西南交通大学学报

Symplectic Random Vibration Analysis of Vertically Coupled Vehicle-Track-Tunnel System Considering Frequency-dependent Stiffness of Rail Pads

WANG Ping, YANG Fan, WEI Kai

2017, 30(2): 209-215. doi: 10.3969/j.issn.0258-2724.2017.02.001

[Abstract](619)

Abstract:
In order to accurately predict the frequency-domain characteristics of random vibration of vehicle bogies, wheels, and the fundamental structure under wheels, a symplectic mathematics model of random vibration of a coupled vehicle-track-tunnel system is established using the pseudo excitation method (PEM) and the symplectic mathematics of infinite periodic substructures, with consideration of the low-frequency initial stiffness of rail pads and the frequency-dependent extent of stiffness. The model is used to analyze the influence of the frequency-dependent stiffness of rail pads on the random vibration of the coupled vehicle-track-tunnel system. Results show that the frequency-dependent stiffness of rail pads affects little the vertical random vibration of vehicle body, but it will increase vertical random vibration amplitudes of vehicle bogie at frequencies above 57 Hz and meanwhile significantly increase the peak power spectrum density (PSD) of the vertical random vibration of both wheelset and steel rail, as well as their 1st dominant frequencies. As the stiffness of rail pads increases with frequency, the natural frequency of the track structure shifts to a higher frequency range, and the energy of the wheel-rail resonance frequency band also transfers to a higher frequency region. As a result, the frequency domain of the wheel acceleration PSD distribution shifts upward by 8.6 Hz.

Triaxial Test and DEM Analysis of Ballast Aggregate with Angularity Breakage

JING Guoqing, HUANG Hongmei, SHI Xiaoyi, CAI Xiaopei

2017, 30(2): 216-221. doi: 10.3969/j.issn.0258-2724.2017.02.002

[Abstract](593)

Abstract:
A series of triaxial monotonic compression tests were conducted to study the influence of angularity breakage on the deformation and mechanical properties of railway ballast. Different confining pressures were applied to ballast samples, including 10, 30 and 60 kPa to study the axial strain, volume strain, deviator stress and ballast particle size variation. In addition, breakable ballast model was built using discrete element method (DEM) to study the location and quantity of angularity breakage under different confining pressures. The comparison between test and stimulation results indicates that with increasing axial strain, the ultimate deviator stress increases and finally reaches a stable value; the ultimate deviator stress increases with the confining pressure, showing a linear relationship. When the confining pressure increases from 10 to 60 kPa, the ultimate deviator stress increases from 93 to 387 MPa. The dilation strain deformation also increases with the confining pressure. For example, when the confining pressure is 10 kPa, ballast sample hardly experience dilation strain deformation; when the confining pressure is 60 kPa, the dilation strain deformation is 0.21%.The amount of breakable angularity increases with the axial strain and angularity breakage mostly happens near the loading surface.

Analysis of Longitudinal Coupling of Turnout on Large-Span Tied Arch Bridges and Vehicle Running Performance

CHEN Rong, XING Jun, LIU Hao, TIAN Chunxiang, WANG Ping

2017, 30(2): 222-231. doi: 10.3969/j.issn.0258-2724.2017.02.003

[Abstract](590)

Abstract:
To meet the engineering requirements of laying welded turnouts on tied arch bridges, the longitudinal and lateral-vertical coupling vibration models were built based on the interaction principles of turnout-bridge and coupling dynamics of vehicle-turnout-bridge. Taking an example of a 205 m continuous beam bridge on a new passenger dedicated line, three bridge types and nine kinds of layouts in total were involved to analyze the coupling characteristics of the turnout-bridge system and vehicle running performance. The turnout-bridge longitudinal interaction shows that the temperature span has a great influence on the longitudinal deformation of the welded turnouts. And the disciplines of rail additional expansion and contraction forces of different bridge types are the same, but the force values are different. For the Neilson rigid-frame arch bridge plans, the rail additional expansion and contraction forces, relative displacements between the tip of switch rail and stock rail, relative displacements between the tip of nose rail and stock rail, and rail break are all minimum. However, for the large-span continuous beam-arch bridges, the corresponding values are maximum. As to laying welded turnouts on tied arch bridges, the relative displacement between the stock rail at switch machine and bridge is an important factor in selecting the optimal plan. The vehicle running performance analysis shows that the vertical dynamic displacement of Neilson rigid-frame arch bridge is relatively large, and the rate of wheel load reduction exceeds the limit in an instant. In contrast, for the small-span continuous beam bridge, the dynamic displacement is only 1.33 mm, vehicles have a good running performance in safety and comfort, and the maximum lateral acceleration of the car body is only 0.035g.

Wheel-Rail Profile Matching for High Speed Railway with Different Rail Profiles

QIAN Yao, WANG Jian, WANG Ping, AN Boyang, SU Qian, XU Jingmang

2017, 30(2): 232-238. doi: 10.3969/j.issn.0258-2724.2017.02.004

[Abstract](769)

Abstract:
In order to analyze the influence of different rail profiles on the wheel-rail profile matching of high-speed railway in China, the classic track line method, the 3D non-Hertz rolling contact theory and the vehicle-track coupling dynamics are used to address the profile matching issue between the LMA wheel tread and rails with different profiles, such as types CHN60, 60N and 60D, by analyzing the wheel-rail contact characteristics and the vehicle dynamic performance. The results show that the wheel-rail contact geometry relationship differs with different rail profiles. In whatever cases of wheelset lateral displacements, the wheel-rail contact stress in the CHN60 rail will be smaller than that with the other two rail profiles. When the wheelset lateral displacement is 6 mm, an optimal wheel-rail contact state is achieved in the CHN60 rail, in which the contact spot area is the largest and the contact stress distribution is uniform. In addition, rail profile has a big influence on the critical speed and curve passing performance of a vehicle. The critical speed of the vehicle is about 763 km/h when the 60D rail is matched with the LMA wheel tread, which is the highest of the three. The maximum wheelset lateral force and displacement with the CHN60 rail are 3.584 kN and 3.35 mm, respectively, the smallest of the three, implying that the CHN60 rail owns the best curving passing performance.

Simplified Calculation Method and Experimental Verification for Flexural Failure Skeleton Curve of RC Columns

HE Guangjie, ZHAO Yiding, XIN Yazhou, LIU Chengqing, NI Xiangyong

2017, 30(2): 239-246. doi: 10.3969/j.issn.0258-2724.2017.02.005

[Abstract](635)

Abstract:
In order to meet the requirements of performance-based seismic design and nonlinear dynamic analysis, it is necessary to explore the simplified calculation method for moment-rotation angle (M-) skeleton curve of flexural failure reinforced concrete (RC) columns. Firstly, the curve was simplified as three-linear line M- skeleton curve, which is represented by three feature points, i.e., yield point, peak point and ultimate point. Then, considering the effects of flexure, shear and steel bond-slip on the rotation of RC columns and based on the flexural theory of RC columns and plane section assumptions, the iterative method was used to obtain stress and strain distribution on cross section, and the values of moment (M) and rotation angle () for each feature point were obtained according to the moment-curvature relation of cross section. Then, a simplified calculation method of M- skeleton curve was proposed. Finally, the calculated and test results of six cases were analyzed, and the ratio S between the calculated and test values was calculated. The coefficients of variation for each feature point ratio S are less than 15%, which show good agreement between the calculated and test results, and validate the proposed simplified calculation method.

Experimental Study on Steel Reinforcement Protection in Magnesium Oxychloride Cement Concrete under Sulfate Environment

QIAO Hongxia, GONG Wei, WANG Penghui, CHEN Guangfeng, CHENG Qianyuan

2017, 30(2): 247-253. doi: 10.3969/j.issn.0258-2724.2017.02.006

[Abstract](534)

Abstract:
Aiming at the low brine corrosion resistance of ordinary silicate reinforced concrete in salt lake areas of western China, a magnesium oxychloride cement reinforced concrete with higher brine corrosion resistance was fabricated. The polarization curves and electrochemical parameters, including corrosion potential, corrosion current density and corrosion rate, of steel bars with different coatings were investigated in magnesium sulfate solution using an electrochemical workstation measurement system, and the corrosion and protection of steel reinforcements in the chloride magnesium cement concrete with high chloride content were studied. The results show that the bare steel bar in the magnesium oxychloride cement concrete suffered severe corrosion, the steel bars with DACROMET, BENICE, ZINTEK and MAGNI coatings presented low corrosion, and the steel bar with GEOMET coating was far from corrosion. Specifically, the corrosion rate of steel bars with coatings of DACROMET, BENICE, ZINTEK, MAGNI and GEOMET was 1/36-1/19, 1/20-1/13, 1/31-1/16 and 1/91-1/50, respectively, while the value was 1/22-1/16 for the bare steel bar. This proves that coating technology can slow down the corrosion rate of steel bars in magnesium cement concrete.

Analysis of Wind Characteristics on Double-Mast Cross-Rope Suspension Tower Influenced by Shielding Effect

LI Zhengliang, LIU Xinpeng, YAN Zhitao, XIAO Zhengzhi

2017, 30(2): 254-263. doi: 10.3969/j.issn.0258-2724.2017.02.007

[Abstract](535)

Abstract:
To investigate the wind load distribution of cross-rope suspension tower with occlusion, and provide theoretical basis for wind resistant design, a single-mast and double-mast systems were tested by high-frequency force balance in wind tunnel in type-B landform turbulent flow and uniform flow fields. The influence of shielding effect on the power spectral density (PSD) of the base moment and the mean wind force coefficients was investigated, and the PSD parameters were fitted. The results show that, for the single-mast, the power spectra peaks of base moment across wind locate at wind angles of 15, 30 and 45 in turbulent flow field. The change law of the PSD of base moment across wind is similar to that along wind direction. For the double-mast system, the power spectra peaks of base moment across wind is 10 times the value along wind direction. Based on the basic form of fluctuating wind speed spectrum, the dynamic wind load model including along-wind, across-wind loads and torsion moment under different wind directions was established for single mast and double mast. The wind coefficient change significantly with the occlusion distance of 10D-20D (where D is the width of the cross section of tower) in the uniform flow field, and the occlusion effect is the most significant.

Numerical Experiments of Dynamic Response of Buried Gas Pipeline under the Action of Seismic Waves Induced by Tunnel Blasting

ZHENG Shuangying, YANG Lizhong

2017, 30(2): 264-271. doi: 10.3969/j.issn.0258-2724.2017.02.008

[Abstract](555)

Abstract:
In order to reasonably determine the vibration control standard of buried gas transmission pipeline under the action of seismic waves from blasting,it is important to clarify how the operating parameters of pipeline affect its dynamic response. Taking Xiannvyan tunnel blasting project as example (the tunnel passes beneath a buried gas pipeline),and based on the non-linear dynamic finite element method and the principle of the orthogonal experiment,the numerical experiments on the dynamic response of a buried gas pipeline were carried out. Using the range analysis method, five parameters of pipeline including the outside diameter, wall thickness, buried depth, clear distance between pipeline center and tunnel top as well as operating internal pressure were sorted according to their effects on the response characteristics of pipe stress and vibration velocity. The results show that the peak of the maximum principal stress is mainly affected by the operating internal pipeline pressure and wall thickness, which has obviously linear relationship with the operating internal pressure. Under the action of blasting-induced seismic waves, when the operating internal pressure is 7 MPa, the peak of maximum principal stress is 290.73 MPa and the maximum tensile strain is 0.001 4, which is less than the elastic strain limit of gas pipeline 0.002 3. The characteristics of the pipeline dynamic response mainly depend on its structure,and the pipeline dynamic stress caused by blasting vibration is less than 6% of pipeline allowable stress. The maximum dynamic stress of the gas pipeline can be estimated by the superposing the dynamic maximum principal stress of the pipeline without operating pressure and its static principal stress with operating pressure.

Damping Modification Factors for Response Spectra of Pulse-like Near-fault Ground Motions

PU Wuchuan, HUANG Bin, KABANDO E K

2017, 30(2): 272-279,378. doi: 10.3969/j.issn.0258-2724.2017.02.009

[Abstract](562)

Abstract:
The damping modification factor quantifies the effect of damping ratio on seismic response of a structure. It is related to the spectral characteristics of ground motion, and is used to obtain the high damping spectra from the low damping spectra. This work aims to explore the damping effect on structural responses induced by near-fault ground motions, and to propose estimation formulas for damping modification factor. A total of 50 ground motions were selected, and the wavelet-based equivalent pulses were extracted. The response spectra were calculated based on the selected ground motions and the equivalent pulses, with the assumed 13 damping ratios ranging from 0.05 to 0.50. The damping modification factors were obtained based on the reference spectra with a damping ratio of 0.05. The results show that increasing damping ratio reduces the spectral values the most significantly if the period ratio T/Tp (structural period to pulse period) is between 0.5 and 1.2, and in this range the same level of damping modification factors are obtained from the equivalent pulses. Based on the numerical results, the empirical functions were suggested for estimating the damping modification factor for acceleration, velocity and displacement, respectively. The proposed formulas take into account the near-fault effect, and are applicable within the period range of 0.5 ＜ T/Tp ＜ 1.2.

Reflection and Transmission of P Waves at Interfaces of Saturated Sandwiched Coarse Granular Structure

LIU Bao, SU Qian, ZHAO Wenhui, LIU Ting, PHAM Duc Phong, ZHOU Heng

2017, 30(2): 280-287. doi: 10.3969/j.issn.0258-2724.2017.02.010

[Abstract](546)

Abstract:
In order to study the reflection and transmission of stress wave at interfaces of the sandwiched coarse granular structure in embedded pile-board subgrade, an interface effect model for the coupled elastic solid-saturated coarse granular layer-elastic solid sandwich structure is established according to the structure characteristic of embedded pile-board subgrade, taking into consideration the superimposed effect of plane P waves reflected from the coarse granular interlayer. Based on the Biot theory and the elastic wave theory, reflection and transmission coefficients at the upper and lower interfaces in the model are derived theoretically by introducing scalar and vector potential functions. Using the derived theoretical formulas, influences of various factors on the reflection and transmission coefficients are discussed through numerical examples. The results show that thickness, porosity and shear modulus of the sandwiched coarse granular structure will change the energy distribution on interfaces, and make it present a periodic resonance characteristic. As the porosity varies from 0.2 to 0.4, the reflection coefficient increases by about 25%. In addition, the propagation of shear wave causes the reflection coefficient to oscillate with damping at the resonant frequencies of the shear wave, and the permeability and flow conditions also have significant effect on the wave reflection.

Automatic Detection Method for Highway Pavement Cracking Based on the 3D Shadow Modeling

YANG Enhui, ZHANG Aonan, DING Shihai, WANG Kelvin C. P.

2017, 30(2): 288-294. doi: 10.3969/j.issn.0258-2724.2017.02.011

[Abstract](604)

Abstract:
Automatic detection method for pavement cracking based on 3D image technology has been a hot topic. In order to improve the accuracy and reliability of the cracking detection, a new method based on the 3D shadow modeling was proposed, which utilizes that the height of the fracture zone is lower than the surrounding area, and the shadow model was used to identify the cracking by the virtual light projection and then, the linear shape analysis method was used to discriminate cracks detection. Furthermore, both the connected-component analysis method and linear shape analysis method were adopted to remove the image noises. The results show that the automatic detection method can achieve 92.93% of accuracy in pavement cracking detection.

Application of StaMPS-MTI Technology in Monitoring Ground Subsidence

JIANG Zhaoying, YU Shengwen, TAO Qiuxiang

2017, 30(2): 295-302. doi: 10.3969/j.issn.0258-2724.2017.02.012

[Abstract](562)

Abstract:
In order to improve the spatial sampling rate of monitoring technologies, based on the methods of PS (permanent scatters) and SBAS (small baseline subsets), the point set of high coherence was optimally selected using StaMPS-MTI(stanford method for persistent scatterers-multi-temporal InSAR) technology, and the phase and amplitude stability of PS and SDFP(slowly-decorrelationg filtered phase) points were considered to achieve the weighted average of the pixel phases which met a given threshold. The ground subsidence and mean subsidence rate of the test area were then extracted using the deformation model of SBAS technique. PS, SBAS and StaMPS-MTI technology were respectively used to process the ground displacement data of Beijing areas from 2007 to 2010 with 29 ENVISAT ASAR images, retrieving the temporal deformation sequence and the annual mean subsidence rate. The monitored subsidence results of the test area were compared and analyzed theoretically. Theoretical results and experimental results on real SAR data show that by using StaMPS-MTI technology it can obtain 404 276 points of high coherence, and spatial sampling rate increases 62.3% compared to PS technology, and 129.4% compared to SBAS technology, which demonstrates the accuracy and reliability of monitored results.

United Programming Model for Dispatch of Emergency Rescue Teams and Road Reconstruction under Earthquake Disaster

ZHOU Rongfu, WANG Tao, WANG Ying

2017, 30(2): 303-308. doi: 10.3969/j.issn.0258-2724.2017.02.013

[Abstract](485)

Abstract:
In order to solve the problem of dispatch of emergency rescue teams and road reconstruction under earthquake disaster, considering the uncertainty of dispatch time under roads damaged and the demand of emergency rescue teams, a united programming model which took the constraints of rescue teams, rescue time and survival probability into account was built to maximize the survival probability of trapped people and the effect of the rescue task. To solve this model, the linear weighted method was proposed based on the characteristic of the multi-objective programming model. In addition, a numerical example was given to verify the effectiveness of the model and its solution. The results show that compared with the original schemes, the optimal dispatch scheme of emergency rescue teams generated by the proposed method can improve the rescue efficiency by 75%, and the optimal scheme of road reconstruction can save 89% rescue resources.

Investigation on Driving Comfort of Passenger Cars on Mountain Roads Based on Naturalistic Driving

XU Jin, YANG Kui, LU Gongyuan, SHAO Yiming

2017, 30(2): 309-318. doi: 10.3969/j.issn.0258-2724.2017.02.014

[Abstract](587)

Abstract:
Naturalistic driving tests were conducted using real vehicles on six roads to study the level of driving comfort on two-lane mountainroads and the key influencing factors. In the tests, acceleration data of passenger cars were collected; after filtered using Matlab software, the peak value of each waveform of the measured data was extracted to obtain the cumulative frequency profiles of peak accelerations of different axes, as well as the characteristic percentile values and the root mean square (RMS) values. The results show that the longitudinal acceleration rate ax on two-lane highways is only half the deceleration rate ab in braking. The locations where the acceleration and deceleration cause occupants discomfort account for 6% of the total test points at the most. The ratio of road sections where occupants feel discomfort in lateral direction ranges from 7% to 10% of the total trip; Among all the axial accelerations, lateral acceleration ay, braking acceleration ab,the longitudinal acceleration ax and vertical acceleration az make the greatest part of contribution to the discomfort.

Integer Programming Model of Passenger Flow Assignment for Congested Urban Rail lines

LU Gongyuan, MA Si, WANG Kun, DENG Nian

2017, 30(2): 319-325. doi: 10.3969/j.issn.0258-2724.2017.02.015

[Abstract](662)

Abstract:
Urban rail transit lines are often hard to give full play to its passenger transport capacity in condition of oversaturated passenger flow. In order to maximize the passenger transportation capacity of congested urban rail transit lines, a linear integer programming model for urban rail transit passenger flow control is built on the basis of network topology and definition of passenger demand. First, a flow-timetable network model is proposed to describe passenger movements in the rail line with timetable guidance. Then, by converting a passenger's departure time to the expected train by the passenger, origin-destination (OD) parameters of passenger flow, including origin, destination and expected train, are defined along with the parameter of passenger's waiting time in station. Based on these definitions, the linear integer programming model is finally built to maximize the passenger turnover volume. In addition, to verify the effectiveness of the model, a case study on a urban rail transit line with a network scale of 1 000 passenger OD pairs and 909 nodes is conducted, and the model is solved with software GAMS24.3. The results show that the optimal solution can be obtained in 0.09 s. In saturated situations, the total passenger turnover volume under different in-station waiting time deviates from the mean value by less than 1%, the waiting-time parameter conspicuously affects the passenger flow assignment solution.

Transfer-Oriented Dispatching Optimization of Rail Transit Network

HUANG Minghua, QU Hezhou, LIU Xiaobo, TANG Youhua

2017, 30(2): 326-333. doi: 10.3969/j.issn.0258-2724.2017.02.016

[Abstract](623)

Abstract:
As bottlenecks of rail transit network due to its high volume of transfer passengers during peak periods in big cities, transfer stations are facing problems of increasing safety risk, operation inefficiency, etc. To solve these problems, a mathematical model is developed using the nonlinear programming method to minimize the total transfer time in the rail transit network. Taking passengers' walking time in transfer into consideration, this model selects the adjustment amount of train dispatching time as the decision variable to optimize the transfer coordination time, by adjusting the departure time of trains at the start terminal and their timetables. Then, optimal solutions of train departure time and timetables are obtained using a simulated annealing algorithm. As a case study, the proposed methodology was applied to optimization of a real-life metro network with five lines intersecting at thirteen stations. The results show that compared to the existing operation plan, the total transfer waiting time of the optimized schedule in the morning peak hour is reduced by 689 h, and the system transfer efficiency is increased by 22%.

Location of U-Turn Openings at Signalized Intersections Based on Optimal Traffic Capacity

SUN Feng, SUN Li, LI Qingyin, SUN Shaowei

2017, 30(2): 334-339. doi: 10.3969/j.issn.0258-2724.2017.02.017

[Abstract](561)

Abstract:
In order to solve the unreasonable deployment of U-turn openings at signalized intersections, a method is proposed to calculate locations of optimal U-turn openings based on the optimal traffic capacity by taking the traditional four-phase control intersection as an object. Firstly, a loss time model of lanes shared by left-turn and U-turn vehicles is built to reveal the interaction mechanism between left-turn and U-turn traffic flows in different traffic conditions. Then, a capacity calculation model of lanes shared by left-turn and U-turn vehicles is established using the probability distribution function of vehicles in different flow directions. The capacity-location (C-L) curve drawn by the model can fully reveal the capacity characteristics of the shared lanes under influence of the U-turn openings. Based on the maximum capacity, the optimal location of U-turn openings is finally determined. In addition, the validity of the method was verified through a case study in the central area of Zibo City. The result shows that the proposed method can improve the traffic capacity of the shared lane of left-turn and U-turn vehicles from 432 to 509 pcu/h by 17.82%.

Joint Probabilistic Data Association Algorithm Based on Adaptive Cluster Probability Matrix

LI Shouqing, XU Yang

2017, 30(2): 340-347. doi: 10.3969/j.issn.0258-2724.2017.02.018

[Abstract](726)

Abstract:
A novel JPDA method for data association on multi-target tracking system was presented for reducing the class of JPDA algorithm computational complexity and solving the problem of coalesce neighboring tracks. To improve the computational complexity, the joint association event probabilities were calculated with Cheap JPDA algorithm, then the cluster probability matrix was reconstructed by thresholding method to further optimize the computational complexity. Finally, the measurement prone to make wrong association were eliminated by measurement adaptive cancellation method to avoid the track coalescence problem for neighboring tracks. Theoretical analysis and simulation results showed that the proposed algorithm was able to reduce the complexity of the algorithm and improve the timeliness on the basis of preserving the tracking accuracy, and it was also capable of avoiding track coalescence with less errors when tracking the neighboring tracks and cross tracks, comparing with the standard JPDA and Scaled JPDA algorithm.

Effects of Space Harmonics on Series-Connected Symmetrical Six- and Three-Phase Permanent Magnet Synchronous Motors Driver System

LIU Lingshun, YAN Hongguang, HAN Haopeng, ZHAO Guorong

2017, 30(2): 348-354. doi: 10.3969/j.issn.0258-2724.2017.02.019

[Abstract](562)

Abstract:
The decouple operation of the series-connected symmetrical six- and three-phase permanent magnet synchronous motors (PMSMs) driven by single inverter is theoretically based on the sinusoid electromotive force. To study influences of space harmonics on the decouple control of the series-connected system, mathematic models for the series-connected system with the 2nd and 4th harmonics of a symmetrical six-phase PMSM are established in three different coordinates. The torque ripple expression of the six-phase PMSM induced by space harmonic is setup, which reveals mathematically the essence of harmonic effects on the decouple control of series-connected system. In addition, simulations are conducted for two PMSMs with variable speed and variable loads. The results show that the torque ripple changes are caused by the 2th and 4th space harmonics of the symmetrical six-phase PMSM; consequently, operations of the series-connected two PMSMs cannot be controlled independently and need a corresponding compensating control.

Maintenance Decision Modeling and Optimization Based on Markov Process for Combined Co-Phase Power Supply Equipment

LIU Hang, LI Qunzhan, GUO Kai

2017, 30(2): 355-362. doi: 10.3969/j.issn.0258-2724.2017.02.020

[Abstract](568)

Abstract:
To ensure reliability and economic efficiency in the engineering application of co-phase power supply systems, maintenance decision modeling and optimization for combined co-phase power supply units used in electrified railways was studied. Firstly, according to construction plan and operational mode of units, the reliability of new combined co-phase power supply unites were analyzed. Secondly, maintenance decision modeling based on Markov process and iterative algorithm based on optimal maintenance strategy were presented by analyzing the maintainability and degradation of units. Finally, let the lowest maintenance costs as the target and take a overall consideration on the factors such as state transition probability of system and maintenance time, the best condition-based maintenance time was calculated using this model. The calculation examples show that if system degradation states is categorized into 6 classes from good to bad, according to the maintenance time and cost of each state, maintenance in the fifth degradation status has the highest economic efficiency, and the cost is only half the regular replacement cost of failed components.

Defect Detection of Solder Balls Based on Multi-Physical Field

ZHOU Xiuyun, XUE Yun, ZHOU Jinlong

2017, 30(2): 363-368. doi: 10.3969/j.issn.0258-2724.2017.02.021

[Abstract](544)

Abstract:
A pulsed eddy current thermal imaging method that is based on a coupled electric, magnetic, and thermal physical field was proposed for defect detection of solder balls in the production and service process of flip chips. In this method, an electromagnetic-thermal model for solder balls was established using the finite element software COMSOL. Through this model, temperature distributions on the top surface of solder balls were extracted to analyze their thermal conduction properties and identify their defects (i.e., voids and cracks). The effects of defect size (crack length or width and void radius) on the temperature distribution were discussed for quantitative analysis of solder ball defects. Simulation results show that at the end of heating, the solder ball with a crack of length 200 m and height 20 m has a higher surface temperature than the normal solder ball, while the solder ball with a void of diameter 150 m has a lower surface temperature. The surface temperature rises when there exists a crack close to the top surface of the ball, but increases linearly for voided solder balls when the void radius increases from 35 to 75 m. Therefore, solder balls with different defects can be identified according to their surface temperature distribution.

Fault Diagnosis Method for Analog Circuits Based on Matrix Perturbation Analysis

ZHOU Qizhong, XIE Yongle

2017, 30(2): 369-378. doi: 10.3969/j.issn.0258-2724.2017.02.022

[Abstract](540)

Abstract:
To integrate the fault detection, fault localization and parameter identification of analog circuits in one system and reduce the cost and facilitate the engineering implementation of fault diagnosis, an fault diagnosis and parameter identification method for analog circuits based on matrix perturbation theory was proposed. First, curve fitting for the sampled time series of the faulty circuit was conducted, and the phase deviation of the circuit was treated as one fault signature . Then, a matrix was built using the sampled time series, and the trace of this matrix was used as the other fault signature. Finally, the phase deviation and trace were used as joint fault signatures, and the fault diagnosis model was established according to the correspondence between the changes of the fault signatures and the fault device parameter variations. The experimental results of two international standard circuits show that the accuracy of fault location ranges from 98.5% to 100% and the error of fault parameter identification is in the range of -1.2% to 1.72%.

Topology and Matching Capacity of Direct-Connected Converter for Co-phase Traction Power Supply Substation

HUANG Xiaohong, LI Qunzhan, YANG Naiqi

2017, 30(2): 379-388. doi: 10.3969/j.issn.0258-2724.2017.02.023

[Abstract](501)

Abstract:
To optimize the topology, improve the compensation capacity and decrease the space occupied by the equipment for co-phase power supply substations, universal transformation method about electrical parameters from three phase to single phase was adopted and three types of direct-connected converters are investigated including full power converter, active power compensation converter and reactive power compensation converter. Based on active integrated compensation characteristics and power sub-module cha-racteristics, the topologies of three types of direct-connected converters were designed respectively. The matching relation between transformer connection mode and compensation capacity of direct-connected converters was also established. And, the capacity utilization ratio of power electronic device was determined in the end. The research results show that the associated compensation capacity is closely related to the connection modes of traction substation, as well as the connection port of the traction load and the type of load. For the converter with active power compensation, when the load power factor is greater than 0.961, it is better to choose the 90connection traction transformer; when the load power factor is less than 0.961, it is better to choose the 120connection traction transformer. For the converter with reactive power compensation, if the load is AC-DC-AC type, 90connection mode is preferable; if it is the inductive load, the connection mode of 120 is better than 90. Under the conditions of the same AC-DC-AC traction load and the modulation index is 0.8, the converter with active power compensation has the highest utilization ratio of 11.34% in device power capacity.

Wheel-Rail Profile Matching Relationship of EMU Train

XU Kai, LI Fu, LI Dongyu, ZHONG Hao

2017, 30(2): 389-399. doi: 10.3969/j.issn.0258-2724.2017.02.024

[Abstract](616)

Abstract:
In order to study the matching relationship between different wheel treads and rail profiles for EMU (electric multiple unit) trains, a comparative study was made by investigation of the wheel-rail contact geometry parameters, static mechanical properties, running stability of vehicles, and wheel-rail wear. Computational results by CONTACT and SIMPACK show that the running stability of vehicles on the 60N rail is better than that on the 60 kg/m rail because the 60N rail head is improved to be more smooth and the wheel-rail contact area is kept in the middle position of the rail head. When using two types of wheel treads, LMA and S1002CN, to match with the 60N rail, the contact spot area of the 60N rail surface can get a better proportion of sticking area and slipping area, so the general wheel-rail damage and wear are reduced effectively in the operation. However, the contact stress between the 60N rail surface and the LMA tread or the S1002CN tread with a small displacement is big, and hence may result in a large vertical wear. When the lateral displacement is 4-8 mm, the contact stress between the 60N rail surface and S1002CN tread is smaller than that of the 60 kg/m rail, and the wheel-rail wear is lower for vehicles negotiating curves. Therefore, the contact relationship between the 60N rail surface and the wheel tread is more favorable for the running stability of EMU vehicles, but wheel-rail contact points focused on the middle will aggravate the vertical wear.

Coupled Dynamics Analysis for a Flexible Beam with a Trolley Subjected to Pendulum Payload

LIU Huasen, CHENG Wenming, YIN Hao

2017, 30(2): 400-407. doi: 10.3969/j.issn.0258-2724.2017.02.025

[Abstract](602)

Abstract:
The vibration of the crane beam and the residual swing of the payload cause fatigue damage of crane and affect the precise positioning of the payload. In this paper, a crane flexible beam with a moving trolley subjected to pendulum payload multibody coupled dynamic system was set up based on an elliptical pendulum constituted by payload with trolley and moving mass passing a bridge model. The differential equations of motions of the coupled system were deduced based on Lagrange equation. The numerical solution was derived by using the Newmark- step-by-step integration method. The effects of the crane speed and the payload mass on the vibration of the beam and the load swing were analyzed. Numerical analysis results indicate that the crane speed affects the vibration mode of the beam overhead crane, and vibration amplitude is proportional to the mass of payload. The bend at the beam midpoint is 4% larger than the results calculated by ANSYS. The swing of payload leads to periodic changes of the driving force and driving power of the overhead crane. The payload acceleration is positively related to the crane driving force and driving power range.

Investigation on the Applicability of Pantograph and Catenary Model Urban Railway System

ZHOU Ning, ZOU Huan, ZOU Dong, TAN Mengying, ZHANG Weihua

2017, 30(2): 408-415,423. doi: 10.3969/j.issn.0258-2724.2017.02.026

[Abstract](593)

Abstract:
In order to analyze the applicability of pantographs and catneary models to the urban railway system, the pantograph was modeled as a lumped parameter system with two or three degrees of freedom and a multi-rigid model, while the rigid catenary was simplified as a beam model and a spring model with different stiffnesses. Combining different pantographs and catenary models, the dynamics simulation of the coupled system model was conducted to obtain the dynamic performance of the pantograph-catenary system. The results show that at low speeds, different catenary models with the same pantograph show a little difference in current collection, and the standard deviation of contact force is less than 10 N. With the increase of speed, the difference of models become evident, and the standard deviation of contact force varies beyond 80 N. When the natural frequency and mode shape of pantograph and catenary that match the span-pass frequency exhibit a discrepancy between different models, there appears a critical speed where current collection performance of models changes dramatically. By comparing the simulation and experimental results, it is indicated that the three-lumped-mass model of pantograph is more applicable than the other kinds of models, because it takes into account the elasticity of pantograph upper frame.

GAO Xueyao, LI Huinan, ZHANG Chunxiang, YU Xiaoyang

2017, 30(2): 416-423. doi: 10.3969/j.issn.0258-2724.2017.02.027

[Abstract](534)

Abstract:
Model similarity computation is a key technology in retrieval of 3D CAD models. In order to accurately distinguish differences between two models, a method for model similarity calculation based on ant colony search was proposed. According to the difference of edge numbers, shape similarity between source model face and target model face was calculated. A matrix which describes the correspondence relationships of face adjacency was introduced to evaluate two models' structure similarity. At the same time, ant colony algorithm was used to find a sequence of optimal matching faces between source model and target model. Based on this sequence, the similarity of two models was computed. Greedy algorithm and the proposed method were applied to compute the similarity between source model and target model. Experimental results show that computation results of the proposed method are improved 8.33% than those of greedy algorithm for the key model's similarity. Compared with greedy algorithm, the proposed method can distinguish 10 models in experiments effectively.

Security of Finite State Machines in Sequential Circuits

PENG Kaibei, JIA Ruiqing

2017, 30(2): 424-428. doi: 10.3969/j.issn.0258-2724.2017.02.028

[Abstract](493)

Abstract:
In view of the potential security problems brought by the don't care state in the optimization of finite state machine (FSM), the definition of safe state and its design method are presented after analysis of the factors leading to intrusion into FSM and the attack paths. Without affecting the flip-flop function, state protection of FSM is realized by adding a feedback signal to the T-type flip-flop. Results show that the experimental circuit with state feedback signal is 144.7% higher than the original experimental circuit in the power consumption, delay and area; the experimental circuit optimized with T-type flip-flop is 3.6% lower than the original experimental circuit in power consumption, 18.9% lower in area, and 19.6% higher in delay.

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2017 Vol. 30, No. 2