Non-Destructive Evaluation (NDE) and Testing Facilities

X-ray inspection systems

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The Non-destructive Evaluation group operates two, industrial, x-ray inspection systems that are used primarily to characterize internal features of one-of-a-kind engineering samples and/or high-value components.

Both systems utilize commercial, solid-state, imaging detectors to produce electronic/digital images of the components under test.
Multi-axis, motion-controlled stages are coordinated with image acquisition to produce both conventional two-dimensional (2D) projection images and cross-sectional slices from three-dimensional (3D) volumetric data sets using Computed Tomography (CT).
CT images are produced using software developed in-house for use with high-end desktop workstations or Linux-based Beowulf clusters.
Digital images are acquired from either a 16-inch square area detector or a 36-inch long line detector.
The systems are works in progress and can generate a CT slice from a 9-inch diameter object in less than 30 minutes.
From image acquisition to final image display, all data is stored in computer memory. A raw image data size of up to 22 gigabytes/sample can be handled.

Description

X-rays are generated from either a 30 Watt, IRT HOMX-161 Micro-focus source or a 4200 Watt, Philips MG-450 industrial x-ray source which operate in a continuous, open beam mode. The sources, stages, samples, and detectors are enclosed in a shielded room with interlocked doors.

IRT HOMX-161 Micro-focus source

The Micro-Focus source can produce electron beam spot sizes between 5 and 200 microns on a water-cooled tungsten target. Smaller spot sizes produce better edge detail with the X-ray detector. The beam voltage may be varied between ~ 10 and 160 kVp. X-rays exit the source tube through an aluminum window in a 40 degree cone.

Figure 1: HOMX-161 source (left) with PerkinElmer RID detector (behind lead shield). A carbon composite sample is located on the 3-axis controlled stage in front of the detector.
Click on photo to view a larger image.

Philips MG-450 industrial x-ray source

The Philips source can generate two beam spot sizes, 1500 and 4000 microns, on an oil-cooled tungsten target. The beam voltage may be varied between 20 and 420kVp. The beam current can be set between 0.1 and 10.0 mA. X-rays exit the source tube through a beryllium window in a 37-degree cone. The cone-beam X-ray allows image magnification as objects being examined are moved closer to the x-ray source. Practical magnification factors range between 1.1X and 5X.

Figure 2: Philips MG-450 source with RID area detector and CMOS linear detector (above RID). A prototype ceramic rotor is shown on the Multi-Axis controlled stage (in front of RID detector).
Click on photo to view a larger image.

Imaging

The X-ray radiation can be imaged by using:

either a 16-inch square (419304 pixel) area detector at a resolution of 170 microns/pixel or
by using a 36-inch long (11,116 pixel) line detector at a resolution of 75 microns/pixel.

The area detector is an array of 2048x2048 thin-film transistors (TFT). Each TFT has a sensitive area of 200 microns square.

The line detector is a linear array of 11,116 CMOS elements with each pixel having a sensitive area of 83 microns.

The detectors are interchangeable with either source.

Requisites for samples

Practical sample sizes can be:

around 14 inches in diameter for the area detector and
around 30 inches in diameter for the linear detector, which is limited by the image magnification.

Image Processing

With custom software developed in-house for CT applications, cross-sectional slices of a 3D volume may be generated.
Each CT slice is equal to the height of the sensitive pixel divided by the magnification factor (~1.1X to 5X).
The reconstructed volume CT data may be manipulated with a software package such as IDL (ITT Visual Solutions) to visualize any slice within the 3D volume from an arbitrarily angle.
Construction of 2D images that are larger than the physical limits of either detector is possible through the use of motion controlled positioning stages.
The resulting overlapping images may be assembled electronically by using a number of commercial software packages such as Photoshop, Gimp, Scion, and IDL.