This paper presents an experimental investigation of the use of an optical fiber laser phased array to measure solidified weld pool penetration depth in butt and v-groove joints. The purpose was to determine the optimum distances between the ultrasound source (the array), receiver, and the weld joint, in order to measure weld penetration depth. The relationship between penetration depth and wave amplitude was approximately linear. A narrow range of distances between the ultrasound receiver and weld joint permitted the ultrasonic system to detect penetration depth over the entire thickness of the base metal. Maximum resolution in measuring penetration depth was achieved by keeping the distance between the array and the weld joint as small as possible.

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