Refraction contrast X-ray imaging experiments were conducted on acrylic resin with an artificial cylindrical hole, A7075 aluminum alloy, A6063 aluminum castings, mild steel with cracks or voids, and low alloy steel with inclusions, using a ultra-bright synchrotron radiation X-ray beam in BL24XU hutch C of SPring-8. Conventional absorption contrast X-ray imaging experiments were also done for the comparison. The X-ray beam was controlled to be monochromatic by Si double-crystals and collimated by a slit. The distance between the sample and the detector was changed from 0 to 3 m, and the X-ray energy was 15 to 25 keV. Photographs were taken by X-ray film and/or X-ray CCD camera. As a result, the refraction imaging method gave a much more distinct image of the artificial cylindrical hole in acrylic resin as compared with the absorption method. The fatigue cracks in aluminum alloy and mild steel were also distinctly observed. The Xray imaging revealed the presence of MnS nonmetallic inclusions in low alloy steel. Void defects in aluminum castings were clearly detected by the imaging. In addition, in-situ observation of tensile fracture of aluminum alloys using a high resolution X-ray CCD camera system was successfully conducted. The observations by use of asymmetric reflection technique for X-ray imaging experiment were also well performed. From above, the X-ray imaging method using ultra-bright synchrotron radiation is concluded to be very useful for fracture research of materials.KEY WORDS: synchrotron radiation; X-ray diagnosis; structural materials; fracture; refraction imaging. different information from conventional methods such as absorption contrast X-ray imaging, because much highly directional property is also available. That is why, based on the fact that the phase shift cross section for light element is almost a thousand times larger than the absorption one, especially in a hard X-ray region, new X-ray imaging techniques such as refraction method, 10-15) diffraction method, 15,16) inter-ferometric method 4,9,18) have recently been studied and proposed actively.The principle of refraction contrast X-ray imaging is shown in Fig. 2, as compared with conventional absorption X-ray imaging, illustrating the X-ray intensity profiles of the absorption contrast and refraction contrast for a void in material. In the conventional absorption method, the X-ray beam passing through the void is less absorbed, and the intensity pattern of the void area is simply stronger due to increased density of the X-ray transmission beam. On the other hand, the refraction contrast imaging, which is obtained by setting the sample some distance apart from the detector, forms a very weak line along the X-ray absorbed region (strong intensity region) due to the distribution of Xray direct beam differentiated from the refraction effect. As a result, this method provides a higher resolution image than the conventional absorption method. It is thought 20) that these refraction contrast X-ray imaging can be well performed only in the thir...
