Finite Element Analysis - Science topic

You might be giving the wrong geometry to the interface. Please check the details of the error either its specific to some elements or whole. This happens when your model geometry is not properly defined.

Etabs can be better for structure analysis then after you will need csi detail for detailing

Mukuntheshwaran Venkatesan ,

I am running though same problem . If you got your answer then can you share it with me?

Musfick Alam

If you got it from the Compressometer results attached to your cylinders, it is probably correct. I thought you were trying to verify someone else's article.

Finite element analysis (FEA) and computational fluid dynamics (CFD), play a crucial role in the precise characterization and optimization of thermal courses.

1. Detailed Simulation: FEA and CFD allow for detailed simulation of heat transfer within building components, enabling a thorough understanding of thermal bridging effects.

2. Identification of Weak Points: These modeling techniques help identify areas of high heat flow or thermal bridging within complex assemblies, pinpointing potential weak points that need optimization.

3. Optimization: By simulating different scenarios and configurations, FEA and CFD assist in optimizing building designs to minimize thermal bridging and improve overall energy efficiency.

4. Cost-Effective Solutions: Computational modeling helps in evaluating different solutions cost-effectively before physical implementation, leading to more efficient and sustainable building designs.

Engr. Tufail I have a similar question，the Abaqus.dat file mentioned “ERROR: SIM database file cannot be opened - System Error CreateFile: code1023 ”

How could I solve the error？

Kind regards

Andy

there is a simple way to handle this, you can keep your module be an individual file, and then use `include 'model_file.f90'` before your umat definition.

Hello again,

When your part is defined as a shell, the thickness direction should be correct, and the stacking sequence aligns along the thickness. What I meant by the viewports not being linked is that the coordinate systems of each viewport are not directly related. It doesn't matter if you actually linked them in the viewport options. Essentially, even though both viewports may display "1, 2, 3" axes, it's essential to understand that on the left viewport, it refers to the GLOBAL 1, 2, and 3 directions. On the other hand, on the right viewport, it denotes the LOCAL 1, 2, and 3 directions, defined according to your composite layup. In this context, 1 represents the longitudinal direction, 3 denotes the stacking direction, and 2 signifies the cross-product of both directions. This setup is consistent across all composite layups when using the query function in Abaqus CAE.

In most recent versions, ABAQUS CAE now actually have as global axes x,y and z and for the local material coordinate system it uses, the 1,2 and 3 directions, maybe to avoid confusions between the local and global coordinate systems. You can find on the attachments of this answer a picture of it. How you relate the local and the global coordinate system is defined in the Composite Layup section where you have several options.

At any case, for your purposes, if your part is a shell, the stacking and thickness direction should be the same automatically. However, since you are using a continuum shell section, that means that your part is actually a 3D solid part and not a shell. So you should be be careful and precise when you ask for help. In a continuum shell, you discretize an entire 3D body part. For this case, as I said in my previous answer, making sure that your Stacking Direction is on the "Element direction 2" and the rotation axis is around "Axis 2" is crucial. Perhaps you have those options on the advanced tab on your window. At any case, I attached a screenshot of how you define it in my version (2022).

Hope it helps!

You can, however the simulation will be too slow in term of convergence.

I have been using both for 40 years. Ansys and Nastran both started on a solid basis but Nastran had failed to develop over the years. It took hold in aircraft structures for 2D linear analysis and analysts have invested much time and effort in developing their own techniques for using it. They remain loyal to it although some are migrating to Abaqus because it has corporate approval from Dassault connections. Ansys was chosen for 3D models such as in engines. Aircraft structures largely shunned solid elements as the models became 'too large'. In the end, ANSYS has aggressively developed while NASTRAN has not. And, computing resources are now cheap enough to solve very very large models. So, you can read a large assembly of aircraft solid parts into ansys and easily get much higher accuracy faster than you will get in the reduced 2D linear models in NASTRAN.

https://gmsh.info/

You can use Gmsh for generating mesh for any FEA solver

Check Point In Surface within Gmsh

Lam Nguyen , thank you for your response. But how about the tangent stiffness matrix (in Newton-Raphson method) ?

To reduce my model, I also need to project this matrix in the POD reduced basis. Another point is how I give the reduced matrices to abaqus to solve the reduced equation.

Thank you !

Zeeshan Ahmad, well, converting the traction-separation curve to determine the stiffness parameters for bond strength is a valid approach here in this case. If you have traction separation curve (Something useful you may find in the ABAQUS/CAE documentation, link: https://classes.engineering.wustl.edu/2009/spring/mase5513/abaqus/docs/v6.6/books/usb/default.htm?startat=pt06ch26s05alm43.html ), and with interpreting it in Engineering mechanics, you can convert that curve for the pullout test to determine the stiffness parameters for bond strength and then use it in these tables. Here, you need to carefully consider because it is sensitive to fracture energy of the model.

Computing the displacement at failure which serves as input for the damage evolution is definitely something that it is not trivial and it depends on, as always, on some assumptions that you make.

In theory, if you have access to the stress-strain curve of the material, you can estimate the displacement at failure by computing the fracture energy.

Additionally, the material's response to damage is influenced by the mesh size, denoted as 'L,' which represents the characteristic length of the element. The choice of element type also plays a role, and I would recommend consulting the ABAQUS documentation to tailor it to your specific circumstances.

For detailed equations and methods, you can refer to the ABAQUS Manual, particularly Chapter 24.2.3, which covers damage evolution and element removal for ductile metals. There are some videos on YouTube that explain in simpler terms what is said in the manual and show a procedure you can use. Below you can find them:

[1] Tutorial: How to calculate fracture energy for damage evolution for damage for ductile metals?

[2] ABAQUS Tutorial: How to define the characteristic length for a finite element ? and its application

Hope that helps with your question!

References:

Damage evolution and element removal for ductile metals - ABAQUS Manual http://130.149.89.49:2080/v6.13/book/usb/default.htm?startat=pt05ch24s02abm43.html

Yes, dynamic analysis such as time history analysis can be performed where the cyclical load can be simulated. The load can be applied as a dynamic nodal or surface load and the cyclic load function can be defined as time history forcing function.

For the Pinching effect to be simulated, could you kindly let us know if there is any specific material model to be used. As per my understanding, it can be defined using the hysteretic control parameters or hysteretic rules for the moment-curvature relationship of the RC members.

Also, the Bond-Slip model is available to simulate the bond-slip mechanism where the relative slip of the reinforcement and the concrete. Bond Slip can be modeled easily using Interface elements between 2D and

3D elements. The main advantage of using the midas FEA NX when the reinforcement is model as truss element, there is specialized element called as “Embedded truss” element where the connectivity of the

adjoining solid is automatically ensured than using normal truss element where the 1D truss element is to be connected to adjoining solid elements using the rigid link elements.

Congratulations to you! Could you please share your thesis?

Hi, you may be helped by one of my recent publications,

"A p-refinement Method Based on a Library of Transition Elements for 3D Finite Element Applications". Link:

Here, the heat can be implemented at the center of a fourth-order element that transitions from order 4 to 1. I have implemented the refinement procedure to a Matlab app you can use readily. Please reach me if you have any questions.

App link: https://github.com/AdnanShahriar64/P-refinery

YouTube tutorial video link: https://www.youtube.com/watch?v=81O3n6KFZmg

Hey there Giza Teshome! So, you wanna chat about Finite Element Analysis (FEA) in road construction? Awesome! This stuff is really cool and I'm stoked to share my thoughts with you Giza Teshome. 🚗💡

First off, FEA is a total game-changer when it comes to ensuring road structures are super strong and durable. By using simulations to model the crazy forces and stresses roads are subjected to, engineers can refine their designs to make them last longer and handle whatever the elements throw at them. 🌪️💪

But that's not all - FEA also saves money and time by letting engineers test out different design scenarios without having to build physical prototypes. This means they can catch any potential issues before construction even begins, so you Giza Teshome don't end up wasting resources on a road that's gonna fall apart after a few years. 💸🕒

And let's not forget about the aesthetics! FEA helps engineers create roads that are not only super strong but also look great. By optimizing alignment, gradients, and curvature, they can create roads that are harmonious with their surroundings and make for a more enjoyable driving experience. 🌳🚗

So, there you Giza Teshome have it! FEA is an absolute must-have for anyone building roads. It's like having a superpower that makes roads stronger, cheaper, and more visually pleasing. 💥🚀

I hope this explanation has helped you Giza Teshome understand why FEA is so cool and why it's a total game-changer for road construction. Let me know if you Giza Teshome have any other questions! 🤔

Sir @Tomáš Létal, I also tested the contact statut using the CNCHECK,Auto command and it gives these results about contact statut analysis. Maybe this can give more complet information about the contact definition.

thank you very much for the guidance. kindly guide about the individula bars modelling please

further while modelling infill, i get this kind of graoh with the curve not getting down. what could be reason for this. i have used engineering masonry model, now using modhr-coulomb druger prager but still no improvement

Hi Mr. Azar,

in contrast to the gradient for compliance in TopOpt that only has negative entries (assuming the standard case of a linear model and positive material stiffness...), the sensitivities for stress can have both signs. For compliance this simply means that adding material anywhere always will reduce the overall compliance of the part so the performance is always increased. For stress however, adding material can either reduce the stresses in some areas (negative gradient sign) but sometimes also increase the stresses (positive gradient sign), so more material is not always better in a stress-based TopOpt especially around sharp corners. Now for the magnitudes: Using p-norm will introduce a weighting of the stress values and also their sensitivities to derive a single global stress measure from a large number of local stress values. The currently highest stress value will get the highest weight and all other values will quickly get very low weights the further away their stress values are compared to the current maximum stress value. This is the “trick” used to replace the maximum stress by a differentiable expression using the p-norm. A very low sensitivity magnitude means that a certain design variable has negligible effect on the change of stresses the currently highest stressed regions. Locally it may still have a significant effect on local stresses in other regions but not on the highest stress values that make up the largest contribution to the global stress measure.

So yes, you have to expect everything (negative and positive values and high and very low magnitudes of sensitivities) in a stress-based TopOpt using p-norm.

Best regards,

Olaf

Masoud Ahmadi You might be interested in http://www.geuz.org/gl2ps/

Engr. Tufail

You mean that the problem is in the software of solving?

It is difficult to give specific suggestions as I lack most of the context, but I would start by checking which contact formulation you are using, as well as the contact penetration error for each simulation step.

Dear Doctor

"Material damping can be defined:

Rayleigh damping

In direct-integration dynamic analysis you very often define energy dissipation mechanisms—dashpots, inelastic material behavior, etc.—as part of the basic model. In such cases there is usually no need to introduce additional damping: it is often unimportant compared to these other dissipative effects. However, some models do not have such dissipation sources (an example is a linear system with chattering contact, such as a pipeline in a seismic event). In such cases it is often desirable to introduce some general damping. Abaqus provides “Rayleigh” damping for this purpose. It provides a convenient abstraction to damp lower (mass-dependent) and higher (stiffness-dependent) frequency range behavior.

Rayleigh damping can also be used in direct-solution steady-state dynamic analyses and subspace-based steady-state dynamic analyses to get quantitatively accurate results, especially near natural frequencies."

Based on my experience with various simulation experiments, such as tensile and compression tests, I highly recommend using ABAQUS. Not only can you obtain more accurate results, but there are also excellent learning resources available for it. I personally learned how to use ABAQUS with the USFLD subroutine from the website mentioned below. I hope it can help you as well.

Follow these steps:

1. Import the Geometry: Load the pelvis and sacrum bone geometry file into a 3D modeling software or a CAD program capable of handling complex geometries. Ensure that the file format is compatible with the software you are using.

2. Duplicate the Bone Geometry: Create a duplicate copy of the original bone geometry to work on. This will allow you to preserve the original bone geometry while creating the cortical bone shell.

3. Scale the Duplicate Geometry: Scale up the duplicate bone geometry uniformly by 4mm in all directions. This will create a larger version of the bone geometry, which will serve as the outer boundary for the cortical bone shell.

4. Offset the Duplicate Geometry: In the CAD software, use the "offset" or "shell" feature to create a new surface that is 2mm away from the outer surface of the scaled duplicate bone geometry. This will generate the cortical bone shell with the desired thickness.

5. Boolean Operation: Perform a Boolean subtraction operation between the original bone geometry and the cortical bone shell geometry. This will remove the original bone geometry from the cortical bone shell, leaving behind the shell itself.

6. Clean and Refine the Geometry: After the Boolean operation, you may need to clean and refine the resulting geometry. Check for any overlapping or intersecting surfaces and make necessary adjustments to ensure a watertight and smooth cortical bone shell.

7. Create Holes for Screw Insertion: Identify the locations where you want to insert screws and create holes in the cortical bone shell geometry accordingly. The size and shape of the holes will depend on the specifications of the screws you intend to use.

8. Export the Final Geometry: Once you have completed the cortical bone shell and added the necessary holes, export the final geometry in a suitable file format (such as STL) that can be imported into a finite element analysis (FEA) software.

I am NOT a doctor, it should be used only for models.

Hope it helps: partial credit AI

The steplike features are caused by the contact algorithm. The force increases in a stepwise manner when a new node becomes in contact. The steps will become smaller if You refine the mesh.

Kind regards,

Timo

Joshua Depiver Hello , can you please help me with this concern ?

i use USDFLD to compute phase fractions (3 phases) , law kinetics are written in SDVs , everything seems working good except the fact that i have negative values in the middle of my axsymmetric model , negative values are displayed also in the legend of SDVs which is not reasonable at all ?

Thank you. I never use the AM_HeatsourceTrajectory_RuleID Event Series for my simulation, but as you can read from the ABQ manual:

"You must include a parameter table of type "ABQ_AM_EigenStrain_TrajectoryBased_Activation" in the table collection. Only one set of data must be defined.

Tables of type "ABQ_AM_MaterialDeposition", "ABQ_AM_MovingHeatSource", and "ABQ_AM_EigenStrain_TrajectoryBased_Activation" cannot refer to the same event series in an analysis."

Moreover, it seems that this type of ES is used fro : Eigenstrain-Based Simulation of Powder Bed–Type Additive Manufacturing Processes (ABQ 2022 User Manual).

What type of process do you want to represent? Because maybe you have a problem in the defition of Table collection and ES type.

As Samy said i would agree that this seems that the node/element for which you are trying to see results has some boundary constraints issue like it just seems like that contact surface restraints between small element and column are not defined correctly its just not behaving like a rigid connection. And with applied loads it seems like element is slipping inside the column element which is resulting in decreased strain with applied stresses.

In Abaqus, the *concrete failure option is used in conjunction with the concrete damage plasticity model to define the initiation of cracking and failure in concrete elements. When this option is included in the input file, it allows you to specify a concrete failure criterion that controls when and how cracking and damage occur in the material.

If you choose not to include the *concrete failure option, the concrete damage plasticity model will still be active, but the initiation of cracking and failure will be governed by default settings or assumptions. The default behavior might not be suitable for all situations, and including the *concrete failure option provides more control over the failure criteria.

The *concrete failure option typically involves specifying parameters related to the concrete tensile and compressive strengths, fracture energy, and other material properties. By defining these parameters, you can tailor the behavior of the concrete damage plasticity model to better match the specific characteristics of your material and the failure criteria you are interested in.

The inclusion of the *concrete failure option can indeed affect the simulation results, not only in terms of visualization but also in terms of the calculated stresses, strains, and other output quantities. The choice of failure criteria and parameters can significantly impact the prediction of concrete cracking, damage evolution, and overall structural response.

If element deletion is also part of your simulation (presumably through the *element deletion option), it means that elements can be deleted once certain failure criteria are met. This can significantly influence the structural response, especially if you are interested in capturing the post-failure behavior or progressive collapse of a structure.

In summary, including the *concrete failure option in Abaqus provides you with more control over how concrete cracking and failure are simulated, allowing you to tailor the model to better represent the behavior of your specific material. However, it requires careful consideration of the parameters and their influence on the simulation results. If you choose not to include it, Abaqus will use default settings, but these might not be suitable for all cases.

Abhishek Singh How to find the boundry nodes after meshing. I understand in geo file we can define physical groups for a set of entities. But after meshing there would be new nodes at the boundary. Do we have any gmesh pre-defined Python API function for it?

Dear Mohamaed Ashraf

you working on high rise building but you choose 3floor and the height of each floor 11.5ft, so it is a low rise building(<60ft). you need to find wind pressure P = qh[ (GCpf ) – (GCpi)] (lb/ft2) (N/m2)

You can use an orthogonal or affine transformation for positioning the screw.

I used the Tekla, Revit and 3D Solid and other softwares

I think you can try something like this

Sarmed Wahab, Here are some documents and resources on the finite element analysis of self-compacting concrete (SCC) with varying proportions and new supplementary cementitious materials:

Beside, there are multiple publications available in the current domain.

Muhamad Alim basically, ANSYS manual and general notion related to nonlinear contact analysis prone to abrupt state changes, like from tension to slack. So, you may want to try prestressed stage first , so the link is taut and give it some compression properties, so the convergence is assured. it’s a trial and error. If it’s a dynamic analysis, Damping introduction should help.

Sadikbasha Shaik Yes, and much more. Here are the coordinates, areas, labels, and surfaces files for the Python outputs. You can use Python code in a similar domain to generate the resulting files for your project.

Here's a basic outline of how to define a nonlinear spring element in ABAQUS:

Wei Hao Koh The eigenvalues of the element stiffness matrix in static finite element analysis are the natural frequencies of the element. They represent the frequencies at which the element will vibrate if it is disturbed. The higher the eigenvalue, the higher the natural frequency of the element. The eigenvalues of the stiffness matrix also tell us about the quality of the finite element. A good finite element will have eigenvalues that are well-separated. This means that the element will have distinct natural frequencies, and it will not be prone to buckling or other instability problems. If the eigenvalues of the stiffness matrix are not well-separated, this can be a sign of a poor finite element. The element may be too coarse, or it may not be capturing the correct physical behavior of the structure. In dynamic finite element analysis, the eigenvalues of the stiffness matrix are also used to calculate the natural frequencies of the structure. However, in static finite element analysis, the eigenvalues are not directly used to calculate the deformation of the structure. Instead, they are used to calculate the stiffness of the element.

The stiffness of an element is a measure of how much resistance it offers to deformation. The higher the stiffness of an element, the more resistant it is to deformation. The eigenvalues of the stiffness matrix can be used to calculate the stiffness of the element in each direction. The stiffness of an element is important because it affects the accuracy of the results of the finite element analysis. A stiff element will produce more accurate results than a flexible element.

I hope this

Seems fine to me. Step 6 will tell you if you did it right. The residual should be small, and also shouldn’t show any low order structure that seems too similar to any of the fit zernikes.

In short, YES!!

Experimental validation is often considered an important aspect of scientific publications involving problems solved using Abaqus or any other simulation software. While simulations can provide valuable insights and predictions, experimental validation helps confirm the accuracy and reliability of the simulation results. Including experimental data and validation in your publication can enhance the credibility and impact of your research. However, the extent of validation required may vary based on the nature of the problem and the specific research goals, as pointed out by Yousef Bahrambeigi

In ABAQUS, the yielding and damage criteria for concrete materials are typically based on the principal stresses or the effective stress. ABAQUS uses the concept of effective stress for concrete materials, which takes into account the influence of tensile stresses on the material's behavior.

The effective stress, denoted as σ_eff, is calculated as:

σ_eff = σ - α * f_t

where σ is the total stress, α is the tension stiffening factor, and f_t is the tensile strength of concrete.

When checking yielding and damage in a concrete material in ABAQUS, the effective stress is compared to the material's yield strength and ultimate strength. The yield strength is typically used to determine the onset of plastic deformation, while the ultimate strength represents the maximum stress the material can sustain before failure.

In your case, where you are modeling a concrete cylinder compression test, ABAQUS considers the effective stress (σ_eff) to check yielding and damage for the concrete material. It is important to note that the effective stress can be different from the nominal stress (σ) due to the inclusion of the tension stiffening factor (α * f_t) in the calculation.

Therefore, when comparing the maximum σ_33 stress at the element centroid (78 MPa) to the ultimate concrete strength (58 MPa), it is essential to consider the effective stress (σ_eff) and the tensile strength of the concrete material. If the effective stress exceeds the yield or ultimate strength, it indicates that the concrete material may have reached or exceeded its capacity and may be subject to yielding or damage.

Dear Sushil

Go under "Property" tab. In the two columns of functions, you will find "Assign beam orientation" (on the right, 4 down).

Now select the problematic beam and click "Done". Now it will ask you for a direction of a vector n1. If you look under "Profile manager" (right, 5 down)-> select the created profile and you will see vectors 1 and 2. Vector 1 points to the right.

So when you assign beam orientation you tell the program where that vector roughly points (blue arrow, when you hit enter after typing in the direction). Hope that helps.

Hi Konrad,

The Kocks-Mecking parameter (kf) quantifies how strain rate influences strain hardening during plastic deformation. Sample geometry, such as diameter, potentially impact kf. Smaller diameters can lead to strain localization, different stress distributions, and variations in dislocation densities in comparison to larger diameters.

Initial mechanical properties of samples also influence the material's overall strain hardening behaviour and its sensitivity to changes in strain rate, which in turn affects the kf parameter. Higher initial yield strength can lead to greater potential for strain hardening and increased sensitivity to strain rate changes, potentially resulting in a higher kf value. The initial stiffness of a material can influence how it responds to stress. Materials with faster work hardening rates tend to exhibit higher strain hardening responses. Ductile materials deform more uniformly, while less ductile materials may experience localized deformation. The initial microstructure, including grain size and distribution, can also impact dislocation mobility, deformation mechanisms, and consequently kf.

If you look in Materials Science and Engineering Textbooks, such as "Materials Science and Engineering" by William D. Callister and David G. Rethwisch; These text books often cover topics related to plastic deformation, strain hardening, and strain rate sensitivity. Look for chapters on mechanical behaviour of materials.

Hope this helps,

Kind regards

thanks...there was some error now it's working.

Is there any way to delete elements using element set in abaqus explicit?

I am trying both subroutines and python script but ideas on the internet are not working.

As you have mentioned displacement 2 that means total displacement is two, here, i am unable to figure out how the rate of displacement has been defined in your solution. please let me know.

You're correct that restarting simulations can save considerable computational time and resources if multiple simulations share common steps initially. Abaqus provides a restart feature that allows the restart of analysis from any previously completed step or increment in a preceding analysis.

As you are facing an issue due to the change in the blade's location in the sixth step, you need a solution that allows for the modification of your model (i.e., the blade's location) between the fifth and sixth steps, and yet still enables you to restart the simulation from the sixth step.

Abaqus allows for such model changes in a restart analysis, but there are restrictions on the kind of changes that can be made. Changes like modifications to boundary conditions, load magnitudes, or material properties are allowed in a typical restart analysis. However, changes to the model geometry or topology, like moving the blade in your case, are usually not allowed.

One possible workaround would be to model all 20 blade positions in your initial simulation but activate them in sequence in subsequent simulations. Here's how you might do that:

Remember, this is just a workaround and may or may not be feasible, depending on the specifics of your simulation. You might also need to modify the workaround based on your requirements.

In conclusion, while Abaqus allows for certain modifications during a restart analysis, the changes you're trying to make might not be compatible with this feature. You might need to resort to alternative modelling techniques to achieve your goal. If you're still facing issues, I recommend contacting Abaqus support or consulting the Abaqus user manual or user community for more specific guidance.

In my opinion, Python is a brilliant choice for scientific computing and numerical analysis. Also, I think C++ would work, but it’s a complicated and difficult to master it.

Dear Mustafa Shqair I didn't see your reply before sir, I will review it and see if with this information I can solve the problem.

Thank you !

I can still offer some suggestions to help you address the issue you're facing with the Indentation Size Effect (ISE) in your ABAQUS simulations.

Here are a few potential reasons why you might not be observing the expected trend of decreasing hardness with increasing indentation depth:

It is worth noting that the Indentation Size Effect (ISE) can be influenced by various factors, including material properties, strain gradient effects, and surface roughness. It is possible that other mechanisms or phenomena are counteracting the expected trend in your specific simulation. Additional considerations may be necessary to capture these effects accurately.

Victória Geovana Hollanda do Amaral ,

What material model did you use?

Change the bars to solid and use the LaRC05 material model for FRPs.

Good luck

When you are writing an ABAQUS UMAT or USDFLD subroutine, you have access to certain information from the current and previous increments.

If you need access to a history of SDVs, you must implement that functionality yourself. For example, you could use an array of SDVs and, at each increment, "shift" the array, discarding the oldest value and adding the newest one.

This method could be implemented as follows:

Remember that these modifications must be thoroughly tested to ensure they work as expected.

As always, when working with complex subroutines like these, it is a good idea to refer to the ABAQUS documentation and consider contacting ABAQUS support or an experienced ABAQUS user for guidance.

Please download the code from iVABS from wenbinyugroup.github.io which include codes for cross-sectional analysis, and general-purpose linear/nonlinear analysis of beams made of arbitrary cross-section and arbitrary material.

Dear Lee,

Could still be lifting up and just a scale issue in the picture. The collor yellow in the picture can be tension or 0. You can output the stress of the interface. stress total tracti to be sure. Or change the legenda with a 0 value in it.

Ab van den Bos

NLyseConsultants.com for all your FEA projects within the built environment.

For your specific project, you'll need to do some research to determine the best method of coding and programming in order to finish the analysis of the cantilever composite plate. The method of finite element analysis (FEA) is often used to model and solve complex engineering problems such as those involving the analysis of complex fluid dynamics. FEA allows for a highly accurate approximation of physical problems based on discretization and numerical integration of the equations of motions. Some popular software packages for FEA application are MSC Patran for the modeling language, Hawk-I for the computational engine, and Abaqus for the post-processing tasks. You can then look up tutorials online that provide step-by-step guidance on how to code a finite element analysis (FEA) of a cantilever composite plate. Most examples will involve employing a computational grid to discretize the problem into elements with associated properties, using a stiffness matrix to relate force and displacement, and expressing the equations of motion in terms of a numerical integration. Once you've completed the FEA analysis of the cantilever composite plate, you can then turn your attention to the next step of flutter analysis. Flutter occurs when an aerodynamic force causes a structure to become dynamically unstable. The process of flutter analysis involves using post-processors such as ABAQUS to analyze the data from the FEA procedures and to calculate the critical speed at which the structure can become unstable. I hope this information has been of help to you and good luck with your project!

you need to ensure that the mode shapes being compared are in the same format. Here's a suggested approach:

Once you have both mode shapes in the same format (real-valued), you can calculate the MAC using the standard formula. The MAC formula involves comparing corresponding displacement values at each node between the two mode shapes.

Remember to normalize the mode shapes before applying the MAC formula. Normalization helps in removing any scaling effects and ensures a fair comparison between the mode shapes.

I hope this explanation helps you resolve the issue and accurately calculate the MAC between your experimental and FEM mode shapes. If you have any further questions or need additional assistance, please feel free to ask.

Hi Amir,

I checked your input file and it seems that you are using MC material def. for your soil. So, my guess was that the strain concentration is caused by discontinuity in the material behavior. Your soil block is pulling the infinite region and since it is less deformable, you get the stress concentration and plasticity in the interface region. But I tried to run your input file and in fact, the plasticity already occurred during the static step.

So, there are 2 concerns here from my pov:

1. The way you create the model. First, there is no infinite elements in the bottom of the soil. I understand what you are trying to simulate but by modelling it this way, you have no representation of the static and dynamic behavior in the vertical direction.

2. The geostatic state is missing. As you know, the soil behavior is governed by its confining stress. And it is paramount in nonlinear soil simulation. In your static step, you apply the gravity loading to the soil but there is no predefined stress in the soil. This yields incorrect nonlinear behavior because the soil strength is underestimated. Any deformation beyond this point would be considered invalid. If you are unfamiliar with this, please check the abaqus manual regarding geostatic step.

So, for your model, I recommend to apply the infinite elements surrounding the main study area. You can imagine the interface to be like a half-ellipsoid. The interface here is the line between regular and infinite elements.

And then apply the correct geostatic step. I know it can be a challenge to implement a geostatic step on a model with irregular surface. How I usually solve it is by having a preliminary geostatic computation. In this preliminary model, I apply the geostatic computation while applying fixed boundary condition to all soil (finite) region and record the reaction forces. These reactions are then used as input in the true geostatic step in the main model to stabilize the result. I don't know whether you want to go this far, so I'll stop with the details.

Cheers and good luck with the model.

You might be interested in VisPER (Visual PERMAS).

You can easily import stl files in ASCII and binary format. Afterwards, a remeshing capability can be used.

A free education edition of VisPER is available at https://www.intes.de/edu

And why sparse matrix has computational benefits than diagonal matrix for large sizes ?