Ultrasonic testing (UT) is a widely used non-destructive testing technique that utilizes high-frequency sound waves to detect and evaluate flaws or characteristics of materials. The success of UT largely depends on the type and quality of probes used. There are five common types of probes that are frequently used in ultrasonic testing:
1. Contact Probes
Contact probes, also known as straight beam probes, are the most basic and commonly used probes in UT. These probes consist of a single crystal element that emits and receives ultrasound waves. They are typically used for flaw detection and thickness measurement in various industrial applications. Contact probes provide reliable and accurate results but require direct contact with the test material.
2. Angle Probes
Angle probes, also called angle beam probes, are designed for inspecting welds and other structures where access is limited. These probes have a higher incident angle than contact probes, allowing them to introduce sound waves into the test material at an angle. The sound waves will then reflect back and show indications of flaws or discontinuities. Angle probes are well-suited for detecting cracks, delaminations, and other defects.
3. Immersion Probes
Immersion probes are primarily used when testing large and/or irregularly shaped objects, such as turbine blades or composite structures. These probes consist of a transducer embedded in a water bath or couplant-filled tank. The water or couplant transfers the sound waves from the transducer to the object being tested, ensuring optimal coupling. Immersion probes offer excellent signal-to-noise ratio and produce high-resolution images.
4. Phased Array Probes
Phased array probes are advanced and versatile instruments that utilize multiple elements and electronic steering to create a beam of ultrasound with adjustable angles. By changing the timing and amplitude of each element, the probe can generate different beam angles and focal points. This capability allows for rapid scanning of large areas and improved flaw detection. Phased array probes are widely used in industries like aerospace, oil and gas, and manufacturing.
5. Time-of-Flight Diffraction (TOFD) Probes
TOFD probes employ two angled elements on either side of a central element to detect diffraction signals produced by discontinuities within a material. These probes are highly sensitive to small cracks and provide accurate height measurements of flaws. TOFD is commonly used for weld inspection, particularly in thick materials where other techniques may be insufficient.
In conclusion, the choice of probe in ultrasonic testing depends on the specific application and requirements. Contact probes, angle probes, immersion probes, phased array probes, and TOFD probes are all valuable tools in identifying defects, determining characteristics, and ensuring the integrity of various materials.
Nina She