# Questions tagged [finite-element-method]

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### Problem with model constraints in ANSYS mechanical

I've been trying to run an analysis of the geometry in the attached images. The geometry consists of an inner tube with protrusions along an axis (this axis is not parallel to the Y axis) and an outer ...
76 views

### Iterative Method through FEM

Due to reasons, I can not fully describe the process explicitly so I will be using substitutes to represent the variables. Nomenclature: x - an independent variable y - another independent variable Fz ...
3k 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 ...
1 vote
253 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
306 views

### FEM of beam with unsymmetrical UDL

I have two different UDLs for 6.5m and 3m spaced side by side on a primary beam. If I were to calculate the FEM of this beam, how should I proceed as there're no formulas for situation particularly ...
191 views

### Imposing/ensuring a constant mass flow rate in turbulent flow simulation

I'm trying to simulate using Finite Elements (non commercial software) the Tube Bundle benchmark problem: http://cfd.mace.manchester.ac.uk/ercoftac/doku.php?id=cases:case078&s[]=tube&s[]=...
10 views

### Modifying Johnson Cook Model in ABAQUS simulations

I am currently simulating a high strain rate impact of commercially pure nickel and found a constitutive equation in DOI: 10.1051/jp4:2006134015. They have a modification of the Johnson Cook model to ...
14 views

### COMSOL multipysics - thermal stress for cubeSat in low earth orbit eigenvalue slover error

I'm using COMSOL version 6.2 for my simulation work. I'm dealing with Heat Transfer involving Radiation and Thermal Stress in solids phisics only after inserting all the constants and boundry ...
1 vote
66 views

### Is there a specific way to simulate porous structures?

I tried to simulate an axial compression test for a lattice (porous) structure but It takes too much time and it doesn't give me the right answer (when I compare with experimental results). So, I was ...
778 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 ...
219 views

### What is the difference between maximum principal strain and maximum in-plane principal strain?

For the purpose of answering/explaining this, it does not need to be restricted to strains (i.e., it can be stresses too). I am mainly trying to understand when to use which one (i.e., if I am ...
62 views

### Finite element method approximation

In the picture above, we have on the left a figure representing spatial element, and on the right a figure representing reference element. The type of element used in the method here is a linear ...
38 views

### Deformation Due to Material Removal and Residual Stress

Suppose I have a piece of metal (of arbitrary geometry) with some residual stress profile. I then remove a chunk of the metal and the piece of metal deforms (due to the residual stress). For ...
1 vote
218 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 (...
1 vote
1k views

### Are there any instructions on how to install and run Natran-95?

there is a source code for Natran-95 on Github. I need to install it on Window 10 but searching on the web there is no clear tutorial on installation. while I click on the nastran.exe on this package ...
22 views

### Case studies in Carbon Fiber composite tubes to verify FEA

Whenever I build a model of something new, I like to have some analytical results that I can compare with my model so I can reassure myself the model is correct. I have some resources that show me ...
60 views

### Beam deflection for FEA model validation

I'm trying to validate an FE model that I'm using by comparing to a simplified analytical solution to the problem. The part I'm analyzing is a lug that is constrained on one end and has a point load ...
83 views

### Preliminary way to estimate damping quality factor (Q) from a SolidWorks FEM

I am analyzing the modal response of a structural FEM for a spacecraft structures course. I'm using Solidworks Simulation Premium. Need first mode to be above 40Hz and the damping Q-factor (quality ...
66 views

### Find hotspots in a system

In the image, I have a depicted a system which is undergoing fatigue. Using appropriate solver I have determined the life of each nodes and it is stored in a .csv file. Also I have the connectivity of ...
369 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-...
171 views

### Most efficient fillet design given an envelope (for stress)

If one has a specified allowed X length and Y height, into which a fillet can be placed to reduce stress concentrations, is there an equation which can be used to determine the optimal shape of the ...
1 vote
577 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 ...
1 vote
84 views

### Are there any advantages of using BEM for contact problem over FEM, apart from lesser computational cost?

FEM - Finite Element Method BEM - Boundary Element Method If we had access to "enough" computational resources (to discretize the entire volume domain in FEM to the same degree of fineness, ...
96 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
12 views

### Is it possible to use the results from Abaqus Standard as a predefined field in Explicit analysis? If so, how is the time mapped between the analysis?

I have nodal results from an Abaqus UEL subroutine, where I am solving coupled heat and moisture transport. I have three degrees of freedom in this analysis and several more state variables. I want to ...
14 views

### How to suppress longitudinal stress waves in a beam in FEA

When simulating a bending beam in FEA mimicking the textbook model and approach, unwanted stress waves appear. How to suppress longitudinal stress waves in a beam in FEA? To add friction/damping?
132 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 ...
366 views

### What is the difference between Frictional non-linearity and Geometric non-linearity in FEA? (In terms of Stiffness matrix)

For geometric non-linearity, we know that as the geometry changes during the analysis, the global stiffness matrix changes since it already is a function of geometry of the structure. What I want to ...
1 vote
60 views

### What is the meaning of the traction continuity condition in the generalized momentum balance (continuum mechanics)?

In Nonlinear Finite Elements for Continua and Structures by Belytschko and al. it is stated: As we have already noted, the strong form, or generalized momentum balance, consists of the momentum ...
1 vote
80 views

### Why do Eigenmodes of a rigid system also diagonalize the Mass and the stiffness matrix seperately?

To set up my question, I will briefly recap the derivation that is usually given for eigenmodes of a system: If there is no force present, and a body is described by a vector $u$, then the equations ...
1 vote
953 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 ...
68 views

### Curve-linear vs. Cartesian coordinate systems: linear-elastic & isotropic elasticity tensor

For shell elements, is the elasticity tensor for linear-elastic & isotropic materials the same in a local curve-linear (convected) system vs. a local Cartesian system? I wonder because ...
1 vote
3k views

### Calculate the Euler buckling load of a column using the finite element method

I am trying to find the buckling load of following column: I started from the system of equations $P = (K + K_g(N))U$, where $K$ is the stiffness matrix of a single 2D frame element and $K_g$ is the ...
277 views

### In FEM, what is the difference between a single element with a quadratic shape function and two elements with linear shape functions?

Using Finite Element Analysis to obtain a Weak form of a PDE, what is the difference between the two cases: A single element with a quadratic shape function Two elements with linear shape functions. ...
131 views

### Determining the critical load of a fixed beam with non-uniform cross-section?

I am a computer scientist, not a mechanical engineer, so it is absolutely possible that I am missing some basic understanding here. I have a beam that is fixed in both ends and my goal is to ...
22 views

### Is it OK to separate fire and structural analyses when analyzing a fire induced building collapse?

This is from NIST NCSTAR 1-6 It seems to me there are problems with this approach. The heat distribution depends on fire spread and ventilation paths, which in turn depend on the shape of tjr ...
1 vote
119 views

### Finite Element Method for Spherical Objects

I am familiar with the procedure of the FEM for simple planar objects like truss and etc. but my question would be whether it would be possible to use this method to calculate the stiffness or ...
13 views

### Deformation in nano timescales for stress > UTS

I am investigating the deformation of high-strength carbon steel past its UTS, subject to extreme pressures of order 1e+19 Pa, but applied in small timescales (100-500 ns). For a material, such as ...
35 views

### Finding the best fit between Ansys model results and measurd values to optimize the parameters

I have the final element model of an experimental rig respresenting a vibrating system. The time domain results from both are known. I need to reduce the error between the results/find the best fit ...
1 vote
36 views

### Displacement vectors and linearised angles vectors from local finite element frame to rotated global frame

$s=R\tilde{s}$ is fine, but why $\theta=R\tilde{\theta}$? Namely: why vectors of linearised rotations $\theta_i$ and $\theta_j$ (at nodes $I$ and $j$ respectively) are rotated like they were vector ...
69 views

### Can someone help me with solving this beam problem using Rayleigh Ritz Method, my trial function is not working

The question is there is a two element beam joined together. The first element is 5m long and the other is 4m long. At the outer nodes there are roller supports and at the middle point where two ...
1 vote
87 views

### Why is FEA used for structural analysis?

Is there a reason for using FEA to perform structural analysis over for example Finite volume method for example?
29 views

### COMSOL modelling wicking of paper in 3D

I am trying to model wicking of paper in 3D, by following the tutorial for paper wicking in 2D on the COMSOL Application Library , but ran into this error: Undefined variable. Variable: phtr.pc_s2 ...
58 views

### When to use MPC Contact formulation in Ansys?

I was suggested to use MPC while analysing with beam elements. It's for an analysis of a table to be used in harsh shock conditions.
22 views

### How can I determine the best thicknesses of a circular plate to achieve minimum weight and high strength?

I want to design a circular plate made from iron ductile material, So I want to determine the best thicknesses of the profile (t1,t2,t3,...etc) as shown in the image tyo achieve the best plate weight ...
38 views

### FEA meshing of irregular geometry

I work on the simulation of sand particles and usually use tetrahedral free-meshing to represent their complex geometries for finite element analysis. I have recently spent some time looking into ...
19 views

### Checking if a Residual Stress Field Achieves Mechanical Equilibrium

Suppose I told you the Cauchy Stress Tensor at every point inside a chunk of metal. And, yes, I know this means that I would need to tell you about an infinite number of points - let's ignore that ...
56 views

### Creating a state-space representation (.m format, Matlab) via Simcenter 3D (NASTRAN) using Component Mode Synthesis Reduction

I'm trying to create a state-space representation of my FE-model using a "Component Mode Synthesis Reduction" (general form of Craig-Brampton reduction). The picture underneath shows (...