Cryogenic NDT - Aircraft Engine Overhaul

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Demanding Maximum Performance & Longevity

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Cryogenic Technology

Cryogenic Non Destructive Testing

Victor Sloan's cryogenic non destructive testing (NDT) patented process using electromagnetic acoustical transmission (EMAT) or ultrasound (UT) real-time recognition technology along with other physical shape change measuring and acoustic techniques quantitatively offers significant breakthroughs beyond existing techniques.

It can measure the changes in microstructure and validate material property characteristic changes under certain cryogenic non destructive testing processes. Victor Sloan’s innovations not only facilitate better understanding of the effects of cryogenic testing of materials, but also residual stress, precipitation hardening and phase transformation of materials.

Technicians are Certified in Accordance with National Aerospace Standards (NAS-410)

Cryogenic (NDT) non-destructive testing method is based on the effect of the microcrystalline structure on the transmission of ultrasound. This method can be used to non-destructively evaluate the kinetics and completion of the time-temperature-transformation between structural phases. The basis for ultrasonic testing is based on the difference between the Young’s moduli of the two phases at any given transformation temperature. Since the velocity of longitudinal sound waves is a function of the square root of the elastic constants, an increase in velocity is expected during a typical transformation. Hence, the velocity should be somewhere between the two extremes with a mixture of the phases having a velocity in between. Fortunately, voids do not affect velocity since the sound waves will pass only through the solid material. In addition to velocity changes, sound attenuation is also highly structure sensitive which may also give insight into the mechanism of the transformation.

LongitudinalVelocity More specifically, the velocity of the longitudinal sound wave (Vl) relates to the elastic constants as described by Hooke’s law. The elastic constant relates to the linear stress and strain which are fundamentally functions of the thermodynamic state of the material and the interatomic binding forces in the microcrystalline lattice structure. The longitudinal velocity is related to the Youngs’s modulous (E), density (P), and Poisson’s ratio (o) by

transittime
In order to utilize this to non-destructively assess the transformation within an alloy, sound waves are assessed for transit time through a structure. This time (T) will be related to longitudinal velocity (V) and path length (L) by

Since changes in length will be small during the phase transformation, changes in transit time will reflect changes in the properties of the product and the progress of transformation. Hence the use of ultrasonic transit time measurements can allow the non-destructive assessment of the materials.

By performing real-time ultrasound testing procedures using electromagnetic acoustic transmission (EMAT) or conventional ultrasonic (UT) while performing cryogenic NDT testing, any changes in a materials velocity and amplitude can be documented. The time and temperature is recorded upon any change in velocity or amplitude and phase transformation detection of the start of transition and completion of transition can be documented. This cryogenic (NDT) testing process becomes quite valuable in establishing quality control procedures for materials manufacturers and as an incoming materials inspection process.

Research Affiliates

Air Liquide is the world leader in gases for industry, health and the environment. The Group offers innovative solutions based on continuously enhanced technologies. We produce air gases (oxygen, nitrogen, argon, rare gases, etc.) and many other gases, including hydrogen.

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"Cryogenic NDT Inspection"

Victor Sloan, President of Victor Aviation, Inc. was the November speaker at the Golden Gate Section meeting. The title of his talk was “Cryogenic NDT Inspection.” Sloan is well known for pioneering many product improvements and process changes to the way piston engines and other components are built, inspected and overhauled. That now includes cryogenic applications at –184.4 °C (–300 °F) or colder. He has worked with many famous aircraft, automotive and motorcycle racers, and raced a bit himself in his younger years. After the meeting, Sloan was presented with the Section’s special Speakers Plaque by Section Vice Chair Dave Arms. The plaque contains an original rivet from the Golden Gate Bridge.