In the modified Williamson-Hall method, the parameters Ch00E, Ch00S, qE and qS play an important role to determine the dislocation character. These parameters are obtained from elastic stiffness c11, c12 and c44 but the values of elastic stiffness are sensitive against the data of Young’s modulus in poly-crystal. Young’s modulus of poly-crystal is changeable depending on the texture and this causes some confusion on the calculated results for the parameters Ch00E, Ch00S, qE and qS. In this paper, reliable values are proposed for Ch00E, Ch00S, qE and qS in aluminum, copper, nickel, bcc-Fe and fcc-Fe.
In this paper, we proposed a double exposure method using synchrotron white X-rays (DEM-WX) to measure strains of coarse-grained materials, and examined its feasibility. The X-ray diffractions were measured by a CdTe pixel detector. The CdTe pixel detector can resolve photon energy by changing a threshold voltage. Calibrating each pixel of the detector using characteristic X-rays of Pb and W foils, the images by threshold X-ray energy were obtained. The difference image, which is like a diffraction image with mono-chromatic X-rays, could be calculated by the difference between the images by the threshold X-ray energy. The material of the bending specimen was an austenitic stainless steel with a grain size of 300 µm. The strains of the bending specimen were measured using the DEM-WX, and the results corresponded to the applied strains measured by the strain gauge.
The internal strain distribution in an injection-molded plate of crystalline thermoplastics, polyphenylene sulfide (PPS), reinforced with 40 mass % of glass short fibers was measured by the diffraction method using synchrotron X-rays with an energy of 20.0 keV. The injection molded plate has roughly three-layer structure where the fiber orientation is parallel to the molding direction in the shell layer and is nearly perpendicular in the core layer. The strain scanning technique was successfully applied to measure the change of in-thickness distribution of strain in PPS matrix under uniaxial tensile loading both in the molding and transverse directions. The change of PPS strain in the loading direction is roughly identical to the applied macrostrain; strictly speaking, it is larger in the direction perpendicular to fibers than that parallel to fibers. The PPS strain in the thickness direction decreased with increasing applied strain. The rate of the change of PPS strain with the applied strain measured by X-rays is smaller than that predicted by the micromechanics of composites with aligned short fibers. The influence of three-layer structure on PPS strain in injection-molded plates subjected to tensile loading was successfully predicted by the finite element analysis combined with micromechanics.
White etching area may be recoginized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial X-ray measurement equipment (B method) were investigated. The former was moddified by surface residual stress accoding to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
It is important to determine to local strain/stress fields in power devices in order to improve their performance and reliability. Micro Raman spectroscopy is of the excellent methods to analyze local strain/stress fields in very small area. When the strain/stress tensors are identified via micro Raman spectroscopy, the phonon deformation potential constants and the elastic stiffness of measured materials are used. These parameters are determined by numerous mechanical loading tests of several single crystal specimens with different crystallographic orientations under various loading conditions, which is labor- and time-consuming. Moreover, it is very difficult to prepare several single-crystal specimens of the newly developed materials with dimensions that are capable of performing several loading tests. This study aims to predict ab-initio the phonon deformation potential constants and anisotropic elastic stiffness of a single crystal Si through first-principles calculation to determine the local strain/stress tensors using micro-Raman spectroscopy. First, the triply degenerate Raman peak with F2g vibration mode for unstrained single-crystal Si was accurately computed by Quantum ESPRESSO based on density functional theory, plane wave and pseudo-potentials. Second, on the basis of first-principles calculation of two types strained single-crystal Si, degenerate single Raman peak of Si was split into singlet and doublet peaks or three independent singlet peaks for each loading condition. The relations between the wave number shift of Raman shift and applied strain become linear with different slopes. The values of the phonon deformation potential constants calculated from them were in good agreement with experimental values obtained by plate bending tests of Si wafer. Finally, to illustrate the application of these predicted parameters to micro-Raman stress measurements, the stress distribution from an indentation-induced crack tip in Si wafer was estimated from an experimentally measured wave number shift of Raman shift during plate bending of the cracked Si wafer.The measured stress components were in good agreement with the experiment values. Therefore, the proposed estimation method of phonon deformation potential constants and elastic constants that utilizes first-principles calculation is very effective as a simple technique without performing numerous loading tests on several single-crystal specimens.
In this study, in order to obtain new findings concerning the occurrence mechanism of dry crack in wood, we investigated the effects of drying temperature and drying rate on occurring behaviors of microcracks during wood drying with using tangential wood samples thin in the longitudinal direction. The development of microcracks occurring in the early stage of drying, furthermore, the possibility of preventing cracks remaining after drying was shown by the obtained results. By controlling the drying temperature and drying rate and thus the state of microstructures in amorphous regions of wood cell wall, it would be possible to prevent the development of microcracks that occurs at the beginning of the drying and the cracking that remains after the drying. And, in order to control the cracks remaining after drying for the actual size wood, it is necessary to clarify not only the mechanism of occurrence for microcracks in the early stage of drying but also the mechanism of the progress of microcracks. The importance became clear in this study.
This study aims to develop a new light-shielding gel sheet, which can change its transparency and opaqueness reversibly in response to temperature with little volume change, composed of poly N-isopropyl acrylamide （PNIPAM）, which is a temperature responsive polymer with a lower critical solution temperature（LCST）of 32°C, and agar. For this purpose, the influence of PNIPAM concentration（0.6-6 wt%）and agar concentration（0.6-3 wt%）on the transmittance of visible and near infrared light and volume shrinkage ratio of PNIPAM gel sheet during heating and cooling were investigated. Furthermore, the structural change of PNIPAM gel sheet with temperature change was discussed from these results. The transmittance of PNIPAM gel sheet increased at 25°C（below LCST）and decreased at 50°C（above LCST）with the increase of PNIPAM concentration and the decrease of agar concentration. In addition, the volume shrinkage ratio of PNIPAM gel sheet by heating decreased when the agar concentration increased. These results reveal that the PNIPAM gel sheet prepared with 6 wt% of PNIPAM and 2 wt% of agar has the highest performance.
Because deterioration due to chloride attack progresses in some reinforced concrete members, safety and security are threatened. As a countermeasure, high corrosion resistant rebars such as FRP rod, stainless steel rod, and epoxy coated rebar are used for a reinforcement for concrete. However, the conventional thermosetting FRP is disadvantageous due to its expensiveness, and it has not spread to widespread use. Therefore, the authors are working on mass production of thermoplastic FRP. If it will be developed, cost reduction may be expected. This research focuses on thermoplastic FRP, and evaluates the applicability to a reinforcement for concrete as a substitute for steel bar. That is, first, in order to confirm the basic performance for embedding in concrete, the influence of immersion in a high alkaline aqueous solution and water on the tensile strength of reinforcing bar itself is confirmed. Next, the adhesion strength between concrete and reinforcement bar is confirmed. Furthermore, a bending load test of concrete beam specimen with FRP rod is carried out and simultaneously FEM analytical is performed. As a result, it is clarified that the thermoplastic FRP rod may be applied to the reinforcement for concrete as a substitute for steel bar.