Papers by Keyword: Non-Destructive Inspection

Abstract: Conventionally, the sin²ψ method has been used as X-ray stress measurement. However, in recent years, the XRD² method and the cos α method have been put into practical use and spreading. In addition, the Fourier analysis method that shares the same measurement principle of the cos α method has been developed and is attracting attention. Therefore, in this paper, the Fourier analysis method is examined from the measurement theory and the measurement accuracy is investigated. It is reviewed that the basic equation is a finite Fourier series, and that stress can be determined from the Fourier coefficients by using coordinate transformations. Then, while comparing it with the multiple regression analysis, the accuracy of the Fourier analysis method is discussed by using numerical calculations.

Abstract: The X-ray stress measurements by the sin²ψ method, the cos α method and the XRD² method are basically composed of the fundamental equations based on diffraction vectors and the calculation for determining X-ray stress. The fundamental equations are expressed differently, which are due to the fact that the measurement systems associated with the incident X-ray control device and the diffracted X-ray detector are different. Although the dependent variable that is the measured quantity is the same diffraction angle theta in the fundamental equations, the main independent variable is different like the tilt angle ψ in the sin² ψ method and the central angle α, γ of the Debye-Scherrer ring in the cos α method, the XRD² method, respectively. Therefore, the stress determination method has been devised based on each the fundamental equation. By clarifying the differences between each X-ray stress measurement method and making a relationship, a unified representation for the fundamental equations is formalized. Therefore, a comparison of each X-ray stress measurement method is expressed in the same Euler space, and a conversion method for each X-ray stress measurement method is presented.

Abstract: This paper presents the feasibility of developing an electromechanical in-situ viscosity measurement technique by analyzing the detectability of small variations in the viscosity of different shear thickening fluids and their different compositions. Shear thickening fluid (STF) is a kind of non-Newtonian fluid showing an increasing viscosity profile under loading. STF is utilized in several applications to take advantage of its tunable rheology. However, process control in different STF applications requires rheological measurements, which cause a costly investment and long-lasting labor. Therefore, one of the most commonly used in-situ structural health monitoring techniques, electromechanical impedance (EMI), was used in this study. In order to actuate the medium electromechanically, a piezoelectric wafer active sensor (PWAS) was used. The variations in the spectral response of PWAS resonator that can be submerged into shear thickening fluid are analyzed by the root mean square deviation, mean absolute percentage deviation and correlation coefficient deviation. According to the results, EMI metrics provide good correlations with the rheological parameters of STF and thereby enabling quick and low-cost rheological control for STF applications such as vibration dampers or stiffness control systems.

Abstract: Currently, the sin²ψ method is established as an effective technique as how to measure the residual stress state of metal materials non-destructively by X-ray diffraction. In recent years, new X-ray stress measurements with two-dimensional detector are developed and spreading in the world. There is the cosα method as one of the new techniques. However, the research about the statistical errors in the method continues. The measurement theory of the cos α method is reviewed on the triaxial stress state. The triaxial stress analysis by the method is examined and discussed from a viewpoint of the derived errors for the determination.

Abstract: The sin² ψ method [1] is conventionally used well as how to measure non-destructively the residual strain and stress states of polycrystalline materials by X-ray diffraction. In the conventional method, there are Dölle-Hauk method [2] and Winholz-Cohen least squares analysis [3] as the determinations of the strain and stress states for limiting the influence of measurement errors. Many researches are made about the statistical error in those methods. In recent years, use of the X-ray stress measurements with two-dimensional detector from the conventional method is spreading. One of the measurements is called the cos α method. The measurement errors have attracted a great deal of attention for users as the spreads. Therefore, the basic equations and determinations of the strain and stress states are examined. The confidence intervals of measured stress by the cos α method. The research and development is performed for the the cos α method which took the influence of measurement errors into consideration.

Abstract: Duplex steels are an important group of materials which are generally used for applications where resistance to corrosion, or high strength and creep resistance at elevated temperatures, are required. They are used extensively in nuclear plant. Although ultrasonic inspection methods have been routinely used in industry for some three decades, it is well known that cast or welded austenitic components can be difficult, or even impossible, to examine ultrasonically. Development of ultrasonic techniques is therefore in progress in several countries to provide improvements which are being sought on safety and economic grounds.The aim of this paper is a brief description of the relevant metallurgical characteristics given before a consideration of the physical properties of the weld metal and the current theoretical models used to describe ultrasound propagation in it. The paper deals with the steps taken to improve the capabilities of ultrasonic inspection and includes a discussion of the problems of flaw location and sizing.

Abstract: The non-destructive inspection of duplex steels is a big challenge, being composed of ferrite and austenite, have some particularities. When using ultrasound, for instance, its waves propagate well in ferrite, but suffer strong attenuation, scattering and refraction in austenite. The aim of this work is to use the Phased Array ultrasonic inspection method for the thin (4 mm) duplex steel weld joint inspection. The experimental sample was made ​​of duplex steel shaped tube with an outer diameter of 44 mm and a wall thickness of 3.8 mm welded with a laser beam. The experiment was necessary to verify attenuation of duplex steel. On the base material and the weld joint were made the artificial defects, in which the adjusted sensitivity of the ultrasonic device was set.The result of the measuring was the defect echo coming from the weld root layer. The length (about 25 mm) can only be estimated due to the inaccurate constant velocity of probe motion along the surface.

Abstract: The use of non-destructive inspection techniques in conventional stainless steels is well established. However the non-destructive inspection of duplex and superduplex steels is a big challenge as those steels, being composed of ferrite and austenite, have some particularities. When using ultrasound, for instance, its waves propagate well in ferrite, but suffer strong attenuation, scattering and refraction in austenite. An extended research is proposed on the inspection of duplex steels, especially in welded joints, which presents the worst problems in those steels (incorrect ferrite/austenite balance and precipitation of deleterious phases). The aim of this work was to use the TOFD ultrasonic inspection method for the thin duplex steel weld joint inspection.

Abstract: This study was performed to develop a non-destructive inspection system to detect grinding burn, which is capable of quantitative 100% inspection inside a production line. An eddy current sensor, which has advantages of short inspection time and low cost, was used. It was shown that the grinding burn detection technique had been developed and is possible to detect grinding burn by using this technique, in the 1st report¹⁾ and the 2nd report²⁾. In this report, an experiment of in-process detection of grinding burn was conducted, by applying the grinding burn detection technique which we have developed. The eddy current sensor has been combined with an in-process gauge in order to keep the clearance between the sensor probe and the work piece constant. It was shown that grinding burn can be detected successfully during cylindrical machining.

Abstract: In the reinforced concrete structure, steel corrosion is a major factor affecting the durability of existing structures, it is necessary to explore the extent of steel corrosion in order to take the necessary measures. Based on non-damaged concrete components or structures, by measuring the performance of concrete-related physical quantities, non-destructive inspection could presume strength, compactness, uniformity and defects of concrete components or structure. Combined with engineering example, non-destructive inspection technique and its application in the degree of steel corrosions inspection have great prospects through further validation.