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Articles about engineering

  1. Folded leaf spring ball joint flexure

    The Dutch-language engineering book “Constructieprincipes” by M.P. Koster contains flexure made out of four folded leaf springs that kind of acts like a ball joint.

    The point where the load is applied should rotate around a virtual center formed by the point where the fold lines meet. The goal of this article is to simulate that and see if it works.

  2. Corrugation against buckling

    Composite sandwich products loaded in bending tend to fail by buckling of the laminate under compression. The author’s intuition is that corrugating the surface under compression should help. So the question is; does it help, and how much. That is what will be investigated in this article.

  3. Hex versus tet meshes in FEA

    In this article the difference in the images of the stresses between a quadrilateral hexahedron (“hex”) mesh and a tetraeder (“tet”) mesh will be investigated. In both cases, second order elements will be used.

    Hopefully this will make it clear to the reader why hex meshes are generally preferred.

    The plate with a hole that was the subject of a previous article will again be used. The analyses will be done using CalculiX.

  4. Resonance frequency of a composite tube

    Based on a question I ran into at work, I wanted to explore the influence of parameters like cross-section, wall thickness and laminate lay-up on the resonance frequency of a carbon fiber composite tube.

    The goal of this exercise is to determine which of the parameters are dominant.

  5. 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.

  6. 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.

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