19 votes

What is the difference between FEA and CFD?

CFD (computational fluid dynamics) includes any numerical method used to solve fluid flow problems. FEA (finite element analysis) is one numerical method for solving partial differential equations, ...
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  • 12.5k
9 votes

Modeling Transient Heat Transfer between two 1-D materials

I am guessing, you are solving the following system: $$\partial_t T = \alpha_i \partial_x^2 T$$ with $\alpha_i=\kappa_i/\rho_i c_{p,i}$ for material $i$, subject to the conditions: $$T\left(x,0\...
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  • 147
9 votes
Accepted

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

The basic difference between implicit and explicit dynamics solutions is that an explicit solution takes account of the finite propagation speed (at the speed of sound) of dynamic effects through the ...
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  • 12.5k
9 votes

Meshing of complex geometrical domains

There are a number of techniques for meshing complex domains for Finite Element Analysis. They generally fall into two categories: Structured vs. Unstructured. For structured meshes, basically the ...
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  • 493
9 votes
Accepted

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

Assume a 1d version of the equation. Then the K matrix becomes a k, spring constant. In 1-D The equation reduces to : $m \ddot{q} + kq = f $ The q matrix also becomes x vector in one dimension. ...
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8 votes
Accepted

How should one model a structural model with both line elements and area elements?

Say we have a slab supported on a beam. The centroid of the slab and the centroid of the beam are not coincident. Fortunately, in FEM software packages the geometric centroid of the element can be ...
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  • 2,770
7 votes

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

Yes, getting a second opinion can be useful. This is done routinely in weather forecasting where exact solutions are unknown, and there is some judgement about how to apply various factors. There ...
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  • 11.2k
7 votes
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How to derive Equivalent Static Load for irregular structure modeled with FEM?

The short answer to your question, How can we compute the Equivalent Static Lateral Forces, the overturning moment and other quantities in an irregular building/structural discretized by finite ...
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6 votes
Accepted

Simple Finite Element Modeling of Wall Piers

I'll go through your questions one by one: A simple model like you have shown is fine to get model loads. Once you get those loads, you can then use a more specific technique to design the pier. (...
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  • 10.6k
6 votes

Meshing of complex geometrical domains

While the other guys explained the theoretical framework behind meshing, the practice is markedly different and it is not at all automatic in industries where quality of mesh is of utmost importance ...
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  • 95
6 votes

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

I write this from the perspective of an engineer who develops simulation software. I think the practice described is bad, and I recommend you do not use two different softwares to "confirm" the ...
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6 votes
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Determining the microstructure of steel after welding in modern computer software

Summary: 1) The answer to this question is difficult. You would need to know how austenite and ferrite behave in relation to what you are doing to them. You would also need to know their compositions,...
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5 votes
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Modelling splashing water in FEA

This may be only a partial answer since I don't have any idea what to do for the Young's modulus of the fluid. Consider the paper Dynamic Pressures on Accelerated Fluid Containers by G. W. Housner. ...
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  • 3,587
5 votes
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What amplitude is used for a finite element modal analysis excitation?

The short answer is, there is no amplitude used. Even more important though, is the fact that the displacements and stresses shown in the results of a modal analysis cannot be used to say anything ...
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5 votes

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

The amplitudes of the modes from a vibration analysis are arbitrary. Often they are "mass-normalized" which is mathematically convenient for using them in a subsequent step in the analysis. There may ...
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  • 12.5k
5 votes

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

As far as I understand your question you are looking for a way to diffuse/mix two gases into each other. The process is very hard to simulate "correctly" because of the characteristics of the ...
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  • 1,202
5 votes

Evaluating performance of heat sink designs without finite element simulation

First, to counter what some people are saying about printed metals, selective laser sintering can produce parts that are as thermally conductive as their base metals. They are limited only by ...
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  • 1,167
5 votes

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

It's easier to understand this identity if you start with the partial differential equation for the Euler-bernoulli beam deflection equation $$\frac{d^2}{dx^2}\left[ EI \frac{d^2u}{dx^2}\right] = 0$$ ...
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  • 2,559
5 votes

Why doesnt steel melt when pouring titanium through it

Firstly you're mixing units The melting point of titanium is 1668C (3000F) The melting point of steel starts at around 1300C up to around 1500C depending on carbon content. For brief contact ...
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5 votes
Accepted

FEM - is symmetry a boundary condition?

The symmetry itself is not a boundary condition. It is a property of your system which means that both the geometry and the load are symmetric with respect to an axis or a plane. It allows to reduce ...
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  • 174
4 votes

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

I think this is a good practice overall. By using two different softwares, you may be able two avoid two kind of errors: 1) errors that come from an inaccurate software (which should not be ...
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  • 149
4 votes

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

Preliminary results I added a conical structure before the choking point to separate the flow. Basically cutting the fluid. This cone is attached with 4 supports. This configuration increased ...
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  • 331
4 votes

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

I would ignore the fact that the keyway makes the actual forces slightly off-center at least when calculating the forces themselves. The forces can be placed at their true locations once they are ...
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  • 10.6k
4 votes

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

Just to let you know, I solved the problem. The element stiffness matrices had an error due to a typo, actually they were not even symmetric! Moral of the story: it's good to test for symmetry when ...
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4 votes

How to model elastic support in FEM?

What you need is the modulus of subgrade reaction (MSR) of the soil. This is a measure of soil deflection under a given pressure, so the unit is in (for example) kPa/m, or equivalently, as I'm more ...
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  • 12.7k
4 votes
Accepted

Unit Conversion for Mass Density

First Part Simplifying the $$ 1 \ lbf = 1 \ slug .ft/sec^2 $$ then $$ 1 \ lbf \ sec^2 / in^4 = 1 \ (slug .ft/sec^2 ). (sec^2/in^4) = 12 \ slug /in^3 $$ $$ 12 \ slug / in^3 * (14.6 kg / 1\ slug)*(in/25....
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  • 228
4 votes

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

Regarding the problem you have, without reviewing the results its difficult to make a definitive answer. However, if you are observing high loads near the weld, I think you should try to make ...
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  • 22.6k
4 votes

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

Yes, it increases and decreases strength in traditionally steels. Depends on what steel you have and what you mean by "thin rods", and the weld process , and the specific weld parameters. ...
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  • 5,728
3 votes
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ANSYS Workbench/Mechanical: Automatically export chart?

There are several options for doing this: If there are only a few values to be saved per design point, you could use 'output parameters'. If there is a lot of data to be saved, the report generator ...
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  • 156
3 votes

Modelling splashing water in FEA

Section 2.1.14 of the Abaqus Example Problems Manual is 'Water sloshing in a baffled tank', which might be useful (even if you don't use Abaqus at your own institution, the manuals are hosted by many ...
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