Fundamental property of ultrasound
• Ultrasonic testing is based on time-varying deformations or
vibrations in materials.
• All atoms of material may be forced into vibrational motion about
their equilibrium positions.
• When the particles of a medium are displaced from their
equilibrium positions, internal restoration forces arise.
• It is these elastic restoring forces between particles, combined
with inertia of the particles, that leads to the oscillatory motions of
the medium.
Examples