氏名　LE CHI CUONG
学位の種類　博士（工学）
学位記番号　博甲第330号
学位授与の日付　平成17年03月25日
学位論文題目　DEVELOPMENT OF AUTOMATED X-RAY STRESS ANALYZER AND ITS
APPLICATIONS IN STRESS MEASUREMENT OF TEXTURED MATERIAS　（自動X線応力測定装置の開発とその集合組職材料の応力測定への応用））
論文審査委員
　主査　教授　栗田　政則
　副査　教授　秋山　伸幸
　副査　教授　福澤　康
　副査　助教授　永澤　茂
　副査　助教授　武田　雅敏

• 論文目次
• 論文要旨

［平成16（2004）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Contents

NOMENCLATURE　p.1

Chapter1 INTRODUCTION
　Background of the Thesis　p.3
　Structure of the Thesis　p.6

Chapter2 THEORY OF X-RAY STRESS MEASUREMENT
　Introduction　p.8
　X-ray Diffraction Using the Bragg Law　p.8
　Basic Equations of X-ray Stress Measurement　p.9
　X-ray Stress Measurement Methods　p.11
　Correction of X-ray Diffraction Line　p.13
　Methods of Peak Position Determination　p.15
　References　p.18

Chapter3 DEVELOPMENT OF X-RAY STRESS MEASUREMENT SYSTEM
　X-Ray Stress Measurement System　p.19
　Programmable Controller and scaler-timer　p.20
　Goniometer, Scintillation Counter and X-Ray Generator　p.22
　Transferring Data Using RS232C Interface　p.23
　Measurement with Oscillation　p.25
　References　p.25

Chapter4 MEASUREMENT PROGRAM FOR X-RAY STRESS ANAKYZER
　Introduction　p.27
　Flow Chart of the Measurement Program　p.27
　Operation of the Measurement Program　p.29
　Sample Measurement　p.33
　Conclusions　p.38
　References　p.40

Chapter5 ABSORPTION FACTOR AND INFLUENCE OF LPA FACTOR ON STRESS MEASUREMENT AND DIFFRACTION LINE WIDTH
　Introduction　p.41
　Absorption Factor in the Iso- and Side- inclination Method　p.42
　Without limitation of irradiation area　p.45
　With limitation of irradiation area　p.46
　Standard Deviation of Difference in Stresses Determined With and Without Correction for LPA Factor　p.54
　Experimental Procedure　p.56
　Results and Discussions　p.57
　Conclusions　p.66
　References　p.67

Chapter6 X-RAY RESIDUAL STRESS MEASUREMENT AUSTENITIC STAINLESS STEEL
USED FOR SHROUD OF NUCLEAR POWER PLANTS
　Introduction　p.69
　Stress Measurement Method for Anisotropic Materials　p.71
　Influence of shearing Stress to the Strain in the x Direction　p.76
　Half-width of X-Ray Diffraction Line for Anisotropic Material　p.77
　Standard Deviation of Stress　p.80
　Experimental Procedure　p.82
　Results and Discussions　p.83
　Stress Measurement of Annealed SUS316L Specimen　p.94
　Conclusions　p.101
　References　p.102

Chapter7 CONCLUSIONS　p.104

Chapter8 ACKNOWLEDGEMENTS　p.106

Publications and research activities

　Since residual stress in the surface layer of crystalline materials induced by heat treatment and machining will strongly affect the strength and deformation of materials, the determination of residual stress plays an important role in manufacturing processes. Various methods for determining the residual stress, such as the hole-drilling method, sectioning method and x-ray diffraction method are used. However, the x-ray diffraction method is most effective because it can nondestructively and accurately measure the residual stress in a localized area in the surface of a specimen.
　In the x-ray stress measurement, the stress is determined from the peak positions of an x-ray diffraction line. Four methods for determining the peak position of an x-ray diffraction line, the Gaussian curve, parabola, half-width and centroid methods, are used. However, commercially available x-ray stress analyzers are not equipped with the Gaussian curve method which is the most useful of the four methods. An automated x-ray stress measurement system with the measurement software was developed using the Visual C++ language. This x-ray stress analyzer can determine the stress together with its standard deviation which represents the magnitude of fluctuations in measured stresses due to intrinsic x-ray countingstatistics.
　In this system, the measurement conditions such as a preset time, step size and scanning range can easily be chosen, and the peak positions and stress together with their confidence intervals are simultaneously calculated with a personal computer.
　To accurately determine the stress, the diffraction lines have to be corrected for the Lorentz-polarization and absorption （LPA） factor. The absorption factors for the fixed-ψ and -ψ0 methods using the iso-inclination method and the fixed-η and -η0 methods using the side-inclination method were given.
In the stress measurement in a fixed area, an area of x-ray irradiation on the surface of a specimen must be restricted. A new absorption factor for measurement in a restricted area is proposed. The effect of the LPA factor on the stress value was investigated using quenched and tempered steel specimens having various diffraction line widths. The influence of the correction for the LPA factor on the stress value becomes stronger as the line width increases. In the side-inclination method, the correction for the LPA factor has little influence on the stress and it can be omitted. The equation for calculating the standard deviation of the difference between stresses with and without correction for the LPA factor was also derived.
　Recently in some nuclear power plants, the stress corrosion cracking occurred in the shroud of a boiling water reactor due to the residual stress in the welds.
The shrouds are made of austenitic stainless steel SUS316L. A new x-ray method for nondestructively measuring the stress of textured materials was proposed and it was applied to rolled austenitic stainless steel SUS316L used in the shroud.
It was shown that the stress in the transverse direction has little influence on the stress in the rolling direction and that the residual stress can be deter mined from the slope of the straight line fitted to the oscillatory peak positions in the sin2ψ diagram.