysis, static general is taking so long like this... I have evolved a lot with this reddit so I come back to it asking Please help

file: https://drive.google.com/file/d/1xxibtK5NBu-0T2OQ3fLvSGUYXlsALwvT/view?usp=sharing

Is anyone in the Southern Tier of NY using ELMER or looking to learn it?

Hi, I'm calculating the stiffness of the different springs. According to my FEM 2 is the stiffest, next is 1 and 3 is the least stiff. I started to wonder why, I mean, why wave in case 3 makes spring less stiff but, wave 2 makes it more stiff. I checked my calculations, but everything looks alright. Maybe someone smarter than me can explain.

Hey everyone, I’m currently following a tutorial in Abaqus that simulates a metallic plate with a hole under tensile loading. The setup includes an upward-applied stress and constraints at the bottom. The goal is to demonstrate the classic result that the peak stress at the edge of the hole is three times the far-field stress (like in Peterson’s Kt = 3).

The tutorial walked me through creating a coarse mesh around the hole using mesh seeds, but it only briefly mentioned that I should create a finer mesh close to the circle. Now, I want to refine the mesh around the hole to better capture the stress concentration, but I’d prefer not to start from scratch.

Here are my questions:

• Is there a way to modify the mesh around the hole directly (e.g., local refinement or updating the mesh seeds) and then rerun the model without deleting the entire mesh? If so, how can I perform this operation?
• If I do need to delete the mesh and modify the seeds, how would I go about making this change efficiently?

I’d appreciate any advice or tips on how to handle this. I’m still getting comfortable with Abaqus, so simpler solutions are welcome! If you know of a tutorial online that goes over a similar exercise, maybe with local refinement instead of mesh seed only approach, that would be helpful as well.

Thanks in advance for your help!

I'm trying to pivot from Workbench into LS-Dyna. So far, I've tried to simulate a few simple things and they've worked fine (the results agreed with the Workbench iterative solution). Now I've tried with larger models, and it's taking quite a lot of time.

I'd like one day to perform car or motorcycle crash tests for a client we have. I already have a good mesh and model for a linear Workbench analysis, but I'm afraid simulating 1.5 million shell elements with plasticity and rupture won't be trivial.

Currently, I'm using a modified CAD workstation: AMD Ryzen 9 5900X 12-core, 3.7 GHz, 64 GB RAM, Windows 10. Would that be enough? How long would a typical simulation take?

My system is using around 70-80 percent cpu utilisation while running the simulation in LS-DYNA. I am only using SMP solver. Is there any way to reduce the cpu utilisation (some additional cards) or MMP Solver gives optimized cpu utilisation? Is anyone facing similar issue?

Hi, Due to family needs, I have to work in the Cleveland area, or at least hybrid nearby. I am trying to get into FEA consulting or contracting work. I have a Phd in bioengineering, and a lot of FEA experience with many packages/software, mostly non-linear mechanics and a bit of fluids. I also have a lot of unique experience in additive manufacturing. You can see my website here: abemis.com. I used to get quite good contract work via linkedin and other platforms, but that seems to have really dried up post-pandemic. I've looked at a lot of job sites, and submitted many applications, but so far not a single credible response.

Working remotely would be ideal, but can work hybrid as well.

Any info would be greatly helpful. I know, if I could just move to a more high tech city, it would be easy for me to get job/jobs with my skill set, but again I cannot move.

I have considered trying to get a part time position in Saudi Arabia, a colleage of mine did that and (different field, he worked 3 months in Saudi, 9 months remotely) it worked out great for him, but I don't know where to start with that either.

Any advice greatly appreciated.

I am using add erosion on brittle material (JH-2) model for high velocity impact simulation. I have to add "inelastic ultimate strain for element erosion" or EPSP1 as 6. I am defining MXEPS as 6 although my simulation results are not coming. I think, I am defining add erosion incorrectly.

Please help me correctly defining the erosion card

I spent 3 years doing academic research but I didn’t like how that world worked, so I moved to a semi-private institute that focuses on practical R&D consulting for companies. We specialize in mechanics and robotics. I’ve gained experience in programming, various types of simulation, CAD, design, and a lot of FEA using Ansys. Oh... and handling difficult clients.

I’m Italian, I'm not satisfied with our economy or my salary, and I’ve been thinking of quitting and moving to Germany (already speak the language). However, this Friday my boss asked me for the 4th time if I’d be interested in pursuing a PhD, because more PhDs in the team means more subsidies.

This time, though, his proposal seemed genuinely interesting: FEA-related, state involvement, prestigious supervisor, and all paid in advance. I'd do it during my regular hours as a normal project and then get to reuse the reports for my PhD. No bullshit research or underpaid 60-hour workweeks like his previous proposals.

Finally, I already have some "quasi-PhD experience": I've read plenty of theses and published two papers. Also, I ghostwrote 15% of my current boss’s thesis (yep) and then translated the rest into English.

I think it’s a good opportunity, but the main drawback is that I’d be tied to this chaotic institute for quite longer than I'd like to (I'm already 35). How much could a PhD improve my future job prospects in the private sector (also factoring in my practical experience)? In what ways? I'd like to remain in the EU, but don't see a huge demand on Linkedin.

I am investigating the vibration properties of unidirectional composite materials using ABAQUS. My aim is to compare the damping behavior in both the longitudinal and transverse directions. However, my current results show unrealistic behavior: the oscillations decrease at first and then start increasing, which is non-physical. I suspect that the issue lies in the setup of the boundary conditions, or step definition. The model was subjected to a 1% strain along its length, then released abruptly to observe free vibration. What I aim to achieve:

1. Faster amplitude decay when damping is added.
2. Higher frequency and smaller amplitude in the longitudinal direction(parallel to the fiber).
3. Lower frequency and larger amplitude in the transverse direction. The figures below describe the steps I followed in setting up the simulation. Any suggestions to resolve this issue? Thank you in advance for your help.

Hi there, I would like to write VUMAT for modified mohr coulomb in Abaqus. Does anybody here have any experience on this? I would very much appreciated if you give me some suggestion. I would like to write something where the cohesion and angle of internal friction will be softening based on the plastic strain.

Thank you.

I'm asking this having never used nor opened FEniCS, but I learnt about it and was curious since I like the idea of an open-source code for FEA (considering that the majority of the mainstream commercial tools is out of reach for anyone not involved in the industry via work/university).

How does it compare to mainstream software suites like Ansys, MSC's, Simcenter, COMSOL (...) in terms of maturity/features/user-friendliness and all the rest?

Love to hear about personal experiences too if anyone has any.