Development of New Ultrasonic Inspection Technique for Spot Welds with Matrix Arrayed Probe and SAFT

Abstract

A portable type of 3D ultrasonic inspection system, named “Matrixeye”, was applied to the spot welds, in which a matrix-arrayed probe was used as a sensing unit, and the welding zone in the spot welds was visualised 3-dimensionally. The matrix-arrayed probe, in which 64 piezoelectric elements are embedded as 8 × 8 matrix arrangement, can acquire more than 4 000 ultrasonic echo data points due to their transmission and reception in 0.2 seconds. This system can synthesise 3-dimensional ultrasonic images by SAFT (Synthetic Aperture Focusing Technique) installed in the parallel signal processing board. This system can also inspect the weld quality of spot welds with additional data; e.g., an averaged diameter, area, major axis, minor axis, thickness, and indentation depth of the welded region. In addition, this system has an automatic measurement function, in which the measurement automatically starts by sensing the probe contact with the welding surface, and automatically stops by sensing the position and tilt of the probe within a setting level. The results measured by this system have good correlation with the weld size on the fracture faces and the tensile-shear strength in the destructive tests. It was shown from the evaluated performance of the system that the developed system is applicable to the inspection of spot welds.