The application of ultrasonic testing technology in non-destructive testing

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1 Principles, advantages, disadvantages, and basic classification methods of ultrasonic flaw detection
1.1 Principles of flaw detection
When utilizing ultrasonic flaw detection technology in non-destructive testing, it is necessary to first understand the basic principles of this technology and master its operational techniques. Only then can the practical value of this technology be fully realized in actual work, ensuring that the accuracy of the testing process meets the required standards. Generally speaking, ultrasonic testing relies on phenomena such as the reflection and refraction of ultrasonic waves; by examining the changes in the waveform of these sound waves when they encounter objects, it is possible to determine whether there are any internal defects. Visual instruments are used to generate graphs of the sound waves, allowing for the observation of the amplitude and frequency of the wave vibrations, as well as the calculation of the depth and length of the defects. In addition, it is necessary to utilize pulse-echo equipment, which is a core device for ensuring the efficiency and quality of inspections; thus, personnel must be capable of operating this equipment. 1.2 Advantages and Disadvantages of the Technology 1.2.1 Introduction to Advantages: Ultrasonic testing relies on ultrasonic waves for detection; it features compact detection instruments that are easy to carry. The reflection of sound waves varies in different media, and this method is often used for assessing the quality of items, offering significant directivity. It can not only determine whether there are structural defects in an object, but also identify the location and severity of those defects, estimate the object’s utility value, and provide a reference for subsequent repair work. In addition, the safety factor throughout the entire technical operation process is high. 1.2.2 Disadvantage analysis: Ultrasonic testing technology still needs further optimization; the key issue is that there are some difficulties in conducting quantitative and qualitative analysis of defects that have not yet been resolved. For example, if the surface of an item is uneven, too small, or too thin, it cannot be inspected non-destructively using ultrasonic testing methods. Furthermore, for objects with cavities, the detection accuracy needs to be further improved. 1.3 Type of technology (1) The method of reflecting ultrasonic waves is a relatively common type of ultrasonic testing; it focuses on the time and waveform of the sound waves after they penetrate an object and are reflected back to the instrument. (2) Depending on the method of coupling, flaw detection techniques can be divided into those that involve direct contact with the object, those that use liquids to submerge the object under inspection, and those that employ electromagnetic or laser methods for indirect detection. Different methods have varying degrees of applicability and specific requirements for use. In practical applications, the most suitable non-destructive testing method should be selected by conducting a comprehensive analysis of factors such as cost, convenience, and accuracy, based on the type and quantity of the objects to be tested. (3) Based on the display of the flaw detection results, during the process of pulse signal reflection, depending on the type, quantity, placement location, and usage method of the instruments, there are three categories of flaw detection techniques: Type A, Type B, and Type C. Class A applications yield good results; they carry out flaw detection by placing two points at the work surface, emitting sound waves and receiving the reflected signals. Since its overall shape during operation resembles the letter A, it is called the Class A detection method. (4) In today’s era of rapid development in science, technology, and information technology, intelligent flaw detection methods have emerged within ultrasonic testing techniques. This requires professionals to possess the operational skills for these technologies and to engage in innovative research work. 2 Basic principles for applying ultrasonic testing technology in non-destructive testing 2.1 It is necessary to standardize the work process. Ultrasonic testing technology features high detection efficiency and a wide range of application, offering significant practical value and good prospects for further development. However, when using this technology in practice, it is essential to ensure that the staff have practical experience and an understanding of the principles behind it. Each step must be carried out in accordance with the established procedures, and care must be taken during operation to carefully identify any issues; these factors are crucial for ensuring the accuracy of detection, and the staff are required to pay close attention to them. Since the human ear cannot directly receive ultrasonic signals, it is also necessary to ensure that the infrastructure is adequate and to conduct preliminary trials of the equipment, in order to provide a solid foundation for the safe and stable operation of the detection system. 2.2 The principle of adaptability must be followed. Given the wide range of areas that require inspection, as well as the different materials and sizes of the items to be inspected, and the fact that some items have complex structures, it is necessary to use ultrasonic inspection technology to carry out inspections without compromising the functional performance of those items; therefore, the principle of adaptability must be adhered to. A comparative analysis can be conducted based on the common types and characteristics of flaw detection techniques, allowing for the selection of the appropriate method; this is also a key prerequisite for reducing the difficulty of inspection work. 2.3 The object under inspection must not be damaged. When using ultrasonic testing techniques, it is necessary to comply with the regulations for non-destructive testing, so as to avoid causing irreversible damage to the object. Given the characteristics of ultrasonic waves, many materials absorb sound waves; this is one of the key issues that technicians should take into account when optimizing detection methods to improve detection efficiency. Relevant work requirements should be integrated into the management system to ensure strict and comprehensive oversight of employees’ technical skills and equipment operation practices. 3 Key Aspects of the Practical Application of Ultrasonic Testing Technology in the Non-Destructive Inspection of Tracks and Vehicles 3.1 Rail Inspection Rail transportation is one of the most commonly used modes of travel in people’s daily lives, and trains as well as high-speed trains are all types of rail vehicles that operate along pre-built tracks following predetermined routes. To reduce the maintenance costs of tracks and improve their durability, construction workers choose to use steel when carrying out track construction work. To prevent quality issues such as cracks and crushing in the rails during use, which could pose safety risks, it is necessary to carry out flaw detection without moving the rails or damaging their structural integrity. Taking the use of ultrasonic flaw detection technology as an example, it is necessary to bring the device’s probe into contact with the surface of the rail in order to transmit sound wave signals into the rail. Generally, when a signal encounters a location with internal defects, it gets reflected ； If there are no defects, the signal will pass straight through the rail without any reflection. Based on this, the operator only needs to record the locations where reflective signals appear on the working surface; the distance between internal defects and the detection surface can then be calculated based on the time of reflection. 3.2 Wheel Inspection Wheels are essential components for the stable and safe operation of vehicles. Moreover, as they are in constant contact with the ground, they wear out frequently. Therefore, when performing maintenance and repairs on vehicles, technicians need to pay special attention to inspecting the wheels for any defects. To ensure that the wheel can continue to be used after the inspection task is completed, non-destructive testing methods should be employed. Note that the rim and tire should be inspected separately. Taking the rim as an example, the main thing is to check whether there are any cracks on this component. Generally, simulation tests are required, involving drilling and grooving on a prototype wheel to simulate defect issues and study solutions. Furthermore, the probe of the ultrasonic inspection device should be placed at the edge of the wheel, and an appropriate type of ultrasonic testing technique should be selected to detect various types of rim defects. For example, when performing phase compensation on acoustic wave signals, a phased array is required; this can be done using two methods: longitudinal wave detection and transverse wave detection. Regarding circumferential and radial defects, it is not appropriate to use shear wave detection methods, and it is necessary to determine the placement position of the probe. For axial defects, one can flexibly choose to use longitudinal or transverse waves for detection based on the actual circumstances; the key is to properly record the parameter information obtained during the detection process. 4 Key Points of the Practical Application of Ultrasonic Testing Technology in Non-Destructive Testing in the Construction Industry 4.1 Structural Strength After the construction of a building is completed, a comprehensive non-destructive testing should be carried out to determine whether the quality of the building meets the required standards and to identify any potential safety hazards. At the same time, during the regular daily use of buildings, non-destructive testing should also be carried out periodically to enable the early detection of safety risks in the buildings, allowing for timely implementation of effective measures to address those issues. Taking concrete structures as an example, during building construction, concrete is often used as the primary material for constructing walls, beams, and columns. During the inspection phase, the overall strength grade of the concrete structure should be tested in accordance with the building’s usage requirements. Ordinary workers are more concerned about the compressive strength of concrete. Based on work experience, it can be seen that when ultrasonic waves penetrate concrete, the elastic modulus of the concrete directly affects the speed at which these sound waves propagate. Generally, the smaller the modulus, the slower the transmission speed; there is a direct proportional relationship between them. A mathematical model can be established to visually observe the changes in sound waves. Furthermore, to ensure that the coupling effect meets the requirements of non-destructive testing, the surface of the concrete structure should be cleaned first to maintain a smooth working surface. It is also possible to use a coupling agent to prevent the inspection results from being affected by other factors, thereby improving the accuracy of the structural strength assessment. 4.2 Structural Thickness: The construction of building projects involves not only strict control over the quality of use of the building structure, but also scientific management of the structural thickness in accordance with the requirements specified in the design plans. Ultrasonic testing technology can also be used in thickness inspection. Based on the principles of this technology, the simplest method is to accurately determine the thickness of the structure by examining the reflection of sound waves. Normally, when sound waves pass from one solid into another, the waveform of the sound waves undergoes various changes. In practice, due consideration must be given to the variations in acoustic impedance data. A common practice is to install two probes at different locations on the same working surface of the building structure. The sound wave signals emitted by one probe are sent to the other probe through refraction, reflection, and other mechanisms. By applying the principles of trigonometry, along with the distance between the two probes as well as the length and angle of sound wave refraction, it is possible to calculate the vertical height. This allows for an accurate determination of the structure’s thickness. By comparing the actual values with the design specifications, construction errors can be identified. 4.3 Welding seams In the construction of building structures, many metal materials are used. Depending on the structural characteristics of the building frame, processes such as cutting and welding of these materials are also involved. Therefore, the connection condition of each weld point is a key issue that construction workers need to pay attention to in quality management. In the new era, the application of ultrasonic flaw detection technology enables effective detection of welding seams. First, staff need to understand the common types and characteristics of welding quality issues. Secondly, an appropriate choice of ultrasound technology is necessary. For example, pulse-echo methods can be used to detect whether there are gaps at the weld points, while phased arrays combined with imaging techniques can be employed to identify defects in the welded areas. Especially in the installation of underground pipelines, this method can be used to thoroughly check for cracks, leaks, and other issues in the pipelines, and it is necessary to conduct a proper analysis of the imaging results. After completing the inspection task, it is possible to estimate the service life of the materials, providing reference data for timely replacement with new materials and ensuring that the structural integrity of building frameworks and underground pipelines can be fully maintained. 5 Key Points of the Practical Application of Ultrasonic Testing Technology in Non-Destructive Testing in Other Fields 5.1 Inspection of Composite Materials In material production, companies manufacture composite materials based on the market’s demand for various types of materials. Taking composite bars as an example, during non-destructive testing in the production process, electromagnetic ultrasonic testing is a technique that is used quite frequently. Compared to pulse-echo methods, this technique relies on the principle of electromagnetic induction to divide the material’s surface and interior into different areas, thereby enabling defect detection in each of those areas. The serpentine coil can be used to control the winding direction and current direction at both ends. In practice, upon detecting defects, the generated electromagnetic waves must be scanned; the specific characteristics of the defects can then be visually analyzed through graphical representations, enabling a systematic approach to defect repair. 5.2 Inspection of high-temperature equipment: Electromagnetic ultrasonic testing technology can be used for high-temperature inspections, and it also yields good results when inspecting certain high-temperature pressure pipelines. Therefore, in many applications related to the storage and transportation of new energy sources, this testing technique can be used to address issues related to the quality of equipment containers. Its advantage is that it does not require direct contact with the equipment, and it does not impose high demands on the surface smoothness of the objects being tested. However, electricity is required for operation, so the issue of conversion efficiency should be given careful consideration. 6 Conclusion The common ultrasonic testing methods primarily involve using pulse-echo devices to emit sound waves into an object, and completing the testing process based on the refraction and reflection of these sound waves; electromagnetic ultrasonic testing technology can also be employed. When conducting inspections of the quality of rails and wheels, as well as the strength, thickness, and welding seams of building structures, as well as inspections of composite materials and high-temperature equipment, it is necessary to ensure the integrity of the infrastructure, determine scientifically the placement of the inspection probes, and properly clean the work area. In most cases, the proper use of coupling agents is an effective way to improve detection performance. Pay attention to enhancing talents’ innovation awareness and professional skills, to ensure that they can use equipment and technologies flexibly in order to achieve the objectives of non-destructive testing.