Defect Evaluation

Discrimination and evaluationof defect for material and technology
In the process of industrial manufacturing, various defects inevitably appear in the internal of workpiece, such as pores, cracks, looseness, shrinkage, inclusion and slag inclusion, etc.

Traditional methods such as ultrasonic testing and magnetic particle testing have limitations. It can’t get detailed information of defects such as types, dimension and location using traditional methods and it is difficult to make an accurate evaluation.

Industrial CT systems can realize diversified non-destructive functions for various workpieces with different material or different structure. Industrial CT systems can acquire CT images of workpiece after scanning. The images are saved as digital images and processed by customized software, and then internal defects of workpiece can be clearly displayed. According to the distribution characteristics of gray scale in the region of defect, type of defect can be recognized. Dimension, area and location of defect can be acquired by measurement function, which are benefitial to evaluate defects accurately.

Three-dimensional images can be constructed based on two-dimensional CT image by using the corresponding 3D reverse software, which can benefit to observe 3D shape of defect, to realize 3D measurement and localization, and to make a final evaluation. 

1.1Inspection points for industrial CT systems

CT image is a cross section image of workpiece obtained by industrial CT systems, and the defect displayed in CT image shows 2D distribution in cross section of workpiece.

The image grey value is proportional to X-ray radiation attenuation coefficient of workpiece which is determined by physical principle of industrial CT system. It can also be considered that the image grey value is approximately proportional to the density of workpiece. Defects can be detected when there is density difference between defects area and background area. Otherwise, defects can’t be detected in CT image.

An industrial CT systems has certain specifications. Defect can not detected when its dimension or density difference is less than specifications of industrial CT system. That is, Range of defect dimension or density difference should not be beyond the detection ability of the industrial CT system.

1.2Difference between defect and internal structure in CT image

It is needed to distinguish difference between defects and internal structure in CT image due to the defect in CT image is shown depending on the difference of gray value, which can be confused with internal structure of workpiece.

1.3Features and legends of CT image for diversified defects

It is needed to know various features of defects and gray distribution in CT image, and then correctly distinguish type of defects.
Evaluation service system of defects
2.1Evaluation service system of defects for industrial CT systemAs the most advanced NDT system, industrial CT system can realize various NDT functions for various material workpieces or various dimension workpieces. It can accomplish the interpretation for internal structure of workpiece and identification and evaluation of defect according to the CT image, which the identification and evaluation of defect is the most basic goal of NDT.
 GRANPEC has built evaluation service system of defects inspected by industrial CT system, and has formed mature and efficient X-ray NDT solutions based on the goal of defect evaluation.

2.2Function of defect evaluation software for industrial CT system  
Image inspection & processing software of industrial CT system is the direct tool to realize defect evaluation, and use of software functions is an important part of effective evaluation defects.