A safe form of testing that has endured for ninety years

Introduction



Ultrasonic testing is a non-destructive testing method that uses high frequency sound waves to reveal subsurface flaws. Ultrasonic sound waves are emitted from a transducer into an object and the returning waves are interpreted by the device to reveal an image. The ultrasonic waves are produced by applying electricity to a thin disk made of crystal in the transducer. Sound absorbing material prevents any of the ultrasonic waves from returning to the device and distorting the results. Ultrasonic testing is used in industries such as manufacturing, aerospace, automotive, and transportation.

Origins

Soviet Scientist Sergei Y. Sokolov is considered the father of modern ultrasonic testing. In 1928, Sokolov successfully demonstrated how to use ultrasonics to detect flaws in metals. Unsurprisingly, Sokolov proposed that this technique would be beneficial in the industrial arena for testing irregularities in solid materials. Sokolov's experimentation laid the groundwork for future developments in ultrasonic testing (Portal of Non-Destructive Testing).

Commercial Use

In 1942, British scientist Donald Sproule successfully adapted the principles of echo-sounding for the detection of defects in steel. Sproule's apparatus was unique, because it had separate transmitting and receiving transducers. Across the pond in the United States, scientist Floyd Firestone had independently developed a similar ultrasonic device. In 1945, Firestone's 'Supersonic Reflectoscope' became the first commercially available ultrasonic flaw detector. In the twenty years that followed, ultrasonic testing was refined and became a trusted resource by manufacturers for flaw detection.

Not long after the United States and Britain began to develop ultrasonic testing, Japanese companies developed their own ultrasonic flaw detectors. By 1949, Mitsubishi Electric Corporation, the Japan Radio Company, the Shimadsu Manufacturing Company, and the Toyko Ultrasonic Industrial Company began to commercially produce ultrasonic devices (Portal of Non-Destructive Testing).

Evolution in Technology

Ultrasonic testing equipment has evolved significantly since its initial development. Early instruments used bulky vacuum tubes that required a lot of energy. In the 1960s, solid-state circuitry allowed for smaller, battery-operated instruments that could be easily transported for field applications. All early ultrasonic devices exclusively used analog signal processing, but in 1984 the non-destructive testing company Panametrics introduced a portable, digital flaw detector. Now, digital instruments are the default in the industry, because it provides stable calibration, precise measurements, data retention, and screenshot sharing capabilities (History of Flaw Detection).



Phased Array Testing

In recent years, there has been growing interest in phased array ultrasonic testing (PAUT) that use a multiple probes to generate steered beams and create cross-sectional pictures similar to the sophisticated imagery of medical ultrasounds. This technique has become an essential tool for weld inspections (History of Flaw Detection).

Advantages of Ultrasonic Testing



Higher penetration power than other NDT methods



Only need access to one side



Sensitive to both surface and subsurface flaws



Instant results provided to the client



High resolution images



Light preparation for this testing method



Highly accurate results in determining size and shape





Disadvantages of Ultrasonic Testing



A higher learning curve compared to training with other NDT methods



If defects run parallel to the sound beam, it may go undetected by the transducer.



Surface must be accessible to transmit the ultrasonic waves



Ultrasonic waves can have low transmission and high signal noise in some materials (course-grained stone and cast iron).



Ultrasonic testing does not work well with irregularly shaped, small, or thin objects



Contact

Whether it's Phased Array, Shear Wave, or Straight Beam, Magnum NDT's Level II ultrasonic technicians have you covered. Contact us to schedule a free consultation about our ultrasonic NDT services.



Citations:



History of Flaw Detection. (n.d.). Retrieved July 22, 2019, from https://www.olympus-ims.com/en/ndt-tutorials/flaw-detection/history/

Portal of Nondestructive Testing (NDT). (n.d.). Retrieved July 22, 2019, from https://www.ndt.net

