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Questions tagged [finite-element-method]

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Meshing of complex geometrical domains

When using the finite element method, I have always used either already meshed domains or very simple ones. From what I've heard, meshing complex geometries is often outsourced to specialized ...
Bérenger's user avatar
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12 votes
3 answers
497 views

Exploiting fluid dynamics for the optimal design for gas mixing in a furnace

Background This is the standard design for a thermal furnace used in the Clauss process, which converts H2S to SO2. The main problem with the furnace is that gas mixing is rather poor and results in ...
22134484's user avatar
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10 votes
0 answers
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ANSYS APDL Shape memory effect option of SMA not working

I am trying to define the material properties of a shape memory alloy material in ANSYS APDL V15. There are material properties for Superelastic materials (SUPE option) and material properties for ...
imacube's user avatar
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9 votes
1 answer
4k views

Derivation of the weak form for the euler-bernoulli beam equations

I am master student and doing an assignment of Finite element method. In the instruction I could not understand the derivation of the weak form, which should not be difficult. I'm sorry for posting ...
user26767's user avatar
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8 votes
6 answers
746 views

Can two different modeling programs be used to confirm the results of each other?

Computer Models Computer modeling is used in various engineering fields. I am specifically considering structural analysis or finite element analysis (FEA). Sometimes models are used to speed up ...
hazzey's user avatar
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8 votes
3 answers
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How do I use FEM to derive the torsional constant of an arbitrary shape?

In this question I ask about how to perform a first-principle derivation of the torsional constant of a section. It appears that there is no such analytical derivation for torsional constant, so my ...
Graviton's user avatar
  • 1,264
8 votes
1 answer
404 views

Simple Finite Element Modeling of Wall Piers

I'm working on analysis of a bridge wall-pier for dead and live loads. When modeling the pier in finite element software (LARSA), I'm running up against several modeling questions: Is it valid to ...
CableStay's user avatar
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8 votes
1 answer
603 views

How do I best model a torque applied over a non-radial line?

I am looking to use FEA (specifically, Creo Simulate) to re-create the results of a static strength test on a part my company will be testing in our lab. Because the lab results are the ones we will ...
Trevor Archibald's user avatar
8 votes
0 answers
627 views

Incompressible 2D pressure-driven flow: for Navier-Stokes equations in nondimensional form, how should I express pressure boundary conditions?

*I have updated this question. I'm using two codes for modeling incompressible, two-dimensional flow out of a tank. My fluid dynamics experience is pretty basic; I'm using the codes to understand a ...
Ant's user avatar
  • 245
7 votes
1 answer
3k views

Modeling Transient Heat Transfer between two 1-D materials

I have been working on creating a 1-D model of a material with a layer of heat resistant material stuck to it. For this I have been trying to use the implicit finite-differential method. The equations ...
chap178's user avatar
  • 71
7 votes
2 answers
330 views

Modelling splashing water in FEA

I'm running an FEA on a vessel that has a "splashing water" effect with vibrations. The problem I'm really coming up against is what kind of Young's Modulus and Poisson's ratio to use for the fluids? ...
Mark's user avatar
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6 votes
4 answers
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How should one model a structural model with both line elements and area elements?

I am modelling my structure using FEM, and my structure contains line elements (1D) such as beams and columns and area elements (2D) such as walls and columns. My question is that, how can I proceed ...
Graviton's user avatar
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6 votes
1 answer
719 views

How to derive Equivalent Static Load for irregular structure modeled with FEM?

Building codes such as the Uniform Building Code (UBC) or International Building Code (IBC) require the determination of Equivalent Static Lateral Forces in order to compute $P-\Delta$ effect and to ...
Graviton's user avatar
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6 votes
1 answer
1k views

FEM modal analysis computing displacements

I have an FEM model that I am doing a modal analysis of. I wanted to check that how I am computing the physical displacement is the correct way, as I've read a lot of about normalizing modes, ...
engstu95's user avatar
6 votes
2 answers
309 views

How to analyze a bent beam: Stress concentration?

I am analyzing a beam, that has a bend in it. Intuitively and inspecting FEA results using a linear solver, there is a stress concentration at the bend of this I-beam. The part was not a straight I-...
user33108's user avatar
6 votes
0 answers
162 views

How to simulate a crack in a PCB? [closed]

I want to break this PCB with some know force of X newtons in the bottom left tip of the PCB. The problem is that in Static Dynamics I just get infinite deformation and in explicit dynamics I really ...
Gabriel Barros's user avatar
5 votes
2 answers
6k views

What is the difference between FEA and CFD?

Many of us think FEA is used for structural problems and CFD is used for fluid dynamics problems. But I have read that the above statement is wrong. So please explain the exact usage of those two.Also ...
Pradeep Chada's user avatar
5 votes
2 answers
2k views

What amplitude is used for a finite element modal analysis excitation?

In a typical finite elements analysis package, a modal analysis gives the N first natural modes, and it is possible to get the equivalent stress and total deformations for each of these frequencies. ...
Mister Mystère's user avatar
5 votes
2 answers
552 views

Evaluating performance of heat sink designs without finite element simulation

I have the opportunity to do a few metal 3D prints for just the material cost, and would like to experiment with the performance of heat sink designs (mostly for fun). Since I have no experience ...
PlasmaHH's user avatar
  • 161
5 votes
2 answers
4k views

ANSYS Workbench/Mechanical: Automatically export chart?

I'm running a simple tensile test simulation for a single element. Under Results I made a Chart object with Stress vs Strain, which can be manually exported to a csv file by right clicking on the ...
rysciguy's user avatar
5 votes
1 answer
118 views

PATRAN Order of Operations

To preface this question, almost all of my FEA experience has come from SolidWorks, so I haven't had to deal with these types of problems. I'm designing a truss structure in PATRAN composed of 1D ...
Anonymouse's user avatar
5 votes
1 answer
1k views

How can we derived the equivalent Lumped Mass Model for irregular building and how to calculate the errors?

Intuitively, building can be represented as a lumped mass model ( the taller the merrier!): Assuming a building is a lumped mass cantilever column also makes the global stability checks easier ...
Graviton's user avatar
  • 1,264
4 votes
2 answers
886 views

FEM - is symmetry a boundary condition?

In FEM is symmetry technically a boundary condition? For example using the FEM on a symmetrically loaded and supported beam. The FEM can be simplified by using symmetry. However, is this symmetry ...
FEA42's user avatar
  • 245
4 votes
2 answers
2k views

How to model elastic support in FEM?

I need a 8 m x 4 m x 0.6 m RC plinth (mechanical requirement) which needs to be built onto loose gravel. Obviously I am going to over excavate, back fill with selected material and bed my plinth on ...
SlydeRule's user avatar
  • 1,216
4 votes
1 answer
198 views

Determining the microstructure of steel after welding in modern computer software

How can the microstructure of steel after welding be determined in modern computer software? I am aware that there are 'classic' methods of predicting microstructures like Schaeffler, DeLong or WRC ...
bartosz.baczek's user avatar
4 votes
1 answer
459 views

FEA: What boundary conditions am I missing?

I'm working on a 2D-model (in the xy-plane) in NASTRAN and am getting convergence problems. The main cause of these convergence problems is a "high or negative matrix factor diagonal ratio." I've ...
anonymouse's user avatar
4 votes
2 answers
6k views

Results for Bending Moment using BEAM188 on ANSYS APDL

I'm doing a static analysis on a uniformly loaded cantilever beam in ANSYS APDL. I'm using BEAM188 with all the default options, so it uses linear form. for the element behaviour, which I think means ...
Carol's user avatar
  • 43
4 votes
3 answers
953 views

Are linear beam element solutions ever exact and when are they used in practice?

In qualifying the results of a Finite Element (FE) beam model, I'm realizing that I dont understand FE beam elements as well as I should. Is there a procedure to determine what order beam element is ...
OnStrike's user avatar
  • 743
4 votes
1 answer
1k views

What are exact location of Integration Points in STRI3 element in ABAQUS?

Introduction I have a file with .rpt extension from ABAQUS which is output of a model. This .rpt contains stresses of elements and displacements of nodes in plane text format. There is an item with ...
epsi1on's user avatar
  • 228
4 votes
2 answers
91 views

What is a good method (equation) for locally refining a 1D grid at each end?

I have a grid that I plan to discretize in 1D. It extends from 0 to L using N nodes, and I need to refine it at each end. I plan to have something that looks as follows: I have tried the to specify ...
teepee's user avatar
  • 141
4 votes
2 answers
721 views

Interference fit problem in ANSYS Workbench 16.1 - how do I get rid of pressure/displacement raisers?

I have an interference fit problem of two perfect cylinders modelled in 2D using symmetry. The overall interface pressure is around 20MPa lower than the hand calculations and I get non-uniform ...
Josie Colclough's user avatar
3 votes
3 answers
24k views

What is the difference between implicit and explicit analysis in ABAQUS?

How can I choose between Implicit or Explicit Analysis in ABAQUS for a simple rectangular composite structure with 2 layers of unidirectional lamina? I am trying to do a linear-static analysis to ...
Willis's user avatar
  • 81
3 votes
2 answers
3k views

What is the physical interpretation of the eigenvalues of the stiffness matrix in the finite element method?

Given an equation of motion of an undamped system $\mathbf{M}\mathbf{\ddot{q}} + \mathbf{K}\mathbf{q} = \mathbf{f}$, $\mathbf{M}$ indicates the mass-matrix, $\mathbf{K}$ the stiffness matrix, $\mathbf{...
H. Vabri's user avatar
  • 163
3 votes
2 answers
2k 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. ...
Rameez Ul Haq's user avatar
3 votes
3 answers
2k 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 ...
hansophyx's user avatar
3 votes
1 answer
118 views

Unit Conversion for Mass Density

I am doing a Finite Element analysis of a continuum. In my problem definition I use these units: mm for length, kPa for applied stress, and MPa for material stifness (Young's modulus). With these ...
Fritz45's user avatar
  • 133
3 votes
1 answer
53 views

How to properly validate transverse isotropic elasticity Finite Element Code

I have written a piece of code solving the linear elasticity problem on transversely isotropic materials (before that, the code only supported isotropic materials). I would like to validate it before ...
AntoineMazuyer's user avatar
3 votes
2 answers
726 views

How can I reduce the computation time required to simulate a brain tissue penetration model?

I am trying to model the strain generated by inserting an electrode device into brain tissue. I've had some success in doing this in ANSYS Explicit Dynamics. Here's a link to a GIF showing the ...
gottahavemypops's user avatar
3 votes
1 answer
213 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 ...
Rameez Ul Haq's user avatar
3 votes
2 answers
398 views

Stiffness Method FEM - Slender Members

If a member is very slender then its length will be large compared to its cross-sectional area. I've heard and read that slender members can potentially cause the stiffness matrix of a beam/frame ...
pauloz1890's user avatar
  • 1,217
3 votes
2 answers
391 views

How to calculate rotations from displacements?

I'm trying to develop a finite conical shell element with six dof at each node. I want to express the rotations $\phi$, $\theta$ and $\psi$ in terms of the displacements $u$, $v$ and $w$. The ...
Damingow's user avatar
3 votes
0 answers
44 views

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 ...
Worldsheep's user avatar
3 votes
0 answers
38 views

How quadrilateral elements represented in most FEA solvers for structural mechanics problems?

How quadrilateral elements represented in most FEA solvers for structural mechanics problems? I know that Nastran-95 represent quadrilaterals for membrane and bending elements as a set of triangles: ...
Евгений Павлов's user avatar
3 votes
0 answers
35 views

How do FE solvers solve the case of panel buckling under pure shear?

How do FE solvers solve the case of panel buckling under pure shear? The main problem is that global matrix of initial stess is singular in that case. One method is to apply some forces that shear is ...
Евгений Павлов's user avatar
2 votes
2 answers
644 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 ...
Rameez Ul Haq's user avatar
2 votes
1 answer
876 views

FEM 3D truss analyzer produces forces that do not sum to zero at joints

I am writing some code for the analysis of 3D truss structures. The program is a typical implementation of the direct stiffness method for truss elements. While testing it and comparing results to ...
John Kimble's user avatar
2 votes
2 answers
1k 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 ...
Rameez Ul Haq's user avatar
2 votes
3 answers
75 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 ...
gaurav's user avatar
  • 31
2 votes
2 answers
47 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 ...
Rameez Ul Haq's user avatar
2 votes
1 answer
125 views

How to use the Ritz method with the weak form to approximate solution of differential equation

I am having trouble understanding how to approximate the solution to this problem using the Ritz method and the weak form: $$\frac{d^2u}{dx^2} - u=0; \ \ x \in [0,1]$$ $$u(x=0)=0; \ \ \frac{du}{dx} \...
The Bosco's user avatar
  • 123

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