Industrial computed tomography (CT) provides digital 3-D X-ray models of test subjects, thereby allowing the analysis of interior structures. Industrial CT systems typically comprise four subsystems: radiation source, manipulator, detector and PC.
Imaging begins with the capture of 2-D X-ray images, or radiographs. The test subject is rotated 360 degrees on a single axis via a motion-controlled stage, or manipulator, while being exposed to X-rays. The X-ray tube produces a conic X-ray beam that penetrates the test subject through one plane and from many different angles, sending a digital signal to a 2-D detector. The detector interprets the signal as a series of digital radiographs, producing a myriad of cross-sectional 2-D X-ray images. The 2-D images are processed in the PC with algorithms that build a 3-D rendering through a process called reconstruction.
The operator can then manipulate the 3-D model, so that the test subject can be viewed from any angle. In addition, the individual 2-D slices that make up the model can be viewed. Because image features do not overlap, CT images are said to be easier to interpret than conventional 2-D radiographic images. Accurate identification of internal feature positioning is another advantage.
In addition‚ density differences within the test subject can be identified and quantified‚ and related to desirable or undesirable features of the subject or material. And scan parameters such as cross-sectional slice thickness or data collection time can be varied to achieve the best combination of image resolution and inspection time.
Besides nondestructive testing and inspection, industrial CT has applications in materials research, reverse engineering and metrology. The technology is used to detect cracks and air voids; measure distance, area and volume; and image difficult-to-analyze areas within a test subject.
What follows are some CT product offerings available today.
The software’s scan mode option, EasyCT, is a five-step process that guides the operator through automatic calibration and the reconstruction process through an interactive interface and automatic processes.
Through the use of the software’s automatic calibration capabilities, the company has the ability to upgrade a DR X-ray system to a 3-D CT system. The DR to CT upgrade not only transforms a DR system to a CT system, it does so without all of the increased time and cost of purchasing a new CT system.
The software’s GPU-based reconstruction module includes one to four teraflops computing systems, including 240 to 960 cores for fast CT reconstruction.
Three stages of expansion allow adaptation to meet specific requirements: a CMM with tomography sensors; raster tomography, for measuring small features at high resolution, even on large parts; and expansion of application range through the combination of additional sensors.
The CMM has a specification for contact and length measurement deviations. Complete software integration of all functions required for automatic measurement eases use of the system.
The scanner weighs 48.5 pounds and offers a scan resolution that can be varied from a 50- to 130-micrometer pixel pitch. Scan results can be displayed on a connected laptop or a local high-resolution monitor. The output data also can be processed using Rhythm software, which has been designed for NDT applications.
The scanner accepts flexible, phosphor imaging plates up to 14 inches wide and of virtually any length. Plates can be processed on a continuous basis, with one plate being fed into the unit while another plate is being scanned. The plates have been designed to operate in harsh environments and are scratch resistant. They are available in a sensitivity range from D7 to D4 depending on whether resolution or speed is the governing inspection factor.
The system uses touch screen technology and a four-stage rotary system to simplify and ensure successful scanning setup and execution.
Traditional X-ray sources using fixed targets can only receive a limited flux of electrons to avoid damaging the target. By introducing a rotating reflection target that yields much better cooling performance, the electron flux on the rotating target radically increases without the risk of permanent damage. This boosts X-ray flux by a large factor and enables operators to obtain faster CT data acquisition or achieve higher CT data accuracy in the same time span. The rotating target is available factory fit or field retrofit.
