Questions tagged [finite-element-method]

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54 views

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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1answer
37 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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51 views

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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1answer
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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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1answer
62 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?
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19 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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18 views

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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1answer
61 views

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. ...
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2answers
44 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 ...
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2answers
60 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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3answers
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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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1answer
50 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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1answer
66 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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1answer
82 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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2answers
426 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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2answers
40 views

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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25 views

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 ...
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4answers
105 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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3answers
90 views

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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2answers
332 views

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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35 views

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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66 views

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 ...
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1answer
117 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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29 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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42 views

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.&...
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1answer
39 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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2answers
71 views

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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27 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 ...
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1answer
28 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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1answer
36 views

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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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). ...
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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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1answer
55 views

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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3answers
145 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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39 views

(Follow up) Can a thicker model giver a lower critical buckling load?

I present three seperate models with thickness of t = 0.005m, 0.01m and 0.025m respectively, all have a forced displacement of -0.01m in the x-direction, and fixed on the other end. As you can see the ...
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32 views

Perfectly Matched Layer (PML) for Plates in COMSOL

I am modelling infinite plate domain in COMSOL for frequency simulation. I need to apply absorbing boundary conditions all around the boundaries and I could not find PML option for plates. Could ...
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34 views

Solver cannot find any eigenvalues for linear buckling analysis [COMSOL]

I am trying to do a simple linear buckling analysis, where one end is fixed and the opposing end has a prescribed displacement of -0.1m in the x-direction that compresses the structure. Solver cant ...
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2answers
302 views

Which yield strength should I use in FEA in ANSYS; Engineering or True?

Attached is a figure to illustrate the difference in the value of yield strength as observed from the true stress/strain curve and engineering stress/strain curve. While conducting FEA in ANSYS for a ...
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3answers
69 views

Boundary condition at supported end of a rod

I have one end of a rod held in a hole of a 'rigid' part with no clearance, while the other end is loaded with a force. I have shown 3 simple reaction-force models in the picture. If my intent is to ...
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2answers
514 views

Calculating the von mises stress in a 3D beam when given stresses and moments on both ends

I want to calculate the von mises stress in a given structural member. I want to generate a von-mises plot from this data. The forces are according to the local coordinate system of the beam. Also, I ...
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1answer
88 views

Modeling torque as surface pressure

Consider a rod with a length of 150 [mm] and a diameter of 44 [mm]. At the left boundary the rod is fixed to a wall. At the right end a torque of 1000 [N m] is applied. The remaining boundaries are ...
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2answers
45 views

Imposing/ensuring a constant mass flow rate in turbulent flow simulation

I'm trying to simulate using Finite Elements (non commercial software) the Tube Bundle benchmark problem: http://cfd.mace.manchester.ac.uk/ercoftac/doku.php?id=cases:case078&s[]=tube&s[]=...
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Computing the stress field of a structure made of 4-nodes shell elements (accounting for membrane action, bending and shear)

I am trying to implement my own FE code for shell structures. Most literature provide formulations and strategies on how to compute shell element stiffness matrix. I can already compute deformations ...
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1answer
20 views

Frame element stiffness with non-axis-aligned anisotropic area moment of inertia?

I've found equations for the $12\times12$ symmetric stiffness matrix for an element of a frame (a truss with welded joints): http://what-when-how.com/the-finite-element-method/fem-for-frames-finite-...
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Narrowing down injection moulding material selection

How do I narrow down specific values when selecting a plastic for injection moulding? My part is uniform in wall thickness and thins out where a hinge a present. Properties: Will not go under many ...
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Heat Transfer FEA with matlab

I have to write a matlab code using finite element method to solve this problem. I have solved it as follows but I dont know how to apply it in matlab. I have to write a matlab code using finite ...
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Solidworks 2D static nonlinear simulation convergence problems

I'm trying to do the following 2D nonlinear static simulation in SolidWorks (video was made in Ansys): https://we.tl/t-m3XQrUZZ5U However, I've been getting these convergence problems I can't seem to ...

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