Ultrasonic sound starts from 20 KHz and above and the testing frequency ranges from KHz to 25 MHz Ultrasonic examination can be conducted on a wide variety of materials including casting, forging, weld and composites. Difference between Compression wave and shear wave 4. The presence of air between the transducer and the test material causes a great difference in acoustic impedance at the interface.
A couplant can be any of a vast variety of liquids , semi-liquids , paste and even some solid that will satisfy the following requirements. First Critical Angle The angle of incidence at which the longitudinal wave pass through the surface of the second medium or perpendicular to the imaginary line is called First Critical Angle.
Second Critical Angle The angle of incidence at which shear wave passes through the surface of the second medium or perpendicular to the imaginary line is called Second Critical Angle. The refracted shear wave is called surface wave and the refracted longitudinal wave is called plate wave or lamb wave. The energy of the reflected ultrasonic waves depends upon the severity of the defect, the area or the orientation with respect to the direction of sound entry. The reflected wave is picked by a receiver and amplified for evaluation.
Major Components of Ultrasonic Testing Equipment. Pulse Generator: It energise the timer and pulser transmitter. Pulse Transmitter: It energise the piezoelectric crystal in short pulses of regular interval. Probes: It generates the longitudinal sound waves and or shear sound waves. Receiver : It receives the electrical signal and amplify the signals and feed it in to sweep and marker circuits.
Sweep Circuits: The horizontal line or base line of the ultrasonic testing screen is controlled by sweep circuits. Normally the value of sweep reads from left to right at fixed points. Marker Circuits: The amount of refraction in a particular area is displayed in CRT screen with the help of a marker circuit. Timer: It is the heart of the equipment. It is the source of all timing signals in the UT equipment.
There are two indications , one from the initial pulse of the probe , and the second due to the backwall echo. A defect creates a third indication and simultaneously reduces the amplitude of the backwall indication. Structure Of Normal Probe The only available information for determination of the reflector position is the scale position and therefore the sound path, this means the distance of the discontinuity from the index point of the probe.
The mathematics of the right angled triangle help us to evaluate the surface distance and the depth of a reflector which are both important for ultrasonic testing. Christina Russell Dec. Did u try to use external powers for studying? They helped me a lot once. DanEdsall Jul. PandiduraiPandi Jul. Show More. Total views. You just clipped your first slide!
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Download Now Download Download to read offline. Sukesh O P Follow. Assistant Professor at Engineering colleges. MEMS- Micro electro mechanical systems. Hydraulic and Pneumatic Actuators. Intro to mechatronics. Non Destructive Testing. Related Books Free with a 30 day trial from Scribd. Related Audiobooks Free with a 30 day trial from Scribd. Elizabeth Howell. Frequencies from Mega Hertz MHz are typically used. A ripple in a pond and a wave on a string are easily visualized as transverse waves.
Or, light can bounce off the material, which is called reflection. The waves are called the incident and reflected sound waves. It is a function of the transducer diameter and wave length in the medium.
Which states that when a sound beam travels through any medium, its intensity gradually reduces due to scattering and absorption. The transmitter and receiver probes are on the same side of the specimen and the presence of a defect is indicated by the reception of an echo before that of the back wall echo.
In addition good mechanical coupling and alignment of the two probes is essential.
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