In modern industrial production, the safety of materials and structures is crucial. To ensure that equipment and components will not break or fail due to internal defects during use, non-destructive testing technology has emerged. Among them, ultrasonic testing (Ultrasonic Testing, UT) as an efficient and precise non-destructive testing method, is widely used in many fields such as metal materials, welded structures, aerospace, and railway transportation.



The basic principle of ultrasonic testing is to use high-frequency sound waves (usually 0.5-25 MHz) to penetrate the object being tested and to judge whether there are defects inside the material by receiving and analyzing the reflected sound wave signals. When ultrasonic waves encounter cracks, voids, inclusions, incomplete welding, and other defects inside the material, the sound waves will reflect or scatter at the surface of the defects, forming abnormal echoes. These echoes are received by the probe and, after processing and display by the instrument, the technicians can judge the location, size, and shape of the defects.



The process of ultrasonic testing usually includes the following steps: first, select the appropriate probe and frequency. The selection of probe type (such as straight probe, oblique probe) and frequency depends on the thickness of the material being inspected, the surface condition, and the type of defect. Second, during the detection process, coupling agents (such as glycerin, water, or special coupling agents) are often used to reduce air gaps and ensure that ultrasonic waves can effectively penetrate into the interior of the test piece. Then, ultrasonic waves are emitted from the probe into the material, and when they encounter defects or the bottom surface, they produce reflected signals, which are then received again by the probe. Finally, the signals are analyzed through an oscilloscope or other display devices (such as A-mode display, B-mode display, etc.).



Ultrasonic testing has many advantages. Firstly, it has a high sensitivity to internal defects and can detect minute cracks and inclusions. Secondly, it is applicable to various materials such as metals, plastics, and composite materials. In addition, this method is harmless to the human body and has a large detection depth, suitable for the testing of thick-walled components. However, ultrasonic testing also has certain limitations, such as requiring operators to have professional knowledge and experience; for surfaces that are rough or complex in shape, it may affect the detection effect.



In summary, ultrasonic testing, as a mature non-destructive testing method, plays an irreplaceable role in modern industry. With the advancement of technology, ultrasonic testing technology is also constantly evolving, with the emergence of new technologies such as phased array ultrasonic testing and TOFD (time-of-flight diffraction), which further improve the accuracy and efficiency of defect detection. In the future, ultrasonic testing will play an even more important role in ensuring industrial safety and improving product quality.