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ULTRASONIC TEST

ULTRASONIC TEST

INTRODUCTION
This method is used to test a variety of both metallic & non metallic products such as welds, forgings, castings, sheets, etc. It has an advantage of detecting sub-surface discontinues with accesses to only one side of the specimen.
In this method beams of high frequency sound waves are introduced into the material being tested. The sound waves travel through the material with some loss of energy & are reflected back . This is detected & analysed to detect the presence of flaws.
This test employs ultrasonic waves. These waves are mechanical waves that consist of oscillations or vibrations.

METHOD

TRANSMISSION SYSTEM
This method employs two Transducers, one for sending & other for receiving the pulses. These
may be short or continuous & are transmitted through the material. The result gets displayed on the CRO connected. The settings of the CRO can be adjusted with respect to time & distance.
Prior to testing couplant is used to provide a suitable sound path between the transducer & the test surface. It excludes the air between the surfaces & aids the movement of the waves. Oil or water used with glycerin is the commonly used couplant.
ULTRASONIC TEST

ADVANTAGES
  • Testing can be carried out with one side access.
  • Any thickness on higher side can be tested ( Superior penetrating power ).
  • Results are immediate.
  • Exact depth and locations of flaws can be estimated.
  • Compact and portable equipment's are available.
LIMITATIONS
  • Highly skilled and trained personnel are required. Coarse grain weld material like Austenitic stainless steel & Nickel based non ferrous welds are difficult to test.
  • Equipment cost is very high for automated testing with recording I imaging facility.

APPLICATIONS
  • Inspection of large castings & forgings, for internal soundness before carrying out expensive machining operations.
  • Inspection of moving strip or plate as regards its thickness.
  • Inspection of locomotive axles & wheel pins for fatigue cracks
  • Inspection of rails for holes without dismantling the assemblies.

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