交通运输工程学报

Review on detection technologies of railway vehicle wheel flat fault

ZENG Jing, PENG Xin-yu, WANG Qun-sheng, ZHANG Hao, LIANG Song-kang

Abstract: From the impact effect of wheel flat of railway vehicle on track and its damage to vehicle parts, several schemes for the wheel flat detection were systematically combed out.The characteristics of various kinds of wheel flat fault detection methods were discussed, the advantages and disadvantages of different methods were compared, and the development trend of the system for wheel flat fault detection technologies was predicted. Analysis results reveal that the wheel flat fault detection technologies can be divided into the vehicle-mounted detection method and wayside detection method, among which the wayside detection method is widely used. At present, the relatively mature wheel flat detection technologies are mainly divided into the wheel and rail impact detection method, ultra-sonic detection method, noise detection method, wheel tread displacement detection method, vibration acceleration detection method, image detection method, optical detection method, track circuit interruption method and so on.In recent years, with the development of science and technology, methods such as the Doppler effect method, ultrasonic echolocation method and so on have emerged.With the progress of modern intelligent algorithms, intelligent algorithms such as the neural networks are employed to the train equipment for the fault identification, which can greatly simplify the equipment development process and device structure. Therefore, intelligent algorithms may become the main development direction of wheel flat fault identification. As time goes by, the trend of multi-fault integration of detection equipment becomes more prominent, and multi-fault detection integration and functional diversification have become one of the important directions in the development of intelligent detection equipment. In the future, the improvements in operating systems will also focus on the humanization and intelligence of platforms. Suggestions on the detection system are put forward from three aspects, namely, real-time monitoring of the operation line, accurate detection of depot entry, and information-based data platforms. Future development should emphasize simple devices, accurate algorithms, and intelligent operation. 3 tabs, 22 figs, 79 refs.More>

2022, 22(2): 1-18. doi: 10.19818/j.cnki.1671-1637.2022.02.001

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Review on convective heat transfer in internal channel of ventilated brake disc of vehicle

LI Jie, TAO Long, GU Jia-ling, CHEN Cheng, CHEN Ying

Abstract: The research results of convective heat transfer in the internal channel of ventilated brake disc were summarized, and the influences of different structural designs on the heat transfer were analyzed from three aspects: mass flow, convective heat transfer coefficient and effective heat dissipation surface area. The analysis and detection methods of the convective heat transfer were reviewed at home and abroad from three aspects: analytical method, numerical analysis method and experimental test method. Research results show that there are two main flow modes in the channel of radial blade brake disc: the backflow caused by the airflow separation adjacent to the suction side of the blade and the secondary flow rotating in the radial channel. Restraining the formation of the backflow zone can increase the mass flow rate of the pumping air and make the temperature distribution in the channel more uniform. The secondary flow promotes the development of air mixed flow and turbulence between the channels, strengthens the local shear stress and improves the heat dissipation performance of the brake disc. In addition, the comprehensive application of jet impingement strengthening methods (multi-beam, swirl and multi-directional jets, etc.), high porosity and columnar-like structure optimization design can also change the flow state of the fluid in the channel. These measures increase the fluid disturbance in the channel, thin the thermal boundary layer and increase the velocity gradient near the wall, which effectively improve the convective heat transfer coefficient of the brake disc and enhance the heat dissipation capacity. The results obtained by the analytical method and numerical analysis method have strong theoretical reference, but the results obtained by the experimental test method are closer to the changes of the actual internal temperature and air flow rate of the brake disc. Therefore, if the three methods can be seamlessly combined to achieve complementary advantages, it will have the most scientific research value. Besides, in order to obtain the maximum heat dissipation efficiency, the friction pressure drop and flow resistance in the channel are often ignored in optimizing the brake disc structure of high-speed vehicle. Therefore, how to balance the relationship among heat dissipation, frictional pressure-drop and flow resistance needs further exploration and research. 3 tabs, 12 figs, 116 refs.More>

2022, 22(2): 19-40. doi: 10.19818/j.cnki.1671-1637.2022.02.002

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Review on development of heterogeneous smart cooperative vehicular networks in rail transit

DONG Ping, YIN Chen-yang, ZHANG Yu-yang, ZHANG Hong-ke

Abstract: The research status of vehicular networks of rail transit both at home and abroad was analyzed from three aspects, i.e., cellular wireless access technology, non-cellular wireless access technology, and heterogeneous smart cooperative vehicular network access technology. Considering the problems of non-cellular and cellular wireless access technology, the advantages of cooperatively using heterogeneous wireless resources around rail transit for network convergence and cooperative communications were expounded. The convergence schemes of heterogeneous smart cooperative vehicular networks were discussed from the aspects of the network model and network architecture. In view of the business requirements of intelligent rail transit, the existing research on heterogeneous smart cooperative vehicular networks was systematically classified from the perspectives of reliability and resource utilization. The future development trends of heterogeneous smart cooperative vehicular networks were proposed regarding artificial intelligence, security, and cloud-edge combination. Research results show that the reliability of heterogeneous smart cooperative vehicular networks is comprised of network architecture reliability and data transmission reliability. The former mainly proposes improving reliability in the ways of redundant network architecture, vehicle-to-cloud transmission architecture, software-defined network architecture, and smart and cooperative network architecture. The latter focuses on reducing the packet loss rate in the process of transmission through three ways, i.e., multi-path transmission, network coding, and handoff algorithms. The resource utilization of heterogeneous smart cooperative vehicular networks can be divided into wireless access resource utilization and link scheduling resource utilization. The former improves the throughput and resource utilization by three methods, i.e., channel state prediction, spectrum division, and frequency shift compensation. The latter reduces the influence of heterogeneous links on data transmission and the times of data retransmission and raises the utilization of network resources mainly by scheduling algorithm, receiving and buffer algorithm, and congestion control algorithm. 6 tabs, 7 figs, 79 refs.More>

2022, 22(2): 41-58. doi: 10.19818/j.cnki.1671-1637.2022.02.003

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Review on nonlinear model updating for bridge structures

WANG Zuo-cai, DING Ya-jie, GE Bi, YUAN Zi-qing, XIN Yu

Abstract: Due to the weakening of the structural mechanical properties during the service period of bridges, the nonlinear vibration with time-varying characteristics occurs. Considering this, the development of nonlinear model updating was reviewed, and on this basis, some critical problems existing in nonlinear model updating technologies were summarized from the aspects of nonlinear system identification, nonlinear model updating methods, and uncertainty quantification of nonlinear models. In addition, in view of the damage identification, performance assessment, and safety monitoring of complex structures, the application of nonlinear model updating in bridge structures was further discussed. Research results indicate that the response characteristic quantities represented by natural frequencies and modes of vibration can only reflect the physical characteristics of time-invariant structures. However, for nonlinear structures, their mechanical properties change with the external excitation, and thus the model updating methods based on characteristic quantities of linear systems are not suitable for nonlinear structures with obvious time-varying characteristics. The instantaneous frequency and amplitude of the principal component of structural dynamic response contain the phase and amplitude information of vibration response signals. They can comprehensively reflect the non-stationary characteristics of structural responses under dynamic loads. The dynamic characteristics of nonlinear structures can be properly represented by using the instantaneous characteristic quantities with time-varying characteristics to construct the objective function. With the consideration of uncertainty factors, such as the measurement noise, model errors, and numerical calculation methods, the uncertainty model updating method can improve the model updating result by comprehensively using the measured response data. Since many parameters and massive computations are involved in the nonlinear model updating of complex structures, its application in the practical engineering structures is greatly limited. Therefore, the reasonable selection of representative nonlinear model parameters and improving the computational efficiency are urgent problems to be solved. 12 figs, 95 refs.More>

2022, 22(2): 59-75. doi: 10.19818/j.cnki.1671-1637.2022.02.004

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Track alignment irregularity control method for tamping operation of ballasted high-speed railway

SHI Jin, ZHANG Yu-xiao, CHEN Yun-feng, WANG Xiao-kai, WANG Ying-jie

Abstract: In order to improve the quality of tamping operation of ballasted high-speed railway to meet the requirement of track alignment irregularity control, the influencing factors of lining effect were analyzed according to the operation characteristics of large machine, and the relationships between lining value range, lining strategy, lining value slope rate, equipment accuracy and operation effect were studied. Combined with the analysis result, based on the medium-long wavelength irregularity control theory, the optimization model of lining plan was established, and the method for evaluating the lining effect based on the lining correlation was proposed to realize the effective combination of the factors affecting the lining effect and the formulation process of lining plan. The effectiveness of track alignment irregularity control method was verified in the tamping operation of a ballasted high-speed railway. Research results show that too large or too small lining value, excessive lining value slope rate, unfavorable lining strategy and poor equipment accuracy are easy to lead to poor operation effect of large machine, so it is necessary to strengthen the control and management of the above factors in the formulating process of lining plan. By introducing the lining coefficient into the track alignment irregularity control and effectively controlling to the parameters such as the medium-long wavelength irregularity and the lining limit, the adaptability of the method to the inherent characteristics of tamping machine improves. The method is applied to formulate a lining plan for a certain operation section, and the lining effect meets the requirement of track alignment irregularity management and the characteristics of tamping machine. After the implementation of the plan, the 30 and 300 m vector distance differences reduce to 2 and 7 mm, with a decrease of 50% and 48%, respectively. The static track quality index reduces from 0.89 to 0.64, with a decrease of 28%. The practice proves that the track alignment irregularity control method can effectively improve the regularity of ballasted high-speed railway. 3 tabs, 15 figs, 26 refs.More>

2022, 22(2): 76-86. doi: 10.19818/j.cnki.1671-1637.2022.02.005

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Control method for insufficient displacement of switch rail in high-speed railway turnout

WANG Pu, ZENG Rui-dong, WANG Shu-guo

Abstract: To simulate the switching process of high-speed railway turnout switch under operating conditions, according to the switching characteristics of high-speed railway turnout switch, an experimental platform of the switching prototype of passenger dedicated railway No.18 turnout switch was established in a production workshop of turnout. The shaft pin type load cell was used to measure the switching force of the switch, and the difference between the actual and theoretical offset distances of straight and curved switch rails was taken as the insufficient displacement of switch rails. Switching experiments were carried out to explore the influence mechanism and characteristics of switch rail pre-bending, movable section length of switch rail, offset distance of fasteners at the fixed end of switch rail, friction coefficient of slide plate, and height of roller on the insufficient displacement of switch rail. Experimental results show that the designed switch rail pre-bending can reduce the insufficient displacement of switch rail by more than 30%, and the shortening of the movable section length of switch rail can reduce the insufficient displacement of switch rail, but decrease the minimum wheel flangeway width of the switch and increase the switching force at the third traction point. The minimum wheel flangeway width of swith rail and the switching force at the last traction point are the control factors for shortening the movable section length of switch rail. After the adjustment of the offset distances of all fasteners at the fixed end in a small range, the change of insufficient displacement of switch rail is small. When only reducing the offset distance of the first group of fasteners at the fixed end, the insufficient displacement of switch rail decreases slightly within the range of 1.2 m close to the fixed end, and the insufficient displacements at other sections change slightly. The measures of reducing the friction coefficient between the switch rail and the slide plate, such as the roller installation and lubricant coating on the slide plate, can effectively reduce the switching force and insufficient displacement of switch rail. After the implementation of these antifriction measures, the switching force decreases by about 30%, and the insufficient displacement decreases by more than 20%. The influence of changing the height of roller on the insufficient displacement of switch rail is not obvious, but the height of roller should not be too low, in order to avoid a surge in the switching force and insufficient displacement caused by the failure of roller in the switching process. The research results can provide important references for the structure optimization of high-speed railway turnout switch and the development of a new generation of 400 km·h^-1 high-speed railway turnout. 7 tabs, 20 figs, 31 refs.More>

2022, 22(2): 87-98. doi: 10.19818/j.cnki.1671-1637.2022.02.006

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Design method for asymmetric grinding profile of rails in sharp curves

LI Li, PENG Jing-kang, CUI Da-bin, LEI Peng-cheng

Abstract: For improving the performance of trains passing through sharp curves, the geometric derivation was performed on the profile of existing CN60 rails in China to design the target rail profile by asymmetric grinding. Taking the geometric parameters of the rail profile as design variables and the multi-body dynamics index of vehicle system as the comprehensive objective function, a multi-objective numerical optimization model for the asymmetric grinding profile of rails in sharp curves was proposed considering the rail grinding constraints. On the basis of the differential evolution algorithm, the corresponding numerical calculation program was written, and reasonable calculation parameters were selected to solve the optimization model. According to the actual line parameters, the wheel-rail contact geometric characteristics of the optimized grinding profile of rails were analyzed, and the dynamics performance of trains passing through sharp curves was verified. Research results reveal that the proposed optimization method is fast in calculations, and the ideal grinding profile of rails can be obtained after only 97 iterations of the optimization model. Due to the asymmetric grinding, the inner and outer rails have different grinding positions and grinding depths, and the centering positions of wheels and rails move to the inner side of rails by about 10 mm, without any change in the wheel-rail matching characteristics at the flange. This effectively increases the wheelset rolling radius difference and the difference in wheel-rail contact angles in the wheelset lateral displacement range of 10 mm, reduces the lateral displacement of wheelset, lateral wheel-rail force, derailment coefficient, and rate of wheel load reduction when trains pass through sharp curves, and improves the lateral stability of the bogie and the wheel-rail wear performance. Although the rail profile obtained by this grinding method increases the wheel-rail contact stress, it does not cause the plastic wheel-rail deformation. Therefore, this design method is feasible to improve the capability of trains passing through small- and medium-radius curves. 3 tabs, 16 figs, 31 refs.More>

2022, 22(2): 99-110. doi: 10.19818/j.cnki.1671-1637.2022.02.007

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Design method of grinding profile of over worn rail

LIN Feng-tao, DENG Zhuo-xin, PANG Hua-fei, WANG Song-tao, YANG Jian, DING Jun-jun, CHEN Dao-yun

Abstract: A rail profile design method with the arc tangency point as the key parameter was proposed for the grinding of over worn rail. Specifically, taking the wheel-rail contact region as the optimization area and the rail wear and the removed amount of grinding material as the optimization objective function, taking the profile boundary, concavity and convexity, derailment coefficient and wheel-rail lateral force as the constraint conditions, the multi-objective function of designed grinding profile of worn rail was established. The multiple simulated annealing optimization algorithm was integrated for solutions. To obtain the rail profile representing the curve of a heavy haul line, which was adopted as the optimized input data, the representative profiles of four kinds of rails were obtained by using the least square distance algorithm, arithmetic average algorithm, weighted average algorithm and scatter reconstruction algorithm. The correlations between the rail representative profiles of the four algorithms and the measured profile contact point probability distribution curve were calculated by using the Pearson correlation coefficient, Kendall rank correlation coefficient and Spearman rank correlation coefficient, and the representative profile with the highest correlation was taken as the actual profile of the curve section of the equivalent heavy haul line. The economical grinding profile of over worn rail in a heavy haul line and the optimized profile using the arc profile design method were analyzed. Analysis results show that compared with the on-site grinding profile of rail, the optimized rail profile has a reduced grinding and cutting amount for its sectional profile by 69.56 mm², a decrease of 64.98%, a slightly increased derailment coefficient, the same lateral wheel-rail force, small lateral wheelset displacement change, and similar curve passing performance. Although the wear area under 800 000 passes increases by 2.19 mm², and the wear rate of rail slightly rises, the overall service life of rail is still prolonged. 3 tabs, 17 figs, 30 refs.More>

2022, 22(2): 111-122. doi: 10.19818/j.cnki.1671-1637.2022.02.008

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Damage detection for floating-slab track steel-spring based on residual convolutional network

ZHU Sheng-yang, ZHANG Qing-lai, YUAN Zhan-dong, ZHAI Wan-ming

Abstract: As traditional fault diagnosis methods can hardly effectively detect the steel-spring damage of floating-slab track (FST), a damage detection method based on the one-dimensional residual convolutional network was proposed. A vehicle-FST coupled dynamics model was built, and the data sets for the floating-slab vibration response caused by the passing vehicles under various conditions were generated. The residual convolutional network was utilized for the feature extraction and data classification of the vibration response under different damage scenarios to achieve the accurate positioning of damaged steel springs. The detection performance of the residual convolutional network on different sensor deployment schemes were studied. The influence of the complex positional relationship between the damaged steel springs and the sensors on the detection performance was analyzed, and the economic and reliable sensor deployment schemes were optimized and determined. Analysis results reveal that when the sensors are closer to the middle of the floating-slab, better classification accuracy and robustness of the residual convolutional network can be achieved on the data under different damage scenarios. As the number of sensors increases, the detection performance of the method also improves, but the excessive concentration of the sensors in the middle of the floating-slab will not bring about significant improvement on the performance. The damage of steel-springs in the middle of the floating-slab is more difficult to identify than that at the end of the floating-slab. The damage detection method achieves a classification accuracy of 99.11% on the full-coverage deployment scheme, boasting good adaptability to complex and changeable detection scenarios. The classification accuracies of the optimized two-sensor deployment scheme and three-sensor deployment scheme reach 98.23% and 98.96%, respectively. The optimized sensor deployment schemes have good detection performance and keep the adaptability of the damage detection method to complex scenarios. 4 tabs, 16 figs, 30 refs.More>

2022, 22(2): 123-135. doi: 10.19818/j.cnki.1671-1637.2022.02.009

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Control threshold of pier settlement in high-speed railways based on train vibrations

CHEN Zhao-wei, ZHAI Wan-ming

Abstract: For the safety and smoothness of running trains in the pier settlement area of high-speed railways, a method to investigate the control threshold of pier settlement in high-speed railways was proposed based on the train-track-bridge dynamic interaction theory. The limit values of pier settlement in existing standards were discussed, and the key factors affecting the control threshold of pier settlement were determined. In view of the nonlinear factors including the track random irregularity and wheel-rail nonlinear contact relationship, a high-speed train-track-bridge coupled dynamics model considering the pier settlement and multi-factor was built based on the train-track-bridge dynamic interaction theory. On this basis, the influence of pier settlement on the train-track-bridge system under the multi-factor influence was studied, and the control threshold of pier settlement for high-speed railways in China was proposed to ensure the safety and smoothness of the running train. Research results show that the factors including the track random irregularity, temperature action, and concrete shrinkage and creep cannot be ignored in studying the control threshold of pier settlement in high-speed railways. As the bridge span is broader, the concrete shrinkage and creep and temperature action cause the increases in the carbody vertical acceleration and wheel unloading rate, while the pier settlement leads to the decrease in the above indicators. The carbody acceleration and wheel unloading rate considering the multi-factor are significantly higher than those without considering the multi-factor. As the pier settlement is larger, the carbody vertical accelerations and wheel unloading rates exceed the limit values when the train runs through different irregularity samples. The control threshold of pier settlement for high-speed railways is suggested to be 10 mm to guarantee the running safety and ride comfort of the running train. Based on the control threshold obtained in this paper, the accurate standard limit value can be obtained by further considering other factors, such as construction errors. The research results can provide a method and data supporting for the final determination of the limit value of pier settlement. 3 tabs, 15 figs, 30 refs.More>

2022, 22(2): 136-147. doi: 10.19818/j.cnki.1671-1637.2022.02.010

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Tunnel crack recognition method under image block

YIN Guan-sheng, GAO Jian-guo, SHI Ming-hui, JIN Ming-zhu, TUO Hong-liang, LI Chang, ZHANG Bo

Abstract: Considering the strong visual interference such as the non-uniform lighting, water seepage, and noise in tunnel lining surfaces, a crack inspection method based on image blocks was designed for tunnel lining. A rapid and automatic non-contact intelligent inspection system for the tunnel structure appearance was developed according to the geographical characteristics in West China and the appearance diseases of tunnel lining. With the tunnel image data set under the non-uniform lighting as the research object, an image recognition algorithm for the characteristic extraction of tunnel cracks was proposed on the basis of image blocks. The noise generated by the electronic components was studied, and the hazard characteristics of tunnel lining were analyzed and summarized. The image matrix was divided into an appropriate number of area blocks in view of crack characteristics and resolution, and the original image was divided into the target-background area, target-disease area, disease-background area, and other areas according to the grayscale characteristics of these area blocks. Then, the rough image of tunnel cracks was obtained by the maximum inter-class variance method and the local threshold segmentation. On this basis, the crack characteristics of the rough image were extracted. Each area block of the original image was subjected to a contrast limited adaptive histogram equalization and a local threshold segmentation for a detailed image. The overlapping area of the detailed image and the rough image was set as the ideal image of crack binarization. On the basis of the inspection system for the tunnel structure appearance, binarization tests were carried out on the crack images in different directions, and the location information and directions of cracks in tunnel lining images were obtained by the positioning of tunnel cracks and the projection method. Research results reveal that the accuracy, recall, and F value of tunnel cracks under the proposed algorithm can reach 90.34%, 98.78%, and 94.37%, respectively. The proposed algorithm can not only ensure the integrity of tunnel cracks, but also retain the details of target cracks to the maximum extent under the non-uniform lighting. Thus, it can be used to deal with the binarization problem of general grayscale images. 1 tab, 13 figs, 37 refs.More>

2022, 22(2): 148-159. doi: 10.19818/j.cnki.1671-1637.2022.02.011

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Calculation model of rock joint stiffness considering anisotropic morphology characteristics

BAO Han, XU Xun-hui, LAN Heng-xing, YAN Chang-gen, XU Jiang-bo, LIU Chang-qing

Abstract: To accurately and conveniently achieve the shear and normal stiffnesses of rock joint and analyze the deformation behavior characteristics of rock joint, the diorite joint from the Guanshan Tunnel was scanned to obtain the digital information of morphology. According to the digitized joint surface, the replicate joint samples were made by the 3D printing technology. The uniaxial compression tests and anisotropic shear tests were performed for the joint replicas. The new shear and normal stiffness models were established based on the new anisotropic morphology parameter. Research results show that the proposed new morphology parameter takes into account the climbing angles and heights of positive asperities, which is helpful for expressing the anisotropic roughness of joint surface. The morphology parameter of joint profile in the same direction follows a lognormal probability distribution. On the basis of mechanical tests on the physical models, the new shear stiffness calculation model of rock joint established by considering the morphology parameter, joint compressive strength, and normal stress can lower the difficulty in obtaining the shear stiffness, and better reflect the anisotropy of tangent deformation as well. In consideration of the quantitative relationships of joint compressive strength with the initial normal stiffness and joint maximum closure, the improved hyperbolic-function normal stiffness model can simplify the calculation of normal stiffness by avoiding complex mechanical experiments. Compared with the classical calculation models and the mechanical test results, the stiffnesses calculated by the new models are closer to the test values. The average relative error between the calculated and experimental values of shear stiffness is 2.09%-27.88%, and the average relative error between the calculated and experimental values of normal stiffness is 3.25%-17.25%, which demonstrates that the new models can obtain the deformation parameters of the joint more precisely and conveniently. 5 tabs, 19 figs, 46 refs.More>

2022, 22(2): 160-175. doi: 10.19818/j.cnki.1671-1637.2022.02.012

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Regression analysis of influence law of urban pavement settlement caused by underpass tunnel construction in Beijing

WU Yi-min, LIU Yan-an, WANG Heng, HAN Da-you, CHEN Zi-fan, WANG Chao

Abstract: Taking the pavement settlement caused by pipe jacking tunnels in thermal engineering in Chaoyang District of Beijing as an example, the on-site measurement value and the theoretical computation values that only considering natural factors were compared and analyzed. With 279 tunnel underpass projects in Beijing as samples, the multiple regression analysis was carried out with the statistical software Stata 14.0, where four design factors, three construction factors, and nine human factors affecting the pavement settlement were involved. Then, the robustness of regression analysis was verified by the replacement of the construction methods and the addition or subtraction of interpretation variables, and the elasticity coefficients, standard errors, and the confidence levels of each factor affecting pavement settlement were obtained. Analysis results show that a huge difference exists between the on-site measurement and the theoretical computation in the pavement settlement, which is related to the existence of moving loads on the pavement and the thickness of the overlying soil of tunnels, with a maximum of up to 3.75 times. Of the natural factors, the influence of geological condition, construction method, moving load on the pavement, and tunnel diameters are significant, and the degree of influence decreases in turn. Of the human factors, on-site supervision plays a significant role, and working years of constructors and technical disclosure also have a great impact. In the construction of an underpass project with a non-excavation method, we should reduce the manual pipe jacking, accelerate construction, and consolidate synchronous grouting to decrease the pavement settlement, and great significance should be attached to the construction technology and process, personnel organization, and process supervision. The research results can provide a reference for the technical management, safety assessment, and administrative approval of the construction of tunnels undercrossing urban roads. 6 tabs, 4 figs, 30 refs.More>

2022, 22(2): 176-186. doi: 10.19818/j.cnki.1671-1637.2022.02.013

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Numerical simulation and law analysis of water accumulation distribution at superelevation transition section of multilane expressway

ZHAO Jian-you, GUO Wan-jiang, JIA Xing-li, CHEN Xing-peng

Abstract: In order to reveal the distribution law of water accumulation at the superelevation transition section of multilane expressway, the design parameters of the typical superelevation transition section of multilane expressway were selected based on the fluid dynamics theory, and the road design software BIM was used to establish 40 groups of 3D road models. By analyzing the relationship between road area water quantity and drainage facilities runoff, a rainfall simulation scheme considering the influence of drainage facilities and pavement structure depth was established. The discrete phase model and multiphase flow model were coupled to simulate the water accumulation state of road area under rainfall condition. By analyzing the water accumulation thickness data of superelevation transition section under different combination parameters, the influence modes of synthetic slope, road width, rainfall intensity and superelevation gradient rate on the water accumulation thickness were obtained. The maximum water accumulation thicknesses of each lane were calculated, and the horizontal distribution laws of water accumulation at six-lane and eight-lane transition sections were revealed. Analysis results show that the thickness of stagnant water is negatively correlated with synthetic slope and superelevation gradient rate, and positively correlated with rainfall intensity and road width. The rainfall intensity has the greatest influence on the ponding water thickness, and the superelevation gradation rate has the least influence on the ponding water thickness. When the synthetic slope is 2.02%-8.54% and the rainfall intensity is 1-5 mm·min^-1, the minimum water thickness at the superelevation section of multilane expressway is 0.58 mm, and the maximum is 28.35 mm. When the rainfall intensity is 5 mm·min^-1, the maximum water thicknesses of the inner and outer lanes at the superelevation transition section of the expressway are significantly different. The maximum water thickness ratio from the inner lane to the outer lane at the six-lane transition section is 1.0∶3.1∶3.3, and the ratio is 1.00∶0.96∶1.03∶1.36 at the eight-lane transition section. The peak value of water accumulation thickness at the superelevation transition section of multi-lane expressway first appears near the middle of the expressway and then moves outward, and the maximum water accumulation thickness generally appears in the outer lane. 3 tabs, 13 figs, 26 refs.More>

2022, 22(2): 187-196. doi: 10.19818/j.cnki.1671-1637.2022.02.014

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Study of noise reduction effect and influencing parameters for a resilient wheel considering rotation effect

SHENG Xiao-zhen, GE Shuai, CHENG Gong, ZHOU Xin, HUANG Zhen-xin

Abstract: An resilient wheel and its prototype ordinary wheel were taken as the research objects, the 2.5D structural finite element method and 2.5D acoustic boundary element method were used to predict the vibration and sound radiation of the wheels under the excitation of a given wheel-rail roughness and considering the moving load effect and gyro effect caused by the wheel rotation. The noise reduction mechanism of the resilient wheel was analyzed at the three running speeds of 40, 80 and 120 km·h^-1, and the effect of the material parameters of the resilient wheel rubber layer on the noise reduction effect was studied. Research results show that the wheel rotation makes the acoustic power peak at the original non-zero node-diameter mode frequency bifurcated into two peaks, one of which is higher than the original mode frequency, and the other is lower than the original mode frequency. The difference between the two peak frequencies is approximately equal to the wheel rotation frequency multiplied by two times the number of mode node-diameter. Under considering all cases, the effect of the wheel rotation on the sound radiation of the wheel can be as high as 3.2 dB(A). Therefore, the vibro-acoustics of the wheel must be predicted by considering the wheel rotation. If the Young's modulus of the rubber layer is too low, the wheel rim will vibrate so strongly that the wheel radiates higher sound power than the ordinary wheel. In terms of sound radiation, there is an optimal Young's modulus for the rubber layer, at which the resilient wheel radiates lowest sound power more than 10 dB(A) lower than the ordinary wheel. Increasing rubber damping will reduce the sound radiation from the wheel, however, the reduction is adversely affected by the Young's modulus of the rubber. With the increase of running speed, the noise reduction effect of resilient wheel decreases continuously compared with the prototype common wheel, and the reduction is more than 4 dB(A) when wheel speed increases from 40 km·h^-1 to 120 km·h^-1. 4 tabs, 10 figs, 27 refs.More>

2022, 22(2): 197-207. doi: 10.19818/j.cnki.1671-1637.2022.02.015

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Thermal-mechanical coupling analysis of three-dimensional elastic-plastic wheel-rail sliding contact

YANG Bing, RONG You-xin, YANG Guang-wu, XIAO Shou-ne, ZHU Tao

Abstract: To improve the accuracy of thermal response analysis of wheel-rail sliding contact, on the basis of the Johnson-Cook material model, fully considering the temperature correlation of various material properties including the friction coefficient, three heat transfer modes, and the actual wheel-rail profile, a full-scale three-dimensional elastic-plastic wheel-rail sliding contact finite element model was established. The thermal-mechanical coupling analysis of the wheel-rail in sliding contact state was carried out by using the fully coupling method. The wheel-rail temperature field and stress field distribution characteristics were studied when the wheel slid along the rail at a speed of 1 m·s^-1 for 0.1 s, and the effects of the axle load and relative sliding speed on the temperature field of the wheel-rail contact area were analyzed. The variation relationships of the depth of the heat-affected layer, the width of the heat-affected layer, and the temperature of the wheel-rail surface with the axle load and relative sliding speed were obtained. Analysis results show that the maximum equivalent stress of the wheel and rail occurs at the center of the subsurface contact patch, and the maximum temperature on the wheel surface occurs at the center of the rear part of the contact patch. The maximum temperature on the rail surface is lower than that on the wheel surface as the latter is 848 ℃, and the former is 768 ℃. The heat-affected layer of the wheel and rail is very thin, with the depth of the heat-affected layer for the wheel being about 4.22 mm and that for the rail being about 3 mm. The depth of the heat-affected layer for the wheel and rail has no significant change with the increase in the axle load, but the width increases with the increase in the axle load. The depth of the heat-affected layer for the wheel and rail decreases with the increase in the relative sliding speed, but the width has no significant change with the increase in the relative sliding speed. The temperature of wheel-rail surface increases with the increase in the axle load and relative sliding speed, and the relative sliding speed has a greater effect on the wheel-rail thermal response. The full-scale three-dimensional finite element model for the elastic-plastic wheel-rail sliding contact and the thermal-mechanical fully coupling method can more accurately predict the thermal response of wheel-rail sliding contact, which is of great significance for the rational research on the wheel-rail thermal damage and thermal fatigue. 3 tabs, 15 figs, 31 refs.More>

2022, 22(2): 208-218. doi: 10.19818/j.cnki.1671-1637.2022.02.016

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Acquisition method of dynamic load of high-speed train gearbox bearing based on bench simulation model

DOU Shuo, LIU Zhi-ming, LI Qiang, REN Zun-song, YANG Guang-xue

Abstract: To acquire the dynamic loads of gearbox bearings for high-speed trains under the operational vibration environment, a bench simulation model for the gearbox of a high-speed train was built using the dynamics software SIMPACK. The multi-point coherent random vibration control algorithm based on the spectrum correction was used to reproduce the multi-point coherent line excitation on the gearbox by applying the longitudinal, lateral, and vertical measured acceleration power spectra of the axle box with a virtual exciter. Moreover, for the cylindrical roller bearing on the motor side of the gearbox input shaft, the bench simulation model was employed to obtain its radial load and center trajectory and the contact load between the roller and outer ring raceway under the operational vibration environment. Analysis results indicate that by the control algorithm based on the spectrum correction, when the optimization speed index is 0.3, the relative error between the simulated and measured acceleration power spectra of the axle box tends to be stable after 10 iterations, and the maximum relative error is less than 10%. Under different input torques of motors, the dynamic loads of gearbox bearings with and without line excitation show that the input torque of motors determines the mean of the dynamic loads, and line excitation is the main reason for the fluctuation in the dynamic loads. The spectrum analysis reveals that the line excitation increases the energy of the radial load of the bearing in the middle and low frequency bands and gear meshing frequency. Meanwhile, the line excitation increases the contact load between the roller and the outer ring raceway, but the contact area and mean of the contact load have no significant change. When there is no line excitation, the trajectory of the bearing center vibrates along the pressure angle of gears, and the angle with the vertical axis is 26°. The line excitation makes the fluctuation range of the trajectory of the bearing center larger and more random, and no obvious characteristic is shown in any direction. So, the input torque of motors and line excitation are the main sources of the dynamic loads of gearbox bearings for high-speed trains, and the bench simulation model can provide a valuable reference for the dynamic response evaluation and load spectrum establishment of gearbox bearings for high-speed trains. 2 tabs, 20 figs, 28 refs.More>

2022, 22(2): 219-232. doi: 10.19818/j.cnki.1671-1637.2022.02.017

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Modeling and simulation of rescue boat's launching from a ship

QIU Shao-yang, REN Hong-xiang, ZHANG Xiu-feng, WANG De-long, SUN Jian, XIAO Fang-bing

Abstract: The model of rescue boat launching was built by using the Kane's method, and the coupled motion of the rescue boat, flexible boom, sling, and ship was considered. The boom model was constructed by using the lumped mass method, and the internal force of the boom was calculated by the elastic strain energy function and dissipation function. The collision between the rescue boat and the ship was divided into the phases of compression and restitution, and the collision force was calculated according to the Hertz contact theory and the contact force model of permanent indentations separately. The boom model was compared with the model based on the Bernoulli-Euler beam theory, and the boom's profiles were almost the same in a steady state. The model of rescue boat launching was compared with the existing method, and the simulation experiment of rescue boat launching and error analysis of rescue boat trajectories in horizontal and vertical directions were carried out under the cross wave. Analysis results show that at a wave height of 3 m and a wavelength of 245 m, the average absolute errors of the proposed method are 0.11 and 0.12 m, respectively, and 0.54 and 0.34 m with the existing method. At a wave height of 2 m and a wavelength of 60 m, the average absolute errors of the proposed method are 0.09 and 0.14 m, respectively, and 1.72 and 0.31 m with the existing method. The average absolute errors of the proposed method are lower than those of existing method. Thus, the proposed method improves the calculation accuracy of the rescue boat's launching under the cross wave. Compared with the results of the collision experiment, the relative errors of horizontal and vertical acceleration peaks are about 0.5% and 60.0%, respectively, and as the horizontal acceleration peak is highly accurate, the model of rescue boat launching can assist the analysis of the collision experiment. On the basis of the model of rescue boat launching, the minimum initial distance between the rescue boat and the ship's side is 2.0 times the width of the boat in sea state 4 and 2.5 times the width of the boat in sea state 5 to avoid collision under the cross wave. 4 tabs, 22 figs, 27 refs.More>

2022, 22(2): 233-245. doi: 10.19818/j.cnki.1671-1637.2022.02.018

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Non-FIFO vehicle trajectory estimation algorithm under non-free traffic flow

HU Yao, ZHAO Rui-sha

Abstract: The traffic state of the triangular fundamental diagram (TFD) was subdivided into free flow, breakdown, and jam. According to the non-free flow characteristics, the U-shaped spatial-temporal domain was re-divided to find the suitable wave velocity range. The cumulative flow of the upstream boundary was redefined so that the description of the boundary function was not too broad. The Newell's model under non-free flow was established, and the criterion of whether the model can be used was proposed. A parameter of vehicle's rank was introduced to realize the goal of describing multilane overtaking phenomena, and a more accurate estimation model of vehicle's rank was established. Then the Newell's extended model under non-free flow was developed. The vehicle trajectory estimation algorithms were proposed for the two situations of non-free flow, namely first-in-first-out (FIFO) situation and non-first-in-first-out (non-FIFO) situation, which were divided according to whether there was an overtaking phenomenon. The effectiveness of the algorithms was then verified by numerical simulation and real traffic cases. Analysis results show that the trajectory estimation algorithms are effective in both situations. When an overtaking phenomenon occurs, the estimation effect of the non-FIFO situation is more accurate and robust. In the numerical simulation study, the estimation error of the non-FIFO situation decreases by 13.45% compared with that of the FIFO situation, namely that the result of the non-FIFO situation is better. In the real traffic cases, the non-FIFO situation has 2.38% and 2.04% lower estimation errors than the FIFO situation on two car datasets, respectively, and the estimation errors all follow the Gaussian mixture model (GMM). Because there is no overtaking phenomenon in the bus dataset, the estimation errors of the non-FIFO situation and the FIFO situation are equal, which are both 4.90% and follow the Gamma distribution. Therefore, the established Newell's model under the non-free flow is effective and feasible for the traffic data with a large proportion of breakdowns or jams, and the proposed trajectory estimation algorithms of FIFO and non-FIFO situations perform well. 6 tabs, 13 figs, 30 refs.More>

2022, 22(2): 246-258. doi: 10.19818/j.cnki.1671-1637.2022.02.019

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Global bilevel polynomial optimization model for continuous traffic network design

YU Li-jun, CHEN Rui

Abstract: A global bilevel polynomial optimization model for a typical continuous traffic network design problem was proposed. In this model, all the functions are polynomials, and the lower-level problem is a convex problem. The upper-level problem is to optimize the network performance, and the lower-level problem is to characterize the traffic flow pattern of the deterministic user equilibrium (DUE). The bilevel polynomial optimization model was transformed into an equivalent single-level optimization problem by replacing the lower-level programming with the Fritz John conditions and multipliers, and then the moment semi-definite programming (MSDP) method was employed to obtain its global optimal solutions. The ranks of moment matrices were taken as sufficient conditions to guarantee the global optimality and were used to estimate the number of global optimal solutions. Moreover, a numerical example for the optimal toll problem was given, and the optimal toll problem was depicted by the proposed bilevel polynomial optimization model. The total toll revenue was maximized by adjusting the traffic flow on the existing road sections under the Wardrop user equilibrium constraint. Research results reveal that the maximum revenue in this simple example is 13.5 yuan, and meanwhile, the rank of the moment matrix for the example is 1, which proves the global optimality of the results. The classical approaches to solving the bilevel optimization problem, such as the mathematical program with equilibrium constraints (MPEC) and value function methods, can only find local optimal solutions due to the inherent nonconvexity in the continuous traffic network design. However, the proposed approach overcomes the problem existing in classical algorithms, and the proposed global bilevel polynomial optimization model and algorithm provide a better exploration tool for a typical continuous traffic network design. 2 figs, 37 refs.More>

2022, 22(2): 259-267. doi: 10.19818/j.cnki.1671-1637.2022.02.020

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Rapid prediction and rerouting planning method of suborbital debris hazard zones during high-density space launches

CHEN Wan-tong, TIAN Shu-yu

Abstract: Considering the potential risk of aircraft disintegration that may occur in the increasingly frequent commercial suborbital launch activities, a covariance propagation method was used to predict the propagation range of debris from the suborbital disintegration accidents. The method converted the debris motion equation into a Gaussian-Markov process and used the probability density function to construct a probability ellipsoid of the Gaussian-Markov process at a certain confidence level for the characterization of debris distribution. To avoid the collision risk between debris from suborbital disintegration accidents and aircrafts within the civil airspace, a hazard zone prediction and routing planning method of suborbital debris for air traffic control was proposed. The mathematical boundary of the probability ellipsoid of suborbital debris was determined according to the acceptable risk probability of civil aviation, and the projection of the probability ellipsoid in the horizontal direction was calculated. The hazard zone of debris was processed into a convex polygon by a geometric method. The number of diversion points in the diversion path was reduced by the constrained method, which was conducive to the smooth diversion of aircraft. Simulation results reveal that the covariance propagation method can rapidly and effectively predict the propagation process of debris from suborbital disintegration accidents in a complex atmospheric environment, showing the ellipsoid boundary range of 99.999% and 95.000%, respectively. The higher the confidence degree, the larger the boundary range of the probability ellipsoid, and the closer it is to the real debris falling propagation range. By using the constrained method of number of diversion points, the optimized rerouting path distance increases by 0.13% compared with that before the constraint, but the number of diversion points reduces by 50%. Therefore, the covariance propagation method can timely and accurately predict the propagation range of debris from suborbital disintegration accidents, and on this basis, efficient and safe redirecting strategies can be presented. 1 tab, 7 figs, 30 refs.More>

2022, 22(2): 268-276. doi: 10.19818/j.cnki.1671-1637.2022.02.021

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Operation optimization of container train liner based on railway freight capacity

LIAN Feng, DU Yi-ying, YANG Zhong-zhen

Abstract: The OD passenger flows between railway stations were estimated by the big data mining method, and the choice preferences of railway passengers for high-speed and non-high-speed railways were analyzed by investigation, and thus the supply-demand relationship and equilibirum of passenger transportation on non-high-speed railways after the opening of high-speed railways were determined. The passenger flows of non-high-speed railways were converted into the corresponding number of passenger trains, and the carrying capacity of non-high-speed railways occupied by passenger transportation was estimated. The total carrying capacity of non-high-speed railway links was measured, the remaining freight capacity of non-high-speed railway links was calculated based on the deduction coefficient method, and the alternatives of railway container liner terminals were given based on the container's arrival volumes. The train departure frequency of the alternatives was taken as a discrete endogenous variable, the optimization model of terminal locations and the departure frequency was built based on the trunk highway network and non-high-speed railway network in the reality, and the economic and technical indexes of container railway service network were determined by solving the model. The Shanghai Port, Ningbo Port, and their hinterlands were taken as examples to carry out a numerical analysis. Calculation results show that in terms of the non-high-speed railway links within the hinterlands of the two ports, the minimum average daily carrying capacity is 79 trains while the maximum is 137 trains. Based on the remaining freight capacity of non-high-speed railway links, the calculation result shows that the minimum average daily departure frequency of container trains of liner terminals is 6 trains while the maximum is 19 trains. From the calculated flows of the non-high-speed railway links, the average daily containers transported by the railway to Shanghai Port and Ningbo Port are 13 677 and 12 094 TEUs, respectively, accounting for 25% and 33% of their total daily arrivals, respectively, which is a significant increase compared with the current 5%-7%. 9 tabs, 2 figs, 27 refs.More>

2022, 22(2): 277-286. doi: 10.19818/j.cnki.1671-1637.2022.02.022

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Virtual port modeling method based on dynamic fluid field data

CHEN Li-jia, WANG Kai, WEI Tian-ming, HAO Guo-zhu

Abstract: To achieve the digital upgradation of ports, a virtual port modeling method based on the dynamic flow field data was proposed. The geometric feature of a port was reconstructed by the three-dimensional (3D) reconstruction model with the aerial image data of unmanned aerial vehicle (UAV) oblique photography, and a high-precision 3D model was established. The simplified model of the edge collapse algorithm based on the quadric error metric was introduced to prevent low rendering efficiency caused by the data overflow. The high time consuming step in the numerical calculation of Euler method was analyzed. A neural network model was built to learn the evolution feature of the flow field. The calculation of the projection term was accelerated to produce the dynamic flow field data that were used to drive the dynamic rendering of water flow. The smoothed particle hydrodynamics (SPH) method was employed to reflect the interactions of water flow with ships and land. In this way, not only was the real-time performance of rendering ensured, but also the realistic effect of rendering was improved. Research results show that the 3D reconstruction model of the reconstructed port has 3 320 937 vertices, and the rendering frequency of the reconstructed grid model is 78.7 Hz in Meshlab. After almost 90.0% of the vertices are removed from the model via model simplification, the number of vertices reduces to 332 836, and the rendering frequency enhances to 108.7 Hz. The geometric errors of the model are smaller than 2.0% after simplification. In a 256×256 flow field grid, the average update interval is roughly 17 ms for the water flow velocity field obtained by the grid fluid calculation method accelerated by a neural network, and the average simulation precision is 88.6%. When the flow field data and 3D port model were driven by an open scene graph (OSG) engine, the average rendering frequency can reach 50.5 Hz. In conclusion, the proposed method can effectively solve the key problems in high-precision real-time rendering to achieve the dynamic balance between simulation precision and rendering efficiency. It enables high-precision virtual port modeling and real-time dynamic simulation without great precision loss. 1 tab, 11 figs, 30 refs.More>

2022, 22(2): 287-297. doi: 10.19818/j.cnki.1671-1637.2022.02.023

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Early warning method for heavy landing of civil aircraft based on real-time monitoring parameters

CAI Jing, CAI Kun-ye, HUANG Shi-jie

Abstract: It was considered that the heavy landing events of civil aircraft can only be reported by pilots or checked passively by the maintenance personnels afterward at present, an early warning method for the heavy landing of civil aircraft based on real-time monitoring parameters was proposed. The influencing factors in heavy landing were analyzed, and on the basis of the preprocessed data of a quick access recorder (QAR), the grey relational analysis (GRA) was employed to extract 26 feature monitoring parameters from 52 monitoring parameters related to the heavy landing of aircraft. Taking the landing weight, vertical acceleration, vertical decreasing rate, and pitch rate as the prediction parameters and the 26 feature monitoring parameters as the inputs, a prediction model for the heavy landing of aircraft was built based on the long short-term memory (LSTM). The prediction model was trained with heavy landing cases, and the influence of the flight height range and the input/output step size on the prediction accuracy was analyzed to optimize the prediction model. The confusion matrix was introduced into the case verification to verify the prediction results of the model. Research results indicate that the LSTM-based prediction model can make use of the information that reflects the trend of heavy landing in the real-time monitoring data to realize early warning of heavy landing, the prediction accuracy of the model can reach 98% for 8 seconds of warning, and the average absolute error is only 0.018 3, which means the model can provide pilots adequate time margin to take measures to avoid the heavy landing. 6 tabs, 17 figs, 29 refs.More>

2022, 22(2): 298-309. doi: 10.19818/j.cnki.1671-1637.2022.02.024

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Evaluation method of train communication network performance based on normal cloud model and fuzzy analytic hierarchy process

HE De-qiang, LIU Guo-qiang, CHEN Yan-jun, MIAO Jian, YAO Xiao-yang

Abstract: To ensure the safety and reliability of high-speed trains, a method for evaluating the performance of train communication networks (TCNs) was studied. A suitable system of performance evaluation indexes was proposed by considering the stringent requirements for TCNs in terms of real-time responsiveness, reliability, and service quality. Fuzzy analytic hierarchy process (FAHP) was used to determine the weights of performance evaluation indexes of TCN. To address the uncertainty of TCN evaluation process, a two-dimensional (2D) evaluation model based on the normal cloud model and fuzzy entropy was constructed. A TCN simulation platform was constructed by using switched Ethernet with large capacity and high reliability, and then used to obtain sample data for each index. The membership degrees of each index were computed by using the 2D evaluation model, and the performance grade of the TCN was determined by the maximum membership degree (from fuzzy theory) principle. Research results show that 60% of the evaluated samples have network performance grades of Ⅰ and Ⅱ when the TCN is in a good state. When the network has high packet loss rate and bit error rate, 40% of the evaluated samples have performance grades of Ⅲ and Ⅳ. Therefore, the result of the 2D evaluation model accurately reflects the state of the TCN. The result is largely consistent with the result from the fuzzy comprehensive evaluation (FCE), indicating that the 2D evaluation model is accurate. However, as it is not possible for the FCE method to exclude the influence of uncertainty in the evaluation process, its result lacks precision. Hence, the proposed method is more suitable for the evaluation of TCN performance. 6 tabs, 15 figs, 32 refs.More>

2022, 22(2): 310-320. doi: 10.19818/j.cnki.1671-1637.2022.02.025

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2022 Vol. 22, No. 2

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