Application of X-ray Industrial CT nondestructive testing technology

Date：2022-06-02 15:30:08Views：895

Industrial CT is the abbreviation of industrial computed tomography technology. It can clearly, accurately and intuitively display the internal structure, composition, material and defect of the detected object in the form of two-dimensional sectional image or three-dimensional image without damage to the detected object. It is known as the best nondestructive testing and nondestructive evaluation technology today. Industrial CT technology involves nuclear physics, microelectronics, optoelectronic technology, instrumentation, precision machinery and control, computer image processing and pattern recognition, and is a technology intensive high-tech product.

Industrial CT is widely used in automobile, material, railway, aerospace, aviation, military industry, national defense and other industrial fields. It provides important technical means for the successful launch of space launch vehicles, spacecraft and spacecraft, the development of aeroengines, the inspection and test of large weapon systems, the analysis of geological structures, the safety of railway vehicles in speed-up and heavy load, the prediction of oil reserves, and the determination of mechanical product quality.

Detection scope: mainly describes the detection object of the CT system. For example, it can transmit the maximum thickness of steel, detect the maximum rotation diameter of the workpiece, detect the maximum height or length of the workpiece, and detect the maximum weight of the workpiece.

Used ray source: ray energy, working voltage, working current and focus size. Ray energy is the main factor influencing the ability to penetrate the equivalent steel thickness.

Scanning mode: commonly used CT scanning modes include generation II scanning and generation III scanning. Generation III scanning has higher efficiency, but it is easy to cause ring artifacts due to poor correction methods; The scanning efficiency of generation II is about 1/10-1/5 of that of generation III, but it is beneficial to the inspection of large rotating diameter workpieces. In addition, the X-ray CT system usually has the digital radiography imaging (DR) function.

Scanning detection time: refers to the time required to scan a typical section data.

Image reconstruction time: refers to the time required for image reconstruction. Due to the fast running speed of modern computers, the reconstructed images can be displayed almost immediately after the scanning, generally no more than 3S.

Resolution: the core performance indicators of the X-ray Industrial CT system include:

1. spatial resolution: the ability to distinguish the smallest structural details from CT images.

2. density resolution: the ability to distinguish the minimum density difference from the CT image (usually evaluated in combination with the size of the characteristic area).

The relationship between spatial resolution and density resolution. When the radiation dose is constant, spatial resolution and density resolution are two contradictory indicators. Increasing the spatial resolution reduces the density resolution, and vice versa.

For ordinary X-ray Industrial CT system, its core performance indicators are only spatial resolution and density resolution; For a high-precision industrial CT system, in addition to the above two core performance indicators, there are two other core performance indicators:

1. geometric measurement accuracy: the absolute error between the geometric size of an object measured on the CT image and the real size of the object.

2. density measurement accuracy: the relative error between the density value of an object measured on the CT image and the real density value of the object.