Questions tagged [finite-element-method]

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Finite element welding simulation with commercial software? [closed]

I am looking forward some libraries/add-ons to perform welding simulation (thermomechanical coupling, steel alloys) using commercial software, like Ansys or Abaqus. My aim is to determine better ...
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25 views

How to determine the stiffness matrix for finite element matrix

I'm having difficulty understanding how the stiffness matrix for finite elements is obtained. I am only having a difficult time understanding how to obtain the matrix values for K from the given ...
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FEM matehmatical methods

Are all advanced methods used in FEM, other than the Direct Stiffness Method, also ultimately based on Direct Stiffness Method? If not is there still a common starting point? Why did other methods ...
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Applying finite element analysis to solar panels [closed]

I am new to finite element analysis, but I was wondering if it would be effective to use finite element analysis to map the heat of solar panels, and draw conclusion based on data?
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Mesh generation in FEM [duplicate]

When a frame structure is analyzed using a FEM computer software, does the program still generate mesh, even as a line mesh, on frame members, or we must do it ourselves?
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Does Finite Element Method use direct stiffness method?

Does Finite Element Method use direct stiffness method? Or it is another mathematical method? We definitely use direct stiffness method to solve frames. FEM is based on entirely this or depending on ...
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how to Implement linear tetrahedral elements for finite element computations? [closed]

I am trying to implement 3D tetrahedral elements in my finite element code (which works fine for linear triangles and quadrangles in 2D). But my simulations are crashing with tetrahedral elements. My ...
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Remote point vs point mass in Ansys

I have seen the feature of promoting a point mass to remote point and I cannot figure out what are the use cases of using that feature. I understood that you can add command snippet below remote point ...
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1answer
699 views

How to avoid contact penetration in Ansys?

I am trying to simulate contact between a flat rigid plate and a sphere. I am applying a load on the flat rigid plate and the sphere is flexible. How can I avoid this flat from penetrating into the ...
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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}}}{...
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1answer
322 views

Model Reduction - Export matrices from ANSYS to MATLAB

I am trying to reduce my model in ANSYS using Craig-Bampton Method. My ultimate goal is to read system matrices, stiffness, damping and mass matrix with MATLAB. The size of stiffness matrix that I ...
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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 (...
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1answer
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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 ...
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2answers
157 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-...
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1answer
105 views

Modelling acoustic instruments — predicting frequencies, decays, levels, and phases of modes of a circular membrane (drum head)

I have been working on some acoustic synthesis software for modelling several acoustic instruments. I am using the principle of modal synthesis, where every mode of vibration is individually ...
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3answers
51 views

Do finite elements have to be planar?

Is it possible to define a finite element that isn't planar? For example the shell element shown in the picture below...
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2answers
30 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.
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496 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 ...
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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 ...
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1answer
591 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 ...
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1answer
91 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 ...
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1answer
42 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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1answer
617 views

Meshing Complex models in abaqus

I'm trying to mesh a model of a morphing wing in Abaqus and have been running into issues. It was recommended that I partition the model into smaller parts, but it seems that the more I try to ...
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1answer
302 views

Debugging Ansys ACT C# Extensions

I'm using the Ansys ACT Api with C# to create an extension for Ansys (Mechanical). When developing the extension I need to build a dll file from C# code (using Visual Studio). My problem is that ...
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1answer
38 views

Find amount of sliding between 2 surfaces

in my project I am required to find how much two surfaces slide against each other (to see how much it'll will rub against skin). Does anyone know how I can find these results? Thanks
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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 ...
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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 ...
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2answers
154 views

How to perform 3 point bending test by using force instead of displacement in ABAQUS?

I know you can apply displacement to a rigid body (cylindrical rod) to perform a 3 point bending test in ABAQUS. Is it possible to apply force to the rod (e.g. rod with super high young's modulus so ...
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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 ...
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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.
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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 ...
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2answers
42 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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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 ...
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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 ...
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2answers
281 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 ...
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1answer
218 views

Should one use multiple elements through the thickness with multiple materials?

To get realistic results from a FEM calculation, it is common (or so I've been taught by someone who may not be up to date) to use at least four or five elements through the thickness of a beam or ...
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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 ...
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1answer
136 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 ...
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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?
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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 ...
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20 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 ...
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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 $...
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1answer
92 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 ...
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1answer
27 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 ...
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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 ...
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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 ...
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2answers
56 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 ...
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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?
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How to Solve this error message on Abaqus 'time increment required is less than specified' and 'too many attempts made for this increment'?

I am currently working on my dissertation project using abaqus, my model is an arch bridge consisting of a shell and solid elements, there are concrete and steel materials also, I have checked all of ...
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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 ...