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RISS 인기검색어
- 검색키워드
- 저자 : Gezaei Abera, A. (검색결과 3 건)
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Gezaei Abera, A.,Song, Sung-Jin,Kim, Hak-Joon,Kishore, M.B.,Lee, Teak-Gyu,Kang, Sung-Sik Elsevier 2018 The International journal of pressure vessels and Vol.168 No.-
<P><B>Abstract</B></P> <P>Ultrasonic nondestructive testing plays an important role in structural integrity monitoring of dissimilar metal weld (DMW) structures in pressure vessels and piping of nuclear power plants. Inspection of DMW components is too complicated due to its anisotropic behavior to ultrasonic beam propagation. Many researchers are working rigorously to model the grain orientation and ultrasonic beam skewing in DMW structures but still not completely resolved yet. This paper is intended to estimate the grain orientation with the help of numerical simulation for a given asymmetric DMW component with specified scatterers. The DMW is fabricated from austenite stainless steel and carbon steel base metals with austenite stainless steel filler metal using Gas Tungsten-Arc Welding. To study this research a finite element method (FEM) based numerical simulation has been used to exactly evaluate the grain structure. This model mainly depends on the elasticity matrix which is a function of the grain orientation and attenuation of ultrasonic energy of the weld. Iterative measurement of grain orientation using macrograph of the etched weldment with 5 × 5mm mesh size was carried out then the attenuated elasticity matrix was fed into the FEM COMSOL software model as input parameter. Result obtained from numerical simulation (time of flight and amplitude) are validated with the experimental result and good agreement (above 0.8 correlation coefficient) have been observed at higher iterations. This macro-graphic information based numerical model shows the potential to predict the grain orientation of DMW.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Motivation to DMW components to qualitatively improve the mechanical properties of structures and to radically increase its application. </LI> <LI> Measure the grain structure from macro-graphic of DMW prepared by etching to find easiest practical way of defect prediction. </LI> <LI> Estimate the grain orientation with the help of numerical simulation for a given asymmetric DMW component with specified scatterers. </LI> <LI> Grain orientation modeling plays an important role in distinguishing defect signal during practical DMW testing and optimization of signal to noise ratio during ultrasonic testing. </LI> <LI> This opens advanced mathematical modeling of grain orientation to simplify ultrasonic testing in DMW for wide spread application in safety and micro structural integrity of pressure vessels and other heterogeneous anisotropic solids. </LI> </UL> </P>
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matte kishore babu,Ho-Girl Lee,A. Gezaei Abera,H. J. Kim,C. S. Seok,S. J. Song 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.1
Adoption of thermal barrier coatings (TBC) will help to improve the durability and thermal efficiency of turbine engines. Delamination of TBC owing to thermally grown metal oxides is a critical issue that needs periodical evaluation to ensure safety and effective maintenance for the financial benefits of industry. In this paper, a methodical approach using ultrasonic C-scan technique for quantitative evaluation of partial delamination area in TBC specimens was investigated. Preliminary studies were conducted using acoustic simulations and the experiments were carried out on a set of coin shaped TBC specimens prepared using plasma spray technique and isothermally degraded at 1100 °C for 25 h, 50 h, 100 h, and 150 h. Ultrasonic C-scans were performed using pulse echo technique with incident ultra sound radiation inclined normal to the surface of base metal of TBC system. Delamination maps of respective specimens were formulated from ultrasonic signals through proper signal processing and analysis techniques and the degree of delamination was evaluated with the help of existed mathematical model. The simulation results shows good agreement with the experimental data and this approach shows ability to estimate the degree of delamination from base metal surface.
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