A Brief History of Phased Array Testing

During their first couple decades, commercial ultrasonic instruments relied entirely on single-element transducers that used one piezoelectric crystal to generate and receive sound waves, dual element transducers that had separate transmitting and receiving crystals, and pitch/catch or through transmission systems that used a pair of single-element transducers in tandem. These approaches are still used by the majority of current commercial ultrasonic instruments designed for industrial flaw detection and thickness gaging, however instruments using phased arrays are steadily becoming more important in the ultrasonic NDT field.The principle of constructive and destructive interaction of waves was demonstrated by English scientist Thomas Young in 1801 in a notable experiment that utilized two...

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Introduction to Ultrasonic Testing

Ultrasonic test instruments have been used in industrial applications for more than sixty years. Since the 1940s, the laws of physics that govern the propagation of high frequency sound waves through solid materials have been used to detect hidden cracks, voids, porosity, and other internal discontinuities in metals, composites, plastics, and ceramics, as well as to measure thickness and analyse material properties. Ultrasonic testing is completely nondestructive and safe, and it is a well-established test method in many basic manufacturing, process, and service industries, especially in applications involving welds and structural metals. The growth of ultrasonic testing largely parallels developments in electronics, and later in computers. Early work in Europe and the United States in the...

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API 570 Examination Formulas

Sl # Formula Description Formula Para/Ref. No Ref. Code 1 Soil Resistivity (ohm-cm) = 191.5 x d x R 10.10.1.4.3 API 574 2009 Edition The number 191.5 is a constant that takes into account the mathematical equation for the mass of the Soil, and a conversion factor to convert feet to centimeters. "d" is the distance in feet between any 0f the equally spaced pins (with all of the pins in a straight line), "R" is a resistance factor of the voltage drop across the two inner pins divided by the induced current flow in the earth between the...

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