Welcome

This is my home in the virtual world, where I write about things that I want to share. The freely available software that I've written as well as some of the photographs I've taken over the years can also be found here. Please use the navigation links on the right if you are looking for something.

Recent articles

1. Switching to SSH keys for github

   This article covers some aspects of using SSH keys with github that are left out of the original documentation on github.

   It assumes that you’ve been using HTTPS with a password for remote access to github.

2. Making ringtones with open source tools

   Most smartphones come with a range of ringtones.

   But if you don’t like those, you can make them yourself from music that you are allowed to use.

   All software that is used here is open source. They should work on all recent UNIX-like operating systems. In my case, I installed all of these programs using the FreeBSD ports system.

3. Automating CalculiX with make(1)

   The make program is a staple UNIX development tool. In this article I will show how it can be used to automate and simplify the usage of CalculiX.

   My CalculiX projects are all kept in their own directories. In each of those directories there exists a Makefile. This contains instructions for the make program.

   By default, invoking make in this directory runs the pre-processor and the solver. But there are also specific sub-commands, for example:

   • “make mesh” shows the mesh used in the FEA.
   • “make disp” shows the deformed product in the post-processor.
   • “make stress” shows the stresses in the product in the post-processor.

4. Mooney-Rivlin rubber data for CalculiX

   Recently I was looking for material data for 60 Shore A rubber for a simulation. This article describes what I found and how I transformed that to material data.

5. FEA with Calculix (3)

   This is the third installment of a series of articles about how to analyze sandwich structures with FEA.

   It might be a good idea to read part 1 and part 2 first.

   In this part we will look at a simplified simulation of a three-point bending test of a sandwich panel.

6. FEA with Calculix (2)

   This is the second part in a series how to analyse sandwich structures with FEA. The first part is here. If you haven’t done so, you should probably read that first.

   In that part we built and analyzed a sandwich where the core and skins shared nodes. We saw how that leads to incorrect stress distribution images because of nodal averaging. In this article, we’re going to fix that by using *TIE constraints.

7. FEA with Calculix (1)

   This is the first part of a series of articles where I hope to show how to analyze deflection and stress in structures using the free CalculiX software. I’m using version 2.17. The focus will be on sandwich structures because that is the area in which I’m most interested. Compared to parts consisting out of a single material this is a bit more tricky as we will see in this article. The main reason for using finite element analysis (“FEA”) in general is that it allows for complete analysis of problems where no integral solution exists.

   Additionally, some of the assumptions used in Euler–Bernoulli beam theory for analyzing deformation and stresses in beams and plates do not hold for sandwiches.

8. Why I think engineers should be programmers

   During my engineering education and the start of my career, a lot of design and drafting work was still done on paper. During that time I also discovered computers, and how they could be an extra tool in my toolbox.

9. Engineering category

   Although my training and career has been in mechanical engineering, there is not much about that on these pages. In this new category, I hope to remedy that.

10. Opening vim in a new terminal

    By default, when you open vim it runs on the current terminal. When running X11, I want to start it in a new terminal.