What is pulse in ultrasonic testing?
A pulse echo is an A-scan presentation broadly used for thickness measurement and sizing the defect in an ultrasonic inspection involving identifying the indication echoes when the signal is reflected from a discontinuity in a test material structure.
What is the first step in ultrasonic testing?
Step 1: The UT probe is placed on the root of the blades to be inspected with the help of a special borescope tool (video probe). Step 2: Instrument settings are input. Step 3: The probe is scanned over the blade root.
What are the two basic methods of ultrasonic inspection?
Ultrasonic testing can be performed using two basic methods – pulse-echo and through-transmission.
How pulse echo method of ultrasonic testing is performed?
In the pulse-echo ultrasonic technique, an ultrasound wave is excited and detected by two identical piezoelectric transducers (transmitter and receiver), which are glued to polished opposite sides of a sample.
What are the 3 basic ultrasonic inspection methods?
There are three main types of ultrasonic testing methods:Through transmission. Through transmission employs two transducers, each placed on opposite sides of the material being tested. ... Pulse echo. Pulse echo is more sensitive than through transmission. ... Resonance.
What is sensitivity in UT?
Sensitivity and resolution are two terms that are often used in ultrasonic inspection to describe a technique's ability to locate flaws. Sensitivity is the ability to locate small discontinuities. Sensitivity generally increases with higher frequency (shorter wavelengths).
What is the minimum thickness for ultrasonic testing?
ISO 13588:2012 specifies the application of the phased array technology for the semi- or fully automated ultrasonic testing of fusion-welded joints in metallic materials of minimum thickness 6 mm.
What is the maximum thickness for ultrasonic testing?
Conventional ultrasonic testing (according to BS EN ISO 17640) (1) limits thicknesses that can be examined to less than 8mm. Similarly, the draft phased array standard BS EN 13588 (2) goes down to 6mm.
What is range in ultrasonic testing?
Most ultrasonic testing is available within 400 kHz to 25 MHz. These vibrations are beyond the audible range and propagate in the test material as waves of particle vibrations. Sound beams of all frequencies can penetrate fine-grained material without difficulty.
What is pulse-echo principle?
The second key principle is the pulse-echo principle, which explains how the image is generated. 5. Ultrasound waves are produced in pulses, not continuously, because the same crystals are used to generate and receive sound waves, and they cannot do both at the same time.
What is the principle of pulse-echo testing?
The principle of the pulse-echo method is shown in Figure 1. The transmitter (T) generates an ultrasonic pulsed wave which is reflected by an inhomogeneity like a defect or the back wall of the specimen, and obtained by the receiver (R). The received signal is displayed on a screen, see Figure 2.
What is pitch catch mode?
Pitch-Catch Mode: Two sensors configuration – one sensor transmits, while the other receives the ultrasonic signal. Defects along the material will cause time-of-flight (TOF) shifts and decrease in amplitude.
What is ultrasonic method?
Ultrasonic methods of NDT use beams of mechanical waves (vibrations) of short wavelength and high-frequency, transmitted from a small probe and detected by the same or other probes. Such mechanical waves can travel large distances in fine-grain metal, in the form of a divergent wave with progressive attenuation.
Where is ultrasonic testing used?
In industrial applications, ultrasonic testing is widely used on metals, plastics, composites, and ceramics. The only common engineering materials that are not suitable for ultrasonic testing with conventional equipment are wood and paper products.
What are the steps followed when conducting magnetic particle inspection?
Magnetic Particle Inspection is performed in four steps..Induce a magnetic field in the specimen.Apply magnetic particles to the specimen's surface.View the surface, looking for particle groupings that are caused by defects.Demagnetize and clean the specimen.
What is ultrasonic inspection in aircraft?
Ultrasonic Testing in Aircraft Applications Ultrasonic testing uses pulses of high-frequency sound energy to detect surface and subsurface cracks and other defects. These pulses come from a transducer or probe, which a technician manually moves over the surface of the component under inspection.
How to perform ultrasonic testing?
Ultrasonic testing can be performed using two basic methods – pulse-echo and through-transmission. With pulse echo testing, the same transducer emits and receives the sound wave energy. This method uses echo signals at an interface, such as the back of the object or an imperfection, to reflect the waves back to the probe.
How does ultrasonic testing work?
What is Ultrasonic Testing and How Does it Work? Ultrasonic testing (UT) comprises a range of non-destructive testing (NDT) techniques that send ultrasonic waves through an object or material. These high frequency sound waves are transmitted into materials to characterise the material or for flaw detecting.
What are the advantages of ultrasonic testing?
The advantages of ultrasonic testing include: 1 High penetration power, allowing for flaw detection deep within a part 2 High sensitivity, allowing for the detection of very small flaws 3 Can be used to test when only one side of an object is accessible 4 Greater accuracy, when compared to other non-destructive testing methods, for determining depth of internal flaws and the thickness of parts with parallel surfaces 5 Able to estimate size, shape, orientation and nature of defects 6 Able to estimate alloy structures of components with differing acoustic properties 7 Non-hazardous to nearby personnel, equipment or materials 8 Highly automated and portable operations possible 9 Immediate results can be obtained, allowing for immediate decisions to be made
What is immersion ultrasonic?
Immersion ultrasonic testing is a laboratory-based or factory-based non-destructive test that is best suited to curved components, complex geometries and for ultrasonic technique development. In this method, the component or material is submerged in a water, which acts as a couplant in place of the gels used for contact ultrasound.
What is ultrasonic inspection?
Periodic ultrasonic inspections can also be used to check for corrosion or for growth of known flaws, and thus potentially prevent to a failure of a part, component or entire asset. It is used in a wide range of industries including aerospace, automotive, construction, medical, metallurgy, and manufacturing.
Why is ultrasonic imaging used?
Ultrasonic technology has been successfully employed in the medical sector for many decades, and is increasingly the preferred option for both routine diagnostic imaging and medical research because of the absence of ionising radiation.
How does pulse echo work?
With pulse echo testing, the same transducer emits and receives the sound wave energy. This method uses echo signals at an interface , such as the back of the object or an imperfection, to reflect the waves back to the probe. Results are shown as a line plot, with an amplitude on the y-axis representing the reflection’s intensity and distance or time on the x-axis, showing the depth of the signal through the material.
What is ultrasonic testing?
Ultrasonic testing is a broad group of NDT techniques based on the propagation of ultrasonic waves in the object or material tested.
How are defects detected in ultrasonic waves?
Defects are detected if they produce a change in the acoustic impedance in the path of the ultrasonic beam. An open crack filled with air has very low acoustic impedance so it reflects virtually all the acoustic energy incident on it. Hence, the sound waves travel through the material and are reflected back from cracks or flaws. ...
How to test for UT?
The basic method of ultrasonic testing is transforming a voltage pulse to an ultrasonic pulse using a transducer. Transducers used for traditional UT consist of a piezoelectric crystal enclosed within a plastic or stainless steel housing. The piezoelectric crystals expand when electrically charged, thus generating an acoustic wave. The signal travels through the object with respect to its geometry and existing defects and then is either transmitted to another transducer or reflected back to the original transducer. Defects are detected if they produce a change in the acoustic impedance in the path of the ultrasonic beam. An open crack filled with air has very low acoustic impedance so it reflects virtually all the acoustic energy incident on it. Hence, the sound waves travel through the material and are reflected back from cracks or flaws. Defects and flaws affect its way and a small portion of the pulse will be sent back to the transducer/receiver before it hits the end of the object.
What is the purpose of reflected sound energy?
Since the speed of sound in the parent material is known, the reflected sound energy is then displayed versus time and analyzed to define the presence and location of flaws or discontinuities.
What is Ultrasonic Testing?
As I discussed earlier, To evaluate or examine an object through the high-frequency waves, Known as Ultrasonic Testing.
Principle of Ultrasonic Testing–
As you know, UT uses high-frequency sound waves to conduct or evaluate the test piece.
How Ultrasonic Testing Works?–
A transducer converts electrical waves into high-frequency sound waves, which propagated inside the test object.
Methods of Ultrasonic Testing–
This method is most commonly utilized in the ultrasonic testing of materials. 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.
What is the Ultrasonic Wave?–
Sound waves are vibrations of particles of gases, solids, or liquids. The audible sound range of frequencies is usually taken from 20Hz to 20KHz. Sound waves with frequencies higher than 20KHz are known as Ultrasonic Waves.
Why Ultrasonic Testing is used?
Ultrasonic testing is the most convenient and easy to navigate testing in the methods of Non-destructive testing.
What Materials can be tested from Ultrasonic Testing?–
There are several materials, which can be tested by UT. The category of materials is given below-
What are the advantages of ultrasonic testing?
Advantages of Ultrasonic Testing 1 High penetrating power, which allows the detection of flaws deep in the part. 2 High sensitivity, permitting the detection of extremely small flaws. 3 In many cases only one surface needs to be accessible. 4 Greater accuracy than other nondestructive methods in determining the depth of internal flaws and the thickness of parts with parallel surfaces. 5 Some capability of estimating the size, orientation, shape and nature of defects. 6 Some capability of estimating the structure of alloys of components with different acoustic properties 7 Non hazardous to operations or to nearby personnel and has no effect on equipment and materials in the vicinity. 8 Capable of portable or highly automated operation. 9 Results are immediate. Hence on the spot decisions can be made.
What is ultrasonic thickness measurement?
A common example is ultrasonic thickness measurement, which tests the thickness of the test object, for example, to monitor pipework corrosion. Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution.
How is an ultrasonic transducer separated from an object?
The transducer is typically separated from the test object by a couplant (such as oil) or by water, as in immersion testing. However, when ultrasonic testing is conducted with an Electromagnetic Acoustic Transducer (EMAT) the use of couplant is not required.
What is reflection ultrasound?
In reflection (or pulse-echo) mode, the transducer performs both the sending and the receiving of the pulsed waves as the “sound” is reflected back to the device. Reflected ultrasound comes from an interface, such as the back wall of the object or from an imperfection within the object.
What frequency is UT?
In most common UT applications, very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz, and occasionally up to 50 MHz, are transmitted into materials to detect internal flaws or to characterize materials.
How does a probe work?
As shown in below figure (left) : A probe sends a sound wave into a test material. There are two indications, one from the initial pulse of the probe, and the second due to the back wall echo.
How Does It Work?
Pulse-Echo and through-transmission
- Ultrasonic testing can be performed using two basic methods – pulse-echo and through-transmission. With pulse echo testing, the same transducer emits and receives the sound wave energy. This method uses echo signals at an interface, such as the back of the object or an imperfection, to reflect the waves back to the probe. Results are shown as a lin...
Contact and Immersion Testing
- Ultrasonic testing can also be split into two main types: contact or immersion testing. Contact ultrasonic testingis typically used for on-site inspections accessibility or portability. Contact ultrasonic inspection can be performed where only one side of a test specimen as reachable, or where the parts to be tested are large, irregular in shape or difficult to transport. Immersion ultra…
Why Is It used?
- As a non-destructive testing method, ultrasonic testing is ideal for detecting flaws and defects without damaging the object or material being tested. Periodic ultrasonic inspections can also be used to check for corrosion or for growth of known flaws, and thus potentially prevent to a failure of a part, component or entire asset. It is used in a wide range of industries including aerospace…
What Materials Can Be Tested?
- Ultrasonic testing is used in a wide range of industries due to its suitability for many different materials. UT is ideally used for inspection of dense, crystalline structures such as metals. Ceramics, plastics, composites and concrete can also be successfully inspected but with reduced resolution, since the attenuation in these materials is higher. Ultrasonic technology has been su…
Advantages
- The advantages of ultrasonic testing include: 1. High penetration power, allowing for flaw detection deep within a part 2. High sensitivity, allowing for the detection of very small flaws 3. Can be used to test when only one side of an object is accessible 4. Greater accuracy, when compared to other non-destructive testing methods, for determining depth of internal flaws and …
Limitations
- There are, however, a few limitations to ultrasonic testing, as follows: 1. Requires experienced technicians for inspection and for data interpretation 2. False positive results, also known as spurious signals, may result from tolerable anomalies as well as the component geometry itself 3. Objects that are rough, irregularly shaped, very small or thin, or not homogeneous are difficult to …
Applications
- Ultrasonic testing has a variety of applications across industry, including testing the integrity of a material or component. This can include testing of welds to determine if there are any discontinuities present. This testing can be performed on both ferrous and non-ferrous materials as well as for thicker sections and those that are reachable from one side only. UT is also capab…
Twi Services and Courses
- TWI provides a number of ultrasonic testing services to our Industrial Members as well as a range of non-destructive testing training coursesfor those wishing to learn about the techniques involved. We can provide a full range of testing services and expertise, including in methods such as phased array ultrasonic testing (PAUT), laser ultrasonic testing and manual ultrasonic testing.