Questions tagged [finite-element-method]
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186
questions
0
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0answers
5 views
Tangent matrix terms in Abaqus UEL
I have problems in the calculation of the tangent matrix terms in an Abaqus UEL subroutines, do you have suggestion on how to take tensor derivatives? For example:
$$
\frac{d\underline{\underline{T}}}{...
0
votes
0answers
19 views
How to accurately use the approximation formula in a ritz approximation?
I have been able to do all the steps required in the question poised in the problem below to get to
The issue I am running into is trying to use
to actually obtain values to obtain numbers for my ...
0
votes
1answer
15 views
Is the compatibility condition based Cauchy-Green strain used in FEM
I'm currently studying continuum mechanics, with a view to solving some problems using the finite element technique. I have studied, and understand, the proof of the compatibility conditions based on ...
0
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0answers
35 views
Global stiffness matrix from element stiffness matrices for a thin rectangular plate (Kirchhoff plate)
I have the element stiffness matrix for a thin "kirchhoff" plate. The plate is 3 [m] x 5 [m] and is simply supported on all edges. It's thickness is 0,2 [m]. On the plate there acts a ...
0
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2answers
27 views
Shell vs. solid elements for a fatigue analysis using FEM
What are the advantages and disadvantages of using quads (shells) vs using hexas (solid) in my mesh for a fatigue analysis using a finite element software. Thanks.
3
votes
0answers
27 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 ...
0
votes
1answer
41 views
What is the meaning of “load case consistent” in stress analysis terms?
I’m a (junior) stress engineer and have been tasked with sizing a lug. Various loadcases have been run through FEM and loads have been distributed into the lug bolt for each. In other words, each ...
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0answers
29 views
Why is the functional of an elastic system equal to it's total potential energy and why is it stationary at it's minimum?
Okay this was even quite difficult to formulate but let's start with some statement's in my FEM book:
Elastic continuum has a functional which is equal to it's total potential energy
Elastic system ...
2
votes
3answers
78 views
Why is the derrivative of a displacement at the end of a rod equal to 0?
I'm studying a book on finite elements method and well, simply, I don't understand how they get this boundary condition.
0
votes
1answer
34 views
Analytical solution of thermal stress in a bi-metallic cylinder
As a side project I have looked to solve using Python an analytical solution for one-dimensional transient heat transfer in a thick cylinder with cladding on the inside surface, wherein the fluid in ...
1
vote
0answers
19 views
Pin connection on beam - FEA analysis
I am establishing a MatLab FEA code for determining the stiffness of a structure. Diagram of the structure is added below.
I have established a code for determining the stiffness of the structure, but ...
-1
votes
2answers
35 views
Representing slabs in FEM
When making structural analysis with FEM, do we normally use plate or shell elements to represent slabs? I checked and did some reading for the difference between shell and plate elements in FEM in ...
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0answers
4 views
Magnetization characteristics and static characteristics of SR motor from Ansys Maxwell. Part II
Continuing the topic:
Magnetization characteristics and static characteristics of SR motor from Ansys Maxwell
Are there any people in the community who are more or less familiar with Ansis Maxwell's ...
3
votes
2answers
260 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 ...
1
vote
0answers
21 views
How accurate should Rayleigh-Ritz approximation be?
For a simply supported beam with a UDL, with boundary conditions of X=0, V=0 & X=L, V=0. Using a cubic trial function.
$$V=a+bx+cx^2+dx^3$$
The following curve is obtained (Red Line). It is ...
1
vote
1answer
115 views
Rayleigh-Ritz method, calculating slope of beam?
For a simply supported beam with a UDL if the deflection is assumed to be:
$$V=a+bx+cx^2+dx^3$$
What is the formula for calculating the slope?
I thought it would be:
$$θ=dV/dx$$
However, working ...
0
votes
0answers
33 views
Provide stability for a 3D object with a support structure
This is a follow-up to this question. I wonder if structural engineering tools like Finite Element etc. might help create such support structures. If so, how?
0
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0answers
40 views
ABAQUS UMAT SDVINI problem
I'm trying to write a UMAT code for unsaturated soil model and I need to define some state parameters. I found that I can do that by using SDVINI subordinate. Should I put it at the and of UMAT? How ...
1
vote
0answers
16 views
Ansys Fluent - Turbulent model and mesh
I am currently working on a project that involves CFD simulation on ANSYS and i need some help as it has got me stuck. I am designing a faucet atomizer and it's functioning is similar to a nozzle.
I ...
2
votes
0answers
18 views
Solidworks Simulation- Large displacement with Inertia Relief
I'm trying to use the Solidworks simulation package to solve for the stresses inside a body as it accelerates (very rapidly). Because I expect some small features to deform quite a bit, I need to use ...
-1
votes
3answers
31 views
How to solve a system of second order ODE from time t = T to t = 0
I have a system of second-order ODEs
$$
\mathbf{M\ddot{x} + C\dot{x} + Kx = f}
$$
I want to know some good numerical methods to solve this system of the equation given the initial conditions at time $...
1
vote
1answer
36 views
How to repeat on ABAQUS FEM simulations without reloading the mesh?
I would like to perform several FEM simulations on a given mesh with ABAQUS, where only the orientation of an element set would change in between.
Currently, I'm just generating several inp files (...
0
votes
1answer
90 views
Calculate deflection of a beam with an arbitrary shape
I have a beam with rectangular cross section, but rather an strange shape in the length wise direction as seen below:
So I have taken out the symmetry part of it:
And it actually has some nice ...
-1
votes
1answer
22 views
How do we know the displacement function in finite elements method?
When analysing a beam, my book starts off by saying that the displacement in a beam is linear:
u=a1+a2x
u-displacement
x-distance from the left end of the beam to the point of interest.
But it ...
1
vote
0answers
14 views
Linear FEM: Infinitesima Strain tensor at different element mesh
Hi guys,
I am solving an exercise for a course of Computational Continuum Mechanics. Briefly, my question is how can i compute the infinitesimal strain tensor at different nodes of the finite element ...
2
votes
1answer
45 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 ...
2
votes
0answers
30 views
Can the critical buckling load from non-linear FE calculation be higher than the one from linear?
Let's consider a FE buckling calculation without plasticity.
Is there theoretically any chance that the non-linear analysis will give a higher buckling load than the linear one?
-1
votes
2answers
51 views
Bending moment in Euler-Bernoulli finite Element
I'm trying to calculate the bending moment distribution on a fixed-fixed Euler-Bernoulli beam. It is known that interelement nodes show different values for the bending moment. What is customary to do ...
0
votes
0answers
18 views
Simulating heat conduction on a 1-D Fin
I am trying to simulate the heat conduction on a 1-D fin. The problem I am having is that I do not know how to properly calculate the temperature in the last point of my 1-D grid. We were asked not to ...
2
votes
1answer
33 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} \...
1
vote
0answers
18 views
In Nastran, how to ignore fatal error due to failed convergence and move on to next subcase?
At the moment the whole analysis stops when 1 subcase fails to converge. How can I keep the analysis going such that all subcases are are run, even if they all might produce an error?
I'm pretty sure ...
0
votes
0answers
22 views
Defining appropriate test function spaces for the finite element solution of Euler's fluid equations
I have the following coupled equations for the conservation of mass and momentum of a compressible fluid
\begin{equation}
\rho_t + (\rho u)_z = 0,
\end{equation}
$$
(\rho u)_t + (\rho u^2)_z + \...
1
vote
0answers
20 views
Assign a name to surface in CAD STEP file
I have a CAD model designed in FreeCAD and need to export it to a STEP file (neutral CAD format) to be used in numerical anaysis software. I would like to assign names to selected surfaces in order to ...
0
votes
0answers
13 views
Assigning different thicknesses to single part - ABAQUS
I am trying to validate the results of linear analysis from RSTAB (structural analysis tool) with ABAQUS. The model comprises of approximately 800 members.
Each member is composed of built-up sections ...
1
vote
1answer
173 views
Free pre-processor for Nastran?
I want to do a non-linear analysis (possibly SOL 400) on Nastran. I used PyNastran (python module) to set-up the BDF file for a Linear buckling analysis (sol 105). However I feel like it might be too ...
1
vote
1answer
35 views
How would I do a buckling analysis with an additional fixed known lateral force?
I am using Nastran for buckling analysis, and I'm new to all of this so please bear with me.
For a linear buckling analysis, I understand that you must first apply any compressive load in the static ...
0
votes
0answers
14 views
MATLAB code implementing the Finite Difference solution of the BVP
I'm having a hard time refiguring this code we used in class to do a 1D finite-difference solution. If anyone could help it would be greatly appreciated. The problem set is listed below as well as the ...
-2
votes
2answers
184 views
Zero Deflection
The best possible way to prevent the
bracket from failure is to ensure that it is enough rigid thereby ensuring absolute zero deflection at all points of the bracket. What is the view on the real ...
1
vote
0answers
30 views
Extracting load info on Abaqus with Python
I have a model on Abaqus that I've managed to run some 85 jobs on manually. Between jobs, only the loads vary, and I select these loads by resuming what I need and suppressing what I don't with my ...
0
votes
2answers
102 views
2D- Truss Member Analysis
I am a graduate student trying to sharpen the direct stiffness method skills. However, I am stuck at the beginning.
The problem is given in the image.
Can someone help me to write down all the nodal ...
0
votes
2answers
48 views
Finite Element software for chemical diffusion in liquid
I'm an engineer who needs to do FEA for the first time. I need to model chemical diffusion in a liquid in a container with specific geometry. For now fluid is assumed to be not flowing.
What ...
0
votes
0answers
110 views
How to get version from an abaqus output database file?
I want to read some data from an .odb file, but when I open it using the C++ API I always get this error message:
file.odb is from a more recent release of Abaqus.
The current Abaqus installation ...
1
vote
0answers
30 views
What is the difference between $K$ ,$K_{IC}$ and $K_t$?
I have seen three representation of stress concentration factor values $K$,$K_{IC}$ and $K_t$ now all that I know is $_I$ in suffix represents opening mode of crack.The suffix $t$ stands for tip....
0
votes
2answers
120 views
Why is finite elements method not part of electrical engineering curriculum?
The question is straightforward. FEM is a third year course in mechanical engineering but not generally taught in electrical. Why is this?
0
votes
1answer
84 views
Issue with collapsed element in LISA Finite Element Analysis
I'm new to the FEA world and trying to learn the ropes through resources available online. I've imported a model into LISA FEA that I would like to analyze, however, when I press solve to conduct my ...
1
vote
1answer
344 views
How do I import an .inp and an IGES together into Ansys workbench?
I have an .inp file of Ansys that is basically a mesh, that could be imported into Ansys APDL and converting to .cdb file.
But ...
0
votes
0answers
27 views
Simufact / MARC and Fortran
I am using Simufact from MSC Software to perform numerical simulations.
To be able to create my own sub-routines I need to have Fortran compiler installed.
Simufact manual mentions only Intel Fortran +...
0
votes
2answers
57 views
How are the location of Gausian points determined in Finite element theory?
From the finite element theory, what is remained a bit unclear for me, is that how do we know the location of gausian points where the integration is done for each specific type of element ? it is not ...
0
votes
1answer
49 views
Is Belytschko beam defined for 3D or 2D?
from the paper in this link , which is the Belytscko beam. I could not figure out if it is a 3D beam or a 2D one.
if you don't have access to that paper, please check the page 73 on this link.
what ...
0
votes
2answers
30 views
Is Model order reduction good for complex models with a lot of contact points in them?
we know that MOR ( or model order reduction ) is used to reduce the size of heavy FEM models. but if there are so many faces, edges of the part that are in contact with another part in the model or ...
