NDT related knowledge: what is industrial CT?

Date：2021-09-14 17:39:03Views：1539

Industrial CT, industrial computed tomography, It is known as the "best nondestructive testing method". Using industrial CT, the internal structure of the object can be detected non-contact and non-destructive, and the data and images without overlap can be obtained. It can not only accurately give the three-dimensional position data of the internal details of the object, but also quantitatively give the detailed radiation density data. It can quickly, accurately and intuitively find the internal defects of the product (defect type, location, size, etc.), such as cracks, pores, porosity, inclusions and other defects, and analyze them to find the root cause of defects, so as to improve product performance and prolong product service life. For this reason, industrial CT has become a versatile and comprehensive expert. It plays an irreplaceable role in defect detection such as pores and cracks in precision workpieces, welding quality diagnosis, internal structure and assembly condition detection, and provides an ideal data source for high-end equipment manufacturing and industrial nondestructive testing.

Main technical features of industrial CT:

1. Industrial CT gives the tomography image of the specimen. From the image, we can intuitively see the spatial position, shape and size of the details of the detection target. The target is not blocked by the surrounding detailed features, and the image is easy to identify and understand.

2. Industrial CT has outstanding density resolution. High quality CT images can reach 0.1% or even smaller, which is one order of magnitude higher than conventional ray technology.

3. Industrial CT adopts high-performance detector, with a dynamic range of more than 10000. The dynamic range of film photography is generally 200 ~ 1000, and the dynamic range of image intensifier is generally 500 ~ 2000.

4. Industrial CT image is the result of digitization, from which physical information such as pixel value, size and even density can be directly given. The digitized image is convenient for storage, transmission, analysis and processing.

High energy industrial CT means that the energy of the X-ray source in the system exceeds 1MeV. This high-energy X-ray is generated by accelerators (such as cyclotron, induction linac, RF linac, etc.). High energy industrial CT technology is mainly used to detect workpieces with large geometric size, high density and high value. For example, high-energy solid fuel in solid rocket motor.

Industrial CT testing can be used for defect analysis, installation analysis, scale measurement, CAD digital model comparison, wall thickness analysis and other tests:

Defect analysis: quickly, accurately and intuitively discover the internal defects of the product (defect type, direction, size, etc.), Such as cracks, pores, porosity, inclusions, etc., And analyze to find out the root causes of defects, so as to improve product performance and prolong product service life.

Installation analysis: using industrial CT, you can intuitively understand the two-dimensional and three-dimensional partial whole, perspective or cross-sectional analysis of the product, analyze and measure the installation gap between components, evaluate technology, find fault causes, deal with relevant problems, and reduce the R & D investment cost.

Scale measurement: the actual scale of products is often essential, but due to the confusion of object shape or the limitation of objective physical conditions, it will be impossible to obtain. Industrial CT skills can deal with these problems well. Different from the traditional measurement methods such as CMM and imager, the advantage of industrial CT measurement lies in the internal measurement of products. It can accurately measure all dimensions of the workpiece without damaging the sample, with high precision and high speed.

Comparison of CAD digital models: through industrial CT and analysis software, the scanning results can best match with the CAD digital model, and can be displayed quickly and vividly with intuitive color error. It can not only obtain the overall error of the workpiece, but also obtain the detailed error value of the key position.

Wall thickness analysis: automatically locate the direction of insufficient area, excessive wall thickness and excessive gap directly on CT data, especially the internal size of confined space, and can quickly and accurately measure the small change of wall thickness of disordered parts.

The purpose of industrial CT image defect detection is to find the defect of the workpiece from the CT image and obtain the defect information as accurate as possible. For most people, CT detection may only refer to the detection technology of hospital medical treatment. In fact, the application of CT has been extended to flaw detection industries such as industrial measurement. With the transformation of industrial measurement from external traditional measurement to internal nondestructive analysis and full-scale measurement, industrial CT technology came into being.

Generally speaking, industrial CT is a testing tool with broad application prospects and has many important functions that other nondestructive testing methods do not have. In foreign countries, industrial CT is not only applied to the testing of important products such as aerospace, initiating explosive devices and precision machinery, but also used in many fields such as automobile, petroleum, geology, archaeology, wood and so on, In recent years, its application and development in China are also very rapid.