Abstract
In recent years, the observation of the behaviour of components during the production process and over their life cycle is of increasing importance. Structural health monitoring, for example of carbon composites, is state-of-the-art research. The usage of Fibre Bragg Gratings (FBGs) in this field is of major advantage. Another possible area of application is in foundries. The internal state of melts during the solidification process is of particular interest. By using embedded FBGs, temperature and stress can be monitored during the process. In this work, FBGs were embedded in aluminium alloys in order to observe the occurring strain. Two different FBG positions were chosen in the mould in order to compare its dependence. It was shown that FBGs can withstand the solidification process, although a compression in the range of one percent was measured, which is in agreement with the literature value. Furthermore, different lengths of the gratings were applied, and it was shown that shorter gratings result in more accurate measurements. The obtained results prove that FBGs are applicable as sensors for temperatures up to 740 °C.
Highlights
Residual stresses in castings arise primarily because of temperature differences and its changes.These are internal loads that are present without the appearance of external forces and torques and that are internally balanced [1]
Most testing methods are destructive and change the internal balance of the casting because they rely on material removal, which results in the deformation of the component. This can be measured with strain gauges and converted back to residual stresses
The aim of this work was to embed Fibre Bragg Gratings (FBGs) during the casting process in a preliminary investigated moulding process to observe the behaviour of the sensors during the solidification process
Summary
Residual stresses in castings arise primarily because of temperature differences and its changes. These are internal loads that are present without the appearance of external forces and torques and that are internally balanced [1]. Knowledge of the condition of residual stresses and their occurrence is of great interest for predicting such disturbances with the help of simulation tools. Most testing methods are destructive and change the internal balance of the casting because they rely on material removal, which results in the deformation of the component. This can be measured with strain gauges and converted back to residual stresses. Only the strain on the surface will be recorded, and an analysis of the internal stresses is generally impossible [3]
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