Deformation properties of austenitic stainless steel foils of 0.05 mm in thickness were evaluated by using transmitted polychromatic X-rays under monotonic tensile loading. A conventional laboratory X-ray equipment with a rotating Mo anode was adopted at a tube current of 40 mA and an acceleration voltage of 60kV. Soller slits with a divergence angle of 0.5 deg were attached on both divergent and receiving sides. By the preset time of 500s, enough diffraction intensity was obtained to determine the stress. The diffraction elastic constants were measured under monotonic loading by the cos2χ method. The diffraction energy decreased almost linearly with increasing cos2χ, and the slope of the cos2χ diagram decreased with increasing applied stress. Measured diffraction elastic constants were compared with the theoretical values calculated by the Kröner model. The experimental value obtained from a single peak with high intensity agreed well with theoretical one, and the standard deviation was enough small. The lattice strain measured during plastic deformation depended on the diffraction plane. For the single peak profile, the full width at half maximum increased with applied plastic strain. From the the diffraction-plane dependence of the lattice strain, the full width at half maximum and the diffraction intensity, deformation properties of the materials can be evaluated. Diffraction method of laboratory polychromatic X-rays is effective as a simple technique to measure multiple X-ray parameters.
In materials such as Ni-based alloys, the microstructures are formed by mono-phase solidification without solid-state transformation. Measuring the welding residual stress by X-ray diffraction is difficult because of the preferred orientation of the unidirectional solidification and the grain growth in the heat-affected zone. To exclude these effects, a method that records the diffraction peaks in a two-dimensional detector combined with multi-axial rocking is proposed. It is clarified that the equilibrium of shrinkage and the recovery of strain during the thermal cycle determines the site of the maximum tensile stress. In addition, dynamic re-crystallization, which occurs during solidification, contributes to the decreased residual stress at the fusion line. If the spatial resolution of the proposed and the conventional measurement methods can be correlated, the results of each method agree well. Therefore, the proposed method is an effective tool for measuring the residual stress in welded joints of Ni-based alloy.
In welded pipe joints of austenitic stainless steel, the mismatch of residual stress distribution often occurs between a variety of measurement method and the numerical simulation. It is especially known that non-destructive measurement such as X-ray diffraction method makes remarkable different due to the microstructure evolution by the welding. Meanwhile, the multi-pass girth welded pipe joints of austenitic stainless steel in this work were consistent with the thermal-elastic-plastic analysis and the typical stress distribution due to the welding was obtained. This reason was clarified from the welding metallurgical evaluation. The material of FA (ferrite to austenite) mode solidification with K-S relationship has the random and fine structure, compared with other systems. Therefore, specific systems facilitate the X-ray stress measurement in the welded zone of austenitic stainless steel and the pure stress by the welding could evaluate.
The relaxation behavior of residual stress induced by laser peening during mechanical loading was investigated on an aluminum alloy A2024. The residual stress relaxation process was measured by x-ray diffraction method and analyzed by a finite element method (FEM). The plastic deformation behavior was evaluated from the x-ray diffraction peak width and the FEM. The surface residual stress relaxation under tensile loading occurred when the plastic-deformation started at the inside of material where the balancing tensile residual stress existed. Under the compressive loading, the surface residual stress relaxation started due to the plastic deformation beneath the surface where the maximum compressive residual stress existed. The plastic deformation at the inside of material caused the redistribution of the residual stress and resulted in the relaxation of the surface residual stress. For both tensile and compressive loading, the surface compressive residual stress relaxation occurred before the total stress ( = (residual stress) + (applied stress)) at the surface reached the yield condition. All discussions in this study based on the mechanical deformation behaviour of the material. Therefore, the conclusions of this study are thought to be able to apply to the behavior of the residual stress under the mechanical loading on metallic materials treated by any mechanical surface treatment.
Residual stress distribution at the cylinder block wall in 1500cc class aluminum engine was measured using RESA in JRR-3 of JAEA. In order to increase neutron flux at the gauge volume measured, newly developed vertically focused collimator was employed. Since the grain size in cast aluminum engine block was large, the oscillation method was applied. The residual stresses near the surface layers of cylinder block wall were compressive all in the tangential, the thickness and the cylinder axial directions, but tensile in the middle part of cylinder block wall. This means the residual stress distributions are likely to be hydrostatic. The residual stresses in the tangential direction were not balanced in the cylinder block wall. If the residual stress distribution in the hoop direction is approximated by 2 dimensional power equation, the residual stresses on the cylinder wall surface is estimated as about -140MPa and the mean residual stress in the cylinder wall is 15MPa.
A hollow circular cylinder specimen with an annular U-notch of chrome molybdenum steel with 0.20 mass% C (SCM420) was carburized in carrier gas and quenched in oil bath. In order to determine the case depth, the specimen was cut off and carbon content and Vickers hardness gradients were measured experimentally near the carburized surface. The residual strain mapping in the interior of carburized cylinder was conducted nondestructively by neutron strain scanning. In this study, the neutron diffraction from Fe-211 plane was used for strain scanning. The neutron wavelength was tuned to 0.1654nm so that diffraction angle became about 90°. Radial, hoop and axial residual strains were measured by scanning diffracting volume along the axial direction of cylinder specimen. Each residual strain was calculated from lattice spacing change. Unstressed lattice spacing was determined experimentally using reference coupon specimens that were cut from the interior of same carburized cylinder. As a result, the diffraction peak width at half height, FWHM, near the carburized surface was about 3.7 times wider than that of coupon specimens. On the other hand, the most peak widths in the interior equaled to that of coupon specimens. Peak width broadened slightly as the diffracting volume approached the carburized case layer. From the center to the quarter of cylinder specimen, the hoop and axial strains were tensile, and the radial one was compressive in the interior. From the quarter to the edge of the cylinder specimen, the hoop tensile strain increased, radial and axial strains changed to tensile and compressive, respectively. Therefore, the interior of the cylinder specimen was found to be deformed elastically to balance the existence of compressive residual stresses in the carburized case layer.
An X-ray stress measurement technique applicable to a confined area - dual-axis inclining method - has been developed to measure three stress components of an plane stress state. The present method is composed of the iso-inclination scanning (angle : ±ψ) and the side-inclination scanning (angle : Ω). The ±ψ scanning under the condition of Ω ≠ 0 results in the ψ-splitting even if the measured area is in the plane stress state. The amount of the ψ-splitting depends on the value of Ω and the shear stress component. The average of the diffraction angles in the ψ-splitting is proportional to sin2ψ. The proportional constant indicates not a true normal stress but an apparent normal stress because of the condition of Ω ≠ 0. The apparent normal stress is proportional to sin2Ω. Its gradient and y-intercept depend on the two orthogonal normal stress components respectively. The difference of the diffraction angles in the ψ-splitting is proportional to sinΩsin|2ψ|. Its gradient is proportional to the shear stress component. The validity of the present method was verified by applying the present method and the conventional method to a flat specimen respectively, and by comparing the values measured.
Stress analysis with X-ray diffraction (XRD) for hexagonal polycrystalline materials in the Laue classes 6/mmm and 6/m has been studied on the basis of the crystal symmetry of the constituent crystallites which was proposed by R. Yokoyama and J. Harada [“Re-evaluation of formulae for X-ray stress analysis in polycrystalline specimens with fibre texture”, Journal of Applied Crystallography, Vol.42, pp.185-191 (2009)]. The relationship between the stress and strain observable by XRD in a hexagonal polycrystalline material with  fibre texture was formulated in terms of the elastic compliance defined for its single crystal. As a result, it was shown that the average strains obtained in the crystallites for both symmetries of 6/mmm and 6/m are different from each other under the triaxial or biaxial stress field. Then, it turned out that the line width of XRD changes depending on the measurement direction.
Block specimens of chrome molybdenum steel with 0.20 mass% C, SCM420, were carburized in carrier gas and quenched in oil bath. The hardness and carbon content gradients in the hardened layer were measured experimentally. The carburized surface of one block specimen was gradually removed by electrolytic polishing. Ten thin plates were cut from the total case depth of the other block specimen. An experimental method to determine the stress-free lattice plane spacing of the hardened layer was examined using x-ray and neutron radiations. As a result, the stress-free lattice plane spacing change in the hardened layer could be determined successfully by measuring neutron diffraction peaks from Fe-211 of the thin plates during rotating ±90° around the specimen axis. Using x-ray, the stress-free lattice plane spacing at the carburized surface could be also determined by measuring the 2θ-sin2ψ diagrams of either removed surface of block specimen or thin plate. However, under the carburized surface, the Kα2 diffraction from the heat-treated eutectoid phase was superimposed on x-ray diffraction peak because the subsurface microstructure was composed of martensitic and heat-treated eutectoid phases. The stress-free lattice plane spacing under the carburized surface could not be determined using x-ray. Furthermore, the stress-free lattice plane spacing of Fe-211 was found to decrease with increasing the distance from the carburized surface and be expressed by the cubic function of the carbon content in the hardened layer.
In order to clarify the mechanism of creating a transferred layer of shot particles on the substrate surface by Fine Particle Peening (FPP), the surface of aluminum alloy was modified with SiC shot particles at room temperature, 100°C, 200°C and 300°C. The treated surfaces were characterized using a field emission - scanning electron microscope (FE-SEM), an energy dispersive X-ray spectrometer (EDX) and an X-ray photoelectron spectroscope (XPS). An SiC-rich layer in which small chips of shot particles were embedded was formed on the substrate surface by FPP treatment. EDX and XPS analyses revealed that the transferred fragments were only embedded into treated material without any chemical binding. The SiC-rich layer became thicker with an increase in heating temperature and was uniformized on the specimen treated at 300°C. The mechanism of the adhesion of a part of the shot particles induced by FPP treatment was analyzed. Analyses using EDX revealed the presence of particle fragments transferred to the collision dents. With an increase in the amount of collision, transferred fragments were embedded into treated material by deformed material due to a micro ploughing effect. In addition, analyses using a high-speed camera revealed that collision of shot particles occurred during FPP treatment.
Collision safety and reliability of cars under impact loading become more and more important in the vehicle industries. This study is concerned with the development of a fracture criterion for the impact fracture of jointed steel plates of a bolted joint used in a car body, which may contribute to crash simulations by computer-aided engineering (CAE). The impact behavior and fracture of jointed steel plates of a bolted joint were examined by experiments and numerical simulations. The impact pull-out test of jointed steel plates by a bolt was performed by making use of an one-bar method for impact tests, together with the static test using a universal testing machine INSTRON 5586. In order to understand the mechanism of fracture process of the jointed steel plate, numerical simulations by FEM code ANSYS and LS-DYNA were also carried out. The rupture of steel plates jointed by a bolt with washers occurred along the circular outside of washers and made a hole with the same diameter as washers for both of static and impact loading conditions, and then the pull-out load (F) increased with increasing of the diameter of washers. On introducing the pull-out stress defined as (F/A) for convenience, in which A is the cross-sectional area of the steel plate along the circumference of a washer, the pull-out strength showed almost the same value regardless of the washer size. This result suggests that a stress-based fracture criterion may be developed for the impact fracture of jointed steel plates of bolted joint used in a car body.
The Japanese sword is interesting not only from the viewpoint of traditional crafts of arts, but also from the aspect of modern science and technology because the way of making and its functionality as a weapon are really consistent with modern science. The present study is concerned with the joint between tohshin (blade) and tsuka (hilt) of the sword. Only one mekugi-take (retaining peg made of bamboo) with about 5mm in diameter holds Nakago (tang) in the hilt. However the slender mekugi might not be broken, even in the case of violent sword-fighting. This fact has been historically demonstrated in many battles by Japanese swords. In this study, using a Japanese sword model, it is examined theoretically and experimentally why a mekugi used in Japanese swords might not be broken from the viewpoint of impact engineering. Consequently, it is presumed that such a strong force as breaking mekugi-take does not act on it, because of the location of mekugi-ana (a hole for mekugi) in the tang, which has been made by following the traditional code of swordsmiths.
A novel chemical sand-fixing material of hydrophilic polyurethane resin, which was prepared by excessive MDI polymerizing with hydrophilic polyol, was studied in this paper. The structure of this sand-fixing material was characterized by termination with -NCO. It can react with water in several minutes to become a gel and a sand-fixing layer was formed by spraying the material on the sand surface. Several properties relating to the sand fixation were studied systematically, including curing time, permeability and porosity, mechanical properties, water retention capacity and durability from UV radiation. From the results, after 3 hours, the reaction rate of the sand-fixing materials was 95%, and after 4 hours, it was close to 100%. The curing time can be controlled by changing the temperature and concentration of the sand-fixing material according to the application for the best sand fixation effect. By increasing the amount of sand-fixing material sprayed on the sand, the thickness of the sand-fixing layer increased linearly. The relationship between the concentration and Yamanaka soil hardness was approximately linear. When the concentration of the sand-fixing material was 8%, the index of the layer reached to 28∼29 mm. The compressive strength of the sand-fixing specimen was increased by increasing the concentration of the sand-fixing material, when the concentration increased from 3% to 7%, the compressive strength increased from 1.1 MPa to 3.8 MPa, respectively. When the sand-fixing material of hydrophilic polyurethane was sprayed on the sand, it basically formed a protective layer on the sand surface and prevented water vapor from penetrating. When the concentration of the sand-fixing material was more than 3%, the water retentive rate was more than 60% two weeks later, However, when the concentration was less than 3%, it was more than 80% in 6∼8 days. Moreover, It is found that the amount of sediment decomposed by UV radiation increased almost linearly with increasing radiation amount. The lifetime of the sand-fixing layer is approximate 4∼8 months.