Non-destructive testing is a way of checking manufactured parts and finding the flaws (cracks or corrosion) without destroying them. There are three kinds of non-destructive testing: ultrasonic, X-ray and Eddy-current, explains Laura PUCCI from French CEA List:
The eddy currents are generated by a coil that emits a magnetic field close to the conductive part and in the presence of a flaw the current will deviate and it’s these deviations that we measure with a receiver. We’ve programmed our robotic arm so that it turns around the part and the sensor moves around the part, this part has a flaw right here. We are able to detect very small flaws on the surface, for example down to 100 micrometers in dimension. This is a technique that could replace penetrant testing, a test that can be onerous and messy for parts whereas our technology is clean and can be automated.
With new manufacturing processes like additive manufacturing, non-destructive testing can be performed while the part is being made. A lack of fusion or material are the main flaws that are looked for in a part that’s been 3D-printed.
The most common flaw is a lack of fusion. Material that hasn’t melted and won’t stick to the part at a certain spot will create a flaw. To compensate for this, new technologies and non-destructive testing can be used to test the part while it is being made. It’s a process. Ultrasonic lasers are one method of detection for example when there is a lack of fusion with the pipette that delivers the material, the laser will detect the lack of material and stop the manufacturing process and start again where the problem was detected.
The nuclear, railway and oil and gas industries are especially interested in non-destructive testing.