Today,
we will discuss a non-destructive testing method known as ultrasonic testing but related to welds and steel. Before jumping to the
topic, let's first understand what Ultrasonic Testing means!
Ultrasonic testing, which is also referred to
as UT, is a type of non-destructive testing method. This specific technique
utilizes ultrasonic waves to pass through an object. Ultrasonic waves are of
high frequency that are made to pass through various substances to identify the
deformities present in the given object.
The
applications of ultrasonic testing can make use of frequencies up to 50 MHz.
However, various applications usually restrict these frequencies to 0.1-15 MHz. The major benefits of ultrasonic waves are that they are
typically utilized for ultrasonic testing to observe the thickness of the given
material when examining the level of corrosion in pipelines.
At
present, ultrasonic testing techniques are being implemented in different
sectors all over the globe. It is utilized to assess the integrity of the
substances. For Instance — Examine whether the welding process has been performed correctly by identifying the welded substance's flaws.
The
test is conducted on both types of materials, iron as well as non-iron based!
Also, for those substances that are not completely accessible. In addition,
because of the benefits of ultrasonic waves, ultrasonic testing has become
better at identifying delicate deformities that are not possible to detect
easily with the help of radiographic testing. Ultrasonic testing is
broadly used in various industries such as aerospace,
healthcare, automobile, construction, oil & gas, and many more.
What Is Ultrasonic Testing Of Welds?
This technique utilizes mechanical vibrations, similar to sound
waves but of much higher frequency. This testing process starts with
projecting a beam of ultrasonic energy directed into the material that has to
be examined. After this, the beam transits through the substance with an
unimportant casualty, except when the beam is thwarted and reflected back by a
deformity.
Then
the ultrasonic contact pulse reflection method is utilized as this specific
system uses a transducer that transforms electrical energy into mechanical
energy. The transducer is then pumped up by a high-frequency voltage, resulting
in a crystal vibrating mechanically. Here, the crystal probe comes to be the
only source of ultrasonic mechanical vibration.
All
these vibrations are transmitted into the test material via a coupling liquid,
a film of oil, known as coupling.
Now, when the pulse of ultrasonic waves hits a defect in the tested object, it
gets reflected back to its original point. Hence, the energy gets back to the
transducers. The transducer then acts as a receiver for the reflected energy.
The
first signal is the return of the echoes from the deformities, and the echo of
the rear surface of the object are all showcased through a trace on the cathode
ray oscilloscope screen. The
identification, position, and assessment of deformities are possible because
the velocity of sound via a given substance is virtually constant. This makes
the measurement of distance possible, and the relative magnitude of a reflected
pulse is more or less proportional to the size of the reflector.
When
it comes to ultrasonic testing, the most beneficial trait is that it has the
ability to specify the right position of the deformities in a weld. However,
this testing technique requires greater skills, training, and competence. Also,
it relies on the application and establishment of favourable testing methods.
Plus this method can also be utilized on ferrous and non-ferrous
substances. It is also suited for examining thicker parts approachable from one
side and can identify finer lines that cannot be detected using radiographic testing methods.
What Is Ultrasonic Testing Of Steel?
Now,
we will talk about the ultrasonic testing of steel; as you know, it is
a non-destructive method that generally uses extremely short ultrasonic pulse
waves with frequencies ranging between 0.1-15 MHz, even though they sometimes
turn out 50 MHz. A 1-4 Mhz frequency range is used for common metals. All these
pulse waves are then transmitted into objects that will truly identify the
internal discontinuities in various metals. They can also be utilized to
classify different types of materials.
The
sound energy produced in the object is introduced and propagates the material
in the shape of waves. If there is a discontinuity in the wave's path, then the
energy will be returned from the defective surface. From the reflected
indication, knowledge about the position, size, orientation and additional
features of the flaw can be obtained.
Advantages Of Ultrasonic Testing
Ultrasonic testing has several benefits, a few
of which are mentioned below:
- Zero or minimal preparation
of the material to be tested.
- To detect the flaws,
thickness measurement can be conducted.
- High sensitivity towards the
surface as well as subsurface deformities.
- While utilizing the
pulse-echo method, the object that has to be tested can only be accessed from
one direction.
- When compared to other
non-destructive testing techniques, ultrasonic testing possesses superior
penetration depth.
- Using digital equipment gives
quick outcomes.
- Provides higher preciseness
& accuracy in specifying the place of the deformity and evaluating its
shape & size.
Disadvantages Of Ultrasonic Testing
However,
ultrasonic testing also has the below-mentioned limitations:
- Due to a lack of sensitivity
towards linear flaws, inclined similarity to the sound beam propagation.
- There is a requirement for reference standards for equipment calibration and the classification of deformities.
- Ultrasonic testing is more
costly when compared to other methods.
- It is quite difficult to use thin substances.
- In this method, training is
very extensive compared to others.
- Requires a relatively smooth
surface to couple the transducer.
- Some complications can occur
due to part geometry.
- The velocity of the part must be
known, and a reference should be present to calibrate against equipment
establishment.
Key takeaways
The
above-mentioned information is a simplified version & introduction to the non-destructive testing method of ultrasonic testing
of weld and steel. However, to effectively conduct testing utilizing
ultrasonics, much more skill, as well as information, needs to be gained. Visit
our website regularly to read more articles about non-destructive testing
methods and if you have any queries, feel free to reach out to us anytime!