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28 June 2020, Volume 46 Issue 3 Previous Issue    Next Issue

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Materials Science and Engineering

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Effects of voltage on electrochemical corrosion behavior of micro-arc oxidation coatings MA Ying, ZHANG Qing-ju, AN Ling-yun, WANG Xing-ping, SUN Le, WANG Sheng 2020, 46 (3):  1-6.  Abstract ( 278 )   PDF (3796KB) ( 316 )   Save The effects of voltage on the electrochemical corrosion behavior of micro-arc oxidation (MAO) coatings formed on pure magnesium were studied by using cyclic voltammetry (CV), potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS). SEM was adopted to characterize microstructure of the coatings. The results show that the voltage has significant effects on corrosion resistance of the coatings. With increase of voltage, the corrosion resistance of the coatings gets improved. This may be attributed to the coating's thicker thickness which may provide a good physical barrier against the erosion of the corrosion medium. During the whole corrosion process, the coating prepared in the high voltage experiences three stages: the corrosion medium gradually infiltrates into the coating, then corrosion medium penetrates the coating to the interface between the coating and the substrate, and eventually corrosion products fill into defects such as micropores and microcracks. In contrast, for coatings prepared under low voltage, the electric resistance of both loose layer out of the coating and dense part in the core of the coating decreases gradually with the immersion time prolonging. This results in the corrosion resistance of the coating decreasing, and finally the coating fails completely as a result. References | Related Articles | Metrics

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Preparation of nanoporous Ni and its electrocatalytic activity for hydrogen evolution ZHOU Qi, DUAN De-dong, ZHENG Cheng 2020, 46 (3):  7-12.  Abstract ( 359 )   PDF (3176KB) ( 406 )   Save Nanoporous Ni was prepared by rapid solidification and de-alloying. SEM and XRD were used for phase analysis and morphology characterization in our study. The electrocatalytic hydrogen evolution performance of nanoporous Ni electrode was meanwhile tested by means of linear sweep voltammetry (LSV), cyclic voltammetry (CV), and alternating current impedance (EIS). The results show that the Ni5Al95 precursor alloy can be de-alloyed at 65 ℃ for 4 h, obtaining multi-layered, bi-continuous nanoporous Ni. At a current density of 50 mA·cm－2, the hydrogen evolution over-potential at 25 ℃ is 257 mV, the electric double layer capacitance is 4.7 mF·cm－2, and the apparent activation energy during the hydrogen evolution reaction is 26.06 kJ·mol－1. Electrochemical desorption becomes the control step for the whole reaction process. After 1 000 cycles of cyclic voltammetric endurance test, the polarization behaviors of nanoporous Ni electrode at 25 ℃ remains its original state. The hydrogen evolution over-potential decreased by 6 mV in the case of current density of 50 mA·cm－2, which demonstrates excellent hydrogen evolution stability. References | Related Articles | Metrics

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Phase-field simulation on the peritectic phase transition in Fe-C binary alloy FENG Li, ZHONG Jun-he, WANG Jun, AN Guo-sheng, WANG Huai-zhi, GAO Ya-long 2020, 46 (3):  13-17.  Abstract ( 253 )   PDF (2296KB) ( 418 )   Save In this study, taking Fe-0.79 mol%C binary alloy as an example, the evolution of austenite in different supercooling degree during peritectic phase transition is simulated by multiphase field method, and the influences of supercooling degree on austenite growth rate as well as austenite morphology are discussed respectively. The simulation results show that in the process of peritectic reaction and influenced by interfacial mobility and solute enrichment, part of δ phase near the three-phase junction remelted, resulting in the growth of γ phase into δ phase. When the peritectic phase transition occurs on the surface of the spherical δ phase in liquid phase, the γ phase grows around the δ phase as a shell, and finally forms a core shell around the δ phase. With the increase of undercooling, the driving force of peritectic transformation increases, the growth rate of γ phase accelerates, and the amount of δ phase surrounded by γ phase increases. References | Related Articles | Metrics

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Nanocrystallization mechanism of graphite during constrained electric explosion ZHU Liang, LIU Qiu-hua, WANG Xu-dong 2020, 46 (3):  18-22.  Abstract ( 214 )   PDF (5629KB) ( 367 )   Save To prepare low-dimensional nano-carbon, a series of electric explosion tests were conducted with a self-developed constrained explosive graphite device by the changed initial charging voltages together with diameters of the constrained pipe. In the experiment, in-situ sampling and microscopic analysis were carried out successively for electro-explosion products in the form of aerosols. On this basis, nano-crystallization mechanism of graphite in the process of electric explosion was studied by combining the results of the microscopic analysis of the products and the relationship between the energy density and the particle size of the products. The results show that the mechanical compression are generated in the constraint tube can exert instantaneous high pressure on the graphite and make the graphite broken. The compression wave repeatedly impacts and peels the broken graphite off in its propagation process, which results in the graphite particles ejecting from the tube. During particle injection, the collision between the graphite particles as well as between the graphite particles and constraint tube wall occurs constantly, resulting in further fragmentation of the graphite particles and formation of low dimensional nano-carbon. References | Related Articles | Metrics

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Effects of electrical parameters on energy deposition of nanoparticles preparation by wire electrical explosion ZHANG Ai-hua, MA Ming-min, ZHU Liang 2020, 46 (3):  23-27.  Abstract ( 191 )   PDF (1166KB) ( 454 )   Save The energy deposition in the process of wire electrical explosion is directly related to the particle size distribution of prepared nanoparticles. In order to study the influence of electrical parameters on energy deposition, the electrode types and air gap lengths were adjusted to carry out the wire electrical explosion experiment. In the experiment, a high sampling rate oscilloscope was used to collect the voltage and current waveforms, and the deposition energy of the alloy wire and the particle size distribution of the prepared nanoparticles were analyzed. The results indicate that there is a harmonic component with high amplitude in the wire explosion current, and the harmonic deposition energy contributes to the total deposition energy of the wire, which can affect the average particle size of the prepared nanoparticles.Between the two types of electrodes, the ratio of harmonic deposition energy to total deposition energy is higher when parallel electrodes are used than when coaxial electrodes are used. Shortening the discharge air gap can reduce the ratio of harmonic deposition energy and reduce total deposition energy also. Investigations to particle size distribution show that the average particle size of the nanoparticles prepared by parallel electrodes is smaller, which further indicates that the total deposition energy increases in this condition. References | Related Articles | Metrics

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Preparation of YAG-ZrO2 composite nanofibers by electrospinning HE Ling, QIN Xing-wen, FENG Yu-jie, PAN Li-li, SUN Wei-min, LI Wen-sheng 2020, 46 (3):  28-33.  Abstract ( 234 )   PDF (3077KB) ( 299 )   Save YAG-ZrO2 composite nano-fibers with smooth morphology and uniform size were successfully prepared by electrospinning and heat treatment. Effects of voltage and concentration on the phase and morphology of composite fibers were studied by XRD, FT-IR and SEM in this research. Obtained results show that the composite fiber has a smooth surface and uniform size if voltage of 25 kV and the PVA content of 11% applied. After annealing at 1 200 ℃ for 5 h, the precursor fiber has a higher crystallinity and a uniform diameter of about 500 nm. In order to make the YAG-ZrO2 fiber reinforced composites, which possesses the function of self-testing, the luminescence properties of YAG-ZrO2 fibers were also investigated. It was found that sharp emission peaks at 581 nm were detected when YAG-ZrO2:Tb3+ composite nanofibers were excited by 290 nm UV light, emitting green light as well. This phenomenon belongs to the 4D4→7F4 transition of Tb3+. Stress-luminescence experiment results show that YAG-ZrO2:Tb3+ fiber could detect the stress and strain of aluminum matrix composites. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Analysis and optimization of machining method of paper-cutting roller with face-cutter YAN Chang-feng, YAN Peng-fei, SHEN Guang-fei, GAO Gang-gang, GOU Wei-dong 2020, 46 (3):  34-38.  Abstract ( 248 )   PDF (1381KB) ( 515 )   Save Aimed at the problem that the parts of category of paper-cutting roller with face cutter are easy to be deformed during their machining process, the effects of self-gravity, cutting forces and cutting heat on the deformation are analyzed. A method for machining this type of roller with obviously smaller deformation is proposed. This method is realized on the basis of determination of the clamping, feeding and supporting modes of the workpiece of the roller. The key of this method is as follows: both left and right ends of the roller are clamped with chucks, the feeding mode is so selected that the turning is reversed and left to right, and meantime, a movable auxiliary support is set additionally between the left and right side of the machine tool, which can be moved according to the need of the machining process. Based on the ABAQUS, the deformation of the roller at different span wise position and with different stiffness is analyzed, the displacement deformation under the condition of double-auxiliary support and single-auxiliary support is compared simulatively. It is verified that the machining method of the roller with single-auxiliary support can achieve the result with double-auxiliary support, the material will be saved and the cost reduced. References | Related Articles | Metrics

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Fault diagnosis method of rotating machinery based on both EEMD and fuzzy information entropy ZHAO Rong-zhen, ZHANG Chen, DENG Lin-feng 2020, 46 (3):  39-44.  Abstract ( 345 )   PDF (1653KB) ( 497 )   Save Aimed at the lower accuracy of fault recognition of rotary machinery, the fault diagnosis method is proposed based on both EEMD and fuzzy information entropy. By using this method and incorporating with the superiority of EEMD and fuzzy information entropy in connection with feature extraction, a feature set is constructed, which can finely measure the complexity of the fault probability of different category of vibration signals. Firstly, the original vibration signal is decomposed with EEMD to obtain several intrinsic modality functions (IMFs), the fuzzy information entropy of the first 5 high-frequency IMF components is calculated to compose high-dimensional feature set then the LPP is used to reduce the dimensionality of the high-dimensional feature set and eliminate redundant irrelevant features, and finally, the reduced sample set is input into the KNN classifier to identify the faults. Foregoing method is validated by data collected from a double-span rotor test rig and compared with the methods of EMD fuzzy entropy, EMD fuzzy information entropy and EEMD fuzzy entropy in connection with the fault recognition accuracy. The result show that this method is able to extract effectively the fault feature of rotor vibration signals.It have higher fault recognition accuracy. References | Related Articles | Metrics

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Formation mechanism of hydraulic damping hole blockage caused by solid particles LIU Xin-qiang, JI Hong, SUN Fei, Li Na-na, ZHANG Jian-jun 2020, 46 (3):  45-49.  Abstract ( 281 )   PDF (3060KB) ( 575 )   Save In order to solve the problem of hydraulic damping hole blockage caused by solid particles, this study uses the Euler-Euler multiphase flow model of software Fluent to calculate and analyze the three-dimensional solid-liquid two-phase flow in the flow region of a slender-type hydraulic damping hole. Simulated results show that near the entrance of the damping hole, the solid particles are in a heap-like silting state, the solid-phase volume fraction appears “step” phenomenon along the flow direction of the central axis. It is also found that the solid-phase volume fraction decreases with the increase of the viscosity of the oil, and increases with the density of the particles. The siltation of particles in the central area of the damper inlet hole is the main cause of the blocking to the damping hole. References | Related Articles | Metrics

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Characteristics of unsteady cavitational flow in centrifugal pump with low specific speed ZHAO Wei-guo, WANG Gui-peng, ZHAO Guo-shou, XIA Tian 2020, 46 (3):  50-56.  Abstract ( 320 )   PDF (3593KB) ( 476 )   Save In order to study the characteristics of cavitational flow within centrifugal pump with low specific speed, the numerical simulation of three-dimensional unsteady cavitational flow in the pump was carried out on the basis of SST k-ω turbulence mode and ZGB cavitation mode and under different inlet pressure, and the regularity of pressure pulsation and the change of bubble volume as well at different positions in the pump were investigated when cavitation occurred. The result showed that the principal frequency of the impeller pressure pulsation would be the blade frequency, and the growth of amplitude of secondary frequency fluctuation at the inlet of impeller channel would be obvious. The growth rate of the amplitude pressure pulsation near the outlet of impeller channel would increase even more obviously when compared with that at the inlet of impeller channel. Also when cavitation took place, the pressure fluctuation at the inlet of the impeller channel would be delayed from that within the impeller, at its outlet and at its separate tongue. The growth of cavitational vapor bubble would be nonlinear. References | Related Articles | Metrics

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Influence of leading edge delamination on flow field around airfoil and aerodynamic performance of wind turbine LI Ren-nian, YU Jia-xin, LI De-shun, LI Yin-ran 2020, 46 (3):  57-63.  Abstract ( 250 )   PDF (3908KB) ( 465 )   Save In order to study the effect of leading edge wear on the aerodynamic performance of airfoil, a special-purpose airfoil S809 for wind turbines was taken as investigation object, and SST k-ω turbulence mode was used to carry out its numerical computation, and study the effect of different leading edge delamination depths on the flow field around airfoil and aerodynamic performance. The results show that the leading edge delamination will change the shape of the airfoil, so that the leading edge flow will become a step flow, causing the flow separation zone at trailing edge to expand and the separation point to move forward. With the increasing of the delamination depth and the angle of attack, the flow separation zone at trailing edge of airfoil on suction surface and the backflow vortex at leading edge of airfoil on suction surface will be changed from mutually independent state of each other to completely fused. Under condition of identical angle of attack, the leading edge delamination will have a greater influence on the pressure coefficient on the blade surface at the leading edge. When the angle of attack is less than 3°, the leading edge delamination will have little effect on the lift and drag coefficient of the airfoil. When the angle of attack is greater than 3°, the lift coefficient of the airfoil will gradually decrease as the degree of delamination becomes higher, but the drag coefficient will gradually increase. Compared to a smooth airfoil, the lift loss rate of airfoil with leading edge delamination will amount to its maximum of 55.08% and the drag growth rate 150.48%. References | Related Articles | Metrics

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Spatiotemporal evolution of turbulence structure in wake ofhorizontal-axis wind turbine LI De-shun, HU Jin-sen, YU Jia-xin, GUO Tao, JIAO Xuan-ping, LI Ren-nian 2020, 46 (3):  64-69.  Abstract ( 283 )   PDF (2002KB) ( 669 )   Save Based on the analysis method of wavelet transformation and incorporated with actuating line model and large eddy simulation, the spatiotemporal evolution of the turbulence structure of wake of a 33 kW horizontal-axis wind turbine was investigated. It was found by the investigation that with the increase of the distance from the rotor rotation plane, the average velocity of wake at each measurement point would decrease first and then gradually increase, the amplitude of the velocity fluctuation would exhibit a decreasing trend; within the region of 7 times of rotor diameter behind the wind turbine, the flow velocity curve would have a pronounced periodicity, reflecting that the passing frequency of the shed vortex was 1.8 Hz, twice as high as the rotation frequency of the wind turbine. The frequency of appearance of blade tip vortices at the measuring point of unit rotor diameter behind the rotor would be from 0.78 to 25.00 Hz, the passing time of the formed vortex tube over the measurement point would be approximately 0.32 s, and the diameter of the vortex tube would be approximately 1.83 m. A low-frequency turbulence structure with frequency from 0.15 to 0.78 Hz would appear at the measuring point of 3-fold rotor diameter from the rotor; the frequency range of blade tip vortex at measuring point of 7-fold rotor diameter from the rotor would be from 1.56 to 25.00 Hz, which was greatly reduced when compared with the case of foregoing blade tip vortex. At the measurement point of 8-fold rotor diameter from the rotor, the vortex tube shape of blade tip vortex similar to that in near wake region would disappear; the blade tip vortex at the measuring point of 9-fold rotor dimeter from the rotor would dissipate almost completely. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Seismic probability fragility analysis of main steam isolation valve YU Shu-rong, CHEN Dong-ran, XUE Rui-yuan, ZHANG Xi-heng 2020, 46 (3):  70-74.  Abstract ( 232 )   PDF (1765KB) ( 673 )   Save The finite element software is used to calculate the equivalent static force of a main steam isolation valve to predict its seismic weak point, and to calculate seismic margin of the main steam isolation valve by using probability vulnerability method. The results show that a seismic weak point of the main steam isolation valve may shift with amplification of seismic vibrations. By doing calculations, the seismic weak point of the main steam isolation valve is determined to be supporting bracket, and the seismic capacity of the supporting bracket under 95% confidence along with 5% failure probability is calculated to be 11.14g. On this basis, fragility curves of the main steam isolation valve with different confidence levels under elastic failure mode were drawn. The calculation method of seismic margin of nuclear power valves was combed out, and the importance of seismic margin for seismic safety was demonstrated when the earthquake occurs beyond the design benchmark. References | Related Articles | Metrics

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Design of TiO2 nanoparticle colloid activation system and its flow field simulation analysis SONG Xiao-zong, YAO Tong, XU Guo-min 2020, 46 (3):  75-80.  Abstract ( 185 )   PDF (4111KB) ( 432 )   Save Ultraviolet (UV)-induced nanoparticle colloidal jet processing can realize the processing of sub-nanometer ultra-smooth surface of hard and brittle crystal materials. It can be known according to the material removal principle that along with the polishing process, the surface of TiO2 nanoparticles in the colloid would absorb a layer of removed atoms of the workpiece, so that the activity and photocatalytic properties of the TiO2 nanoparticle colloid would be affected. In order to achieve the recycling of TiO2 nanoparticle colloids, the O3/UV advanced oxidation process(AOPs) was based to study the reactivation mechanism of the TiO2 nanoparticles colloids and meantime, the TiO2 nanoparticle colloidal activation system was designed as incorporated with the UV-induced nanoparticle colloidal jet processing system. Finally, the structure of reactivation reaction chamber in the system was fluid-dynamically simulated. The simulation result showed that the structural design would meet the activation requirements of TiO2 nanoparticle colloid. References | Related Articles | Metrics

Automation Technique and Computer Technology

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Probabilistic load flow calculation of power distributive network based on Laplace transformation technique CHEN Wei, XIA Chun-hui, PEI Xi-ping 2020, 46 (3):  81-87.  Abstract ( 256 )   PDF (1930KB) ( 437 )   Save After connecting distributive photovoltaic power supply into regional power distribution network, the change of load flow is made to have a certain uncertainty due to the randomness and correlation of the photovoltaic power supply.Therefore, aimed at the uncertainty of the photovoltaic power supply and fluctuating load, a probabilistic load flow calculation method is proposed for the power distribution network based on the semi-invariable method of Laplace transformation technique. By means of the Laplacian transformation feature and semi-invariable, the probabilistic density function or cumulative distribution function of the random variable is estimated effectively and the random variation condition of power distribution network which includes the connected distributive photovoltaic power supply into itself. In order to verify the combination effect of semi-invariable with Laplace transformation technique, the simulation result is compared with the results of Monte Carlo simulation method and maxi-entropy principle-based semi-invariable method. It is shown by a computational example of power distribution network with IEEE-33 node that the proposed method will have a higher computational accuracy, faster calculation speed, and a lower computational burden than the maxi-entropy principle-based semi-invariable method. References | Related Articles | Metrics

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Stimulated Brillouin scattering slow light in double-clad As2Se3 chalcogenide photonic crystal fibers HOU Shang-lin, WANG Dong-ye, LEI Jing-li, LI Xiao-xiao, WANG Hui-qin, CAO Ming-hua 2020, 46 (3):  88-93.  Abstract ( 182 )   PDF (2163KB) ( 399 )   Save The influence of the structure of the inner/outer cladding on the slow light characteristics of Brillouin scattering in double-clad As2Se3 chalcogenide photonic crystal fiber is investigated in this paper. In this study, the high-order mode of the sound field is considered when analyzing the influence of the structure of double-clad As2Se3 chalcogenide photonic crystal fiber on the Brillouin gain spectrum. The results coming out from our studies show that the air filling fraction of inner cladding has a great influence on the slow light characteristics. With the increase of the air filling fraction of inner cladding, the main peak of Brillouin spectrum decreases gradually, the second peak increases gradually, and also the time delay increases as a result. The trend of Brillouin gain is similar. The above characteristics are less affected by the change of the air filling fraction of the outer layer. The second peak of the Brillouin gain spectrum rises slightly, while the time delay and gain change are still small. It can be seen that the slow light characteristics of the dual-cladding As2Se3 sulphide photon crystal fiber are greatly controlled by the air filling fraction of the inner cladding, and these characteristics are less affected by the air filling fraction of the outer layer if compared with the inner cladding. References | Related Articles | Metrics

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Tooth image segmentation research based on improved Gaussian mixture model BAO Guang-bin, YANG Xu-peng, KANG Hong 2020, 46 (3):  100-104.  Abstract ( 307 )   PDF (1974KB) ( 492 )   Save An improved clustering segmentation algorithm based on Gaussian mixture model and K-means is proposed in this paper to fix the problem of difficult to extract tooth target region in oral CT images with blurred boundary and low contrast. First of all, the image is preprocessed by anisotropic filtering to achieve de-noising and smoothing while enhancing details of the image. Secondly, K-means is used to complete a kind of initial division, and initial values of EM algorithm iteration is then given according to the pixel value after classification, so as to speed up the algorithm iteration to an optimal solution. This greatly reduces the number of algorithm iterations and effectively fixes the problem of GMM caused by randomly selecting the initial value points when EM algorithm solves parameters. Finally, we use EM algorithm to learn GMM and complete ML segmentation. Our experimental results indicate that the improved method reduces the computational complexity, has strong robustness to noise, and can obtain more ideal segmentation results. References | Related Articles | Metrics

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Realization of face feature point recognition based on cascaded convolutional neural network ZHANG Yun, LI Lan 2020, 46 (3):  105-109.  Abstract ( 534 )   PDF (862KB) ( 1792 )   Save If a face image is interfered by redundant information, the accuracy of the extracted effective feature points from the image is not high enough. To solve this problem, a face feature point detection algorithm based on a cascade convolutional neural network is proposed in this paper. The algorithm reads in information of an original image via the input-function first, then extracts local features of the image through neurons in a receptive domain, and inputs all local features into a pooling domain. After doing that, the algorithm is able to average all captured local features stored in the pooling domain, and further do down-sampling to the pooling domain, and reduce the dimension of the convolution results, and finally output detection results of those feature points by virtual of iterative training. In this study, Python language is used to program the algorithm, and simulation experiments are carried out with the help of face data set. Simulation results show that the algorithm has a high recognition rate for face feature points. References | Related Articles | Metrics

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Quality evaluation of teaching video content based on user behavior MA Dong-lin, WANG Xiao-tong, ZHANG Shu-huan, GUO Ya-ting 2020, 46 (3):  110-115.  Abstract ( 308 )   PDF (904KB) ( 452 )   Save Currently, the problem that subjective method is the main method for evaluating the quality of online teaching video content, lacking of objective criterion for defining its quality. In this paper, aonline teaching video quality evaluation method is proposed based on user behavior. In this method, the behavior data of single user watching a networked teaching video is collected first and normalized. Data tagging is then implemented based on evaluation standard of video quality and the quality classification of the networked teaching video content is conducted by the single user by means of fully connected neural network and Softmax. Finally, a classification weighted average of the ratings of all users watching this video gives a comprehensive evaluation of the video. The test result shows that the accuracy of this model will be 79.5% and the classification effect will be obvious, having higher practical value. References | Related Articles | Metrics

Architectural Sciences

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Simplified method to calculate displacement of the pile anchor protect structure of deep excavation based on the incremental iteration method ZHOU Yong, ZHANG Kun-yu 2020, 46 (3):  116-121.  Abstract ( 267 )   PDF (1552KB) ( 583 )   Save According to construction characteristics of deep foundation pile anchor retaining structure engineering, an incremental method to design and investigate the deep foundation pile anchor retaining structureis proposed.The nonlinear problem of pile displacement caused by excavation is solved approximately by the linear method, namely, the nonlinear curves are replaced by a series of segmented linear lines. By taking into account the influence of displacement of pile anchor retaining structure during excavation of the base pit, a displacement calculation formula for the soil pressure model based on the pile displacement has been derived. Then the pile displacement calculated in each step is revised by an iterative method, so as to avoid the error accumulation caused by incremental method. Combined with an engineering example, the above proposed method is programmed with MATLAB, and corresponding calculated results are compared directly with those predicted by both finite element simulation software PLAXIS and the conventional incremental method, the correctness and rationality of the method are verified.The proposed simplified method is closer to engineering practice and predictions by the method are more accurate than those by conventional incremental method. References | Related Articles | Metrics

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Analysis of mechanical properties and microstructure of recycled ceramic concrete QIANO Hong-xia, PENG Kuan, CHEN Ke-fan, LI Jiang-chuan, HONG Fen 2020, 46 (3):  122-126.  Abstract ( 407 )   PDF (1962KB) ( 316 )   Save In order to improve the recycling efficiency of ceramics, ceramic particles and ceramic powders are recycled and utilized as recycled concrete aggregate and doped concrete aggregate. Different test schemes are designed, and mechanical properties of recycled concrete which is composed of both ceramic particles and ceramic powders are compared with those of recycled concrete which is composed of ceramic powders only, and then analyzed. Using SEM and X-ray fluorescence analysis, the emerging regularity associated with the concrete microstructure in the case of different schemes has been studied, and the strength varying mechanism of the recycled concrete is revealed in terms of microscopic characterization for the recycled concrete. Our research shows that: with increase of ceramic particle doping, compressive strength of the recycled concrete is gradually increased; the ceramic particle doping can significantly improve hydration reaction rate of the recycled concrete,but the strength of the concrete decreases as a result. References | Related Articles | Metrics

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Newmark design spectrum considering hanging wall and footwall effect HU Jin-jun, ZHANG Yan-jing, XIE Li-li 2020, 46 (3):  127-132.  Abstract ( 246 )   PDF (5653KB) ( 240 )   Save Based on records of the near-fault strong earthquake of the typical slip fault in the world, the effects of hanging wall / foot wall on a seismic design spectrum of a nuclear power plant is analyzed, and a reference is provided, it is for constructing the design spectrum of the nuclear power plant which counts in effects of hanging wall / foot wall of the near-fault is provided. Based on the near fault records of distinct areas of the hanging wall / foot wall, values of control parameters AD/V2 and V/A for the peak ground motion ratio in Newmark method are analyzed. It is found that a inflexion period of seismic design spectrum of the nuclear power plant changes with characteristics of strong earthquake records, and the values of AD/V2 and V/A are affected by the hanging wall / foot wall effect. The V/A value associated with the hanging wall is smaller than that in other areas, while theAD/V2 value is bigger than that in other areas. Since the values of AD/V2 and V/A determine periods of the third and fourth control point of the designed spectrum, the shape of the designed spectrum is also affected. By comparing the determined design spectrum with RG1.60 design spectrum, it is found that the hanging wall / foot wall effect has a significant impact on the spectral values within the short period of the designed spectrum, which makes the spectral values within the short period increase,while the impact on the medium / long period is not evident. Whether either the shape or the values of the designed spectrum, the change of the designed spectrum of the bedrock site is greater than that of design spectrum of soil site. It can be seen therefore that the influence of the hanging wall / foot wall effect should be taken into account in future preparation of standard response spectrum. References | Related Articles | Metrics

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Mechanical performance analysis of monotonic loading of eccentrically braced steel frame with replaceable energy dissipation link YIN Zhan-zhong, AN Shu-zhen, SUN Xiang-yang, LI Jin-ming, ZHANG Xian-dong 2020, 46 (3):  133-138.  Abstract ( 315 )   PDF (4901KB) ( 395 )   Save An eccentrically braced steel frame with replaceable energy dissipation link is consisted of two parts, i.e. the part of energy dissipation link and that of frame beam. The energy dissipation link has advantages of convenient replacement after earthquake as well as low cost. By utilizing software ABAQUS along with different appropriate parameters, ten models with replaceable energy dissipation link of eccentrically braced steel frames were build up for the case of monotonic loading to carry out numerical simulation, trying to predict, for the replaceable energy dissipation link and the whole braced steel frame, the capacity to bear longing, deformation extent and other mechanical properties. All results coming out of our analyses indicate that the eccentrically braced steel frame with replaceable energy dissipation link may concentrate plastic deformation of the structure on the energy dissipation link. Therefore, the eccentrically braced steel frame with this kind of energy dissipation link exhibits better ductility, higher initial stiffness and bigger capacity to bear loading. Consequently, the distribution of both stress and strain becomes more uniform in the frame beam structure. References | Related Articles | Metrics

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Analysis of geometrically nonlinear coupling of poles to cable in externally prestressed structure with tilted belly poles SONG Yu, HE Yong-li, XIE Yang, ZHAO Jiang-lian 2020, 46 (3):  139-143.  Abstract ( 178 )   PDF (696KB) ( 316 )   Save By means of applying the analysis method of increment linearization, taking externally prestressed structure with tilted belly poles as investigation object,and establishing cable element model, the tangential stiffness matrix of the displacement increment of the cable node and the elongation-shrinkage increment array of the belly poles are found for the structure by using its geometric, physical, and balancing relation. The tangential stiffness matrix of foregoing structure will be correlated not only with the parameters of the cable elements such as Young's modulus, cross-sectional area, original length, and current parameter but also with the current paramer of the belly pole. Newton-Raphson's increment iteration method is used to compile a computation flow of cable node displacement. The analysis of geometric nonlinearity of poles-to-cable coupling in externally prestressed structure with tilted belly poles will provide a theoretic bases for reinforcement design of combined structure with tilted belly poles. References | Related Articles | Metrics

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Reinforcement technology of existing buildings adjacent to deep foundation pit of metro in low floodplain area in Yangtze River DENG Hui-yuan, DAI Guo-liang, MU Bao-gang, GONG Wei-ming, QIAN Cheng 2020, 46 (3):  144-149.  Abstract ( 195 )   PDF (2969KB) ( 360 )   Save Based on settlement and cracking problems of existing buildings at Hexi district in Nanjing, a reinforcement technology of super-long steel tube static pile is put forward. In order to improve building safety, two lines of defense made by static piles and reserve piles were further proposed for reinforcement measures, and static pressure piles as the two lines of defense were applied in batches during construction. By monitoring the settlement deformation of the building before and after reinforcement, it is found that the reinforcement building is less affected by adjacent foundation pit construction. Especially, the influence of a foundation pit construction at a distance of nearly 12 m away is much less than that of a foundation pit construction at a distance of 220 m far away. It shows that the reinforcement method reduces effectively appearing disasters of further settlement and cracking of the existing buildings. Thus, the validity and rationality of applying super-long steel pipe static piles in the low floodplain area of the Yangtze River to improve the ability of buildings to resist deformation, has been verified indeed. References | Related Articles | Metrics

Scientific

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Adaptive synchronization of a new hyperchaotic Volta's system with uncertaing parameters ZHANG Zhi-ming, ZHANG Yi-fan, LI Tian-zeng 2020, 46 (3):  150-154.  Abstract ( 175 )   PDF (773KB) ( 267 )   Save A new hyperchaotic system based on Volta's system is presented via adding linear control.The hyperchaotic behavior and chaotic behavior of this new 4D Volta's system are studied by Bifurcation diagram, Lyapunov exponents spectrum and phase diagram.The hyperchaotic behavior and chaotic behavior of this new 4D Volta's system with varying parameters are studied by Bifurcation diagram, Lyapunov exponents spectrum and phase diagram.Then, the Lyapunov stability theorem and the adaptive control theory are both employed to realize synchronization of the two hyperchaos with unknown parameters.Our simulation results have demonstrated effectiveness and validity of the proposed method. References | Related Articles | Metrics

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Fatigue life analysis of Ni-Ti shape memory alloy pipe joints under random vibration LI You-tang, WANG Biao 2020, 46 (3):  155-159.  Abstract ( 262 )   PDF (2364KB) ( 484 )   Save Random vibration fatigue life analysis of Ni-Ti alloy pipe joints in pipeline system was carried out. Taking Ni-Ti alloy pipe joints in a typical hydraulic pipeline of an aircraft as a research object, the formula for evaluating overall fatigue damage in the joints is obtained by using the Steinberg method based on Gauss distribution and Mine linear cumulative damage law. Based on the constitutive model describing thehyperelasticity and memory effect of Ni-Ti shape memory alloy,the finite element model of the pipe joint is established and themodal analysis and random vibration response analysis of the system model are then carried out, and the fatigue life of joint structures is predicted by using the fatigue damage formula. Predicted results show that the Ni-Ti shape memory alloy pipe joints are safe and reliable within the flight life of 80 000 h, which may provide a theoretical reference for design and optimization of the pipe joints. References | Related Articles | Metrics

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Analysis of mechanical postbuckling behavior of functionally graded beams MA Lian-sheng, JIA Jin-zheng 2020, 46 (3):  160-164.  Abstract ( 172 )   PDF (2269KB) ( 289 )   Save Based on the first-order shear deformation theory, the post-buckling behavior of functionally gradient beams under axial loading is investigated in this paper. The basic equation for nonlinear static problem of functionally gradient beam is derived and an accurate solution to post-buckling is obtained. By using the accurate solutions herein obtained, effects of various factors such as material gradients, applied loading, transverse shear deformation and boundary conditions on post-buckling behaviors of functionally graded material beams have been investigated. The results obtained show that properties of gradient material, transverse shear deformation and different boundary conditions have significant effects on the post-buckling characteristics of functionally gradient material beams. References | Related Articles | Metrics

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Nonlinear stability analysis of the single arc bellows diaphragm under static-dynamic load HAN Ming-jun, WANG Wei-bing, LI Hong-rui, ZHOU Chao-yu 2020, 46 (3):  165-172.  Abstract ( 186 )   PDF (1246KB) ( 247 )   Save The single arc bellows diaphragm is regarded as the combined structure of the circular plate with initial deflection by the pseudo-plate method. In the research, the nonlinear dynamic equations of single circular arc diaphragm under static and dynamic loads are obtained by using the nonlinear bending theory for thin plate and thin shell. Given boundary conditions and continuous conditions to the equations, the deflection and tension of the diaphragm under the synergistic effect of static-dynamic loading can be predicted. The forced vibration equation of the nonlinear system of the single arc bellows diaphragm can be also obtained on the basis of the Galerkin method. The bifurcation problem of the system without external excitation is studied and stability of the single arc bellows diaphragm at the equilibrium point is discussed in terms of the Floquet index. Meanwhile, the change of the equilibrium position of the system under effect dynamic load only and under coupling effect of static-dynamic load is taken into account in this research. The results indicate that the Hopf bifurcation of the single circular arc diaphragm system becomes more delayed under dynamic-static loading than under dynamic loading only. References | Related Articles | Metrics