Kazuyoshi Sekine

On the mechanism of texture transition in FCC metals

Polycrystalline copper sheets having orientations (112) [−1−1l] and (011)[−2−1l] were rolled successively at two temperatures. When rolled at the liquid nitrogen temperature, the (112)[−1−1l] texture decreased mainly by mechanical twinning, and it also extended its spread toward (111)[−1−12]. The resolved shear stress on the slip systems, which produce lattice rotations from (112)[−1−1l] to (111)[−1−−12], is smaller than that on the systems giving rise to inverse rotations. The formation of the minor component having (111) planes parallel to the rolling plane in the alloy type rolling texture can be explained on the basis of hardening of the latent slip systems. When rolled at room temperature, the (112)[−1−1l] orientation was gradually rotated toward (011)[−2−1l], but the orientation spread around (112)[−1−1l] has scarcely increased, in the sheet with the (011)[−2−11] orientation rolled up to 92 pct at 100°C. These results indicate that cross-slip does not contribute to the displacement from (011)[−2−1l] to (112)[−1−1l], but retards the inverse rotations. In consequence, the prime factor for texture transition is the ease of mechanical twinning, rather than that of cross-slip.

Magnetic leakage field due to sub-surface defects in ferromagnetic specimens

Abstract This paper describes analytical expressions for the magnetic leakage field of two types of internal defects: two dimensional rectangular and elliptical defects as functions of the applied magnetic field strength, the defect size and the distance below the surface. In this study, the magnetic image effects from the spatial boundary and the defect boundary are taken into consideration. That is, the leakage field of rectangular-like defects or elliptically shaped defects ‘below the surface’ are derived by using the modified dipole model and image theory. The profiles and strengths of leakage fields calculated from the proposed analytical forms are presented under various conditions and compared with experimentally measured ones.

A Study of Influence of Locally Reduced Thickness on Stress of Bottom Annular Plate of Oil Storage Tank During Uplifting by Seismic Loading

In 1978, Off-Miyagi Prefecture Earthquake in Japan caused damage to large oil storage tanks. Their annular plates had been greatly reduced in thickness due to local corrosion, and they were broken by uplifting due to the earthquake. In order to examine the stress tendency of annular plates with local metal loss during uplift by earthquakes, nonlinear static uplift analyses by three-dimensional shell FEM were carried out on a 110,000kl oil tank. The sizes of locally reduced parts, such as the circumferential and radial dimensions, were taken as the analytical parameters. Many useful results were obtained regarding the relationship between the range of local metal loss and the stress in annular plate. The “stress increase ratio” is defined in this study as the ratio of radial surface stress in an annular plate with metal loss to that without metal loss. The following results were obtained. As the radial width of metal loss part decreases, the annular plate radial stress increases. The stress increase ratio is 1.47 when the thickness of radial metal loss part of radial width 23mm is reduced to 18.4mm from an original thickness of 21mm. For a circumferential length of metal loss part of less than 2.1m that is calculated by multiplying the radius of tank with the tank central angle of three degrees, the stress increases proportionally to the length of metal loss part. On the other hand, when the length is more than 2.1m, the maximum stress has a tendency to saturate.Copyright

Evaluation of operative reliability of safety-related part of control system of machine and safety level

This paper concerns the evaluation of SRSC (safety related control system) from the point of operational reliability. The related standard is revised in 2006 and the new standard introduces PL (performance level) to evaluate the SRCS and shows procedure to determine the PL. To examine the procedure in practical point of view, PLs for 5 typical circuits is estimated by the procedure and event tree analysis and the results are compared with each other. From this study, some issues are pointed out.

Development of a pulse heating thermographic NDT technique for detection of latent blister in corrosion protective coating on oil storage tank

Pulse heating thermographic NDT technique was developed for the detection of latent blisters in the corrosion protective coating on oil storage tanks employed for petroleum stockpiling in Japan. Experimental studies were made on the applicability of the proposed NDT method to the quantitative identification of the subsurface latent blisters in the coating. Pulse heat flux by the xenon flush lamp was applied to the surface of the corrosion protective coating and sequential thermal images were taken by the high-speed infrared thermography. It was found that the blisters were clearly identified as the localized high temperature region in the sequential thermal images.

Accident occurrence model for the risk analysis of industrialfacilities

This paper describes an accident occurrence model for the risk analysis of industrial facilities. To better understand the characteristics of industrial accident data, the proposed accident occurrence model is based on a chemical reaction. The model introduces a defensive barrier, which corresponds to the activation energy in a chemical reaction, to prevent an accident. Furthermore, the uncertainty factor in the defensive barrier is mathematically derived as a gamma distribution. The analytical results for the proposed accident occurrence model indicate a Pareto type II distribution, which is the same result found by using a risk curve. Therefore, the analytical model validates the effectiveness of analyzing industrial risk with a riskcurve.

Simulation for a Floating Roof Behavior of Cylindrical Storage Tank due to Wind Load: Part 2 — Sloshing Response Analysis

The floating roofs are used in large cylindrical storage tanks to prevent evaporation of oil. The single-deck floating roof, considered herein, consists of a thin circular plate called “deck” attached to a buoyant ring of box-shaped cross section called “pontoon”. The deck plates are deformed to create waves and they are subjected to cyclic bending due to wind load. This phenomenon may lead to initiate fatigue cracks at the welding joints. It is important to know the vibration characteristics of the waves in the deck plate. The authors have reported a CFD analysis of a cylindrical storage tank due to uniform wind flow in another paper. This paper presents the axisymmetric finite element analysis for the sloshing response of the single-deck floating roofs in a cylindrical storage tank subjected to wind load obtained by the CFD analysis. It is assumed that the liquid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics of the waves in the deck plate, such as frequency and amplitude, are investigated.Copyright

Seismic Response Analysis for Sloshing of a Single-Deck Floating Roof With Center Pontoon in Oil Storage Tank

Floating roofs are widely used to prevent evaporation of contents of large cylindrical oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to floating roofs due to liquid sloshing. Seven single-deck floating roofs deformed to leak oil on them, and they lost buoyancy to sink. Two of them were the single-deck type with center pontoon in large diameter tanks. The present paper deals with an axisymmetric finite element analysis for the sloshing response of a floating roof with center pontoon. The hydrodynamic coupling of the fluid and the floating roof under seismic excitation is taken into consideration in the analysis. The fluid is assumed to be incompressible and inviscid, and the roof is assumed to be linear elastic. In addition, the sidewall and the bottom are assumed to be rigid. In the finite element analysis, the behavior of the fluid is formulated in terms of dynamic pressure using the Eulerian approach. The basic vibration characteristics of the single-deck floating roof with center pontoon, such as the natural periods and vibration modes, can be obtained from this analysis. These characteristics are shown comparing with those of the single-deck floating roof without center pontoon. The seismic response analysis for the input of an earthquake wave is also performed.Copyright

Eulerian Finite Element Formulation for Sloshing Response of Floating Roofs in Aboveground Storage Tanks

The floating roofs are widely used to prevent evaporation of content in large aboveground oil storage tanks. The 2003 Tokachi-Oki earthquake caused severe damage to the floating roofs due to liquid sloshing. The structural integrity of the floating roofs for the sloshing is urgent issue to establish in petrochemical and oil refining industries. This paper presents the axisymmetric finite element analysis for the sloshing response of floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof under seismic excitation is taken into consideration in the analysis. It is assumed that the fluid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The theory for the finite element analysis in which the behavior of the fluid is formulated in terms of dynamic pressure as the Eulerian approach is developed. The basic vibration characteristics of the floating roof, such as natural periods and vibration modes, can be obtained from this analysis. These will give engineers important information on the floating roof design.Copyright

Damage Assessment of Industrial Accidents by Frequency-Magnitude Curve

Damage assessment of industrial accidents by the frequency distribution of accidents considering their magnitude and risk curves were conducted to analyse accident situation changes.