# Roland's homepage

My random knot in the Web

1. ## Continuum properties of aluminium honeycomb

Honeycomb cores are often used in composite structures as an alternative core material to e.g. polymeric foams or end-grain balsa.

In FEA we want to be able to treat honeycomb as a continuous material instead of having to model individual cells. Otherwise even simple FEA models involving honeycomb would become unmanageably large.

2. ## 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.
3. ## 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.

4. ## 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.

5. ## 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.

6. ## 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.

7. ## 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.

8. ## 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.

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