Papers by Author: Hiroshi Suzuki

Abstract: Ultrasonic impact treatment (UIT) is a remarkable post-weld treatment, which reduce not only in external stress concentration, but also in residual stress in a welded joints. Internal and surface stresses were investigated on UIT treated welded joints by neutron and X-ray diffraction method. This paper discuses the effect of internal and surface residual stress and surface stress concentration after UIT on fatigue resistance by the comparison of fatigue experiments to predictions calculated with the results of the experimental investigations.

Abstract: Effects of beam divergence on pseudo-strains observed in time-of-flight (TOF) neutron diffraction, which overlapped with the neutron attenuation effect and the surface-effect, were investigated. The through-surface strain scanning on an annealed steel plate was performed in different instrument resolutions by controlling the incident beam divergence. Typical pseudo-strain distributions were observed, but they showed different trend according to the beam divergence. Furthermore, it was demonstrated that the pseudo-strains induced in strain scanning measurements of coarse grain materials can be suppressed by controlling the incident beam divergence. Therefore, the incident beam divergence must be carefully considered to reduce pseudo-strains in time-of-flight neutron diffractometry.

Abstract: When measuring residual strain distributions of thick structural components such as thick butt-welds using neutron diffraction, it is required to make a gauge volume larger as well as to shorten neutron path length in a material to obtain sufficient diffraction intensity. In this study, neutron attenuation effect on the strain measurement with a large gauge volume was discussed on the normal strain measurement of a thick butt-weld. Influences of neutron attenuation like an apparent strain change were observed, and it was more noticeable when the gauge volume becomes larger. Therefore, the neutron attenuation effect should be considered in the strain measurement with a large gauge volume, and the neutron absorption corrections certainly play an important role for improvement of reliabilities of strain measurement using neutron diffraction with a large gauge volume.

Abstract: Internal stresses in aluminum casting alloy were measured by the neutron stress measurement method with the apparatus RESA in the Japan Atomic Energy Agency (JAEA). In most cases, coarse crystal grains are included in aluminum casting alloy. These coarse crystal grains make it extremely difficult to estimate the internal stresses by the neutron diffraction [1]. The two problems arise because of the existence of the coarse crystal grains. The first problem is the production of an unstable diffraction profile in the necessary direction. The second is the edge effect which is generated by the exclusion of the coarse crystal grains from the neutron irradiation area (gage volume). In this study, two kinds of new techniques used were proposed to resolve these problems. Firstly, the elastic theory based on the sin²ψ method is shown. Diffraction peaks in several directions were found by use of the rocking curve method. Following that, the lattice spaces in each principal direction were calculated from these diffraction peaks using the elastic theory. Secondly, the edge effect was canceled out by the modified measurement method which was done symmetrically. Finally, the aluminum casting sample which included coarse crystal grains was set to the tensile testing machine on RESA’s measurement table and the applicability of these new techniques were confirmed experimentally.

Abstract: In this study, the authors investigated the application of the area detector for the purpose of evaluating residual stress in rails by means of diffraction technique. A rail used in the Hokuriku-Line of West Japan Railway Company (JR-West) was used as a specimen for this study. The rail was removed due to initiation of cracks caused by rolling contact fatigue. The present method refers to neutron stress measurement with a two-dimensional detector and corresponding data analysis.

Abstract: Internal stresses in aluminum casting alloy were measured by the neutron stress measurement method with the apparatus RESA in Japan Atomic Energy Agency (JAEA). In usual cases, coarse crystal grains are included in aluminum casting alloy. These coarse crystal grains make it extremely difficult to estimate the internal stresses by the neutron diffraction [1]. The two problems arise because of the existence of the coarse crystal grains. The first problem is the production of an unstable diffraction profile in the necessary direction. The second is the edge effect which is generated by the overhang of the coarse crystal grains from the neutron irradiation area (gage volume). In this study, two kinds of new techniques used were proposed to resolve these problems. Firstly, the elastic theory based on the sin2ψ method is shown. Diffraction peaks in several directions were found by use of the rocking curve method. Following that, the lattice spaces in each principal direction were calculated from these diffraction peaks using the elastic theory. Secondly, the distribution of edge effect around the gage volume was measured using a small bit of copper single crystal. From this result, the edge effect was canceled out by the modified measurement method which was done symmetrically. Finally, the aluminum casting sample which included coarse crystal grains was set to the tensile testing machine on RESA’s measurement table and the applicability of these new techniques were confirmed experimentally.

Abstract: Tensile deformation behaviors of three austenitic stainless steels, JIS-SUS310S, 304 and 301L, were studied by static tensile tests and in situ neutron diffraction. In the mechanical properties obtained by the static tensile tests, the 304 and 301L steels showed better balance of tensile strength and uniform elongation than the 310S one because of TRIP effect. The angular dispersion neutron diffractions with a wavelength of 0.16 or 0.182 nm were performed during stepwise tensile testing by using a neutron diffractometer for residual stress analysis (RESA) at the Japan Atomic Energy Agency. The lattice plane strain, stress-induced martensite volume fraction, dislocation density and so on were estimated by the profile analysis as a function of applied stress. The change in lattice plane spacing for austenite indicated four deformation stages. In the comparison of lattice plane strain among the tested steels, a phase stress caused by the stress-induced martensite seems to overlap the intergranular stress of austenite phase. Judging from the results of profile analysis, the strain partitioning of austenite phase in metastable austenitic steels became larger with increasing of the volume fraction of stress-induced martensite during tensile deformation.

Abstract: Neutron diffraction measurements of strain in austenitic stainless steel alloys are presented to examine whether there are contributions to the shifts from deformation induced stacking faults. Differences between successive orders of reflections are consistent with the presence of stacking faults for 316 stainless steel but not for a NiCrFe steel.

Abstract: X-ray stress measurement is useful for determining, in a non-destructive manner, the surface stresses of engineered parts.　However, the railway wheels cannot measure because this it is very large. So it should be measured using a scaled-down model. The problem is, however, how the stress release should be considered. In this analysis, the finite element method (FEM) was applied to estimate the initial stress state using stresses released after cutting a sample obtained by the X-ray method. Railway wheels were studied in this experiment. In the early 1990s, several railroads in the northeast of the U.S.A. experienced extensive cracking in the wheels of the commuter trains. Residual stresses in the hoop direction play an important role in mechanism fatigue damage. This paper will discuss about residual stress in the hoop direction in manufactured wheels. The results of FEM analysis and the X-ray diffraction method confirms that these methods can be used to evaluate the residual stress of the hoop direction. There is very good quantitative agreement between the simulated and measured stress distributions. It can be suggested that guessing guess stress release and the redistribution by the FEM analysis is possible. The residual hoop stress of the unused wheel presumed by this research has the residual stress of high compression in the wheel at the center of the rim up to 40mm depth.　It is very safe because the residual stress state is compressive even when a crack occurs, and obstructs the crack’s progress. If a crack occurs by any chance, the stress state can obstruct the crack’s progress.

Abstract: The purpose of this paper is coming thing by the neutron diffraction method in respect of inside residual stress of carburizing-nitriding quenching spur gear measure. Moreover, from Metallo-thermo-mechanical theory, simulation using the coupled analysis by finite element method is carried out, and the residual stress is predicted.