r/fea

Hey everyone,

I posted here twice before about FEMaster, my open-source structural finite element solver. Since the last post: reddit/femaster_1, I continued working on it quite a lot and wanted to share the current state. As before, I was trying to be as close as possible to Abaqus Syntax but deviated from it since I felt like some of it wasnt as clean as it could be. The code is open source and can be found here: GitHub/Luecx/FEMaster

The biggest update is that FEMaster is no longer only a linear structural solver. It now has geometrically nonlinear static analysis with Newton iterations, load control, arc-length control, adaptive step handling and cutbacks. My main motivation for this was to be able to follow unstable equilibrium paths, snap-through behavior and limit-point problems instead of only solving simple load-controlled cases. I also validated these methods on aerospace structural parts and it seems to align well with the analytical equations.

The part I am currently most excited about is nonlinear shell analysis. FEMaster now contains several shell elements, and the nonlinear work is mainly centered around a MITC4FRT shell formulation which is extremly close to Abaqus S4. I have verified parts of the nonlinear shell implementation against several benchmark-type examples. The attached plots show two of them:

https://preview.redd.it/0cut0cc68ebh1.png?width=1440&format=png&auto=webp&s=e63ff4eb88d6f627ecfb6f475041c93995fbcd47

https://preview.redd.it/f0t5pom68ebh1.png?width=1440&format=png&auto=webp&s=df84913d73c64196009c656bfb411ad0b5bd00cd

The labels in the plots are still in German because they come directly from my verification scripts, but the curves show the load-displacement paths and the limit-point / snap-through behavior. I compared these examples against Abaqus and other reference solutions.

I also added a frictionless node-to-surface contact formulation. I would currently describe contact as beta/experimental. It works for simple cases, but I would not yet call it robust general-purpose contact:

Frictionless contact between a beam (made of solids) and a solid plate.

Another thing I improved is the documentation. There is now a fairly detailed PDF documentation in the GitHub repository, including the keyword format and supported commands: document.pdf. I am also working on a Python backend. It already exists and can be used for parts of the workflow, but it is not yet complete.

I want to be transparent about the maturity level: FEMaster is not an Abaqus/Ansys/Nastran replacement. It is a research and development code. Some things are already quite usable, some are implemented but still need broader validation, and some features are intentionally missing for now. But compared to the first version I posted, it has grown into a much broader structural FEM framework. I am very happy about the performance and applicability of my solver so far and would love to share it with you.

Here is a list of the current features in my solver:

• Analysis types
  • linear static analysis
  • geometrically nonlinear static analysis*
  • linear buckling analysis*
  • eigenfrequency analysis
  • linear transient dynamics*
  • topology-sensitivity analysis
• MISC
  • Inertia Relief*
  • Load Rebalancing*
• Elements
  • solid elements: C3D4, C3D5, C3D6, C3D8, C3D10, C3D15, C3D20, C3D20R
  • shell elements: S3, S4, MITC4, S6, S8, MITC4FRT*
  • truss element: T3*
  • beam element: B33
  • point masses, point springs and rotational inertias
  • QSPT shear-panel element*
• Material models:
  • Elasticity:
    • Isotropic linear elasticity
    • Generalised isotropic linear elasticity (making G independent)*
    • Orthotropic linear elasticity
    • Explicit ABD matrices for shells*
  • Other:
    • Density
    • Thermal expansion
    • Local material orientations
• Sections:
  • One for each Element type: Solid Section, Truss Section, Shell Section, Beam Section, Point Mass Section.
• Loads:
  • Concentrated Loads (CLOAD)
  • Pressure Loads (PLOAD)
  • Distribute surface loads (DLOAD, similar to PLOAD but doesnt have to be normal to the surface)
  • Volume loads (VLOAD)
  • Inertia Loads from accelerations (including rotations)*
  • Most load types can be formulated within a custom coordinate system*
  • Most load types can be time dependent (in transient steps)*
• Constraints:
  • Tie Constraints
  • Coupling (kinematic / structural)
  • Connector constraints
  • automatic rigid-body-mode supression (this is pretty cool stuff)*
  • Contact (work in progress, not really robust at all).*
• Solvers:
  • External optional libraries:
    • If supported by the user: MKL (extremly fast on the cpu).
    • If supported by the user: CUDA
    • If supported by the user: CUDA cuDSS (this is crazy fast)*
  • FEMaster can utilise direct solvers (MKL, cuDSS), as well as indirect solvers like PCG on the gpu and cpu.
  • Multiple rhs*
  • Multithreading when using MKL

(Everything marked with an * is new since the last update although this list my not be complete).

Next steps for me:

The next major topic I want to work on is nonlinear material modeling. I would like to add at least a basic but clean material nonlinearity framework first, before adding more advanced features on top of it.

I would be very interested in any feedback from people working with FEM solvers, nonlinear analysis, shell elements or open-source CAE tools.

Thanks again for the feedback on the previous posts. Several things in the current version were motivated by comments and questions from this community.

hello,

I have been using fusion 360 for a few years on an education license however that license will soon expire and I can use a personal license however it does not come with the FEA simulation. Are there any alternatives I can use? I have an Intel based Mac.

I am looking for help on a CAE study for a project. I want to assess for a clip insertion & pull-off forces into a metal interface.

The study needs to be done on Ansys Mechanical.

Non linear contact and elasto-plastic behavior must be considered.

If you are interested, DM me for more information

Hey Guys, I have started using Ansys static recently and I'm not able to mesh due to some extra edges, thin steps etc, I'm used to hypermesh soo I know how to perform CAD Clean up over there, but in Ansys even though spaceclaim has theseauto repair features, it doesn't work that good, any videos or Tips would be really helpful!

I have a problem statement: “ A closed tube, water bubble into it, what happens to its droplet dynamics if we vary internal pressure conditions in a fixed temp.” how to approach and model this using ANSYS Fluent. Can anyone suggest tutorial video or help me with the CFD modelling approach?

The opening is preferablely for female candidates only because our company needs to comply with 30% female workforce internal guidelines. DM if anyone is interested.

Edit 1: Fellow Redditors look, I don't want to be seen like I am promoting gender biased hiring & get caught so, I will refrain from naming my company for my safety until I am convinced you are a genuinely interested & good a candidate I can recommend.

Edit 2: We are looking for people with 3-4 years experience, the role involves vibration & fatigue simulations on automotive components.

Perks & benefits: WFH & full ownership of your design recommendations (no boss or other entity taking decisions for you)

I can't reveal anymore unless I've seen the resumes.

Regards

I am remeshing and decimating in blender then converting to STEP in freecad

Hi, I am a structural engineer MS grad student.

I've been really interested in fea, meshfree methods, and other numerical methods so that I can become capable of solving all sorts of physics problems, maybe even extend it to topological optimization, etc.

I even learned and experimented with these on projects.

I even did ML applications for Computational Mechanics.

But my big query here is: as a structural engineer student, I feel like these things are more in the realm of mechanical and aerospace engineering? Dont get me wrong, I don't mind if that is what I should go for. I am not a big fan of working with fixed building codes and designing structures as much. But I don't want to push that pathway completely and get stranded yk.

So I'm in need of some guidance about the pathways I should or could take.

I have 10 years of experience as a stress engineer, mostly using Ansys Workbench. Due to a complex mix of life circumstances I recently transitioned into academia as a PhD student.

My issue is that my supervisor insists on doing everything via raw APDL code.

While I have experience with the APDL interface and general coding (in Python), working with pure APDL code is incredibly frustrating. The documentation is there, but finding real-world examples online is often a nightmare. Debugging is a chore because the error handling is often misleading or completely silent.

My supervisor's APDL skills seem a bit frozen in time. He clearly has experience, but he can't give me a straight answer half the time when I hit a wall. My workflow often involves building things in Workbench and then digging through the journal file to extract the command snippets.

I think I'm wasting my time and learning a legacy skill that won't serve me when I return to the industry. Is deep APDL scripting still highly valued? Should I keep fighting this battle, or should I try to push for PyAnsys? Any other ideas?

Thanks!

Hi everyone,

I was one of the principal engineers who developed Autodesk Inventor Nastran (originally NEi Nastran) from 1987 to 2023 working primarily on the solver. If you’re stuck on a problem, whether it’s meshing, contacts, nonlinear analysis, bolt pretension, composites, dynamics, vibration, buckling, or interpreting results, I’ll do my best to help here in the thread. If it’s something that requires looking at confidential models or is too involved for Reddit, we can discuss other options privately. I don’t check Reddit constantly, but I’ll answer as many questions as I can. Looking forward to helping the community.

Hi , I have recently got green card (LPR) status after marriage to US citizen. I am currently living and working in India as FEA Engineer in Oil and Gas domain. I want to now switch my job to US , I have updated my CV and applying to US jobs but not getting any calls. Infact I am getting good offers in India but there is no point in those. I am also trying within my company to shift me to US but that would expose me trying to move out which won’t be too good for me. Need Advise and referrals .
PS : I am 8 years experienced in my field and a Technical Expert at my current Organisation.

At my work, one of my fields involves structural optimization, where the same model may need to be solved many times with changing parameters. Because of that, I’m especially interested in small-to-medium models where repeated solve time matters. I'm looking for something that can easily be recreated in different solvers, preferably from a Python-style script. I’m personally also working on a FEM solver, and I’m looking for a fair way to benchmark solve speed during development.

In the LLM world, people often compare models on shared benchmarks. I’m wondering if anything similar exists for FEM solver performance?

Hi guys,

I'm trying to do a FRF correlatiom in Hyperstudy. I have the model in Optistruct (it's a simple metal plate) and I want to adjust the model so the FRF curve fits the experimental results.

I have successfully input the data in Hyperstudy (the curves from .h3d from the simulation and the .csv from the experimental analysis) in the data source tab and I've created another data source of area between the two curves. Then, in the respose tab, I have selected the max(area) with the minimize objetive (as is in the tutorial).

However the area is negative?? And when I try to run an optimization, the response doesn't change when the parameters change. What am I doing wrong?

For the parameters i have density, young modulus, poisson and material damping.

I am a CAE Engineer working at an organisation in India. I am having doubts about some of the methods used in FEA, particularly how stress contours are post processed. I am being asked to report stress in FEA reports by averaging several nodal stress values around the actual maximum nodal value (singularities have been taken care of). I don't have a clue if something like this is actually legit, cuz the only explanation my seniors gave me was that - FEA is an approximate approach, we need to use our own judgement on top of the software's response to your modelled problem, which doesn't tell me much about the reason.

So if there are any experienced pros that can shed some light on this topic on how they post process stress results OR if someone can tell me what the right way is backed by any credible sources would be helpful.....

What software do i need to do a dynamic analysis of respnance and vibratory phenomemon of a valve spring/actuation system ?

I have ANSYS, can it handle it, or do i need something like ABAQUS or MSc Adams ?

Thanks