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, ...
- 12.5k
10
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\...
- 167
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 ...
- 12.5k
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. ...
- 906
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 ...
- 2,760
7
votes
Accepted
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 ...
- 1,107
6
votes
Accepted
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,...
- 4,041
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. (...
- 10.7k
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 ...
- 95
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$$
...
- 2,539
5
votes
Why doesnt steel melt when pouring titanium through it
Firstly you're mixing units
The melting point of titanium is 1668C (3000F)
The melting point of steel starts at around 1300C up to around 1500C depending on carbon content.
For brief contact ...
- 15.2k
5
votes
Accepted
FEM - is symmetry a boundary condition?
The symmetry itself is not a boundary condition. It is a property of your system which means that both the geometry and the load are symmetric with respect to an axis or a plane. It allows to reduce ...
- 174
4
votes
How to model elastic support in FEM?
What you need is the modulus of subgrade reaction (MSR) of the soil. This is a measure of soil deflection under a given pressure, so the unit is in (for example) kPa/m, or equivalently, as I'm more ...
- 13.1k
4
votes
Accepted
How do I use FEM to derive the torsional constant of an arbitrary shape?
You can find an implementation of a finite element used in computation of arbitrary shape section torsional constant here:
http://projects.ce.berkeley.edu/feap/elmt11.f
I don't see any reference in ...
- 56
4
votes
Accepted
Unit Conversion for Mass Density
First Part
Simplifying the
$$
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....
- 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 ...
- 24.3k
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. ...
- 6,112
3
votes
Accepted
FEA: What boundary conditions am I missing?
After a long discussion with the OP in comments and chat, it emerged that the basic cause of the problem is the geometry of the structure. The curved "beam" has a length/diameter ratio of about 50,000:...
- 12.5k
3
votes
Accepted
Rayleigh damping in Finite Element Models using beta-coefficient only
The report in your link explains it briefly in the sentence after your quote. The beta term models "structural" or "hysteretic" damping, which is described earlier in the report.
The key fact about ...
- 12.5k
3
votes
Accepted
How to model elastic support in FEM?
Before jumping into elastic support conditions, you have to realise that it's not a ground beam. For three reasons:
With a minor axis width to depth ratio of 6ish, it's not far away from a square. ...
- 916
3
votes
How do I use FEM to derive the torsional constant of an arbitrary shape?
This is a problem which is usually solved in books on elasticity theory. The underlying math is based on the solution to the Laplace PDE.
If you do a Google search for Larry J. Segerlind's book "...
- 312
3
votes
Accepted
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 ...
- 156
3
votes
Accepted
How can I reduce the computation time required to simulate a brain tissue penetration model?
Given the subject matter my gut tells me to take the time to compute once you've triple checked your conditions. What material properties are you using? You can alter the mesh to decrease cpu usage as ...
- 300
3
votes
How to derive deformation gradient or displacement gradient?
From a theoretical standpoint, the displacement gradient is equivalent to strain (assuming a structural problem).
Numerically, you can obtain the derivate of a quantity through multiplication with ...
3
votes
Accepted
Are there other finite element types besides the usual?
Certain geometries can benefit from polyhedral elements or elements with edge degrees of freedom. I can think of three main developments in that direction:
1) Voronoi cell finite elements, e.g., ...
- 1,443
3
votes
Accepted
How to properly validate transverse isotropic elasticity Finite Element Code
Definitions
Before we can answer your question, let us look at two standard definitions of terms (from ASME Guide for Verification and Validation in Computational Solid Mechanics) :
1) Verification:...
- 1,443
3
votes
Viscoelasticity and Hyperelastic model, history and difference
Let's look at some (very rough) definitions:
1) Viscoelasticity = elastic behavior that changes if the rate of application of the load is changed or, if the load is kept fixed, the change in the ...
- 1,443
3
votes
Accepted
Viscoelasticity and Hyperelastic model, history and difference
The hyperelastic and viscoelastic material models are both constitutive relations that relate:
Stress and strain, in the case of hyperelasticity.
Stress, strain and strain rate, in the case of ...
- 398
3
votes
How to introduce the CONSTITUTIVE equation into structure mechanics
The balance of linear momentum is
$$
\nabla \cdot \boldsymbol{\sigma} + \rho \mathbf{b} = \rho \mathbf{a}
$$
where $\boldsymbol{\sigma}$ is the Cauchy stress, $\rho$ is the mass density, $\mathbf{b}$...
- 1,443
3
votes
Zero Deflection
There is no material with zero deflection in the world. Every thing deflects, to different degrees.
The best possible way to prevent a bracket from failure is to design it for the task it must do.
...
- 22.1k
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