# Questions tagged [finite-element-method]

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### What is the solutions of the following 1D diffusion equality using Crank–Nicolson method?

Through my research I faced to the following equality and need to find $c_i^{t+1}$. Moreover, I found that it can be solved by Crank–Nicolson method (see here: https://en.wikipedia.org/wiki/Crank%...
15 views

### FEM with SolidWorks : order of magnitude of the precision by wich displacements can be computed

My name is Thomas. I am an electromechanical engineering student. For my master thesis, I have to design an underwater end-effector for a robot. I have used SolidWorks and the simulation module to ...
105 views

### Non-Linear Analysis Convergence Problem in Ansys

I am currently conducting a static structural analysis study in Ansys and encountered convergence prolems. I have a very large thermal gradient (almost 600°C) as input from a precedent transient ...
18 views

### Boundary conditions for symmetrical problem of truss

What is the symmetrical problem for this truss, specifically the upper right part of it. What boundary conditions have to be added (i.e. supports). What confused me was the specification for the upper ...
4 views

### Calculating the contribution to nodes from the boundary vector in FEM-analysis - global vs local

The moisture content of a drying board of timber is being calculated with the finite element method and 9-node lagrangian elements, i.e. m = \alpha_1 + \alpha_2x+\alpha_3y+\alpha_4x^2+\alpha_5xy+\...
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### Structured trianglar finite element mesh in MATALB

The available triangular mesh in the MATLAB PDE tool box here gives an unstructured triangular mesh. How can I get a structured triangular mesh from the tool box with a similar data structure [p,e,t]. ...
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1 vote
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### Is there a specific way to simulate porous structures?

I tried to simulate an axial compression test for a lattice (porous) structure but It takes too much time and it doesn't give me the right answer (when I compare with experimental results). So, I was ...
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1 vote
72 views

### Why does the mesh size affect my modal analysis results?

The need for mesh refinement in a structural analysis module such as Static or Transient is quite clear; if we want the overall results such as displacement and stresses to be more accurate within the ...
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### Abaqus Python Scripting for Post-Processing of Composite Laminate

I'm looking to automate the extraction of stress results in my model. The model is a sandwich composite cantilever beam. It was created using CAE's "Composite Layup" tool and consists of ...
29 views

### Can modern residual stress measurement replace finite element calculation?

Residual stresses are created by the manufacturing process and exist in materials and structures. Now, people develop many methods to measure residual stresses. Those methods can be divided into ...
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### Model order reduction - Criag Bampton method

I am trying to understand how model reduction works, more specifically the Criag Bampton method. I would like to implement this method on a simple model in Python. I have been reading the following ...
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### How will the reaction moment on the support be distributed in terms of forces in this model?

Consider a rectangular cross sectional solid beam, fixed at one end and a uniform shear force applied to the other end. Below shows the side view for this beam. Now, I change the support area as ...
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1 vote
50 views

### How do I get the modes shapes (that I got from FEA of a system) in reality?

In FEA, I have a complex system onto which I have applied some boundary conditions and then conducted a modal analysis for it. In return, I got a few mode shapes (as much as I requested) for each of ...
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### In FEA, should I get same results if I apply load in X, Y and Z axis simultaneously, as compare to when I apply them one by one on same body?

Imagine a cantilever beam modelled with solid elements in FEA. Now, I want to apply loads to it in X, Y and Z axis. First option is to apply the load altogether, and then observe the results after it ...
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### ABAQUS STRI3 Element, local coordination system

As you know ABAQUS have a triangle plate bending element named STRI3. After analysis (post-process) when user generate report for internal stress of those STRI3 elements, abaqus give the Cauchy stress ...
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### In FEM, can each instance of a Transient Analysis be thought of as a Static Analysis of its own?

Assume I have a cantilever beam fixed at one end. I can conduct a static analysis in FEM for a case where I apply a load on the other end, condition being the load is consistently applied on it and ...
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1 vote
90 views

### How to find clamping force from bolt preload?

If I have a piece of rubber between two steel plates, and four bolts (at equal preload) compressing the plates, will the total compressive force on the rubber be Preload x 4?
21 views

### How to choose contravariant or covariant bases?

I completed an introductory course on continuum mechanics, but we did not delve into curvilinear coordinates with CM. However, when I read some publications I see the stress-strain relationship is ...
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### Stress divergence of elastically deformed body is not zero

TL;DR According to the analytical solution (link) for a deflection of a cantilever beam $\sigma_{xx} = - \frac{P xy}{I}$, $\sigma_{yy} = 0$ and $\sigma_{xy} = -\frac{P}{2I}(\frac{D^2}{4} - y^2)$ and ...
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### In FEM, what is the difference between a single element with a quadratic shape function and two elements with linear shape functions?

Using Finite Element Analysis to obtain a Weak form of a PDE, what is the difference between the two cases: A single element with a quadratic shape function Two elements with linear shape functions. ...
48 views

### Find hotspots in a system

In the image, I have a depicted a system which is undergoing fatigue. Using appropriate solver I have determined the life of each nodes and it is stored in a .csv file. Also I have the connectivity of ...
63 views

### FEM boundary problem in structural mechanics

I have spent way too much time in the last weeks/months implementing and writing my own finite element solver from scratch. I successfully implemented 2D and 3D elements and wanted to verify a few of ...
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### What is the difference between various surface element types in FEM?

There are many types of surface elements which exist in most of the Finite Element softwares. In ANSYS, I have the option to make my surface element to behave as a plane stress element, plane strain ...
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67 views

### Why am I seeing a moment reaction at the supports for these beams in FEM?

Please observe the Finite Element model below, in ANSYS WorkBench, (Remote force behavior = Deformable). Also, please take a lot at the force and moment reactions at the fixed supports. I couldn't ...
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77 views

### Will the second beam have higher or lower stiffness in X direction than the first beam?

Attached is a picture of two beams. The second beam has exactly the same properties and dimensions as the first one, but is rotated, say, by 45 degrees. I want to know if the second beam will have ...
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201 views

### What are the fundamental and governing equations used for structural/solid mechanics in FEA?

Can anyone please provide me a list of governing equations of structural/solid mechanics which are used by FEA softwares during solving. And how are these fundamental equations implemented onto each ...
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452 views

### Does welding two metal parts together increases or decreases the strength locally there?

I have a structure made out of steel consisting of many thin rods and some of them are welded to each other. I conducted a simple FEA static structural analysis to determine if the structure would ...
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### Why does it take lesser iterations for a stiffer model in my FEA than a less stiffer model to converge?

I am currently using ANSYS FEA software and I conducted a simple geometric non-linear analysis of two same shaped bodies, but different cross sectional areas; one being quite bigger than the other. We ...
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### Abaqus CAE - how to measure/calculate area of a certain threshold within the Visualisation module?

I have been using Abaqus CAE to model a CT-specimen being pulled apart, in order to observe the resultant plastic zone shape around the crack tip. To reduce computational cost, I have modelled a ...
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### Why the model with rebar layer shows one sided plastic strain in Abaqus?

Using the damaged plasticity model, I modeled a concrete coupled shear wall in Abaqus, once with discrete rebar and once with rebar layers for the slab. I used the general static solver to run the ...
107 views

### When a jet engine propels an aircraft forward, where does the thrust force on aircraft act?

I am trying to model the mount structure of an aircraft onto which a jet engine is attached, in Finite Element Analysis. Since I am only concerned about the local mount structure, I have isolated it ...
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### Why is my FEM analysis producing unusually-large stress results?

This is my first time performing an FEM analysis, and I'm using the Ansys Workbench and Mechanical software. My situation is pretty straightforward--it's a straight beam that is fixed at one end and ...
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### What is stress stiffening in Finite Element Analysis?

In a Finite Element Analysis, if we turn ON the geometric non-linearity, it also takes into account the stress stiffening if any structure is undergoing it. That is what I have read in the literature. ...
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### compute nodes and members according to stiffness matrix of truss (inverse the direct stiffness method)

I am familiar with the direct stiffness method (truss), and programmed it from scratch in Java. The member stiffness matrix is determined by any link (member) and the nodal coordinates. The global ...
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1 vote
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### Does numerical dissipation in FE simulations affect system's elastic energy? Does it depend on thickness?

I am running a finite-element simulation in Abaqus, for which I also have a theoretical model. To be precise, I am simulating wrinkling in a thin annular sheet, with shell elements. The model makes a ...
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### Can anyone help validate my FEM results?

Quick background, I'm a programmer not an engineer, but I do have some background in physics and maths - I understand I may have been a little ambitious with this project, but its my master ...
144 views

### Is the calculated shear strain in a beam, engineering strain or tensorial strain?

Recently I came across a FEM code of a linear deformation beam element, and it made me wonder what is the correct relation between shear stress and shear strain in a beam element. In the beam element ...
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35 views

### Computing forces and moments acting on the sides of a rectangular shell element from corner forces and moments

I have a FEM program for shell elements implemented through the direct stiffness method. Using this program corner displacements of shell elements due to external loading are obtained through the ...
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### Cannot measure reaction moment (RM) in Abaqus

I am trying to calculate reaction forces/moments in a simple Abaqus model. I started with a simple static model of a cylinder with applied loads on one end, while the other end was "Encastered.&...
1 vote
49 views

### Why is the amount of force/moment transfer occurring between bodies in FEA is independent of mesh size?

So I read somewhere that the mesh size won't effect the amount of force transfer occurring between bodies if several bodies are in contact, and a global force is applied somewhere. I wanted to know ...
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### What is the difference between Frictional non-linearity and Geometric non-linearity in FEA? (In terms of Stiffness matrix)

For geometric non-linearity, we know that as the geometry changes during the analysis, the global stiffness matrix changes since it already is a function of geometry of the structure. What I want to ...
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29 views

### How do I find the buckling strength?

I am running something called cell periodicity study in comsol, which finds the material properties of a model. It is done by applying a uniaxial compression load, and performing a nonlinear buckling ...
1 vote
31 views

### Linear Nastran model not converging

I am running a SOL 101 linear statics FEA. If I fix down the whole geometry it converges. But anything less than around 90% fix down and it will sit there crunching away at the numbers forever. This ...
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### Why is plastic deformation a non-linearity if I am using Bilinear hardening to model it in FEA?

Attached you may find a picture for isotropic bilinear hardening up until the ultimate tensile strength. The first line is the elastic region while the second one is plastic. I couldn't understand ...
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1 vote
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### Do these linear vs nonlinear buckling plots make sense?

I am doing linear buckling analyses (where everything is linear), and nonlinear buckling analyses where you have nonlinear geometry enabled and nonlinear material behavior (hyperelastic material). ...
1 vote
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### Why do we need to have perturbation in our system to do buckling analysis? [closed]

Do we need it for both linear and nonlinear system?
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### Why should I use a contact between two glued bodies in FEA when I can directly merge the mesh nodes between them?

So I am using ANSYS to conduct a FEA analysis. I have two options to built a connection between two bodies; first is I can use a contact (like bonded) between the touching faces and the other option ...
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1 vote
258 views

### FEM degrees of freedom

Consider a "beam". In order to perform modal analysis using the finite element method, the beam is meshed with 2nd order hexa elements. The total count of nodes is 1280. The same beam can be ...
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1 vote