Gede Bayu Suparta

Application of computed tomography to quality inspection of brass alloy

A research on application computed tomography to quality inspection of brass alloy has been done. The aim of the research was to study the capability of computed tomography system with source radiation isotope I-131 in order to mapping different quality of any type of brass alloy and study on the influence of activity of isotope I131 to the reconstructed image has been done. The inspection has been done by scanning three type of brass alloy, and comparing to the metal Cu and Zn which are the fundamental substances of brass alloy. The quality of brass alloy was identified through the profile of absorption of radiation and the distribution value of linear coefficient attenuation (μ) on the image and image contrast. The influence of activity isotope I-131 was studied by performance through the sinogram and reconstructed image. The result showed that the good quality of brass alloy have highest absorption of radiation than the bad quality of brass alloy, which were represented by the higher value of μ. From the visual observation on the reconstructed image, it showed that the higher activity of isotope I-131 would be used on the scanning process, the sharper sinogram contrast and reconstructed image contrast.

The use of x-ray micro-digital radiography for clay material inspection

An x-ray micro-digital radiography (μ-DR) system has been developed at the Gadjah Mada University Indonesia. The μ- DR system was developed as an add-on unit on an x-ray Diffraction (XRD) system using one extra beam-port as its radiation source. A fluorescence screen encapsulated in a dark tube then coupled by a CCD camera was used as an imaging plate. The radiography objects were some sample clays for earthen or ceramic material of handicraft. The clays differ by particle size, namely: 40 mesh, 60 mesh, 80 mesh, and 100 mesh. The objects were put in front of the imaging plate and then they were exposed by x-ray beam. The image formed on the screen was captured by the CCD camera and then it was converted into digital microradiograph of a size of 720x576. Then, after noise suppression process and normalization procedure, the microradiograph were compared each other by considering particle size. This facility can be used as a non-destructive and testing material studies for examining the quality of earthen or ceramic handicraft.

3D Micro-Radiography Imaging for Quick Assessment on Small Specimen

An imaging procedure for developing a 3D X-ray micro-radiography system has been developed. The idea arose due to the necessity of performing internal inspection and testing nondestructively on a small specimen. The image is generated from multiple x-ray radiograph that were acquire from multiple angle of view. Each radiograph was taken for every one degree. The total angle covers up to 360 degree so that a set of 360 image were collected for each specimen. Then, for those images were rendered to be a 3-D image. A set of image processing procedures were applied such as background subtraction and noise reduction. From the experiment, this manner is very useful for assessing a small specimen nondestructively prior to perform a tomography inspection.

Image Processing for Multiple Micro-Radiography Images

An image processing method has been developed for processing multiple images of x-ray micro-radiography. An x-ray micro-radiography image reflects quantum mottle so that its information content may tends to be corrupted. Therefore, a digital processing method has been developed to reduce the effect of quantum mottle as well as reducing the noise level. A set of radiographs are collected then summed. An image subtraction by a background image is carried out prior to the summation process. The signal to noise ratio (SNR) and contrast to noise ratio (CNR) after processing are compared with the SNR and CNR prior to the processing. As a result the final image for small specimen under x-ray micro-radiography inspection is better than original image without processing based on SNR and CNR assessments.

Quality performance of customized and low cost x-ray micro-digital radiography system

A quality performance indicator for digital x-ray micro-radiography system has been developed. It was used for nondestructive testing on microstructure object. A set of testing apparatus for image quality indicator (IQI) was developed from acrylic sheets that were cut carefully using laser cutting tool. These IQI apparatus imitated common standard such as step wedges, holes indicator, and lines/wires tester. The IQI step wedge was used to measure the relative x-ray penetration capability. The IQI holes indicator was used to measure the Modulation Transfer Function (MTF) of the imaging system and the IQI lines/wires tester was used for pixel calibration and image spatial resolution determination. From this experience, this simple, low cost, customized, quick made and accurate IQI set fulfilled the performance testing requirement procedure.

Image quality comparison of computed radiography and digitized film radiograph

The comparative study on the image quality between Computed Radiography (CR) and digitized film radiograph has been carried out. We have successfully digitized a radiographic film of an aluminum step wedge, an ASTM and coins using a flatbed scanner. Then, a comparative study was developed using CR as a reference. We used 4 set-up variations of kV and mA. The image quality was assessed based on the visual analysis: brightness, sharpness, and contrast, and the physical information analysis. The results show that visually the image quality of CR was better to the digitized film radiographs. However, CR was unable to distinguish the physical information such as the effect of voltage or current and the object characteristic to the image quality.

The development of optical computed tomography apparatus for fault detection on transparent materials

A computed tomography (CT) apparatus using laser beam and photodiode is currently developed for faulty detection in transparent materials such as diamonds and crystals. Faults in diamond and crystals are hard to be detected using visual inspection. A unique and artistic feature may appear on the surface due to internal cracks or anomalies. While those are hard to be distinguished, the unique feature appeared may be more precious compare to any perfect objects. A simulation study for understanding the physics behind the phenomena has been performed. This has been followed by set-up of mechanical and sensor system along with the electronics readings. Previous results on individual testing show that we may develop a pretty optical CT system that can be used for fault detection in any transparent materials.