Ultrasonic Testing of Weld

Ultrasonic Testing of Weld

Ultrasonic Testing or UT of Weld is an efficient and reliable volumetric non-destructive testing method. The test method relies on sending high-frequency (in Mhz) ultrasonic waves beam in the material to detect internal flaws which are otherwise invisible to the naked eye.

Compared to Radiographic testing-RT (other volumetric NDT method), UT can pinpoint the exact depth of the flaw which is a limitation in RT.

How Ultrasonic Testing is used in Welding?

Ultrasonic testing is a valuable tool for the inspection of welds. It is a highly sensitive non-destructive (NDT) method used to evaluate the integrity of welds by examining their internal soundness without affecting their reliability.

During the Ultrasonic Testing or UT, an ultrasonic transducer (Probe) emits sound waves at high frequencies into the material being tested, creating an acoustic wave that travels through it as shown in the below animation.

Image: NDE-ED

The transducer produces pulses at a frequency above 20 kHz which travel through the material via longitudinal wave propagation until they reach an interface between two different materials or reach a defect inside the material itself.

Once it reaches this point, some of these waves are reflected back toward their point of origin creating an echo that can be measured by a receiver within the same transducer (Probe).

By measuring how long it takes for these waves to travel from one side of the material to the other and back again, technicians are able to detect any internal flaws in the weld using the UT machines.

ultrasonic-testing UT

The ultrasonic testing process has several advantages over other types of tests as it can be used on materials with different thicknesses and compositions without damaging them in any way. It also allows inspectors to examine areas that would otherwise be inaccessible.

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Read more: Types of Ultrasonic Testing Scans.

Which types of Welding Defects Ultrasonic Testing can find?

Ultrasonic testing is a powerful NDT method that can be used to detect welding defects, corrosion and internal material flaws. The primary benefit of this type of test is its ability to detect very fine and severe discontinuities in the welded materials, such as cracks, porosity, and lack of fusion.

With ultrasonic testing, it’s possible to identify different types of welding defects, even those that would otherwise go undetected by visual inspection and other non-destructive techniques.

The specific types of welding defects that can be found with ultrasonic testing include:

  1. Cracking (any type),
  2. Lack of Fusion (LOF): Root LOF, Sidewall LOF, and interbead LOF,
  3. Lack of penetration,
  4. Slag inclusion,
  5. Undercut or burn through,
  6. Oxides inclusions,
  7. Welding Porosity,
  8. Pores,
  9. Lamellar Tearing,
  10. Thickness reduction due to excessive grinding.

In addition to detecting these issues early on in the production process, ultrasonic testing can also provide valuable information on the conditions and processes used during welding operations.

This data can help manufacturers optimize their processes for improved quality control and cost efficiency. The advantage to using ultrasonic testing is that it can be used on almost any type of material including steel alloys, aluminum alloys and titanium alloys.

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This makes it an important tool for quality assurance departments who need to ensure their products have been correctly manufactured according to specifications.

Types of Welding Joints Ultrasonic Testing can be used?

There are several types of welding joints that can benefit from ultrasonic testing. This includes

  1. Groove Weld or also called Butt Weld,
  2. Complete penetration Tee-Joints,
  3. -T, -K and -Y Joints,
  4. Flare groove.

Ultrasonic testing is not possible for fillet welds due to their configuration and restriction to probe movement. Simply, any weld that can give access for reciprocating UT transducer movement along the weld, can be tested with Ultrasonic Testing.

What are the Types of Ultrasonic Testing Techniques used for Weld Testing?

There are several different types of ultrasonic testing techniques used in weld inspection, each designed to detect certain characteristics in material welds.

The common Ultrasonic Testing methods include:

  1. Pulse echo,
  2. Angle beam,
  3. Through transmission,
  4. Immersion testing,
  5. Phased array UT (called PAUT), and
  6. Time-of-Flight Diffraction (TOFD).

What are the advantages of the Ultrasonic Testing method?

Here are five benefits of ultrasonic testing:

  1. First, ultrasonic testing is quick and efficient, allowing for large areas to be tested in less time than other methods.
  2. Second, ultrasound can detect many different types of flaws that would otherwise go unnoticed with traditional methods such as corrosion or lack of fusion.
  3. Third, it does not require the use of radiation or hazardous chemicals making it safer for workers and the environment.
  4. Fourth, this method can also be used to measure thicknesses or distances between components accurately thanks to its high-resolution capabilities.
  5. Fifth, it can be used on a variety of materials either conductive or non-conductive.
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Jiten Karmakar is an NDT Specialist, holding ASNT NDT Level III and ISO 9712 NDT Level III Qualifications. He is having vast hands-on practical and theoretical experience with all major NDT Methods and technique.