team:gdeliege:shearo
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- | ==== Shearography ==== | + | ===== Shearography |
- | == Introduction == | + | === Introduction |
- | I am really | + | I am no shearography |
// | // | ||
and itself laterally displaced through an optical shearing device. | and itself laterally displaced through an optical shearing device. | ||
Line 28: | Line 28: | ||
and Arthur Lismonde [3] made finite element simulations of the experiment. | and Arthur Lismonde [3] made finite element simulations of the experiment. | ||
Arthur used ANSYS, which was available at the university where he went on Erasmus. | Arthur used ANSYS, which was available at the university where he went on Erasmus. | ||
- | However, we wanted to make a test requiring a particular post-processing of the results, | + | However, we wanted to make a test requiring a particular post-processing of the finite element |
- | so I made simulations on my own with my personal | + | so I made simulations on my own with my code. |
- | == Problem description == | + | === Problem description |
- | A composite | + | Several |
- | In practice, one or several holes were drilled in the back of the plate to simulate | + | In practice, one or several holes were drilled in the back of the plates |
- | In the models, two kinds of defects were considered: either one circular hole or a circular piece of Teflon | + | In the numerical |
- | inserted between two plies. | + | or a circular piece of Teflon inserted between two plies. |
- | The plate is fixed to a static frame and its surface is heated up with a light. | + | In the experimental setup, the plate is fixed to a static frame and its surface is heated up with a light. |
In view of the time constants of the mechanical and thermal phenomena, one can integrate the heat equation in time and solve a static mechanical problem (small deformations) at each time step. | In view of the time constants of the mechanical and thermal phenomena, one can integrate the heat equation in time and solve a static mechanical problem (small deformations) at each time step. | ||
The only difficulties are the orthotropic thermal and mechanical properties of the material and the post-processing step turning the finite element results into a shearogram. | The only difficulties are the orthotropic thermal and mechanical properties of the material and the post-processing step turning the finite element results into a shearogram. | ||
{{ : | {{ : | ||
- | //Figure 1. Results obtained with my personal | + | //Figure 1. Results obtained with my own code (mesh and visualization |
+ | One can see in Fig. 1 the finite element results obtained when the plate is heated up with a flash, which is represented by a constant heat flux applied for a few microseconds. | ||
+ | The influence of the hole is visible on the shearogram. | ||
+ | However, it is well-known that defects are harder to detect with this technique when they are located deeper in the structure. | ||
+ | One possibility is to use a time-varying heat source instead of a flash | ||
+ | and to apply a Fourier transform to the sequence of shearograms that are recorded over a period of time. | ||
+ | I made simulations with Teflon inserts at different positions, either close to the surface (1 mm) or deeper in the laminate (3 mm). I applied a sinusoidal heat flux at different frequencies, | ||
- | == References == | + | {{ : |
+ | //Figure 2. Phase offset of the Fourier transform of shearograms obtained with my own code. The defect is a Teflon insert and the heat flux is a sinusoidal function of time: (left) shallow insert (1mm), excitation 1Hz; (center) deep insert (3mm), excitation 1Hz; (right) deep insert (3mm), excitation 0.1Hz.// | ||
+ | |||
+ | === References | ||
[1] [[http:// | [1] [[http:// | ||
[2] G. Crabus. //Contrôle non-destructif par shearographie : développements expérimentaux de méthodes de stimulation thermique.// | [2] G. Crabus. //Contrôle non-destructif par shearographie : développements expérimentaux de méthodes de stimulation thermique.// | ||
[3] A. Lismonde. //Contrôle non-destructif par shearographie : simulations thermomécaniques de composites à renforts tissés.// Master thesis, Université de Liège, 2014 \\ | [3] A. Lismonde. //Contrôle non-destructif par shearographie : simulations thermomécaniques de composites à renforts tissés.// Master thesis, Université de Liège, 2014 \\ | ||
+ | \\ | ||
+ | [[team: | ||
team/gdeliege/shearo.txt · Last modified: 2016/03/30 15:23 by 127.0.0.1