西南交通大学学报

Causes of Daily Strong Wind on Bridge Site in Deep Gorge with High Altitude and High Temperature Difference

LI Yongle, ZHANG Mingjin, XU Xinyu, TAO Qiyu, ZHU Ledong, SONG Lili

2014, 27(6): 935-941. doi: 10.3969/j.issn.0258-2724.2014.06.001

[Abstract](1080)

Abstract:
In order to investigate the causes of daily strong wind on a bridge site in a deep gorge with a high altitude and a high temperature difference, the field measurement of wind characteristics was carried out on the Dadu River bridge site with the CAW600-RT automatic-weather-station (AWS), hand anemometer and portable thermometer. The property of wind environment on the bridge site was explored through analyzing its influence factors, including mean wind speed, temperature, sunlight, topography and so on. The research results show that the Dadu River bridge is located in a deep gorge with a high altitude and a high temperature difference, where strong wind occurs nearly every afternoon and its mean wind speed is often more than 10 m/s. The causes of strong wind can be classified into two types. The first type of wind is induced by large-scale general atmospheric circulation, while the second type of wind, i.e. daily strong wind, is driven by local thermal disequilibrium, and the daily strong wind is also influenced by local terrain and time-varying sunshine. Though frequent daily strong wind has not effect on the design wind speed of the bridge, it can affect bridge durability and driving comfort to some extent.

3-Node Sptial Saddle Element for Finite Element Calculation of Suspension Bridge

QI Dongchun, SHEN Ruili, LIU Zhangjun, TAN Yunzhi

2014, 27(6): 942-947. doi: 10.3969/j.issn.0258-2724.2014.06.002

[Abstract](1068)

Abstract:
In order to solve the computational problem of nonlinear contact between main cable and saddle on tower top, a new 3-node spatial saddle element, including the saddle on tower top and both sides of the main cable, was produced. Based on the spatial catenary theory and the geometric relationship between main cable and saddle, the location of the tangent points and the cable force at the tangent points were obtained by solving the element state determination problem with known conditions. The accurate nodal force of the element was derived according to the static equilibrium. The elements of the tangent stiffness matrix were calculated based on its definition by replacing the differential with the increment. The new element could automatically satisfy the condition that the main cable is always tangent to the saddle, and thus the saddle jacking could be conveniently realized by modifying a parameter. Calculation shows that the new element has high calculation accuracy and convergence rate. The calculation results are the same with the numerical analytical solutions. The number of iterations is generally less than 12 in each element state solution.

Damping and Frequency of Simplified Cable-Network-Damper System with Cross-Tie Fixed to Ground

ZHOU Haijun, YANG Xia

2014, 27(6): 948-953. doi: 10.3969/j.issn.0258-2724.2014.06.003

[Abstract](999)

Abstract:
The dynamics of cable network with both cross-ties and dampers are important for cable vibration mitigation. A simplified cable-network-damper system was proposed. It is comprised of two parallel cables and a cross-tie fixed on ground. The cross-tie was simplified as linear spring elements. Based on the string theory, the complex frequency equation of the system was deduced according to the boundary conditons at the fixed end of the cables and displacement continuity and force equilibrium equations at the mounting position of the cross-tie. Then the damping and frequency values were derived by numerical iteration. In the cases of the third and fourth vibration modes, effects of spring stiffness and location on the maximum damping ratio, the optimal damping coefficient and the corresponding frequency were analyzed. It is found that there are odd and even modes in the system vibration; and these two modes have different vibration characteristics. With the increasing in the stiffness of the cross-tie fixed on ground, the upper limit of maximum damping value is increased 2.0-2.4 times of the maximum modal damping ratio of a single cable-damper system; however, the optimal cross-tie locations become less and separated.

Effects of Ballast Bed Section Dimension on Its Lateral Resistance

GAO Liang, LUO Qi, XU Yang, JIANG Hanke, QU Cun

2014, 27(6): 954-960. doi: 10.3969/j.issn.0258-2724.2014.06.004

[Abstract](1190)

Abstract:
In order to reveal the variation characteristics of ballast bed lateral resistance, a three-dimensional model for ballast bed and sleeper was established based on the discrete element method. The effects of important factors of ballast bed section dimension, such as ballast bed slope grade, thickness, top width and shoulder height, were investigated, and proportions of lateral resistance shared by sleeper base, crib and shoulder were analyzed. The research results indicate that when slope grade changes from the ratio of 1 to 1.50 to the ratio of 1 to 1.85, lateral resistance varies from 10.315 to 16.475 kN, and if slope grade equals the ratio of 1 to 1.65 or smaller, lateral resistance can satisfy 12 kN per sleeper. When top width increases from 3.0 to 3.8 m, lateral resistance varies from 10.205 to 15.715 kN, and if top width is 3.4 m or wider, lateral resistance can satisfy 12 kN per sleeper. Lateral resistance increases with the decline of slope grade and the increasement of top width, shoulder resistance increases significantly as a result of the increasement of shoulder ballast. When ballast bed thickness increases from 200 to 400 mm, lateral resistance varies from 9.156 to 15.684 kN; ballast bed drags based on different layers when the sleeper moves laterally; and base resistance increases along with the increasement of ballast bed thickness, and if ballast bed thickness is 300 mm or larger, lateral resistance can satisfy 12 kN per sleeper. When shoulder height increases from 0 to 180 mm, shoulder resistance varies from 2.010 to 5.203 kN and lateral resistance varies from 9.526 to 15.257 kN. Shoulder height affects lateral resistance significantly, and if shoulder height is 120 mm or higher, lateral resistance can satisfy 12 kN per sleeper.

Effects of Contact Loss underneath Concrete Roadbed on Dynamic Performances of Slab Track-Subgrade System

REN Juanjuan, YAN Xiaobo, XU Guanghui, XU Kun

2014, 27(6): 961-966. doi: 10.3969/j.issn.0258-2724.2014.06.005

[Abstract](919)

Abstract:
ANSYS/LS-DYNA, a large general finite element software, was used to establish a vertical vibration model for vehicle-track-subgrade coupling system, and the dynamic responses of a vehicle-track system caused by contact loss underneath concrete roadbed were analyzed. The research results show that contact loss length less than 3.125 m (corresponding to a contact loss area of 10 m2) has a negligible effect on the dynamic responses of a vehicle-track system. The dynamic responses of the vertical displacement of rail and vertical accelerations of bogie and car body will increase significantly when the contact loss is longer than 3.125 m, being unfavorable to the ride comfort and safety, so contact loss length underneath concrete roadbed should be less than 3.125 m.

Stability Analysis of Slopes Reinforced with Sheet Pile Wall

LUO Yu, XU Qiang, HE Siming, HE Jinchuan

2014, 27(6): 967-971. doi: 10.3969/j.issn.0258-2724.2014.06.006

[Abstract](961)

Abstract:
In order to analyze the stability of a slope reinforced with sheet pile wall, based on the multi-wedge translation mechanism the upper bound method was applied to derive the expressions to calculate needed lateral force acting on piles to guarantee the stability of a slope. A new method was presented to analyze the stability of slopes reinforced with sheet pile wall. In addition, an example was given to illustrate the presented method, and the results were compared with those obtained using the rotation failure mechanism. The research results show that needed lateral force acting on piles increases as slope angle increases, and decrease as soil strength increases. The potential sliding surface becomes increasingly shallow as soil strength increases, and the potential sliding surface obtained using the presented method is more critical than that obtained using the rotation failure mechanism.

Disaster Reduction Techniques of Railway Route Selection in Mountainous Regions with High Earthquake Intensity

QIU Yanling, YAO Lingkan, ZHU Ying, WEI Yongxing

2014, 27(6): 972-980. doi: 10.3969/j.issn.0258-2724.2014.06.007

[Abstract](1033)

Abstract:
To reduce earthquake-induced disasters of railway in mountainous regions with a high earthquake intensity from fountainhead, the disaster reduction techniques of the selection of transportation corridors and the space layout of railway lines, were researched based on the concept of risk control. From the fault tectonic geomorphology theory, landform patterns formed by active faults and seismic disasters were analyzed, and the selection principles of transportation corridors were obtained. From the wave motion theory, the topography effects of seismic wave propagation reflected in the Lushan and Wenchuan earthquakes were analyzed, and the key points of line space layout were worked out. The research result shows that lexural basin on footwall of reversed faults, rift basin on hanging wall of normal faults, and rift basin and pull-apart basin on strike-slip faults are available geomorphic units of railway corridors. Elevation amplification effect may not be considered in the route elevation determination of large sections. Canyon routes shall be avoided laying in the incident side of seismic waves. Earthquake near-field routes shall be selected along the hillside facing wave propagation direction, while far-field routes in the opposite side. Sharp curves must be avoided, moreover, deep cutting slopes and tall retaining structures shall be avoided layouting in the convex side of a curve.

Comparative Research on Flat Steel and Damper Strengthening of Straight Type of Tenon-Mortise Joints

PAN Yi, WANG Chao, TANG Lina, LI Lingjiao, GENG Pengfei

2014, 27(6): 981-986,1031. doi: 10.3969/j.issn.0258-2724.2014.06.008

[Abstract](1003)

Abstract:
For better seismic reinforcement of Chinese ancient wooden buildings, based on the mechanical model for straight type of tenon-mortise joints the flat steel strengthening and damper strengthening of straight type of tenon-mortise joints were investigated respectively by taking the Yellow Emperor Temple in Qingcheng Mountain damaged in the Wenchuan earthquake as an example. The vibration period of the structure, the acceleration magnification factor of a strengthened joint and the internal force of adjacent members of the strengthened joint were analyzed by using the two strengthening measures, and compared with those of the original structure. The analysis results indicate that the seismic performance of the structure is significantly improved by the two strengthening measures. However, the flat steel strengthening will increase the structural stiffness of the strengthened joint and the internal forces of its adjacent members to easily result in pulling-out-tenon of adjacent joints. The damper strengthening can significantly weaken the seismic responses of the structure without increasing joint stiffness and reduce the acceleration magnification factor of the strengthened joint by 12.8%and average tension force, shear force and bending moment by 48.3%, 40.6% and 52.1% respectively, so the damper strengthening has the effects of energy dissipation and preventing pulling-out-tenon.

Support Vector Classification Algorithm by Migration Sampling for Structural System Reliability Evaluation

BAI Bing, LI Qiao, ZHANG Qinghua

2014, 27(6): 987-994. doi: 10.3969/j.issn.0258-2724.2014.06.009

[Abstract](951)

Abstract:
In order to avoid the cumbersome bounding operation during system reliability evaluation procedures, a concept of system limit state surface was introduced on account of the characteristic of system multi-failure modes. Employing the support vector classification (SVC) algorithm to divide the security domain and failure domain, reconstitution of the system limit state surface could be achieved. On this basis, a migration sampling strategy using Latin hypercube sampling (LHS) was combined together with the SVC algorithm, finally leading to a new system reliability evaluation method of SVC migration sampling. Two widely used illustrative examples were introduced and analyzed by different methods for comparison. The results show that the SVC migration sampling algorithm possesses good sampling efficiency as well as superior convergence property. Compared with traditional Monte Carlo sampling methods, the algorithm presented can reduce sampling times by 87%with a relative error of less than 1%. The gross assumption of component failure state by β-unzipping method can also be avoided, which is more suitable for practical application to actual structure assessment.

Bayesian Methods for Inferring Representative Values of Variable Actions in Small Sample Situations

YAO Jitao, WANG Xudong

2014, 27(6): 995-1001. doi: 10.3969/j.issn.0258-2724.2014.06.010

[Abstract](1082)

Abstract:
There is a need sometimes in engineering to infer the representative values of variable actions in cases when the test data is not sufficient, but the classical statistics methods do not take into account of the succedent influences of statistical uncertainty, and the inferred results are always on the aggressive side. In order to overcome the above shortcomings, applying the current linear regression estimation for inferring the fractiles of type I minimum distribution, the linear regression estimation of representative values of variable actions is proposed as a reference method for the precision inspection of other inference methods. According to Bayesian theory, applying Jeffreys non-informative prior distribution, a Bayesian method for inferring characteristic and frequent values of variable actions is put forward. The results show that the Bayesian inference method is more convenient than the liner regression estimation, and easy to use in a broader context. The method can give more advantageous results when standard deviation is known. If no parameter information is available, the Bayesian inference method has better precision when the guarantee rates of characteristic and frequent values are no less than 0.90. Compared with other confidence degrees, the inferred results are more close to the true value when the confidence degree equals 0.75; therefore, it is recommended to take a confidence degree of 0.75.

Geometry Simulation of Track Torsion-Irregularity Based on 6-DOF Platform

LIU Yumei, CAO Xiaoning, ZHAO Congcong, XIONG Mingye, ZHANG Jingshi

2014, 27(6): 1002-1009. doi: 10.3969/j.issn.0258-2724.2014.06.011

[Abstract](827)

Abstract:
In order to obtain the geometry information of track torsion irregularity, an inverse kinematics model and a pose correlation model for the double 6-degree-of-freedom (DOF) platform of a track torsion irregularity simulator were established, taking into account the characteristics of torsional irregularity and the structure of the track torsional irregularity simulator. By means of Simulink inverse kinematics model, the inverse kinematics solutions for three types of torsion irregularity of domestic commonly used gauges and wheelbases of bogies were calculated. The results have a good consistency with the forward kinematics solutions, which verifies the correctness of the established inverse kinematics model and pose correlation model. In addition, taking a certain type of bogie as an example, laboratory tests were carried out using torsion irregularity of different basic lengths to study the effect of the basic length on the wheel loading reduction rate. The results show that the smaller the basic length of torsion irregularity is, the larger the wheel loading reduction rate will be. The maximum wheel loading reduction rate for 2.4 m and 5.0 m basic lengths are 0.594 and 0.581, respectively, both within the safety limit of relevant national standards.

Stability Analysis of Parametric Vibration for Gear Transmission System in High-Speed Train

HUANG Guanhua, ZHANG Weihua, FU Yongpei, LIANG Shulin, WANG Xingyu

2014, 27(6): 1010-1015. doi: 10.3969/j.issn.0258-2724.2014.06.012

[Abstract](1226)

Abstract:
In order to study the stability of the gear transmission system in high-speed trains, a dynamic model describing the torsional vibration behaviors of the gear system was developed. In this model, the time-varying mesh stiffness of meshing teeth pairs was calculated through finite element analysis, and the mesh stiffness and transmission error were expanded using the technique of Fourier series. Based on this model, the multiple scales method was used to solve the nonlinear differential equations of gear systems, and the approximate analytical solution and transition curves that separate stable from unstable regions were obtained. In addition, the main factors that influence the stability were discussed. The results show that the unstable regions decrease with the decrease of the train's running speed, but an unstable region always exists at the speed where parametric resonance occurs; increasing the damping is effective to reduce the unstable regions: as the damping increases from 0.01 to 0.05, the amplitude of mesh stiffness fluctuation in stable regions increases from 5% to 20%; and, an increase in the contact ratio can help suppress the harmonic characteristics of mesh stiffness so as to improve the stability of system.

Reliability and Delay of DSPN-Based Ground Communication System in High-Speed Maglev Vehicles

MA Lianchuan, ZHANG Yuzhuo, SUN Yaqing, MU Jiancheng, CAO Yuan

2014, 27(6): 1016-1023. doi: 10.3969/j.issn.0258-2724.2014.06.013

[Abstract](1060)

Abstract:
To achieve the real-time and large-capacity communication of maglev operation control system when the train runs at high speeds, a DSPN-based (deterministic and stochastic Petri nets) model was built according to the communication failure modes of 38 GHz millimeter wave. Further, a vehicle-ground downlink transmission model was established to cover the entire transmission process of sending information frame, processing redundant structure, transmitting in dual channel, electing and voting. Finally, the reliability and time delay of the maglev vehicle-ground communication system were verified by formal method. The results of formal verification show that fault-free probability of the 38 GHz millimeter communication system is 99.452%, and mean time for repairing fault is 373.80 ms, which satisfy the vehicle-ground communication requirement of high-speed maglevs.

Influential Factors and Rules for Insertion Loss of High-Speed Railway Noise Barriers

ZHOU Xin, XIAO Xinbiao, HE Bin, HAN Jiaqi, WEN Zefeng, JIN Xuesong

2014, 27(6): 1024-1031. doi: 10.3969/j.issn.0258-2724.2014.06.014

[Abstract](1073)

Abstract:
Based on the boundary element method and the train noise sources identified by a beam-forming noise source system, a numerical prediction model was established to study the factors and rules relevant to the insertion loss of high-speed railway noise barriers. The effects of noise source locations, noise barrier heights, shapes, and absorbing boundary conditions were investigated. The improvement strategies based on the current structure of noise barriers were proposed. The numerical results show that the noise source height has a significant effect on the sound barrier performance. The sound barrier of 2.15 m height can only reduce noise coming from the lower part of the train. The insertion loss increases with the noise barrier height. When the height exceeds 6.15 m, the insertion loss reaches over 25 dB(A). The sound barriers with different cross sections are listed, according to their noise attenuation effect, i.e., Y-shaped barrier, tilted barrier, T-shaped barrier, inward folded barrier, vertical barrier and outward folded barrier. The Y-shaped barrier produces the highest performance with an increase of 0.7~1.5 dB(A) in insertion loss compared with the vertical barrier. Despite the shape of noise barriers, the absorbing boundary overall lead to more noise reduction than the smooth rigid boundary, but the noise reduction amount relates to the forms of sound barriers ranging from 0.3 to 6.4 dB(A).

A Review of Developments in Reinforcement Learning for Multi-robot Systems

MA Lei, ZHANG Wenxu, DAI Chaohua

2014, 27(6): 1032-1044. doi: 10.3969/j.issn.0258-2724.2014.06.015

[Abstract](1423)

Abstract:
Reinforcement learning (RL) is an effective mean for multi-robot systems to adapt to complex and uncertain environments. It is considered as one of the key technologies in designing intelligent systems. Based on the basic ideas and theoretical framework of reinforcement learning, main challenges such as partial observation, computational complexity and convergence were focused. The state of the art and difficulties were summarized in terms of communication issues, cooperative learning, credit assignment and interpretability. Applications in path planning and obstacle avoidance, unmanned aerial vehicles, robot football, the multi-robot pursuit-evasion problem, etc., were introduced. Finally, the frontier technologies such as qualitative RL, fractal RL and information fusion RL, were discussed to track its future development.

Decision and Control of Catenary On-Line Anti-icing Current in Autotransformer Power Supply System

GUO Lei, GAO Xiaojie, LI Qunzhan

2014, 27(6): 1045-1051. doi: 10.3969/j.issn.0258-2724.2014.06.016

[Abstract](1217)

Abstract:
In order to prevent icing on catenaries and ensure trains' normal operation on electrified railways, a circuit model for the autotransformer (AT) power supply system during anti-icing period was built according to the special structure of long and short loops of the AT power supply system. This model was then used to deduce the comprehensive distribution of the anti-icing current and load current in each AT section, and the current that can prevent icing on the whole line was calculated. After analyzing the relationship between the catenary anti-icing current and the terminal voltage of the power supply arm, the anti-icing current value allowed by the voltage of traction electric network was obtained. On this basis, the decision flow of the on-line anti-icing current was proposed, aiming at maintaining the temperature of contact wire. In addition, simulations were carried out for an AT section, and the simulation results were compared with the measured load data. The results show that the anti-icing current of catenary should be 2 times the critical anti-icing current at least, such that the temperature of contact wire can maintain above 0 ℃ with anti-icing current.

Stability of High Order Fuzzy Cohen-Grossberg Neural Networks with Unbounded Time Delays

ZHENG Weifan, ZHANG Jiye

2014, 27(6): 1052-1060. doi: 10.3969/j.issn.0258-2724.2014.06.017

[Abstract](826)

Abstract:
Using M-matrix theory, matrix inequality and vector Lyapunov methods, the global exponential stability of a class of high-order fuzzy Cohen-Grossberg neural networks with unbounded time delays was investigated. Without assuming the monotonicity, differentiability and Lipschitz continuity of the active functions, the algebraic criteria ensuring existence, uniqueness and exponential stability of the equilibrium point in the neural networks were obtained. The criteria is independent to the reaction diffusion and the time delays of neural networks by the explicit form of M-matrix,and easy to be checked in application. Finally, the correctness and validity of the methods was verified by a numerical example.

Single-Objective Multi-modal Expected Value Programming Based on Immune Optimization

YANG Kai, ZHANG Zhuhong

2014, 27(6): 1061-1067. doi: 10.3969/j.issn.0258-2724.2014.06.018

[Abstract](907)

Abstract:
To solve the problem of single-objective multi-modal expected value programming with unknown noisy distribution, a multi-objective immune optimization algorithm based on immune response principles was proposed. By means of a random function used for checking whether a candidate solution was a locally optimal solution, the expected value problem was converted into a multi-objective expected value programming problem. Moreover, some relations between the original problem and the transformed problem were studied, and a conclusion that an efficient solution must be an optimal solution under certain conditions was developed. Relying upon the idea of sample average approximation, the multi-objective programming was further transformed into an approximate model with variable sampling sizes. Based on the metaphors of clonal selection and immune memory, one such optimization approach was obtained to deal with the approximation model. It searched high-quality individuals toward some regions which the optimal solutions existed, depending on several main modules: recursive non-dominated sorting, adaptive sampling, adaptive proliferation, and adaptive mutation. By comparison with the multi-objective optimization algorithms, the simulation results show that the proposed algorithm with strong noise suppression can achieve averagely about a seventy percent increase in the number of optimal solutions found for the high-dimensional benchmark problem and a twenty percent increase for the low-dimensional benchmark problem; it can gain the stable search effect and has the prominent advantage in solving multiple optimal solutions.

Model and Architecture of Open SaaS Industry Service Platform

GUO Yanqun, HAN Min, SUN Linfu

2014, 27(6): 1068-1072. doi: 10.3969/j.issn.0258-2724.2014.06.019

[Abstract](2039)

Abstract:
In order to satisfy enterprises' multiplex requirements for the extensible and programmable operations of information systems, the conception of open SaaS (software-as-a-service) industry service platform, called as OSISP for short, was put forward by combining the open-system design idea and the SaaS technology. The OSISP can meet the extensible, customized and programmable requirements of different enterprises. The operation architecture of an industry service platform was designed, and the abstraction and formalization of operation roles and the model of operation integration were given. Based on the above works, the system architecture of the OSISP, consisting of a basal layer, a platform layer, a system layer, a user layer, a system management layer and a standard layer, was designed in light of the layered architecture design idea. Through the system design, the OSISP on the platform of an automobile supply chain was used so as to improve the exoteric attribute of information systems and enhance the enthusiasm that enterprises participate in the construction and use of the information systems.

Numerical Simulation of Monitoring Wheel-Rail Contact Conditions Using Ultrasonic Technology

DENG Weili, XIAO Nan, YONG Yuan

2014, 27(6): 1073-1077. doi: 10.3969/j.issn.0258-2724.2014.06.020

[Abstract](1109)

Abstract:
In order to realize the real-time monitoring of train's running state and ensure the safety of train operation, a method to monitor the wheel-rail contact condition using ultrasonic technology was proposed. The W-M fractal function was used for mathematic description of wheel and rail surfaces, and a finite element model of wheel-rail contact monitoring were built with the multiphysics software. Using the model, the proposed monitoring method, the roughness of interface, and the types and thickness of the media layer were simulated, and the sound pressures of the wave reflected from the contact interface were obtained under different conditions. The simulation results show that the proposed method of monitoring the wheel-rail contact condition by detecting the ultrasonic sound pressure level is effective and feasible. When the ultrasonic frequency equals 14 MHz, the rail surface roughness can be detected with the best distinction degree. When the frequency is larger than 14 MHz, the third medium thickness has a good distinction degree. When the frequency is constant and the thickness of the third medium is large enough, the sound pressure level of reflected ultrasonic wave tends to a constant value 102 dB.

Electric-Hydraulic System for Continuously Variable Transmission: Test Analysis and Fault Detection

HAN Ling, ZHANG Libin, AN Ying, ANWAR Sohel

2014, 27(6): 1078-1083. doi: 10.3969/j.issn.0258-2724.2014.06.021

[Abstract](761)

Abstract:
To determine if the performance of the electro hydraulic control module for continuously variable transmission could match the national standards of China, the stress level, pressure regulating curve, repeat accuracy, and speed of step response of the electro-hydraulic control module were analyzed by the hydraulic pressure control principle and Matlab simulation method. An exclusive test system for the hydraulic control module was developed after establishment of a test bench and integral vehicle tests. In the meantime, early faults of the CVT parts were positioned by calculation of the metallic element concentration in the hydraulic oil, using the oil spectrum analysis and immune algorithm. Test results show that the speed ratio of the electro-hydraulic module, the accuracy and speed of pressure tracking, and the thermal equilibrium flow all meet the national standards and the positioning accuracy of the fault parts is above 95.3%.

Identification of Torsional Damping Coefficients for Internal Combustion Engine Crankshafts

HUA Chunrong, DONG Dawei, YAN Bing

2014, 27(6): 1084-1089. doi: 10.3969/j.issn.0258-2724.2014.06.022

[Abstract](963)

Abstract:
In order to solve the difficulty of selecting the damping coefficients in torsional vibration theoretical analysis of internal combustion engine (ICE) crankshafts, an identification method of torsional damping coefficients of main crankshafts components was proposed based on the modal damping ratio of crankshafts angular vibration. In this method, the multi-mass system of crankshafts was simplified to an equivalent torsion pendulum system, and the relationship between the modal damping ratio of crankshafts angular vibration and the torsional damping coefficient of each crankshaft component was derived by vibratory energy theory. Thus, if the damping ratio of crankshafts angular vibration is given, the main torsional damping coefficients of crankshafts could be identified by analyzing the damping property of crankshafts torsional vibration and selecting a proper mode of angular vibration. As a case study, the damping coefficients of a 4-and a 6-cylinder diesel engine were identified by simulation and experiment. The results show that the identified torsional damping coefficients of the main crankshafts components obtained by simulation have a maximum error of 4.89%compared to the experimental one. This demonstrates the validity of the proposed identification method.

Effect of Surface Treatment on Properties of HDPE/EVA/EG Composites

CHEN Xiaolang, SUN Zhidan, MA Yonghong, ZHANG Zhibin, YU Jie

2014, 27(6): 1097-1101. doi: 10.3969/j.issn.0258-2724.2014.06.024

[Abstract](815)

Abstract:
In order to obtain the composites with good thermal stability, flammability, and mechanical properties, high density polyethylene/ethylene-vinyl acetate copolymer (HDPE/EVA) composites filled with expandable graphite (EG) flame retardant were prepared by using a twin-screw extruder technique. The thermal stability, flammability, and mechanical properties of the composites were investigated by the thermogravimetric analysis (TGA), cone calorimeter, mechanical properties tests, and scanning electron microscopy (SEM). The results indicated that the addition of EG significantly enhanced the thermal stability and fire resistance of the HDPE/EVA materials, but obviously decreased the mechanical properties of HDPE/EVA/EG. After the surface treatment of EG with titanate coupling agent, the elongation at break of HDPE/EVA/EG composites increased from 232.3% to 315.3%, the tensile strengths increased from 9.0 to 10.0 MPa, and the impact strengths increased from 88 to 129 kJ/m2. The improvement of the mechanical properties of HDPE/EVA/EG composites was due to the enhancement of interfacial adhesion between EG and polymer matrix.

Evaluation Parameter Research of Asphalt Binder Fatigue

SUN Yanna, LI Lihan, WANG Yukai

2014, 27(6): 1102-1107. doi: 10.3969/j.issn.0258-2724.2014.06.025

[Abstract](939)

Abstract:
In order to determine the evaluation parameter of asphalt binder fatigue performance, fatigue performances of 5 kinds of asphalt binder (including olefin asphalt binder, natural asphalt binder, hard asphalt binder, A70# asphalt, and SBS asphalt)and asphalt mixture were tested in laboratory. Then, 4 evaluation parameters, including fatigue life at 50% initial modulus reduction (Nf50 ), fatigue life at the accumulated dissipation energy ratio deviating 20% from the lossless line (Np20 ), accumulated dissipation energy, and fatigue factor (G*sin δ) were used to analyze the dependence of each evaluation parameter on the loading mode and the relationship between the evaluation parameters. The result shows that the fatigue factor G*sinδ, dissipation energy, and accumulated dissipation energy are inappropriate to be used as evaluation parameters as they cannot determine the fatigue life exactly. The other two parameters, Nf50 and Np20 , however, are suitable to evaluate the binders fatigue performance. Np20 is about 0.725 times Nf50, and it is suggested using Nf50 to evaluate the fatigue performance of asphalt binders.

Simulation of Effect of Train Arrival Delay on Wagon Flow Connection at Technical Stations

CHEN Dong, PENG Qiyuan, LI Yonghui

2014, 27(6): 1108-1115. doi: 10.3969/j.issn.0258-2724.2014.06.026

[Abstract](957)

Abstract:
In order to clarify the interaction mechanism between the flow and lines in railway system, the influence of train delay on wagon flow connection at technical stations was analyzed. By setting the minimum average residence time of transferring wagons as the optimization objective, a generalized wagon-flow organization model for technical stations was established with the constraints such as wagon flow connection. Based on this model, delay times were randomly generated following distribution rule of train arrival delay and added to train arrival time. Thus, a set of delaying trains was formed and input into the generalized wagon-flow organization model to conduct simulation calculation. In the different cases of train delay, taking the delay rate of departing train and total delay time as the indexes, the wagon flow connection results under the same operation were analyzed. The analysis results show that the effect of train delay for a single schedule period on wagon-flow connection at technical stations is uncertain. However, the effect of train delay for multiple schedule periods shows strong regularity though the different values of the number of wagons at stations, delay rate, total delay time, and train formation plan, etc., lead to different wagon-flow connection results. Finally, the necessity and feasibility of joint optimization of flow and lines was validated.

Constraint Propagation and Heuristics Backtracking Algorithm for Static Wagon-Flow Allocation at a Marshalling Station

MA Liang, GUO Jin, CHEN Guangwei

2014, 27(6): 1116-1122. doi: 10.3969/j.issn.0258-2724.2014.06.027

[Abstract](846)

Abstract:
In order to improve the efficiency of stage planning, a hybrid algorithm was designed to solve the lexicographic multi-objective cumulative scheduling model of the static wagon-flow allocation problem at a marshalling station. The proposed algorithm is based on iteration method, constraint propagation technique and heuristic backtracking. The whole model is divided into three layers according to the lexicographical order of the multi-objective. The total priorities of the on-time outbound trains is maximized in the first sub-model, minimizing the total number of the inbound trains providing cars to each outbound trains is the objective in the second sub-model, while, the average dwell time of railcars in the station should be decreased as possible in the final sub-model. Firstly, each sub-model is simplified and the search space is reduced by constraint propagation algorithm. Then, the optimal solution is searched fast by the combined algorithm of heuristic backtracking and constraint propagation. In the lower sub-model, the optimal solution of the upper sub-model is considered as the initial solution, and the constraint is added to avoid degradation of the optimal value of the upper objective, so that the whole model is solved by the iteration algorithm. Experiment results from a marshalling station show that the total running time of the algorithm is less than 20 s, which meets the real-time requirements of scheduling in the field, and the algorithm can solve a better wagon-flow allocation solution compared with other algorithms.

Critical Discharge Flow of Sand Cleaning Fluid Considering Transient Temperature Effect of Horizontal Well

LIU Qingyou, WANG Xingming, XU Tao

2014, 27(6): 1123-1129. doi: 10.3969/j.issn.0258-2724.2014.06.028

[Abstract](1012)

Abstract:
Hydraulic sand cleaning operation of horizontal well in oil and gas fields is difficult because it is hard to obtain a reasonable discharge volumetric flow of the sand cleaning fluid (SCF) in practice. To solve this problem, an annular critical velocity model that is based on the transient thermal model of formation and wellbore during sand cleaning operation was proposed to recognize the SCF critical velocity in horizontal well. Taking into account the influence of transient temperature field on the SCF viscosity, the finite volume method (FVM) was used to obtain the transient thermal distribution, and the transient annulus critical velocity of the whole wellbore was calculated by solving the temperature-viscosity equation of the SCF. On this basis, a new method for calculating the critical discharge flow of SCF was then developed. As a case study, the critical velocities of four typical SCFs were calculated using the proposed method. The results show that the critical velocities of the four SCFs when considering the effect of temperature are 9.20%, 17.26%, 9.85%, and 7.64% respectively lager than that without considering the thermal effect; and the critical discharge flow are 8.33%, 18.18%, 10.00%, and 11.11% larger respectively. Therefore, temperature should be considered to optimize the critical velocity and discharge flow of SCFs in horizontal well.

Registration Method for Point Cloud Based on Feature of One Plane and Two Cylindrical Holes

JIANG Lei, LI Xiangbiao, MA Shuwen, ZHOU Liangming, LI Qiqin, DUAN Changde

2014, 27(6): 1090-1096. doi: 10.3969/j.issn.0258-2724.2014.06.023

[Abstract](885)

Abstract:
For improving the registration accuracy between point cloud and design model of the parts during scan detection, a registration method based on the feature of one plane and two cylindrical holes was proposed. The rough registration applies the features of plane and holes to coincide with the local coordinate systems of point cloud and design model. The fine registration is finished by using the improved iterative closest point (ICP) algorithm to calculate the sum of least squares of the distance between the closest points and point cloud. Since the calculation methods of registration areas and the closest points are different, fine registration is further classed into the global domain and feature domain types. The closest points of global registration are obtained by comparing the distance between point cloud and the nearest design model grid points or projection points, which is suitable for blank parts. The projection points of point cloud on a plane or a cylindrical hole are the closest points of feature domain registration, which is suitable for finished parts. The test results show that the accuracy of global registration will increase with the distance between surface discrete points decreasing. When the distance reaches 1.50 mm, the accuracy is about 0.15 mm, which meets the engineering requirements. For the same registration accuracy, the efficiency will be improved by 10%-20% compared with that of other methods.

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2014 Vol. 27, No. 6