Ayumi Shiro

Internal Stress Measurement of Weld Part Using Diffraction Spot Trace Method

The spiral slit-system was improved in order to make a gauge length regularity. The bending stress was measured by the improved spiral slit-system, and the measured stresses corresponded to the applied stress regardless of the diffraction angle. As a result, the validity of the improved spiral slit-system was proved. On the other hand, the diffraction spot trace method (DSTM), which combined the spiral slit-system and a PILATUS detector, was proposed to measure stress in a coarse grain. In this study, the distribution of the residual stress in a melt-run welding specimen was measured using the DSTM. The welding residual stresses measured accorded with that by the FEM simulation.

Residual Strain of OFC Using Synchrotron Radiation

Residual strain in oxygen-free copper, one of the materials used in high-heat-load components at SPring-8 front end, was investigated. A strain scanning method with oscillation was employed for strain measurement. The results were compared with those obtained using an elasto-plastic creep FEM analysis.

Plastic Strain of GlidCop for Materials of High Heat Load Components

We investigated the plastic strain of GlidCopTM, copper that is dispersion strengthened with aluminum oxide, by X-ray diffraction using synchrotron radiation. The purpose of this study is to verify the accuracy of the elastic-plastic analysis, which has been employed to predict the fatigue life of GlidCop. As a result, the plastic strain was estimated to be 0.7- 1.3% at any number of cycles, which is slightly smaller than the analytic solutions.

In Situ Stress Measurements during Welding Process

Welding technologies are indispensable for fabricating various industrial structures and must be highly reliable. Since tensile residual stresses at surface after welding cause crack progress, it is important to understand how stresses built up during the welding process in order to optimize final residual stresses as reduced tensile or introduced compressive stresses. Therefore, we conducted in-situ measurements of phase transformations, stresses and temperatures during tungsten inert gas (TIG) welding to understand how stresses built up. X-ray diffraction rings were detected per 0.1 sec during TIG welding by using a large-area two-dimensional detector and the accuracy of the stress analysis was estimated to be 8 MPa using the sin2ψ technique. In this paper, we described the phase transformations of ferrite low-carbon rolled steel and the changes in stresses during TIG welding.

Dislocation Density of Plastically Deformed Oxygen-Free Copper

The dislocation density of plastically deformed oxygen free copper (OFC) was evaluated by X-ray diffraction profile analysis with synchrotron radiation. The modified Williamson-Hall and modified Warren-Averbach methods were applied to the analysis. The dislocation densities of OFC samples with compressive plastic strains of 1 % and 4 % were 5.1×1014 m-2 and 9.2×1014 m-2, respectively.

Characteristics of Residual Stress by Water-Jet Peening

The specimen material was austenitic stainless steel, SUS316L. The residual stress was induced by water-jet peening. The residual stress was measured using the 311 diffraction with conventional X-rays. The measured residual stress showed the equi-biaxial stress state. To investigate thermal stability of the residual stress, the specimen was aged thermally at 773 K in air to 1000 h. The residual stress kept the equi-biaxial stress state against the thermal aging. Lattice plane dependency of the residual stress induced by water-jet peening was evaluated using hard synchrotron X-rays. The residual stress measured by the soft lattice plane showed the equi-biaxial stress state, but the residual stress measured by the hard lattice plane did not. In addition, the distributions of the residual stress in the depth direction were measured using a strain scanning method with hard synchrotron X-rays and neutrons.

Evaluation of Internal Stresses Using Rotating-Slit and 2D Detector

The rotating-slit system was developed to overcome the measurement of internal stress using 2-dimensional detector. The diffraction spot trace method was proposed and examined to measure the internal stress of the material with coarse grains.

Micro Stresses within Cu Bi-Crystal and Al Tri-Crystal after Plastic Deformation Observed by X-Ray and Neutron Diffraction

Microscopic residual stresses developed in a copper bi-crystal and in an aluminum tri-crystal after plastic deformation were investigated by X-ray and neutron diffraction. The copper bi-crystal tensile specimen was prepared so as to have a grain boundary along the tensile axis. The aluminum tri-crystal compressive specimen had a triple point and one of the grain boundaries was parallel to the compressive axis. The present study revealed that (1) residual micro-stresses are inhomogeneous within a crystal, (2) average residual stress in each crystal is different from each other, and (3) the direction of principal stress varies from grain to grain. Furthermore, the compatibility of residual stresses existing in both sides of a grain boundary was confirmed in a microscopic scale.

Stress Estimation of Titanium Casting Alloy by X-ray Measurement Technique of Single Crystal

Residual stresses in titanium casting alloy were estimated by X-ray stress measurement technique. There are two problems in the condition of X-ray stress measurement. Firstly, the titanium casting alloy has the large crystal grains. These coarse grains were generated under solidification processes and those sizes are approximately 2 millimeter in this study. These coarse crystal grains interfere with an accurate stress measurement due to the unstable diffraction profile [1]. This is because the existence of a sufficient number of isotropic crystal grains in the X-ray irradiation area are based on the X-ray diffraction theory. In this study, the stress measurement technique of single crystal materials was adopted for the solution of this fundamental problem [2, 3]. Because the coarse crystal grain was treated as a single crystal, the high intensity diffraction profiles were observed from a certain direction with investigations of crystal orientation. The problem with the coarse crystal grain in titanium casting alloy were cleaned up by the employment of the single crystal measurement technique. Secondly, the results from this study show that the position of crystal grain within the X-ray irradiation area greatly influenced the residual stress values. Therefore, in the present paper the erasing method of this position effect was tried and discussed [4]. Finally, the improvement of the accuracy of this method for the residual stress measurement in titanium casting alloy under the several bending stresses was confirmed. These results show that the erasing method in this study is an effective correction method.

Residual Stress Measurement around the Interface of Copper Bicrystal Deformed by Uniaxial Extension

Residual stresses of a copper bicrystal were measured by X-ray diffraction and synchrotron radiation. A copper bicrystal specimen with a 90-degree tilt boundary was fabricated by the Brigdman technique. After the plastic extension of 30%, kink bands developed in a deformed matrix along the grain boundary. In this study, we focused on the residual stress distribution along the transverse direction of the specimen surface and the residual stresses in deformed matrix and kink band near the grain boundary. Residual stresses were evaluated by the X-ray single crystal measurement method. Stereographic projections were used to determine crystal orientations of deformed regions. It was found that crystal orientations were different between the deformed matrix and the kink band. Residual stresses in the direction along the grain boundary were compressive in the vicinity of the boundary and tensile in the region apart from the boundary. Residual stresses in the kink band were large in compression in compared with those in the deformation matrix. The difference in the results between X-rays and synchrotron radiation suggests that there is a depth variation in the deformation and therefore the residual stress development.