03-05-2012, 12:10 PM
ULTRASONIC SYSTEMS
UT basics.ppt (Size: 101 KB / Downloads: 84)
THROUGH TRANSMISSION SYSTEM:
1. Sound Energy is continuous or Pulsed
2. Separate transmitter / reciever
3. Soundness of test specimen based on energy lost
4. Indicates only presence of defect and not the location
RESONANCE SYSTEM
1. CONTINUOUS WAVES ARE NEEDED.
2. USED FOR THICNESS MEASUREMENT, LACK OF BONDING
IN CLAD & FOR DETECTING LAMINATION.
Resonance will occur only when the specimen thickness is equal to a half wave length or an exact multiple of a half wave length.
Fundamental Resonance Frequency F = V/2T
PULSE ECHO SYSTEM
1. WIDELY USED FOR FLAW DETECTION
2. SOUND ENERGY IS TRANSMITTED IN PULSES
3. USED IN CONTACT AND IMMERSION METHODS
4. CRT DISPLAY -
A-SCAN : ANALOG DISPLAY - TIME VERSUS AMPLITUDE
B-SCAN : CROSS SECTIONAL VIEW
C-SCAN : PLANAR VIEW
5. MAY BE USED IN CONTACT AS WELL AS IMMERSION
TESTING OF PLATES, PIPES, FORGINGS , CASTINGS &
WELDS.
Application ( cont..)
Frequency of sound energy used in general for contact testing is up to 5 MHz, whereas in immersion testing the frequency used may be as high as 25 MHz.
Probe angles used in general in angle beam examination are 45, 60 & 70 Deg. Some other angles such as 35, 80 deg etc are also used for some special applications depending on the geometry of the specimen.
In general normal beam testing is carried out using longitudinal mode, whereas shear waves are used in case of angle beam scanning. But in some cases like angle beam examination of weld overlay, longitudinal waves are used for better penetration.
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 equipments 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 / imaging facility.