Ultrasonics is a widely used nondestructive testing technique, which is often applied off-line for weld quality inspection. Laser ultrasonic (LU) inspection systems have the potential for on-line application, providing the means to identify unacceptable welds as they are formed. Because LU systems are non-contacting, they can be used for testing moving specimens or for operation in hazardous and/or high temperature environments. A highly versatile system can be created when an optical fiber delivery system is incorporated into the design. Introduction of a focusing objective increases the allowable working distance and permits stronger generation using material ablation as the generating mechanism. This paper describes the development of a laser ultrasonic probe using an optical fiber delivery system with a distal end, focusing objective. The optical fiber delivery system can be configured as a single fiber source, a linear array (fiber bundle) or a phased array. Results include experimentally obtained directivity patterns demonstrating ultrasonic generation using ablation sources. Thermoelastic source results are also included. This paper demonstrates the potential of the fiber tool and presents an overview of the weld control scheme.
No 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]
Ultrasonics is a widely used nondestructive testing technique, which is often applied off-line for weld quality inspection. Laser ultrasonic (LU) inspection systems have the potential for on-line application, providing the means to identify unacceptable welds as they are formed. Because LU systems are non-contacting, they can be used for testing moving specimens or for operation in hazardous and/or high temperature environments. A highly versatile system can be created when an optical fiber delivery system is incorporated into the design. Introduction of a focusing objective increases the allowable working distance and permits stronger generation using material ablation as the generating mechanism. This paper describes the development of a laser ultrasonic probe using an optical fiber delivery system with a distal end, focusing objective. The optical fiber delivery system can be configured as a single fiber source, a linear array (fiber bundle) or a phased array. Results include experimentally obtained directivity patterns demonstrating ultrasonic generation using ablation sources. Thermoelastic source results are also included. This paper demonstrates the potential of the fiber tool and presents an overview of the weld control scheme.
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