NON-LINEAR ELECTROMAGNETIC ULTRASONIC SENSOR, MINUTE FLAW DETECTOR USING IT AND MINUTE FLAW DETECTING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a non-linear electromagnetic ultrasonic sensor capable of detecting a minute flaw of 100 μm or below of a material to be inspected without using a contact medium, a minute flaw detector using it and a minute flaw detecting method.;SOLUTION: The non-linear electromagnetic ultrasonic sensor is constituted of the ultrasonic transmitter 1 arranged just above the material P to be inspected to respectively excite surface waves and SH waves using electromagnetic force and a plurality of ultrasonic receivers 2a and 2b having receiving characteristics one and real number multiples with respect to the drive frequency of the ultrasonic transmitter 1. When ultrasonic waves are vertically incident on the slitlike flaw of the material P to be inspected by exciting the surface waves and SH waves from the ultrasonic transmitter 1, the surface waves closely bonds a flaw opening part but the SH waves do not closely bond the flaw opening part. At this time, since the width of the flaw is expanded at the time of tensile vibration of the surface waves, the surface waves do not pass and, since the width of the flaw is narrowed at the time of compression vibration, the surface waves pass. By this constitution, a higher harmonic component is generated and non-linear ultrasonic waves can be detected.;COPYRIGHT: (C)2006,JPO&NCIPI