Position Control of Probe and Its Tracking Control along the Specimen Surface for Automatic Ultrasonic Testing of Curved Thermal Sprayed Specimen.

Abstract

Recently, we have proposed an effective method for inspecting the delamination of thermal sprayed coating, which is called the ultrasonic bottom echo method. In this method, it is important to keep the position of an ultrasonic probe normal to the surface of the sprayed specimen during testing. However, the sprayed specimens are often distorted by a high-temperature heat source for spraying, such as electric arc or fuel flames. Furthermore, the shape of the sprayed specimen is not always flat. Thus, it is difficult to perform automatic inspection precisely using a conventional simple testing apparatus. A flexible scanning apparatus with five degrees of freedom was constructed that enables precise ultrasonic testing of curved thermal sprayed specimen. Control systems were fabricated to keep the UT probe normal to the specimen and to move it along its surface precisely. As a result, it was confirmed that the control systems can be applied to the ultrasonic testing of curved specimen by the bottom echo method.