1. Adequate Coupling 1. speed of testing 2. easy automation2.Angulation of the probe1. Subsurface defect detection 2. Choice of angles(SWT)3. Absence of surface wave Convenience of testing4. Less wear Use of high frequency probes1.Conventional2. Semi or squirter method or bubbler method3. Pseudo immersion 0r rubber wheel search units

Bridge and manipulator

Bubbler squirter method-semiWheel type search unit-pseudo

Water path distanceWhat is the position of defect echoin the CRT in normal probeWhere do you look for defect signal in the case of angle probe

Water path distance in immersion testing

Water path distance = thickness of specimen x Wave velocity in water/ Wave velocity in material

Water path for a particular depthWp = F.L in water - depth X V in mat / vel in waterTo make lensR = f ( 1- C1 / C S ) C1- V in liquid : Cs - V in lens material

Through Transmission method - Shadow technique In a flaw free specimen, the amplitude (intensity) reduction is minimal and that is only due to the attenuation loss. However when there is a planar flaw oriented normal to the propagating ultrasonic waves, the reduction is amplitude (intensity) is very large. Why? This large reduction in intensity, indicates the presence of flaw. Two separate probes are usedOne to transmit and other to receive ie one probe is a transmitter probe and other is a receiver probe (which is a good T and which is a good R). What is a TR probe.They are kept on the opposite sides of the specimen to be tested in alignment that is they face each other. Coupling on both sides is necessary. They are moved in synchronisation.The amplitude or the energy of the US waves received by the receiver crystal is measured.

Advantages of the method: high attenuation materials ?? Near surface defects ?? Bond integrity testing Layered structures (FRP) Mainly for bonding (aircraft structures)One limitation or disadvantage of the method is two side accessibility What is the other major disadvantage or limitation of the method (see the transparency)This method is shadow method because like radiography, intensity variations are monitored. What type of wave is usedThe monitoring of intensity variation along with variation in phase angle is the principle of acoustic microscopy

Resonance techniqu not much used except for bond integrity testing What is resonance : condition for resonance

Resonance or Stationary WavesResonance method is used in thickness measurement.Resonance is a character of vibrating body , usually it applies when the thickness of the material is /2 or more.Controlling the wavelength is achieved by adjusting the frequency, Which will produce condition of resonance in determining thick.. Of plate.