This special issue reviews some recent progress in non-destructive inspection (NDI) technology. Some accidents and failures of infrastructures have been reported recently. It is very important to minimize environment load in order to realize a sustainable society, and one of most effective approaches is to extend the life of infrastructures using NDI technology. A lot of new technologies are developing to replace energy derived from fossil fuel. NDI also plays an important role to keep integrity of new types of structures as well as controlling materials process. Structural health monitoring and global sensing with networking are key-words to realize sustainable society supported by NDI.

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  Recent advances in harmonic imaging of industrial materials are reviewed. The conventional ultrasonic testing, which is based on acoustic impedance mismatch between contact materials, fails to detect kissing bonds, micro damage and micro defects within a bond layer of dissimilar materials. To the contrary, the nonlinear ultrasonic method, in particular higher harmonic method, makes use of higher harmonics excited at disordered structures mentioned above under incidence of large amplitude of tone-burst waves of a fixed frequency. This review is composed of three parts; key concept of nonlinear ultrasonics, instruments for higher harmonic imaging and harmonic images of kissing bonds, nonmetallic inclusions in metal, creep damage, microcracks in SiC/Ti composite, and weld boundaries. The higher harmonic imaging could be indispensable technique for quality assurance of bonded interfaces of dissimilar materials in near future.

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  The development of the industrial digital radiography devices has made remarkably progress based on improvement of the medical application and devices. Now we are required to utilize and advance the digital system for in-line testing device and security purpose.
  This article introduces advanced digital radiography devices such as area sensor, line sensor and so on and explains testing equipment using those digital devices. In addition, the examples of the advanced technologies of the radiographic testing are introduced.

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  Fiber Bragg grating (FBG) is a wavelength modulation fiber-optic sensor and the central wavelength of light reflected from FBG varies with vibration impinging on the FBG. Strain, ultrasound as well as acoustic emission (AE) can be measured from FBGs through a wavelength-light intensity conversion technique. This review presents experimental works on dynamic strain measurement and ultrasonic damage inspection using FBG sensors, and demonstrates that FBGs can function as strain and ultrasonic sensors comparable to conventional electric sensors. Furthermore, a novel FBG sensor in which optical fiber is used as ultrasonic waveguide is introduced and an experiment of continuous AE measurement using the FBG sensor is presented.

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  This paper introduces three types of X-ray non-destructive inspection systems developed by the use of micro-focus X-ray technique.
  The micro-CT (Computed Tomography) system reconstructs not only one slice image but also multi-images by only one scan of a inspected sample by acquiring X-ray projection data from many circumferential directions, and it creates three dimensional images from its multiple ones. It is used for the non-destructive testing of small objects such as IC devices.
  The micro-Focus X-ray Fluoroscopic Inspection System has an advantage of high magnification ratio, which is often used for the inspection of the BGA (Ball Grid Array).
  The Oblique-CT (Lamino-CT) system has a mechanism that rotates a sample obliquely to X-ray axis, which can make a sample put closer to the X-ray source, resulting in high magnification ratio. The combination of the micro-Focus X-ray and the Lamino-CT contributes development and inspection of PCBs (Printed Circuit Board).

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  Moire method is a useful method to measure deformation and strain distribution of structures. Moire fringe patterns are analyzed quantitatively and speedy by image processing using a computer. In this paper, the theory of moire method and sampling moire method is introduced. Since the sampling moire method is useful to analyze phases of a moire fringe and a grating from one image of a grating pattern, it is possible to analyze dynamic deformation accurately. Some applications of the sampling moire method to displacement measurement of a beam, and shape and strain measurement of a rubber structure are shown.

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  In this paper, the principle and the feature of the industrial ultrasonic inspection techniques are explained. Industrial problems and the future for their technique are also described.
  Furthermore, the outline of the new developed techniques are related.

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  Computer tomography is a method for reconstructing three-dimensional structure from a series of projection images. By using high brilliance synchrotron radiation X-ray sources and modern X-ray optical systems, high-resolution X-ray tomographic imaging with spatial resolution of micrometer-nanometer has been developed and is currently open to public user experiments. The applications of synchrotron radiation microtomography are spread in various field of science and engineering. In this review article, present status of high-resolution tomography at the Synchrotron Radiation Facility SPring-8 is described. Theoretical limitation of spatial resolution by diffraction of X-rays, and high-resolution tomography with X-ray imaging microscope are also shown.

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  Domestic standards of the leak testing are enacted as one of Japan Industrial Standards. The conformity is advanced between these domestic standards and ISO (International Organization for Standardization) standard. ISO9712 (Non-destructive testing-Qualification and certification of personnel) was revised to include the leak testing of qualification and certification in 2005. The preparation working group of qualification and certification for leak testing is planning start aiming at the system in one and a half years.

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  The current status of the technical committee; TC 135 of International Organization for Standardization (ISO), which is the technical committee for non-destructive testing (NDT), is introduced with a brief explanation of various non-destructive testing methods. The review also describes the characteristics of international standards and the international trend in NDT and the relation between non-destructive testing and vacuum technology.

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