2015 Vol. 15, No. 1

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Rheological properties of warm mix asphalt rubber in wide range of pavement temperature
HE Liang, LING Tian-qing, MA Yu, MA Tao, HUANG Xiao-ming
Abstract: In order to research the rheological properties of warm mix asphalt rubber, the asphalt rubber meeting the technical requirements in Asphalt Rubber for Highway Engineering(JT/T 798―2011)was prepared. The optimum content of warm mix additive Sasobit was determined from the warm mix effect and the impact of Sasobit on the technical indexes of warm mix asphalt rubber by viscosity-temperature relationship test and basic technical index test. The rheological properties of Sasobit warm mix asphalt rubber were evaluated in the wide range of pavement temperature at high(60, 70 ℃), medium(25 ℃)and low(5 ℃~24 ℃)temperatures. Analysis result shows that 3% is the optimum content of Sasobit in warm mix asphalt rubber. Sasobit can improve the high-temperature stability of asphalt rubber, its rutting factor at 70 ℃ increases by 79%, but Sasobit has no significant effect on the viscosity-toughness of asphalt rubber. The fatigue performance of asphalt rubber with 3% Sasobit reduces, its fatigue factor at 25 ℃ increases by 22%, but its fatigue performance is still better than that of SBS modified asphalt. Under the temperature condition of winter warm zone in Chinese standards for the climate zoning on asphalt pavement performance, as the temperature decreases, the low-temperature performance of Sasobit warm mix asphalt rubber is gradually better than that of SBS modified asphalt, its creep stiffness at -24 ℃ is 45% of creep stiffness of SBS modified asphalt, while Sasobit dosage has no excessive effect on the low-temperature performance of asphalt rubber, and the creep stiffness of asphalt rubber at -24 ℃ increases by 10%.More>
2015, 15(1): 1-9. doi: 10.19818/j.cnki.1671-1637.2015.01.001
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Performance test of rubber asphalt based on domestic and abroad test methods
LI Xiao-yan, PING Lu, WANG Hai-nian, ZHANG Chen, YOU Zhan-ping
Abstract: To unify the performance evaluation indicators of asphalt rubber, 70# and 90# base asphalts were modified with different rubber powder contents. The performance tests of rubber asphalts were conducted by Chinese specific tests such as penetration test, ductility test, softening point test and elastic recovery test, and Superpave methods such as dynamic shear rheology(DSR)test, Brookfield rotary viscosity test, and bending beam rheology(BBR)test. Analysis result shows that the addition of rubber powder can improve the high-temperature performance and reduce the temperature sensitivity of asphalt, but increase the viscosity of asphalt at high temperature and increase the difficulties in asphalt mixing and compaction. The swelling of rubber powder would lead big error in penetration test, so it is not recommended to apply penetration test in evaluation of rubber asphalt performance. Softening point can be regarded as one of evaluation indicators for high-temperature performance of rubber asphalt. For 90# base asphalt, its softening point increases by 11.23, 11.97, 15.18 and 21.10 ℃ when the rubber powder content is 10%, 15%, 20% and 25% respectively. For 70# base asphalt, its softening point increases by 4.02, 8.18, 12.83 and 14.45 ℃ when the rubber powder content is 10%, 15%, 20% and 25% respectively. It is also found the influence of softening point caused by rubber powder is larger on 70# base asphalt than on 90# base asphalt. The improvement of rubber powder on the low-temperature performance of asphalt would decease with the decrease of temperature. To test the improvement of rubber powder on the low-temperature performance of asphalt, BBR test is more significant than low-temperature ductility test. Besides, big error will produce in low-temperature ductility test process because of its small value. Therefore, it is recommended to apply BBR test for the low-temperature performance evaluation of rubber asphalt.More>
2015, 15(1): 10-17. doi: 10.19818/j.cnki.1671-1637.2015.01.002
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Surface free energy analysis of asphalt modified with natural asphalt
MA Feng, HAO Jing-xian, FU Zhen, WANG Li-long, WANG Lin-bing
Abstract: In order to accurately evaluate the adhesion of asphalt modified with natural asphalt and aggregate, the contact angles of three liquids on the sample surface of asphalt modified with natural asphalt were measured based on sessile drop method. According to the theory of surface physical chemistry, the measuring method of polar component and dispersion component for asphalt surface free energy under the condition of room temperature was determined. The surface free energies of base asphalt and asphalts modified with different dosages of natural asphalt were calculated. The relationship between asphalt surface free energy and asphalt-aggregate adhesion grade was analyzed based on the test result by using water-boiling method. Test result shows that the surface free energies of 70# grade A base asphalt and asphalt modified with 8% natural asphalt are 10.60, 18.60 mJ·m-2 respectively, so the surface free energy of asphalt modified with natural asphalt increases distinctly with the addition of natural asphalt. There is a good correlation between asphalt-aggregate adhesion and the surface free energy of asphalt calculated by contact angle method. The natural asphalt contains higher polar functional groups such as O, S and N etc. High contents of asphaltene and net structure can absorb the light components of base asphalt such as saturates, aromatics. The increase of surface free energy for asphalt modified with natural asphalt is attributed to the polar functional groups and the absorbing functions.More>
2015, 15(1): 18-24. doi: 10.19818/j.cnki.1671-1637.2015.01.003
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Fractal description method of corrugation for friction surface
CHEN Guang-xiong, HU Wen-ping, WANG Ping, ZHU Min-hao
Abstract: On the self-built pin-on-disc test machine, the sliding friction test under self-excited vibration was carried out. The average contact stress between wheel and track was simulated by using the friction movement of pin-on-disc. The corrugation sizes of friction surface for disc specimen were measured with laser displacement sensor, the corrugation curves of friction surface for disc specimen under different test conditions were obtained. The fractal description method of corrugation for friction surface was carried out with power spectrum method, the fractal dimensions of corrugation under different test conditions were calculated based on the relationship between power spectrum index and fractal dimension, and the relationships between fractional dimension and other parameters such as rotating speed, normal load and revolution were analyzed. Test result shows that under the same normal load, the fractal dimension calculated by using power spectrum method increases with the increase of rotating speed. Under the same rotating speed, the fractal dimension increases with the increase of normal load. Under the same rotating speed and normal load, the fractal dimension decreases with the increase of revolution. The fractional dimension of corrugation of friction surface for disc specimen is from 1.79 to 1.92, the corrugation of friction surface for disc specimen have obvious fractal characteristics. The larger the fractal dimension is, the more serious the corrugation of friction surface for disc specimen is, and the longer the wave length of corrugation is.The result calculated by using power spectrum method is consistent with the experimental result, so fractal dimension can be used to quantitatively describe the corrugation of friction surface.More>
2015, 15(1): 25-33. doi: 10.19818/j.cnki.1671-1637.2015.01.004
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Effect of metro rail corrugation on dynamic behaviors of vehicle and track
LI Wei, CENG Quan-jun, ZHU Shi-you, FAN Jia-feng, JIN Xue-song
Abstract: The characteristics of rail corrugation were measured by using corrugation analysis trolley, the vibration accelerations of vehicle and track components were measured by using acceleration and displacement sensors before and after rail grinding, and the effect of rail corrugation on the vibrations of vehicle and track components was analyzed. Vehicle-track coupling dynamics model was established to analyze the effect of rail corrugation on wheel/rail interaction force and to determine the limit value of rail grinding. Study result shows that the main wavelength of rail corrugation is 30-40 mm and the secondary wavelength is 16 mm. The vibrations of railhead and fastener clip at 650-800 Hz and the vibrations of axle box at 670-800 Hz are in accordance with the passing vibration behaviors of vehicle with wavelength of 30-40 mm. So the short-pitch rail corrugation leads to the strong vibration of metro vehicle and track components, and it is the main cause of fatigue fracture of primary suspension springs and track fastener clips. Rail grinding can effectively solve fatigue fracture problem. Before rail grinding the root mean square values of vibration accelerations of railhead, fastener clip, sleeper and ballast bed are 243.4, 309.3, 17.1 and 2.6 m·s-2 respectively, and after rail grinding they decrease to 51.5, 8.8, 1.5 and 0.5 m·s-2 respectively. When the depth of rail corrugation is 0.1 mm, wheel/rail vertical forces are 307 and 109 kN with wavelengths of 35 and 80 mm respectively, and wheel/rail transverse forces are 56 and 25 kN with wavelengths of 35 and 80 mm respectively. So wheel/rail vertical and transverse forces are very sensitive to the wavelength of rail corrugation. When vehicle operation speed is 90-120 km·h-1, the depth of rail corrugation with wavelength of 35 mm is 0.05-0.08 mm according to the limited criterion of wheel unloading rate, and the depth is 0.03-0.06 mm according to the limited criterion of wheel/rail vertical force. So rail grinding should be carried out when the depth of 30-40 mm short-pitch rail corrugation reaches 0.05 mm.More>
2015, 15(1): 34-42. doi: 10.19818/j.cnki.1671-1637.2015.01.005
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Judgment method of maglev vehicle dynamic stability on flexible track
LI Song-qi, ZHANG Kun-lun, CHEN Yin, GUO Wei, LIANG Hao-ran
Abstract: The dynamic stability of EMS maglev vehicle was analyzed, a simplified dynamics model of vehicle-track coupling vibration system was set up, and the time-varying linear kinetics equations of the system were deduced based on each track mode separately.The state matrix and the correlation coefficients of characteristic equations for the system were produced by simplifying the equations.The basic conditions of the system on dynamic stability were derived from the proper relationship among the coefficients under the condition of asymptotically stable system, and the quick dynamic stability criterion was given.When the criterion value was greater than 1, the system was stable.When the criterion value was less than 1, the system was unstable.Research result indicates that when the speeds of 6kinds of working conditions are 100, 180, 260, 340, 420, 500km·h-1 respectively, the track bending stiffnesses are 4.83×1010, 3.86×1010, 3.38×1010, 3.38×1010, 3.86×1010, 4.83×1010 N·m2 respectively, and the track beam lengths are 24.8, 22.4, 20.4, 20.4, 22.4, 24.8mrespectively, the stability criterion values are1.639, 0.624, 2.339, 0.870, 3.252, 0.571 respectively, and the related Lyapunov characteristic exponents are-3.580×10-2, 2.443×10-1, -3.910×10-2, 1.515×10-1, -5.471×10-2, 1.939×10-1 respectively.Under conditions 1, 3, 5, the stability criterion values are greater than1, the related exponents are less than 0, so the system is stable.Under conditions 2, 4, 6, the stability criterion values are less than 1, the related exponents are greater than 0, so the system is unstable.The two judgment results are coincident, so the criterion is reliable.the stability criterion explains the reason of resonance caused by vehicle speed increase, reveals the relationship among maglev vehicle dynamic stability, vehicle speed and vehicle-track system main parameters, avoids the complexity to solve high-dimension dynamics differential equation, and is simpler and more convenient in engineering application.More>
2015, 15(1): 43-49. doi: 10.19818/j.cnki.1671-1637.2015.01.006
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Electrostatic monitoring of vehicle gearbox
LIU Ruo-chen, ZUO Hong-fu, SUN Jian-zhong, LI Xin, MAO Hui-jie
Abstract: Based on the electrostatic induction principle of wear site, the wear-site electrostatic sensors of gear and bearing for railway vehicle were designed.At 160km·h-1, the root mean square(RMS)of time-domain electrostatic signal for gearbox was extracted as the feature parameter, the influences of different speeds and torques on the electrostatic levels were investigated at noise test stage, and the change trends of electrostatic signals were analyzed at run-up test stage and load fatigue test stage.Study result indicates that the electrostatic signals of gear and bearing remain stable under the same condition, and the former always be slightly higher than the latter.When speed and torque increase, the electrostatic amplitude increases, speed effect on the electrostatic level is larger than torque effect, while the directions of speed and torque have little influence on the signal.The electrostatic signals decrease significantly at run-up test stage and come to stable in the last.The signals remain basically stable and rise very slow at load fatigue test stage.The changing trends of gearbox electrostatic signals are consistent with the theoretical analysis result and the actual test result, so the electrostatic monitoring method is a new technology, can be used for the online monitoring of gearbox state for railway vehicle, and provides the basis for the fault diagnosis and life prediction of further gearbox.More>
2015, 15(1): 50-57. doi: 10.19818/j.cnki.1671-1637.2015.01.007
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Fault diagnosis method of railway vehicle with wheel flat based on self-adaptive multi-scale morphology analysis
LI Yi-fan, LIU Jian-xin, LIN Jian-hui, LI Zhong-ji
Abstract: A vehicle system dynamics model with 56 degrees of freedom and a wheel flat model were set up to calculate railway vehicle dynamic responses.The vibration information of vehicle was often influenced by various interferences, such as track irregularity and vehicle speed alteration.In order to effectively extract the wheel-track impact features from strong background noises, a self-adaptive multi-scale morphology filtering analysis algorithm was proposed to study the axle box vibration characteristics caused by wheel flat.The influences of track irregularity and vehicle running speed on the fault diagnosis result of axle box were discussed.Simulation result shows that the fault frequencies of 10, 15, 20 Hz are obtained by using morphology filter based on 7-scale and 9-scale structural elements at the speeds of 100, 150, 200km·h-1 with the American fifth grade and third grade track irregularities.Test result demonstrates that the fault frequency of 2 Hz is obtained by using morphology filter based on 7-scale structural element atthe speed of 40km·h-1, which is corresponding to the theoretic frequency of wheel flat, so diagnosis result is reliable.More>
2015, 15(1): 58-65. doi: 10.19818/j.cnki.1671-1637.2015.01.008
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Optimization method of frictional braking force distribution for integrated system of electromagnetic and frictional braking of car
HE Ren, ZHAO Qiang, HU Dong-hai
Abstract: The structure and working principle of integrated system of the electromagnetic and frictional braking for car were analyzed.The calculation formula of utilization adhesion coefficient for front and rear axles was derived.The ECE R13 braking regulation and the design requirement of electromagnetic braking were taken as constraint conditions, the minimum square sum of differences between the actual curve of utilization adhesion coefficient and the braking strength of ideal condition for front and rear axles was taken as objective function, MATLAB optimization toolbox was employed, the optimization method of frictional braking force distribution for the integrated system of electromagnetic and frictional braking was established, and the optimal values of frictional braking force distribution under different conditions were calculated.Calculation result indicates when the braking strength is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8respectively, the value of objective function before optimization is 0.03, 0.05, 0.07, 0.07, 0.08, 0.07, 0.06, 0.04 respectively, while the value of objective function after optimization is 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.01, 0.01 respectively.After optimization, the values of objective function reduce obviously, the curve of utilization adhesion coefficient for front and rearaxles is close to the ideal curve and is below the control curve of ECE R13 braking regulation, so the proposed optimization method satisfies the requirement of ECE R13 braking regulation, and the braking stability of car also improves.More>
2015, 15(1): 66-73. doi: 10.19818/j.cnki.1671-1637.2015.01.009
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Calculation method of external characteristic for sheet-metal hydraulic torque converter
HUI Ji-zhuang, ZHANG Guang-hui, NIE Chun-peng, LIU Qiong
Abstract: The signal processing and hydraulic system of original test bench was improved, and the traction test of YJH315sheet-metal hydraulic torque converter was carried out.Based on the numerical calculation method of three dimensional flow field, the angular momentum equation, torque equation and the calculation method of performance parameter of external characteristic for YJH315sheet-metal hydraulic torque converter were put out.The efficiencies, torque coefficients and nominal torques under different rotating speed ratios were gotten by using MATLAB simulation software and measured test respectively, and simulation result and test result were compared.Analysis result shows that when rotating speed ratio is from 0to 0.9, the maximum efficiency is 0.82 under test condition, the value is 0.82 under simulation condition, and the maximum error of efficiency is about 2%.The maximum torque coefficient is 2.41 under test condition, the value is 2.29 under simulation condition, and the maximum error of torque coefficient is about 3%.The maximum nominal torque is 28.7N·m under test condition, the value is 27.3 N·m under simulation condition, and the maximum error of nominal torque is about 3%.All the errors of three indexes are within the acceptable range, so the proposedcalculation method of external characteristic for sheet-metal hydraulic torque converter is feasible.More>
2015, 15(1): 74-81. doi: 10.19818/j.cnki.1671-1637.2015.01.010
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Power matching control strategy of power source for mine truck
ZHENG Shu-yang, JIN Chun, LUO Wei-dong
Abstract: Considering that the working points of mine truck engine were distributed in low efficiency area, the AC(alternating current)drive control strategy based on power matching was designed, and the output power was adjusted by transmission system according to different driving cycles.The power region of electric drive system was determined.Vehicle load degree was introduced to evaluate load degrees of different driving cycles.A three-layer hierarchical control strategy was proposed.The rotational speeds of in-wheel motor were pretreated by using moving average filter algorithm, and vehicle load degrees were calculated in the upper algorithm.In the middle algorithm, the reference power was calculated with vehicle load degree and engine speed, and a three-dimensional fuzzy controller was used in the middle algorithm.In the lower algorithm, the reference power was tracked by driving system to realize power matching of mine truck.The electric drive test bench was built, and the effect of power matching control strategy was verified.Verification result indicates that by using power matching control strategy, the change of load degrees can be quickly identified for common driving cycles of starting, climbing, sudden loading and downhill.The driving power of current load is calculated, which can guarantee the dynamic performance of mine truck in complicated working conditions.The oil saving effect of control strategy for mine truck is examined by steady test, and the working points of engine locate nearby the optimum fuel economy curve.Compared with the maximum power satisfied strategy, the fuel consumption of power matching control strategy reduces by 10.8%for load of 40 kW, and 4.8% for load of 80 kW, so the effectiveness and feasibility of control strategy are validated.More>
2015, 15(1): 82-91. doi: 10.19818/j.cnki.1671-1637.2015.01.011
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Speed-density relation model of congested traffic flow under minimum safety distance constraint
SHAO Chun-fu, XIAO Chong-zi, WANG Bo-bin, MENG Meng
Abstract: Based on the conforming change characteristic of speed and density for traffic flow under traffic congestion state, the reason that the average headway-distance of congested traffic flow was a fixed value was analyzed, and the speed-density relation model under traffic congestion state was put out combined with minimum safety distance constraint.The relation between the average reaction time of driver and the minimum headway-distance under traffic congestion state was discussed, and the parameter calibration of reaction time for speed-density relation model was carried out.The speed-density relations with different vehicle lengths, blocking parking distances and reaction times were analyzed, the traffic data of US-101 Highway and I-80 Highway in America were fitted by using the proposed speed-density relation model, Greenshields model, Greenberg model, Underwood model, Northwest model and Edie model respectively, and thefitting results and absolute errors were obtained.Analysis result shows that by using the proposed speed-density relation model, the change relation of speed and density under traffic congestion state can be explained in theory, and the discrete phenomena of speed-density data can be described.Compared with the other models, the absolute errors of fitting results for US-101 Highway and I-80 Highway are minimum by using the proposed speed-density relation model, and are 4.91, 7.50veh·km-1 respectively.So the proposed speed-density relation model based on minimum safety distance constrain reveals the substantive characteristic of congested traffic flow, and the fitting effect on actual data is better.More>
2015, 15(1): 92-99. doi: 10.19818/j.cnki.1671-1637.2015.01.012
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Optimization model of distribution network with multiple distribution centers and multiple demand points considering traffic flow change
YANG Zhong-zhen, MU Xue, ZHU Xiao-cong
Abstract: Based on the structure of urban road network and the characteristic of traffic flow, the minimum total distribution time was taken as objective function, the traffic flow was taken as constraint condition, and the optimization model of bi-level distribution network was developed.The distribution routing of distribution vehicle was calculated by using the upper model, the lower model was user equilibrium traffic assignment model, the OD trip data in the lower model could be changed by using the calculation result of upper model, and the transit time of road section in the upper model could be changed by using the calculation result of lower model.The hybrid grouping, genetic algorithm and Frank-Wolf algorithm were used to solve the bi-level optimization model, and example verification was carried out through a traffic network with 31 traffic zones, 27 demand points and 4distribution centers in Dalian City.Calculation result shows that when the distribution plan is obtained through the minimum distance method, the total distribution distance for 27 demand points is 94.8km, the total distribution time is 425.2min, and the calculation time is 13 s.Using the bi-level optimization model with the consideration oftraffic flow change, the total distribution distance for 27 demand points is 109.7km, the total distribution time is 329.1min, and the calculation time is 256 s.After using the bi-level optimization model, the total distribution distance increases 14.9km, but the total distribution time decreases 96.1min, the mutual balance process of distribution vehicles and other vehicles can one-off reaches, the calculation speed and efficiency are not the most important factors, and the calculation result more in line with the actual situation can be gotten.More>
2015, 15(1): 100-107. doi: 10.19818/j.cnki.1671-1637.2015.01.013
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Management-control capability evaluation model of radio block center based on improved ANP
CHEN Jian-qiu, TANG Tao, YUAN Lei
Abstract: Various factors affecting the management-control capability of radio block center(RBC)were analyzed.The relationship among the factors was researched.The evaluation model of management and control capability of RBC was built by analytic network process(ANP).In order to reduce the influence of subjectivity and improve the credibility of evaluation results, the experts mean assessment was introduced to ANP evaluation process.Taking the real layouts of the first RBCs(RBC-JH1, RBC-ZX1)in the down direction of Jinghu and Zhengxi High-Speed Railways as example, the ANP evaluation model was built, and SD software was used to solve the model.The quantitative ordering of various influence factors was obtained.Analysis result indicates that the covered line area, control station number, non-cycle data dealing, the number of registered control trains, the maximum control train number of a single RBC, cycle data dealing, station complexity and the transmission delay time of wireless channel are key influence factors, their weights are 0.167, 0.095, 0.092, 0.090, 0.086, 0.072, 0.064 and 0.058, respectively.In the real RBC layout, the key influence factors should be given the priority because they have larger influence on the control capability of RBC.The weight of RBC-JH1is0.037, and the weight of RBC-ZX1 is 0.039.Considering the priority influence factors, the jurisdiction of BC-JH1 can be extended to the sixth relay station.The applicability of improved ANP evaluation model is proved in evaluating the RBC management and control capability.Combination with the calculation formula of RBC layout number, the management-control range and layout number of RBC in a railway line can be determined.More>
2015, 15(1): 108-118. doi: 10.19818/j.cnki.1671-1637.2015.01.014
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Optimal model of regional traffic signal control under mixed traffic flow condition
HAN Yin, XING Bing, YAO Jiao, LIU Jing
Abstract: Considering that traditional regional traffic control technology could not cope with the interference problems of motor vehicles and non-motorized vehicles conflict, the characteristics of mixed traffic flow in China's urban road were combined, and the interferences of non-motorized vehicles on motor vehicles at intersections and links were researched.The traffic characteristics of motor vehicles in regional road network were obtained, and the regions with similar mixed traffic characteristics were defined.Based on the blockade effect of non-motorized vehicle, the capacity reduction of intersections and phase difference optimization of adjacent intersections were analyzed.The total delay of motor vehicles in regional road network was used as optimization objective, the optimal model of regional traffic signal control influenced by non-motorized vehicles was built, and signal cycle length, split ratio and phase difference were optimized.Genetic algorithm was introduced to solve the optimal model.Taking the Wujiaochang annular regional road network in Yangpu District of Shanghai as an example, the optimal model was verified by using VISSIM software.Verification result indicates that for signal control scheme beforeoptimization, the average delays of each motor vehicles are 24.5-42.9sat 7intersections, the average value is 35.99 s, and total vehicle delay is 256.39 hin regional road network.For signal control scheme after optimization, the values are 21.8-36.4s, 30.12 sand 214.57 hrespectively.The decrement rate of average each vehicle delay is 10%-24% at 7intersections, the average value is 16.31%.So the optimal model can effectively reduce each vehicle delay and total vehicle delay in regional road network, and the operational efficiency increases in the regional road network significantly.More>
2015, 15(1): 119-126. doi: 10.19818/j.cnki.1671-1637.2015.01.015
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