Principle of Ultrasonic Testing

 This blog will let you know about the principle of Ultrasonic testing



What is Ultrasonic Testing?

  • Ultrasonic Testing Uses high frequency sound energy to conduct examinations & make measurements.
  • It can be used for flaw detection, Dimensional measurements.

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Principle of Ultrasonic Testing:

Accoustic Impedance (z) Differance

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Detect Ability: Screen (or) Display

  • All materials are comprised of atoms, which may be forced into a vibrational motion.
  • In solid, sound can propagate as longitudinal waves, Shear waves, Surface waves (Rayleigh), & in thin material as plate waves (Lamb waves)

Wave Propagation:

Ultrasonic testing is based on the vibration in materials which is generally referred to as acoustics. All material substances are comprised of atoms, which may be forced into vibrational motion about their equilibrium positions.

Many different patterns of vibrational motion with at the atomic level; However, most are irrelevant to acoustics and ultrasonic testing.

Acoustics is focused on particles that contain many atoms that move in harmony to produce a mechanical wave. When a material is not stressed in tension or compression beyond its elastic limit, its individual particles perform their elastic oscillations.

When the particles of a medium are displaced from their equilibrium position, internal restoration forces arise. These elastic restoring between particles lead to the oscillatory motions of the medium. In solids, sound waves can propagate in four principal modes that are based on the way the particles oscillate. Sound can propagate as longitudinal waves, shear waves surface waves and in thin materials as plate waves longitudinal and shear waves are the two modes of propagation used in the ultrasonic testing as shown in the figure

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Wave length ʎ = Velocity (v) /  Frequency (f)

Wavelength & Defect Detection

  • In UT the inspector must make a decision about the frequency of the transducer that will be used
  • Sensitivity = ʎ / 2 (Thumb rule)

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  • Number of other variables will also affect the ability of Ultrasound to locate defects: Pulse length, type and Voltage applied to crystal, properties of the crystal, backing material, transducer diameter, and receiver circuitry of the instruments.

Velocity of sound in material

How is Ultrasonic Testing done

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