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, ...
alephzero's user avatar
  • 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. ...
Gürkan Çetin's user avatar
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 ...
William S. Godfrey- S.E.'s user avatar
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 ...
m2n037's user avatar
  • 95
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,...
do-the-thing-please's user avatar
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 ...
Chris Johns's user avatar
  • 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 ...
ClariB's user avatar
  • 174
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....
epsi1on's user avatar
  • 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 ...
NMech's user avatar
  • 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. ...
blacksmith37's user avatar
  • 6,144
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 ...
ShuddaBeenCodin's user avatar
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:...
alephzero's user avatar
  • 12.5k
3 votes
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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 ...
alephzero's user avatar
  • 12.5k
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 "...
user16622's user avatar
  • 314
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 ...
Orbit's user avatar
  • 156
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 ...
Robbie van Leeuwen's user avatar
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., ...
Biswajit Banerjee's user avatar
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:...
Biswajit Banerjee's user avatar
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 ...
Biswajit Banerjee's user avatar
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 ...
user190081's user avatar
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, $\mathbf{b}$...
Biswajit Banerjee's user avatar
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. ...
kamran's user avatar
  • 22.4k
3 votes

Rayleigh-Ritz method, calculating slope of beam?

The Euler-Bernoulli beam equation is as follows: $$q = \dfrac{\partial^2}{\partial x^2}\left(EI\dfrac{\partial^2 \delta}{\partial x^2}\right)$$ where $q$ is the distributed load along the beam, $\...
Wasabi's user avatar
  • 13.1k
3 votes

FEM - is symmetry a boundary condition?

Symmetry is used to reduce the size of the object and therefore the mesh or allow more mesh to represent that reduced object. So the “cut plane” of symmetry is not a boundary where the material ...
Solar Mike's user avatar
  • 15.8k
3 votes
Accepted

Representing slabs in FEM

The general rule of thumb is never to introduce a degree of complexity you don't need. Use the expected behaviour of the structure to determine the element type. A two-way slab is usually best ...
ingenørd's user avatar
  • 1,288
3 votes

Is the compatibility condition based Cauchy-Green strain used in FEM

The reason the compatibility equations are important is to ensure that the displacement of the structure is physically sensible, for example the deformed shape can not contain "holes" or ...
alephzero's user avatar
  • 12.5k
3 votes

Stress Concentration Factor – Why a Specific Range?

From what I see, in this picture from the Shigley book, if I really had to, I would extrapolate to 0.5 (or more precisely interpolate between the limit cases). The limit cases for very thick plate (d/...
NMech's user avatar
  • 24.3k
3 votes
Accepted

Computing the stress field of a structure made of 4-nodes shell elements (accounting for membrane action, bending and shear)

Here be dragons. Or, to paraphrase a hadith of the Prophet Mohammed, "There are seventy ways to compute element stresses, and all of them are wrong." The naive approach is to differentiate ...
alephzero's user avatar
  • 12.5k
3 votes

Boundary condition at supported end of a rod

None of the three would occur if the material of the element holding the rod is "rigid", or is much stiffer than the rod. For such cases, my assessment is as shown below. For the case that ...
r13's user avatar
  • 8,194
3 votes

What is stress stiffening in Finite Element Analysis?

My undestanding is that stress stiffening is the additional stiffness in structures when there is an applied prestressed state. The most common example, -I know of- is how the guitar string (or a beam)...
NMech's user avatar
  • 24.3k

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