Papers by Keyword: Attenuation

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Authors: Matthias Militzer, Thomas Garcin, Warren J. Poole
Abstract: Laser ultrasonics for metallurgy (LUMet) is an innovative sensor technology for in-situ measurement of microstructure evolution during thermomechanical processing. This unique sensor has been attached to a Gleeble 3500 thermomechanical simulator for dedicated laboratory studies during processing of steel, aluminum, magnesium and titanium samples. Advanced processing software has been developed for the measurement of grain size and texture evolution from laser ultrasonic signals. Results of austenite grain growth measurements in low carbon steels will be described to demonstrate the capabilities of the LUMet technique. Further, applications of the system to measure recrystallization of ferrite and austenite formation during intercritical annealing simulations of dual phase steels will be presented. The ability to rapidly acquire data both during a single test and for multiple conditions over a range of conditions from different samples has important implications on expediting process modelling and alloy design. Although certain limitations exist, the LUMet technique offers a very reliable characterization platform with a number of potential applications in metallurgical process engineering.
Authors: Shi Long Chen, Jie Zhang, Jia Wei Xie, Li Liu
Abstract: The paper studied the frequency characteristics of UHVDC transmission line and UHVDC transmission line boundary and their attenuation to high frequency components of fault-generated transient signal. The paper points out that existing approaches which utilize protectors to distinguish local side’s internal or external fault can’t protect the whole line. UHVDC transmission line and UHVDC transmission line boundary’s attenuation to high frequency fault-generated transient signal is overall considered, and a single-ended transient based voltage protection method which distinguishes the opposite side’s internal and external fault is proposed. The Yunnan-Guangdong UHVDC model of actual parameters was built up by PSCAD, and simulation experiment was conducted.
Authors: Chuan Fang Wang, Xia Xin Tao, Anastasia Z, Kai Zhao, Wei Jiang
Abstract: The uncertainty of ground motion attenuation and its correction in PSHA is deal with in this paper. Mean values and standard deviations of random errors of three attenuation relationships of NGA-west1 are analyzed statistically from the data base released by the project. The dependences of the mean and deviation on magnitude, distance and peak ground acceleration are checked by the data base. The fact of mean values varying with acceleration is revealed obviously. Ground motion parameter Y is adopted into the probability density function of random error in a form of subsection. Finally, a suggestion to improve the correction is presented as subsection correction in the paper. The result of a case study by suggested procedure shows that the corrected acceleration is slightly higher than that of the traditional correction at the start of hazard curve, and is significantly lower than that of the traditional correction at the end of the curve, if the mean of random error decreases with acceleration.
Authors: Yong Wang
Abstract: seismic wavess energy and frequency will attenuate with its dissemination is one of the important seismic waves dynamic characteristics, and the most influential factors including the frequency, oil and gas saturation and porosity, so we can forecast the oil and gas according to the attenuation characteristics of the wavlet. The article extracted and analysised the attenuation properties of two different time seismic, and it could be seen that the remaining oil should be distributed in the southwest. So the result had a certain guiding significance to the exploration and development of the work area.
Authors: Yan Rong Pang, Zhi Hui Lv, Xiao Min Liang, Han Chang Chai, Ruo Chen Liu, Shao Qing You, Wei Zhou
Abstract: In recent years, acoustic emission (AE) testing technology is the one of the most important non-destructive testing (NDT) methods. The characteristics can be described by AE signals, including the location, nature and severity. In order to obtain the basic data for monitoring the wind turbine blade composite structure, the experiment adopted Φ0.5 mm lead pencil as artificial acoustic emission source and measured AE parameters, attenuation and source location of resin matrix for wind turbine blade. This paper introduced linear location and two-dimensional positioning technology of time arrival location method about the burst AE signal. The result shows that the location of AE source basically reflects the location of stimulation AE source, the location of AE source for resin matrix can agree well with the simulated location of AE source, the more close to the middle area, the more accurate location.
Authors: Jonathan J. Scholey, Paul D. Wilcox, C.K. Lee, Michael I. Friswell, M.R. Wisnom
Abstract: Acoustic emission (AE) is an attractive technique for the structural health monitoring (SHM) of aerospace systems. To reach its full potential in this role a quantitative approach must be adopted to study damage mechanisms in composite materials. In this paper, some of the practical issues regarding acoustic emission testing in composites are addressed. A model describing Lamb wave propagation through plates is described and used to make phase velocity and attenuation measurements in both aluminium and carbon fibre reinforced plastic plates. Results are then implemented in the frequency domain to conduct an experimental study of normal incidence Lamb wave reflections. Comparisons are made with finite element analysis (FEA) models with good results.
Authors: V. Bucur
Authors: Vasil P. Yashchuk, E. Tikhonov, O. Prygodjuk, O. Levandovska, M. Zhuravsky
Abstract: Numeric simulation of light passing through the scattering medium by the Monte-Carlo method was carried out. The influence of multiple scattering on the light beam attenuation in an absorbing media was investigated. The additional absorption appearance was shown to be initiated by multiple scattering. The experimental evidence for this absorption is abrupt increasing of beam attenuation at high particle concentrations. The behaviour of the additional absorption was investigated. The results of numeric calculation are in good agreement with experimental results.
Authors: Ying Li, S.R.Anjaneya Reddy Guntur, Min Joo Choi, Dong Guk Paeng
Abstract: Tofu was suggested as Tissue Mimicking Materials (TMMs) due to its low cost, availability, gelatinous nature, and shape flexibility. However, the similarity in acoustic properties of the different packets of Tofu and acorn curd (Muk) is critical for TMMs but not fully investigated yet. In order to improve the accuracy for time-consuming and multi-stepped measurements of acoustic properties, an automated measurement system was developed. Using the automated system, the acoustic properties Tofu and Muk were measured to know whether they are similar among the different samples. In conclusion, the acoustic properties were measured to be similar among the different packets of Tofu and Muk, suggesting them as potential TMMs.
Authors: Sang Ll Lee, Jin Kyung Lee, Joon Hyun Lee
Abstract: The nuclear power plant has lots of pipes that the fluid of high temperature and high pressure flows. Among the pipe materials used at secondary circuit of the power plant the carbon steels are sensitive to corrosion due to their material properties. In this study, both ultrasonic test and acoustic emission test were used to study the corrosion effect for the carbon steel pipe nondestructively. The carbon steel specimens were in the pipe under 473K temperatures and 10MPa pressure conditions for corrosion processing. According to the degree of corrosion the strength of the specimen was evaluated, and the thickness of the corrosion specimens was also measured by using the ultrasonic wave. The experimental results showed that the attenuation factor was also increased as a depth of corrosion increased. The measured depth of the real corrosion by ultrasonic test shows the good agreement with that by an optical microscope. In order to understand the corrosion effect for the failure mechanism of carbon steel, a failure test on the specimen with various corrosion conditions was performed. An acoustic emission technique was also used to evaluate the degree of damage of corrosion specimen in real time. Acoustic emission technique is proved a useful method for on-line monitoring the microscopic failure mechanism and the damage location for the structures.
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