Laser Array/EMAT Ultrasonic Measurement of the Penetration Depth in a Liquid Weld Pool

Abstract

Ultrasonics has become widespread as a nondestructive testing technique. The most commonly used device for generation and reception of ultrasound are contacting piezo-electric transducers. Because these devices require physical coupling with the sample, test specimens must be stationary, and surfaces both cool and nonabrasive. Obviously, traditional contacting transducers cannot be used for real-time evaluation of certain manufacturing operations, such as weld quality control, where the test specimen could be in motion, and hot as well. This paper presents an evaluation of a noncontacting ultrasonic testing system consisting of a laser and fiber optic probe for generating ultrasound and an electromagnetic acoustic transducer for receiving the signals. This system has been applied to simulated liquid welds to demonstrate the feasibility of using similar equipment for real-time weld quality control. Weld penetration depth is investigated. [S1087-1357(00)70701-5]