Automated inspection systems based on inductive thermography with embedded processing for flaw detection

There are several active thermography techniques used for defect detection. All of them are based on the same fundamentals: a sample or component is exposed to an external excitation source and the propagation of the induced heat is captured with a thermographic camera, analyzing the temperature gradients on the surface for the detection of surface and sub-surface anomalies. 

Inductive thermography consists of generating a variable electromagnetic field that produces induced currents, called Eddy Currents, in the inspected component, which in turn generates heat due to the resistance of the material. The temperature distribution on the surface of the part is recorded by means of a thermal imaging camera, which makes visible the points where there has been an anomalous concentration of heat, the defective areas. These are always small heatings between 5ºC and 10ºC with respect to the temperature of the part, depending on the case.

The inspection can be performed dynamically or statically, by moving continuously along the sample under consideration or by making step-by-step inspections. In this second method, static records are obtained for each inspected area. The inspection time per step is very short (0.5 s - 1 s), which makes this step-by-step procedure feasible.

Once the inspection has been performed, the recording is processed and various defect detection models are applied, according to the customer's needs. The inspection software (ad-hoc), manages the information, executes the inspection and allows to visualize the detected defective areas. The detected defects can imply the rejection of the part or a re-inspection after a repair of the defects found. The system is configured according to the specific needs of each customer.

This technique is applicable in very diverse industrial sectors, aerospace, automotive, offshore, etc., and allows the detection of defects in metallic materials, such as cracks, inclusions, porosities, etc.