Similar to the ultrasonic principles used by an Obstetrics or Gynecology during pregnancy and naval SONAR, Ultrasonic testing uses the transmission of high frequency sound waves, into a material to detect imperfections within the material or changes in material properties. If the sound traveling through a Material hits material with different acoustical impedance, some of the sound will reflect back and received by the Ultrasonic testing unit and will be represented as an indication on the screen. Knowing the velocity at which sound travels through a part, along with the time of travel will result in a distance to the indication (material with a change in acoustic impedance).
Sound waves are introduced to the part via a transducer made up of a piezoelectric crystal that converts electrical current to sound waves and reflected sound waves to electric current. The two most commonly used types of sound waves are Compression (Longitudinal or Straight Beam) and Shear wave (Transverse or Angle Beam).
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