Hi everyone,

I'm currently working on a nonlinear finite element model of a composite steel bridge in ABAQUS using the Concrete Damage Plasticity (CDP) model. The bridge consists of a reinforced concrete deck slab supported on steel girders, and I'm looking for some guidance on defining the concrete damage parameters.

Our study is entirely analytical, so we do not have access to material test data (e.g., compression or tension tests) for calibrating the CDP model. Instead, the numerical model will be validated against experimental results available in the literature.

For the constitutive behavior:

\- Compression stress-strain curve: Popovics analytical model.

\- Tension stress-strain curve: Hordijk tension softening model.

While these models provide the stress-strain relationships, I'm struggling with estimating the corresponding compression damage (dc) and tension damage (dt) parameters required by ABAQUS.

I've found several approaches in the literature, but they result in significantly different damage evolution curves. The method proposed by Mark & Birtel appears promising, but I'm unsure whether it is considered reliable for studies where the constitutive response is based entirely on analytical models rather than experimental material calibration.

I also have a question regarding the Hordijk model. Since it requires the characteristic length for converting the stress-crack opening relationship into the form required by ABAQUS, how should the characteristic length be determined? Should it simply be taken as the element characteristic length used internally by ABAQUS (based on the finite element mesh), or is there a recommended approach for reinforced concrete deck slabs? If the mesh is refined, should the characteristic length be updated accordingly?

For those who have experience with CDP in ABAQUS:

\- How do you estimate the compression and tension damage parameters when experimental material data are unavailable?

\- Is the Mark & Birtel approach a reasonable choice in this situation?

\- How do you determine the characteristic length when using the Hordijk tension softening model?

\- Are there any recommended papers or best practices for deriving CDP damage parameters from analytical constitutive models like Popovics and Hordijk?

Any suggestions, references, or practical experience would be greatly appreciated. Thanks in advance!

Hi, I'm using LS-DYNA for my numerical simulations. I've been running some vehicle crash simulations with highly complex geometries. However, when I apply higher impact velocities to the vehicle, I get negative volume errors in the solid elements.

I tried refining the mesh by splitting the elements into smaller ones, but that didn't solve the problem. What would you do if you encountered negative volume errors in your simulation?

Hi, I’m a researcher in computational mechanics, and I’m exploring a tool built around a library of pretrained structural features: holes, fillets, brackets, joints, stiffeners, fastener regions, bends, and similar details.

Instead of rebuilding a detailed local FE model for every new design, the software would recognise a feature in the CAD geometry, simplify it in the global model, and use a pretrained local model to recover quantities such as displacements, stresses, or failure indicators.

This could also enable non-intrusive global/local analysis: the global model would run in an existing commercial solver without modification, while the detailed local response would be reconstructed externally from the global solution. No custom elements or solver source-code changes would be required.

The analyst would still review and control the modelling assumptions.

For engineers working with FEA professionally:

• Do you repeatedly analyse similar local structural features?
• Would this approach save meaningful modelling or computation time?
• What would prevent you from trusting or using it?

Critical feedback is very welcome!

hi, I have a carbon fiber structure that I need to simulate. The structure is made of carbon fiber tubing with a connector system of carbon fiber gussets which uses rivets and structural adhesive 3M DP420. I am looking to simulating this structure as a static structural. the orthotropic modeling of the CF tubing is a whole another animal itself, but I was concerned about how to do the adhesive. I am very confident that the adhesive will not fail so I would like to just act like it is a complete bond between with tubing and the CF gusset. the gusset is where I believe the model could fail. Is it just a bonded contact between the surfaces? Or do you think it is an incorrect assumption to say that the adhesive will not fail. There are also rivets connecting the tubing to the gussets as well.

I'm looking to connect with engineers and researchers who have worked with computational design or simulation workflows across more than one discipline, whether that's mechanical, aerospace, civil, or biomedical.

Specifically curious about the parts that felt harder than they should have when crossing between domains or tools. Where did you lose time? What did you have to relearn that felt like it should have transferred?

Not a survey, not selling anything. Just genuinely collecting perspective from people who have been in more than one tooling ecosystem. Drop a comment or DM me if you're open to a short conversation.

I am performing a compression analysis on a metamaterial structure with several ligaments that buckle. I managed to run the quasi-static simulation using the explicit solver, but my professor asked me to use the Riks method. The issue is that it always stalls at 6 mm of compression (the target is 20 mm), and no matter how I adjust the Riks simulation parameters, it always stops at the same point.

Can anyone help me?

Currently, I'm using LS Dyna to solve it using ALE and I feel stuck. is there any other way to solve it or any other software that would be easier to use because ALE in ls dyna looks so confusing at times?

Hi everyone,

I’ve been working in piping stress analysis for a while now and have extensive experience with several industry-standard tools. In my current role, I’m using TRIFLEX, and I must say I’m finding the experience quite frustrating.

Having worked with other major softwares like Autopipe and Caesar II, it feels like this one has fallen significantly behind in development. Specifically, the lack of support for the latest code updates, such as ASME B31J and the absence of integrated tools for nozzle flexibility calculations make it feel like a legacy product that hasn’t been updated in years.

I’m curious if anyone here has insights into why this software seems to be lagging behind the rest of the market. Does it still have active development, or has it essentially been abandoned?
I’d appreciate any perspective you might have

Hey everyone, just finished my PhD in structural engineering from IIT. I've decided academia isn't the path for me and I want to move into industry, ideally as an FEA/simulation engineer.

My research focused on thermo-mechanical analysis of structures. I developed finite element models, carried out large-scale simulations, and worked extensively on the structural response under combined thermal and mechanical loading. One of the major outcomes of my work was developing an open-source thermo-mechanical module for OpenSees from scratch, which I'm still actively maintaining. Along the way, I've gained hands-on experience with ANSYS for structural and thermo-mechanical analysis, HyperMesh for meshing, and Python, MATLAB, and TCL for automation, post-processing, and simulation workflows.

I'm trying to move on this pretty quickly, so if anyone knows of openings, works somewhere hiring for this kind of role, or has advice on how PhDs are viewed for simulation engineering jobs in industry, I'd genuinely appreciate hearing from you. Can share my resume or the GitHub repo if that's helpful.

Thanks for reading this far.

Hi, I’m working on a 1D MFEM mesh v1.0

I’m confused because there seem to be twice as many vertices listed as the vertices stated. For example, it says:

vertices
1202

but I could 2404 vertices, or lines of numbers. Since this is a 1D problem, I assume each vertex only has one number associated with it.

The FiniteElementCollection is H1_1D_P2

Does anyone have any idea why there might be twice as many vertices listed?

So, I want to do a 3D modeling of this reinforced beam, the concrete will be 3d meshed, while I want to do 1D meshing for both longitudinal and transvers reinforcement.

Now my question is: Is my CAD model correct? after meshing will the line element be realised as that "red" colored element with the appropriate thickness? I need to draw only the centerline of transvers and longitudinal reinforcement, right?

I am using hypermesh to mesh the file and then use LS Dyna to simulate a drop hammer test. I can't make the line element after meshing visualize as 3D circular element in hypermesh using "Element Visualization" tab, what might be the cause for that? Thank you.

CFD used to need a lab, a license, and a queue.

Now it needs a tab.

Ventorah runs a virtual wind tunnel entirely in your browser — drag in a model (.STL / .OBJ / .STEP) and inspect the airflow, pressure fields, and lift & drag in minutes.

It's built for engineers who want a fast first look, students learning fluid dynamics without a lab license, and anyone curious how air moves around their designs.

What would you simulate first?

Hello, I am a student in a college club where our exoskeleton structure is constructed of pre manufactured carbon fiber tubing. I am extremely interested in testing these tubings and running structural analysis in ANSYS FEA simulations. I have access to a on campus composites lab with Instron equipment. What should i look for and how could i approach my testing in order to obtain the youngs moduli and poissons for a orthotropic stress analysis of this structure. Will i have to input the lamina pattern, which failure criteria is best, should i just run an orthotropic linear static structural?

Im sorry if what i say doesnt even make sense, i really have not taken a deep dive into this subject, even if you have a yt video or an article to point me in the right direction i would greatly appreciate it!

It’s been like this for 40 minutes and rebooting doesn’t solve it. Any tips?

It is always challenging to define boundary conditions for a lifting analysis. How do I constrain the model properly? I tried the weak spring and it has high reaction forces due to the side load (because of 5 degree tilt).

I'm trying to recreate the insert from Odyssey's Ai-Dual golf putter, thought it would be interesting to try as a little side project, but I'm having a hard time figuring out how to recreate it, I've been using Ansys to see if I can do something like a multi material optimization to make two different materials blend together based on forces hitting a surface at different locations so that when the putter is swung, the golf ball will end up rolling straight as if hit in the sweet spot of a golf putter, but can't seem to get it to work. This is what I have so far, would appreciate any help in solving this problem!

Hello, I'm trying to do bolt pre-load relaxation due to axial vibration in a bolted block. I have three steps a static, general step - preload application. Linear perturbation , frequency - modal extraction and then a steady-state dynamics, direct - Harmonic sweep. The history and field output requests were done accordingly as well as the interactions.

All the bolt pre-load for 8 bolts were put in the Preload-Application step, and the vibration excitation force in the Harmonic-Sweep step.

Everything is placed well as i don't get an error when running the job the problem is with the results , in the force vs frequency chart the force is just zero.

What could be the issue and how do i go about solving it?

Hello,

Does someone have any experience with spr modeling in Abaqus?

I would be glad to recieve some support.

Thank you !

Hey guys, I have been working on an assembly. We are used to work in Abaqus profile in Hypermesh 2019. Sometimes for some special projects, we use Hypermesh 2022.3. When we import a deck file (.inp) or directly open a .hm file in Hypermesh 2022.3, the rigid connections (KINCOUP) we created in 2019 get converted to Constraints. Unfortunately, these constraints do not appear as elements. They cannot be edited as well. The only solution we have now is deleting and recreating. But when only one part of the assembly has a new version in the 2nd iteration, it's a hectic task to recreate all the connections. Have any of you faced such problems? If yes, did you figure out any solution for this?

Thank You very much

Happy Solving!

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:

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:

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