## 4 main nonlinear material models – general version

By | February 21st, 2017|• Nonlinear Analysis, FEA: Intermediate, FEA Topics:, RFEM, FEMAP|

Recently a friend challenged me to do something in Nastran. At a certain point, I realized that I know too little about nonlinear material types. So as typical me, I stopped a challenge and decided to learn more about material nonlinearity, starting from the simplest models to the most advanced ones when it comes to [...]

## 4 main nonlinear material models – NX Nastran version

By | February 21st, 2017|• Nonlinear Analysis, FEA: Intermediate, FEA: Advanced, FEA Topics:, FEMAP|

I literally run this blog for posts like this one. Recently a friend challenged me to do something in Nastran. At a certain point, I realized that I know too little about nonlinear material types in NX Nastran and I suspect this is why I have convergence problems in my task. So as typical me, [...]

## Imperfections in buckling design

By | January 31st, 2017|• Nonlinear Analysis, • Stability, FEA: Intermediate, FEA: Advanced, FEA Topics:, Structural Design Topics:, FEMAP|

Using deformations from linear buckling as imperfections in nonlinear buckling case is the most common approach. I will use a simple example to prove that this is not always the best idea. Proper selection of imperfections is a very complicated process – I hope to shed some light on this matter. […]

## Linear vs nonlinear buckling explained!

By | January 24th, 2017|• Linear Analysis, • Nonlinear Analysis, FEA: Intermediate, • Linear Buckling, FEA Topics:, FEMAP|

Choosing between linear buckling and nonlinear buckling in given case can be difficult. Both approaches have positive and negative aspects. I explain here what are the differences, and when to use each analysis. I promise not to use complicated mathematics, nor highly theoretical approach. Instead, I will use a simple example to easily describe differences. [...]

## Nonlinear buckling explained simply

By | January 10th, 2017|• Nonlinear Analysis, • Stability, FEA: Intermediate, FEA Topics:, Structural Design Topics:, FEMAP|

Nonlinear buckling is a really interesting analysis. It gives you enormous possibilities, at only a few minutes worth of work. At the start, it might be frustrating to set it up (there is a learning curve involved), but in the end, it is a default engineering tool for me right now! Possibilities are limitless! [...]

## Linear buckling in plain language!

Buckling is a dangerous phenomenon. It can lead to catastrophic failure of a structure, even if stresses are far smaller than yield limit. You can use linear buckling analysis to verify structural stability. In this post, I will discuss positive aspects and limitations of linear buckling. […]

## One of the best talks I have ever had and my presentation on ICMS 2016

Today I will post about something a little bit different. I had an opportunity to be at International Conference on Metal Structures (ICMS 2016). It was a 3-day event gathering scientists and practitioners from all around the world to discuss new trends and ideas in steel structures. I had a privilege to have 2 presentations [...]

## How to interpret outcomes from MNA

By | June 19th, 2016|• Nonlinear Analysis, FEA: Intermediate, FEA: Advanced, FEA Topics:|

In this post I present a method allowing to read an outcome from a rising stability path obtained from MNA. This method is called “modified Southwell plot” and was published by prof. Rotter. If you ever had problems in estimating plastic capacity this is a must-read! […]

## How to set up materially nonlinear analysis

By | June 5th, 2016|• Nonlinear Analysis, FEA: Intermediate, FEA Topics:, FEMAP|

In this post I will show you how to define and run a materially nonlinear analysis in a video tutorial. This is the type of analysis that will allow you to calculate a plastic collapse load of the model. This is one of the important parameters in numerical design. […]

## Critical bending moment: How to calculate it with numerical analysis (in RFEM)

Lateral torsion buckling (LTB) is a very dangerous phenomenon, that can easily cause the collapse of a poorly designed beam. In civil engineering codes, the critical bending moment is crucial in the proper design of bent beams susceptible to LTB, as it allows for slenderness calculation.  In “typical” cases everything is ok since code equations [...]

## How to set up geometrically nonlinear analysis

By | May 22nd, 2016|• Nonlinear Analysis, FEA: Intermediate, FEA Topics:, FEMAP|

Have you ever performed an analysis that did not converge, or that ended with the result you did not expect? Many of such problems are resolved with correct solver settings, and today I will discuss how to set an arc-lenght geometrically nonlinear analysis of a shell. This means we will do a nonlinear buckling problem [...]

## Nonlinear analysis setup – Steering

By | May 15th, 2016|• Nonlinear Analysis, FEA: Intermediate, FEA: Advanced, FEA Topics:, FEMAP|

As I wrote previously in many cases nonlinear analysis of buckling yield better results than linear buckling. Setting up an analysis like that however requires certain knowledge. Today I will discuss steering of numerical analysis that is crucial in proper task definition. […]

## Linear vs Nonlinear Buckling

Topic of linear and nonlinear buckling is one of the most searched FEA topics. It is understandable, since lack of knowledge about the difference in both approaches can lead to great overestimation of model capacity and following real-life instability failure. In this post I will discuss the difference with a shell example. […]

## Common mistakes in nonlinear analysis

By | April 17th, 2016|• Nonlinear Analysis, FEA: Intermediate, FEA: Advanced, FEA Topics:|

Today I wish to discuss what things can influence the outcome of  stability path method in a negative way. As I wrote before, stability path is a tool, that uses outcomes from analysis steps (or increments) you have defined and computed for a given model. By itself it only presents results in a certain way [...]