Evaluation method of measurement accuracy for Industrial Computed Tomography

Parts must be measured to evaluate the manufacturing accuracy in order to check whether their dimension is in expected tolerance. In engineering, parts with free-form surfaces are generally measured by high-precision coordinate-measuring machines. The measurement accuracy is usually improved by increasing the density of measurement points, which is time-consuming and costly. In this article, a novel sampling method of measurement points for free-form surface inspection is proposed. First, surface inspection is simplified into the inspection of a number of section curves of the surface. Second, B-spline curves constructed with an iterative method are employed to approximate these section curves. Subsequently, data points necessary to construct the B-spline curves are taken as the measurement points. Finally, the proposed method is compared with other two sampling methods. The results indicate that the proposed method greatly reduced the number of measurement points without decreasing the precision of surface modeling.

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Applications of Dual-Energy X-ray Computed Tomography to Structural Ceramics*

Advances in X-ray Analysis ◽

10.1154/s0376030800021005 ◽

1988 ◽

Vol 32 ◽

pp. 629-640

Author(s):

W. A. Ellingson ◽

M. W. Vannier

Keyword(s):

Computed Tomography ◽

Evaluation Method ◽

Combustion Engine ◽

Mass Density ◽

Energy Levels ◽

Dual Energy ◽

Structural Ceramics ◽

X Ray ◽

X Ray Computed ◽

Engine Components

AbstractAdvanced structural ceramics (Si3N4, SiC, A12O3, ZrO2) are rapidly being developed with sufficient fracture toughness to be considered for engineering applications such as internal combustion engine components, rotating turbine engine components, and heat recovery systems. X-ray computed tomography (CT) is a promising nondestructive evaluation method for these ceramics, but beam hardening presents a serious problem in the interpretation of CT images generated with polychromatic X-ray sources by creating artifacts . Dual-energy X-ray techniques have the potential to eliminate these problems. In addition, in theory, dual energy allows generation of quasimonochromatic equivalent images, which should allow verification of theoretically determined optimum energies. In using dual-energy methods, the high-and low-energy images are nonlinearly transformed to generate two energy-independent images characterizing the integrated Compton/photoelectric attenuation components. Characteristic linear combinations of these two "basis" images can serve to identify unknown materials and generate synthesized monoenergetic images.The dual-energy method has been used to study structural ceramics as well as liquids that are close to ceramic materials in atomic number and mass density. The work was done on a Siemens DR-H CT machine with 85- and 125-kVp energy levels. Test samples included Si3N4 cylinders ranging from 10 to 50 mm in diameter, liquid Freon TF, and densified SiC.

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Determination of GD&T Features Varying the Setting Parameters of X-Ray Computed Tomography by Response Surface Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.994.280 ◽

2020 ◽

Vol 994 ◽

pp. 280-287

Author(s):

Anh Dao ◽

Ágota Drégelyi-Kiss

Keyword(s):

Computed Tomography ◽

Response Surface ◽

Response Surface Method ◽

Measurement Errors ◽

Surface Method ◽

Industrial Computed Tomography ◽

Dimensional Parameters ◽

X Ray Computed ◽

Set Up ◽

Non Destructive

Measuring dimensional parameters (such as diameter, distance) by industrial computed tomography (CT) becomes more and more popular because of its advantages such as non-destructive method and short measurement time. However, the goodness of the measured values needs to be evaluated as a requirement of quality control. An aluminium test piece are designed and manufactured for mapping the measurement errors and uncertainties in case of dimensional CT measurements. In this article, the measurement errors are investigated based on the results of an experimental design, response surface method (RSM). Three main factors are varied systematically: the magnification of the CT, the numbers of views (NoV), and the set-up of the scanning mode. In the course of measurement evaluation several GD&T parameters are determined such as diameter of holes, distances between the holes, flatness and perpendicularity. The purpose of this research is to calculate the measurement errors and to determine the factors which have an effect on the dimensional CT measurement process.

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