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Xie X.,Dalian University of Technology | Zhu M.,Dalian University of Technology | Yang H.,Nuclear Industry Research and Engineering Co. | Cui Z.,Dalian University of Technology | And 4 more authors.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2015

In time of flight diffraction (TOFD) technology, the D-scan image has poor lateral resolution, large quantitative error of crack length and arcs at the crack tip due to the wide beam of transducers. In order to improve the sizing accuracy of crack length, the synthetic aperture focusing technology (SAFT) is introduced and a mathematical model of SAFT processing on the D-scan image is built. Based on CIVA software, nine rectangular cracks is established and the ultrasonic TOFD D-scan is simulated. The range of crack length is from 5.0 mm to 45.0 mm. The effective diffraction signals of cracks are enhanced and the arcs at the crack tip are weakened in the simulated D-scan image which is processed and reconstructed by SAFT. For the rectangle crack with a length of 5.0 mm, the measurement error is only -0.4 mm. This method is verified in the experiments of two surface breaking notches, of which the length is 5.0 mm and 40.0 mm, the quantification errors are 0.4 mm and 0.8 mm respectively. It shows that D-SAFT technique can be utilized to obtain high resolution D-scan image and accurately measure the crack length. © 2015 Journal of Mechanical Engineering.

Lin L.,Dalian University of Technology | Yang P.,Dalian University of Technology | Zhang D.,Nuclear Industry Research and Engineering Co. | Zhao T.,Nuclear Industry Research and Engineering Co. | And 2 more authors.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2012

The welding quality of cast austenitic stainless steel (CASS) pipeline welds is critical to nuclear reactors. The mandatory requirements of NDT have been raised in inspection code of nuclear power plant, which is about the welding quality and service condition of CASS welds. However, the complex structure of welds makes the ultrasonic testing of CASS welds challenging. Phased array ultrasonic testing (PAUT) technique is promising to solve this problem. The difficulties of PAUT for thick wall CASS pipeline welds are analyzed, the corresponding key issues and solving strategies are summarized. Furthermore, the research progress and latest research results at home and abroad are described, which provides reference for the PAUT of thick wall CASS pipeline welds. © 2012 Journal of Mechanical Engineering.

Chen Y.,Dalian University of Technology | Luo Z.,Dalian University of Technology | Zhang D.,China Nuclear Industry 23 Construction Co. | Zhou Q.,Dalian University of Technology | And 3 more authors.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2016

Due o the difficulty of the accurate description of the grain structure and orientation, discrepancy occurs between the ultrasonic inspection simulation and experimental results for anisotropic coarse-grained materials. A modeling method based onelectron backscattered diffraction (EBSD) technique is proposed to quantitative describe the grain structure and orientation. A 96 mm×12 mm crystal orientation map for the radial-axial cross section of a centrifugally cast austenitic stainless steel (CCASS) specimen is acquired using the EBSD technique. A 15° misorientation angle is selected for the grain "orientation unification". The bond transformation is used to determine the stiffness matrix of the grains with different orientations in the model, thus realizing quantitative description of the complex elastic characteristics. A CCASS ultrasonic inspection model is built and numerically calculated by finite difference time domain method. The simulation results of CCASS ultrasonic testing reproduced typical structural noise and decrease of central frequency quite well. The modeling method provides effective solution to reveal the mechanism of ultrasonic scattering in the anisotropic coarse-grained structure. © 2016 Journal of Mechanical Engineering.

Yang Q.-Z.,Beijing University of Technology | Wang H.-D.,Nuclear Industry Research and Engineering Co. | Li X.-Y.,Beijing University of Technology | Wang T.,Nuclear Industry Research and Engineering Co. | Zhang W.-D.,Nuclear Industry Research and Engineering Co.
Yuanzineng Kexue Jishu/Atomic Energy Science and Technology | Year: 2016

The P11 heat resistant steel was welded by the narrow gap automatic TIG method, and the bead was filled using multi-layer single pass technology. Then the metallographic structures were observed and mechanical properties were tested, and the relationship between microstructure distribution characteristic and micro-hardness was particular searched. The results show that the filling bead consists of ferrite and troostite, and the coarse and fine grained regions are appeared alternately. When compared with base metal, the microstructure is finer and micro-hardness is higher. The cosmetic bead is mainly composed of coarse lath martensite and granular bainite while reticular troostite emerged, and the micro-hardness is higher than that of filling bead. In heat affected zone (HAZ) of filling bead, ferrite and pearlite with a banding distribution are observed, which is similar with the filling bead. In the thickness direction, the ultimate tensile strengths of top and bottom are almost the same, which is corresponding with microstructure distribution characteristic. And the impact tests show that absorption energy can meet all the requirements. © 2016, Editorial Board of Atomic Energy Science and Technology. All right reserved.

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