4.2. Principles of the thermo-inductive method

This technique is often used to investigate and detect flaws in electrically conductive materials. The inspected piece is heated by induction and, in the presence of a flaw, the anomaly in the induced current distribution creates a concentration of power density around the flaw, which translates to a local temperature contrast to the component’s surface [GRI 05, GUP 05].

4.2.1. Installation schematic

Figure 4.1 shows the principle schematic of a thermo-inductive installation. The component to inspect is heated by induction. The temperature distribution’s inhomogeneity propagates to the material’s surface and can be detected by an infrared camera. A flaw will, therefore, be revealed by combining electromagnetic and thermal phenomena in a complementary fashion [LOU 07, RAM 09].

Figure 4.1. Technique’s principle

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The advantage of this method is to increase the probability of surface flaw detection and to improve the data’s interpretation by correlating the data with two NDT methods: Eddy currents and infrared thermography [RAM 09]. It has the advantage of creating an additional perturbation, which is due to the concentration of induced currents around the flaw as shown in Figure 4.2 where a conducting plate was inspected. The flaw’s presence perturbs the lines of induced current and creates additional overheating, which will add to the ...

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