Overview of Non destructive Testing Technology in the Industry 4.0 Era

2024-01-18

The world-renowned quality management expert Zhu Lan once said, if the 20th century is the century of productivity, then the 21st century is the century of quality.

With the improvement of modern socio-economic level, the concept and awareness of quality have gradually penetrated into people's hearts. In addition, with the progress of modern science and technology and the development of industry, the industrial equipment used has become increasingly sophisticated and complex, and equipment testing has become particularly important.

Traditional testing methods require dismantling equipment components before testing, but with the increasing emphasis on miniaturization in equipment production, dismantling equipment has become a challenge, and non-destructive testing has developed in this context.

Non destructive testing technology (NDT) refers to a method of inspection and testing that utilizes modern technologies such as radiation, ultrasound, infrared, electromagnetic, etc., combined with instruments, to analyze the changes in thermal, acoustic, optical, electrical, magnetic, and other reactions of materials, parts, and equipment without damaging or affecting the performance and internal organization of the tested object.

In 1978, China established the Non destructive Testing Branch of the Chinese Society of Mechanical Engineering, which is a national academic organization for non-destructive testing. Non destructive testing technology to a certain extent reflects the level of industrial development in a country and is an indispensable and effective tool for industrial development. Its importance has been recognized.

The development of non-destructive testing technology has become relatively mature. The main testing methods include ultrasonic testing (UT), radiographic testing (RT), penetration testing (PT), and magnetic particle testing (MT). Other testing methods include eddy current testing (ECT), infrared thermal imaging (TIR), etc.

Ultrasonic Testing Technology (UT)

Ultrasonic testing technology is a sound wave method that utilizes ultrasonic energy to detect defects in materials or equipment. A general ultrasonic testing system consists of an ultrasonic testing instrument and a probe. A coupling agent is used to polish the metal surface in contact with the probe to form a smooth and clean surface. After that, ultrasonic waves are emitted into the tested metal, and then the echo reflected back from the defect is received and analyzed.

Ultrasonic testing technology is widely used for non-destructive testing of metals, non-metals, and composite materials, as well as for internal defect detection of equipment with larger thicknesses. However, it is not suitable for detecting equipment with complex or irregular shapes.

Radiographic Testing Technology (RT)

Radiographic testing technology is a widely used non-destructive testing method, with commonly used types of X-rays and γ There are two types of rays, which have extremely strong penetrating power and can penetrate materials that cannot be penetrated by the naked eye, making the other side of the film photosensitive. Further analyze the information on the film to determine the defect.

There are many advantages of X-ray detection technology, such as high precision in locating defects and intuitive recording of detection results. In practical applications, the technology is suitable for all materials, with high universality. The defect images measured are intuitive and easy to save. Once launched, it has been welcomed by various industries.

The application of X-ray testing technology is very extensive. In the industrial field, it can detect bubbles and cracks in castings and welds, and in the aerospace field, it can detect the quality of precision castings. The common X-ray non-destructive testing technology in daily life is X-ray testing in hospitals.

Penetration Testing Technology (PT)

Penetration testing technology, also known as fluorescence penetration testing, is a type of liquid penetration testing. It consists of four steps: cleaning, applying penetrant, imaging observation (using ultraviolet light), and removing surface developer. It can be applied to the detection of various materials such as metal, non-metal, magnetic, and non-magnetic, with high sensitivity, intuitive display, and easy operation. It can detect the morphology and distribution status of material defects. But it can only detect the surface distribution of defects, and cannot determine their actual depth and make quantitative evaluations of defects.

Nowadays, penetration testing technology has become an indispensable testing method in the maintenance field. It is an important technical method for rating the quality of engineering materials and components, as well as an important means to improve production efficiency and improve processes.

Magnetic Particle Testing Technology (MT)

The basic principle of magnetic particle testing technology is to place magnetic materials such as iron, cobalt, nickel, etc. in a strong magnetic field. After they are magnetized, due to the presence of surface and near surface discontinuities of the magnetic materials, magnetic particles will form visible magnetic marks, mainly divided into five steps: pretreatment, magnetization, application of magnetic powder, inspection, and post-processing.

Magnetic particle testing technology can only be used for defect detection on the surface and near surface of magnetic materials. It can detect non visual discontinuities and display the location, shape, and size of the discontinuities. Its disadvantages are high requirements for the surface smoothness of the tested material and the technical skills of the testing personnel, slow detection speed, and small range.

Eddy current testing technology (ECT)

Speaking of eddy current testing technology, let's first understand what eddy current is. When a coil with alternating current is placed outside the tested metal plate, an alternating magnetic field will be generated near and inside the coil. At this time, a vortex shaped alternating induced current will be generated in the tested part, which is called eddy current.

Eddy current testing technology is a technique that uses the principle of electromagnetic induction to measure the performance of various metal materials and a small amount of non-metallic materials such as graphite and carbon fiber composite materials by detecting the eddy current variation inside the specimen. During detection, the coil does not need to be in contact with the object being tested and can be used for detection. Compared with other detection technologies, it is easier to achieve automation, but it is not suitable for detecting complex shaped objects and most non-metallic materials.

With the development of computer technology, microelectronics, and various signal processing technologies, turbine detection technology is also constantly evolving and updating, and is applied in various high-end fields such as aviation and aerospace.

Infrared thermal imaging detection technology (TIR)

Infrared thermal imaging technology is an emerging detection technology that has gradually been widely used in recent years. Like ECT mentioned earlier, it is a non-contact detection technology that is currently widely used in fields such as aerospace, biomedical, and mechanical engineering.

The process of heat transfer from the higher temperature part of an object to the lower temperature part, or from a higher temperature object to a lower temperature object, is called heat conduction; Research has shown that any object above absolute zero will continuously emit electromagnetic waves to the outside world, which is electromagnetic radiation. The infrared imaging detection technology based on heat conduction theory and electromagnetic radiation can analyze the internal energy flow of objects and judge the defects of objects through the detection results of infrared imaging.

The development of non-destructive testing technology has become an important method for quality control and assurance in national economic production with its solid theoretical foundation and exquisite skills, playing a huge role in various industries. With the development of modern computer technology, digital processing technology, and real-time imaging technology, the application of non-destructive testing technology is becoming increasingly widespread. In the future, non-destructive testing technology will continue to move towards digitization, real-time, and large-scale trends.

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