Nobuaki Minakawa

Slow Neutron Polarization by Polarized Proton Filter Using Ethylene Glycol

A feasibility study of a polarized proton filter for slow neutrons was successfully carried out. Ethylene glycol containing a few percents of Cr V ions was used as filter material in which protons were dynamically polarized. Polarization of protons was varied between 20 and 72%. The maximum polarizability of 0.84±0.01 (flipping ratio of 11.5±0.5) was obtained for neutrons of 80 meV. This value corresponds to the polarization cross section of 27±1.4 b. The idea will open a way for the polarization of intense neutron beams of white spectra. In addition, this method does not impose serious restriction on the angular divergence of the incoming neutron beam.

Internal Stress Measurement of Fiber Reinforced Composite by Neutron Diffraction with In Situ Low Temperature Stress Measurement System

The internal stresses in the continuous tungsten-fiber reinforced copper-matrix composite were examined by the Neutron stress measurement method. The Neutron diffraction apparatus ND1, which is abbreviated from the Neutron Diffraction system No.1 designed and manufactured by the National Nuclear Energy Agency in Indonesia (Badan Tenage Nuklir Nasional, BATAN), was used in the present study. The most common 3-axes measurement method with Hooke’s equation was only possible to measure about 110 plane, because the tungsten fiber became the situation of heavy 110 orientation. Thermal stress alterations caused form low temperature cycling was measured by in-situ stress measurement method making use of a cryostat system. The thermal residual stresses in tungsten-fiber longitudinal direction were compressive state in every stage. Results of in-situ thermal stress measurement were good agreed with a calculated result of simple elastic theory in elastic area.

Formation and crystal structure of UTi2Dx

Abstract Deuterium absorption properties of U-66.7 at.%Ti alloy and the crystal structure of obtained deuterides UTi 2 D 4.5 and UTi 2 D 5.2 were examined by X-ray and neutron diffraction. Consequently the structure was determined as having C15 cubic structure, in which the 2U-2Ti site at 96(g) in the space group Fd3m and the 1U-3Ti site at 32(e) were occupied by deuterium. Interatomic distances UD and TiD in both sites were nearly equal to those in respective binary deuterides. The results explained the formation of UTi 2 H(D) x from UTi alloy with no UTi 2 -type compound.

LOW TEMPERATURE IN-SITU STRESS MEASUREMENT OF W/Cu COMPOSITE BY NEUTRON DIFFRACTION

The internal stresses in the continuous tungsten-fiber reinforced copper-matrix composite were examined by the Neutron stress measurement method. The Neutron diffraction apparatus ND1, which is abbreviated from the Neutron Diffraction system No.1 designed and manufactured by the National Nuclear Energy Agency in Indonesia (Badan Tenage Nuklir Nasional, BATAN), was used in the present study. The most common 3-axes measurement method with Hookes equation was used to measure stresses in the both of tungsten-fiber and copper-matrix. The tungsten-fiber became the situation of heavy 110 priority orientation. The other hand, copper-matrix became the large crystal grain. Thermal stress alterations caused form low temperature cycling was measured by in-situ stress measurement method making use of a cryostat system. The thermal residual stresses of tungsten-fiber and copper-matrix in longitudinal direction were compressive and tensile state respectively. Results of in-situ thermal stress measurement were agreed with a calculated result of simple elastic theory qualitatively.

A Measurement Method of Residual Stress in Quenched Steel by Neutron Diffraction

An experimental methodology was developed for identification of residual stresses inside quenched steel by neutron diffraction considering gradient distribution of martensite phases. A hybrid method is used by which the residual stress in the quenched steel was measured with neutron diffraction integrated with numerical simulation results of microstructure and phase distribution. A coupled finite element analysis based on metallo-thermo-mechanical theory was carried out to predict the microstructure due to phase transformation during quenching process. The non-strain lattice spacing and elastic modulus were measured with rotating specimen method in tensile test. Then, residual stresses in the (110) plane are measured using the cylinder specimens of quenched S45C and SCr420 steel by the neutron diffraction method. Finally the measured results of XRD, neutron diffraction as well as the calculated values were compared and discussed. Introduction Mechanical parts often undergo surface-hardening treatments, such as quenching, carburizing, nitriding, shot-peening, etc., which generate compressive residual stresses in the surface layers and modify their chemical composition, microstructure, and mechanical properties in the bulk material. In the manufacturing process incorporating temperature history and microstructure variation, complex thermal mechanical behavior will lead to macro and micro residual stresses and distortion of phase transformation of mechanical parts. At present, there is a great need for experimental methods to determine the residual stress inside the surface-treated materials. Many measurement methods of residual stress have been developed in industry technology such as X-ray diffraction, rapid drilling and so on [1, 2]. These techniques have only capability to measure residual stresses near the surface of machine parts. Neutron diffraction has been an attractive technique recently as the capability of measuring residual stresses inside of materials. The neutron ray has an absorption coefficient as small as 1/hundreds to 1/thousands compared with that of X-ray on the same grade of wavelength. By using high penetration power of the neutron ray, it allows us to measure the residual stress inside of bulk materials by non-destruction to a centimeter order [3-6]. To determine the residual stress, it is necessary to know the non-strain lattice spacing d0 and elastic constant of the material. Powder diffraction method is a general way of determining the parameter d0. However, after thermal chemical process such as quenching, phase transformations near surface modifies the microstructure of the material, the d0 and elastic constant vary in depth as a gradient distribution. For engineering materials especially those involving large plastic deformations or phase transformations often have preferred crystallographic orientation or non-homogenous distribution of phase or composition, the measured d0 by powder diffraction method could not coincide with the true original lattice spacing of the material with variable phase and texture. Though we can fabricate small samples with a homogeneous cross section representative of those gradually distributed layers, it is very difficult to get each material point or Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 139-146 doi:10.4028/www.scientific.net/KEM.270-273.139

Neutron Diffraction Measurement and Finite Element Method Calculation of Residual Stress of a Heat Treated Steel Pipe

The residual strain of a 13% Cr steel pipe for use in oil wells was measured by neutron diffraction. As the pipe was quenched from 900°C to room temperature by spraying water at 30°C on the outer surface of the pipe for 30 s, it should be exposed to thermal stress. To measure the strain in the pipe, the residual stress analyzer (RESA) using neutron diffraction at Japan Research Reactor No. 3 Modified (JRR-3M) was used. Three directional measurements were carried out at intervals of 1 mm for the wall thickness of 5.51 mm. The residual stress deduced from the observed strain showed that the stress in the axial direction was tensile near the outer surface and compressive near the inner surface. The deduced stress was compared with the stress calculated by the finite element method (FEM).

Development of New Stress Measurement Method Using Neutron Diffraction

In this study, we proposed the high-versatility stress measurement method using neutron diffraction which can determine the residual stress states by measuring the lattice strains in two or three orthogonal directions even if the measured diffraction families were different in all three directions. In addition, we also proposed the stress measurement method without using the stress-free lattice spacing d0 which was measured using the powder sample or annealed sample. To verify this method, the residual stress distributions in a shrink-fit ring and plug specimen of aluminum alloy A7075 with texture were measured. The profile of the measured stress distributions almost agreed with the simulated stress distributions in the assumption of the plane stress condition. Our method which can determine the tri-axial stress states using observed lattice strains in two orthogonal directions was secondly applied to evaluate the stress states of A7075, high tensile strength steel HT1000, and Ni-base alloy NCF600 loaded in-situ. Measured stresses almost agreed with theoretical value with 10 MPa to 60 MPa error. On the other hand, the residual stress states of NCF600 were measured under the uni-axial loading condition by the stress measurement method without using the measured d0. Estimated lattice constant a was almost agreed with the lattice constant of its annealed sample, and changes in stress states evaluated using the proposed method coincided with the theoretical value.

Residual Stress Measurement and Verification of Quenched Steel Based on Neutron Diffraction Method

The purpose of this paper is to deal dealing with residual measurement of quenched steel based on neutron diffraction method and its verification by finite element analysis on the stresses induced by phase transformation. The initial interplanar spacing do and elastic constant were measured with rotating specimen method, the residual stress in quenched carbon steel S45C was obtained by means of neutron diffraction. Then a micromechanical approach and simulation based on metal-thermal-mechanical theory were carried out to estimate the microstructure in the steel due to phase transformation during quenching process. Finally the measured results of XRD, neutron diffraction as well as calculated value were compared and discussed.

Neutron Diffraction Measurements of Inner Local Strain of Fatigued Carbon Steel

The residual strain for three directions x, y, z at every 1 mm mesh point on the notch root of a round fatigued steel bar with a diameter of 8 mm was detected nondestructively, using a special neutron diffraction apparatus, residual stress analyzer (RESA) at JRR-3M, with a beam diameter of 2 mm. The residual stress for the three directions calculated from the observed strain showed that the stress was tensile and large near the surface of the specimen. This result is consistent with the well-known phenomenon that the fracture starts from the surface of the notch root. The residual stress near the center of the notch root was also tensile in the axial direction of the round bar.

Applied Stress on Silicon Perfect Single Crystal for Controlling the Extinction Layer

The extinct layer of Si(311) perfect single crystal has been investigated by neutron diffraction method with the residual stress diffractometer DN1-M installed at the experimental hall of Indonesian multipurpose reactor RSG-GAS, in Serpong, which provides micro beam and point detector arrangement. A Si(311) perfect single crystal with thickness of 5mm was used in this experiment. The crystal was finely polished at one side and roughly polished at the opposite one. It was measured that diffracted beam from the finely polished side shows very low intensity with narrow peak profile, while for the roughly polished surface, shows stronger and broaden peak. The diffraction layer of rough surface was determined to be 0.36mm, while the smooth one was 0.28mm. It was also found that in the direction of crystal thickness in between layers no diffraction peak was detected. By these experiments it was confirmed that the applied stress on Si(311) perfect single crystal produced thicker diffraction layer. This technique is one that can be used in order to enhance the total diffracted neutron, which is desired to produce a good monochromator system.