In the field of non-destructive testing, there is a pair of brother projects - industrial CT inspection and X-ray tube assembly inspection. Both of these inspection methods apply X-ray tube assemblies to explore the interior of objects. So, how are X-rays generated?
From a scientific perspective, X-rays are a stream of particles produced by the transition of electrons in an atom between two energy levels with a significant difference in energy. They are electromagnetic radiation with wavelengths between ultraviolet rays and gamma rays. Discovered by the German physicist W.K. Rontgen in 1895, it is also known as the Rontgen ray.The X-ray wavelength of Rontgen rays is very short, approximately ranging from 0.01 to 100 angths. They have a high penetrating power and can pass through many substances that are opaque to visible light, such as ink paper and wood. This invisible ray can cause many solid materials to emit visible fluorescence, sensitize photographic negatives and ionize air, among other effects. So, engineers took advantage of this characteristic of X-rays to develop various X-ray detection devices.
Since the middle of the 20th century, with the development of computer technology, the X-ray program has had a new development direction, namely the CT program. CT, or three-dimensional X-ray scanning, is a non-destructive X-ray fluoroscopy technology that rotates the object to be measured 360°. The rays passing through a single axis plane penetrate the object to be measured. According to the different absorption and transmission rates of the rays by each part of the object to be measured, Collect the penetration images from each Angle, and then apply computer operations to reconstruct the solid image of the object to be measured. From this, it can be seen that CT can display the three-dimensional structure and internal structure of objects. Compared with the two-dimensional plan of X-rays, it has made a qualitative leap. Technically speaking: CT tomography technology is a means of non-destructive testing and non-destructive evaluation of products. Industrial CT applies tomography technology, which realizes non-destructive visual measurement of products, assembly defects and material analysis. Without being blocked by the surrounding detailed features, the spatial position, shape and size information of the target features can be directly obtained.
The X-ray inspection plan can visually display the size and shape of internal defects in workpieces, thus making it easy to determine the nature of the defects. The X-ray film can be used as the original record of inspection for multiple parties to study and be kept for a long time. It has high flexibility in non-destructive testing of thin-walled workpieces. Sensitive to volumetric defects, the planar distribution of defect images is true and the size measurement is accurate. There is no strict requirement for the surface brightness of the workpiece. The grain size of the material has little influence on the detection results and can be applied to the detection of internal defects in various materials. Therefore, it is widely used in the welding quality inspection of pressure vessels.
However, the X-ray inspection method consumes expensive X-ray films and other equipment, has a long evaluation cycle for film, a slow inspection speed, low flexibility in inspecting thick-walled workpieces, is only suitable for detecting volumetric defects such as pores, slag inclusions, shrinkage cavities, and porosity, can qualitatively but not quantitatively, and is not suitable for structures with cavities. It has low sensitivity in inspecting diagonal welds and T-joints. It is not easy to detect cracks with very small gaps and defects such as incomplete fusion, as well as internal local layering defects of forgings, tubes, bars and other profiles.
In addition, the X-ray tube assembly is harmful to the human body and requires appropriate protective measures, so its limitations are also considerable.
The industrial CT program, on the other hand, has extremely obvious advantages
Firstly, the tomographic images of the objects under test obtained by industrial CT technology have high resolution. More importantly, industrial CT detection is not restricted by the geometric structure of the workpieces under test.
Secondly, industrial CT not only presents the inspected samples in two-dimensional images, but also can perform two-dimensional tomographic images of the workpieces and three-dimensional planar reconstruction. The reconstruction results can directly distinguish the internal details of the inspected objects, including: The internal composition structure, material, whether there are defects at the cross-section of the workpiece to be inspected, as well as the shape, size and location of the internal defects of the workpiece, and the internal target information of the workpiece is clear and will not be blocked by other interfering objects.
Moreover, industrial CT technology features higher spatial resolution and density resolution, has a wider range of adaptability, and can be applied to the detection of different gray levels.
Furthermore, industrial CT images are easy to recognize and understand, and the detection results are more accurate, etc
There is another obvious development direction for industrial CT. Currently, the main method for detecting and identifying defects in industrial CT slice images is still manual judgment by professionals. This identification method mainly relies on the experience of the inspectors, and the detection results are often interfered with by the objective judgment of the inspectors, resulting in less objective outcomes.
With the advent of big data, cloud computing, and especially the quantum era, many companies have begun to explore intelligent defect detection methods, eliminating the obstacles of human objective understanding on detection results, and relying on a large amount of practical data for defect identification. This not only improves efficiency but also ensures detection quality AI intelligent recognition and discrimination of sample information will become a development direction in the field of industrial CT inspection, and this is also an inevitable trend for the future development of defect detection technology.