抄録
The purpose of this paper is to develop a tile-debonding diagnostic device that can perform practical and stable inspection of debonding. Based on new concepts, a diagnostic device was designed and prototyped. Calibration methods and applicability of the device were also examined. The outline and the results of this paper are as follows.
1) Requirements for tile-debonding diagnostic devices were examined, and these requirements were reflected in the design and prototyping a new device. The prototyped device can impact the surface of inspection targets with a frequency of 10 Hz with an actuator stroke of 10 mm. This device can measure the impact force with a piezoelectric element, and measures impact sounds with four microphones which are located around the center of impact position at the distance of 40 mm in four directions.
2) A glass-made and disk-shaped standard test specimen with a circular cavity on the back side was devised for calibration of the device.
3) As basic parameters for the detection of debonding, the maximum striking force F and the first wave maximum amplitude A were defined. These parameters were extracted from striking force waveforms and impact response sound waveforms that were recorded by the prototyped device.
4) Two standard values, F0 and A0, were set for the purpose of calibration of the device. Here, F0 and A0 are the values which were obtained under the measurement condition that the device hits the center point of the surface of the standard specimen with the gap of 1 mm between the bottom plate of the device and the surface of standard specimen.
5) Two relative value parameters, Fr (= F / F0 ) and Ar (= A / A0 ), were defined. Here, F and A are actually measured values obtained from inspection targets by the device.
6) As a stable and suitable parameter, RAF (= Ar / √Fr ) was devised through the analysis of experiment results. It is found that RAF is very robust, despite the change of the driving voltage of the solenoid actuator or the change of the contact condition of the device to the surface of the inspection targets.
7) The prototyped device has four microphones for the purpose of reliable detection in the vicinity of the debonding boundary. In order to verify the effectiveness of these microphones, measurements were conducted for the standard test specimen. From the measurements, it was found that the value of RAF is influenced not only by the position of the impact point but also by the position of the microphones, and consequently, the effectiveness of locating four microphones in four directions evenly around the center of impact point was finally verified.
