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Ultrasonic Testing

Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. To illustrate the general inspection principle, a typical pulse/echo inspection configuration as illustrated below will be used.

A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.

Ultrasonic Inspection is a very useful and versatile NDT method. Some of the advantages of ultrasonic inspection that are often cited include:

  • It is sensitive to both surface and subsurface discontinuities.
  • The depth of penetration for flaw detection or measurement is superior to other NDT methods.
  • Only single-sided access is needed when the pulse-echo technique is used.
  • It is highly accurate in determining reflector position and estimating size and shape.
  • Electronic equipment provides instantaneous results.
  • Detailed images can be produced with automated systems.
  • It has other uses, such as thickness measurement, in addition to flaw detection.
APPLICATION OF ULTRASONIC EXAMINATION
  • Ultrasonic inspection is used for quality control and materials inspection in all major industries.
  • Ultrasonic inspection is used for finding flaws in production of metallic and composite materials.
  • It is used in fabrication of structures such as airframes, piping and pressure vessels, ships, motor vehicles, machinery, jet engines and submarines.
  • In-service ultrasonic inspection for preventive maintenance is used for detecting the impending failure of rails, rolling-stock axils, mill rolls, mining equipment and nuclear systems.
  • Also used for thickness measurement in refinery and chemical pressure
  • Thickness gauging is an example application where instruments have been refined make data collection easier and better.
  • Many ultrasonic flaw detectors have a trigonometric function that allows for fast and accurate location determination of flaws.
  • Inspection of large weldments, castings and forging, for internal soundness, before carrying out expensive machining operations.
  • Inspection of moving strip or plate (for laminations) as regards its thickness.
  • Routine inspection of locomotive axles and wheel pins for fatigue cracks.
  • Inspection of rails for bolt-hole breaks without dismantling rail-end assemblies.
Weld Inspection:

By using Angle Beam Probes we can scan weld. Angle Beam Transducers and wedges are typically used to introduce a refracted shear wave into the test material. An angled sound path allows the sound beam to come in from the side, thereby improving detectability of flaws in and around welded areas.

Angle Beam Transducers and wedges are typically used to introduce a refracted shear wave into the test material. The geometry of the sample below allows the sound beam to be reflected from the back wall to improve detectability of flaws in and around welded areas.

Lamination Checking:

Ultrasonic Testing of rolled sections of plates, pipes are carried out for primary manufacturing defects i.e. lamination check, inclusion, cracks etc.

Laminations in rolled plate or strip are formed when blowholes or internal fissures are not welded tight during rolling, but are enlarged and flattened into sometimes quite large areas of horizontal discontinuities. Laminations may be detected by magnetic particle testing on the cut edges of plate, but do not give indications on plate or strip surfaces, since these discontinuities are internal and lie in a plane parallel to the surface. Ultrasonic mapping techniques are used to define them. When inspecting parts fabricated from sheet or plate, laminations can be detected by noting a reduction in the distance between back reflection multiples.

Ultrasonic thickness measurement (UTM):

Confirmation of component thickness can assist in the determination of life expectancy of any part. Ultrasonic Thickness Gages accurately measure wall thickness and corrosion of all metals, including steel and aluminum, plastic, ceramics and others.

Thickness gauging is a method of performing non-destructive measurement (gauging) of the local thickness of a solid element (typically made of metal, if using ultrasound testing for industrial purposes) basing on the time taken by the ultrasound wave to return to the surface. This type of measurement is typically performed with an ultrasonic thickness gauge.

Advantages

  • Does not require access to both sides of the sample
  • Can be engineered to cope with coatings, linings, etc
  • Good accuracy (0.1 mm and less) can be achieved using standard timing techniques
  • Can be easily deployed, does not require laboratory conditions
  • Digital UTM gives directly Thickness on display.

Multi-Mode thickness gauge Machines that has the ability to measure through painted or coated surfaces and eliminate the thickness of the paint using a dual element style transducer in echo-echo mode.