交通运输工程学报

Research progress of detection, monitoring and running safety of bridge-track system for high-speed railway

GOU Hong-ye, LIU Chang, BAN Xin-lin, MENG Xin, PU Qian-hui

Abstract: To promote the safety performance of bridge-track structure and ensure the structural adaptability and running safety of high-speed railway under complex environmental conditions, the improvement and optimization of detection and monitoring equipment of bridge-track system for high-speed railway were introduced, the dynamic evolution rule of bridge-track structure service performance was analyzed, the evaluation and prediction methods of the running safety of high-speed train under complex conditions were summarized, and the future research priorities and directions were prospected. Research results show that in the detection and monitoring technology research of bridge-track system, existing research focuses on the optimization of traditional detection and monitoring equipment and the deep integration of intelligent technology and damage identification method. The core objective is to improve the efficiency, accuracy and standardization of detection and monitoring of bridge-track structure, and realize the accurate evaluation of infrastructure service status. In the research of bridge-track spatial deformation mapping relationship, considering infrastructure interaction deformation mapping model can accurately describe the change trend, development and spectral characteristics of the track geometry caused by the evolution of the interface state between the structural layers, but lack of in-depth study of high-speed railway bridge-track collaborative design and deformation intelligent control device. The study of structural service performance evolution is mostly based on the idealized elastoplastic constitutive model, and the study of service performance degradation behavior is limited to specific service environment. The research on the traffic safety of high-speed railway bridges under long-term service conditions based on train-track-bridge dynamic interaction theory is being carried out step by step, and the traffic safety evaluation criteria based on different index systems are proposed. Making full use of the monitoring data of bridge-track system, strengthening the research on the performance evolution mechanism and damage failure mechanism of bridge-track structure in complex environment, and proposing new intelligent evaluation and prediction methods for the running safety of high-speed train with high portability under the condition of updated information are the research directions of future focus. 1 tab, 8 figs, 171 refs.More>

2022, 22(1): 1-23. doi: 10.19818/j.cnki.1671-1637.2022.01.001

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Research progress of surface technology in piston assembly-cylinder liner system of internal combustion engines

LYU Yan-jun, LUO Hong-bo, ZHANG Yong-fang, KANG Jian-xiong, LI Peng-zhou

Abstract: Through the analysis and summary of global research statuses and development trends of surface technology in piston assembly-cylinder liner systems of internal combustion engines, the characteristics of surface textures and surface coating technologies in the applications of friction reduction, wear resistance, and energy saving of internal combustion engine key motion pairs were examined. The influences of surface texture processing technology, morphological and distribution characteristics, surface coating preparation technology, surface wear resistant coating, surface thermal barrier coating, and the synergistic effect of surface technology and lubrication on the tribological properties of motion pairs were analyzed in detail. Analysis results show that the laser surface texture (LST) can effectively improve the surface tribological properties of motion pairs. The direct/indirect laser shock surface patterning (LSSP) technology is an efficient and flexible processing method for the surface texture processing. Because the effects of texture processing technology, morphology, and distribution characteristics on the tribological properties are complex, further study and optimization on the morphology and distribution characteristics of surface texture are still necessary based on the operating conditions of piston assembly-cylinder liner systems of internal combustion engines. The wear resistant coatings and thermal barrier coatings (TBC) prepared by the atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) spray, have good wear resistance, heat insulation, and oxidation resistance. The metal matrix composites, diamond-like carbon (DLC) materials, nanocomposites, and ceramic materials on the surface of piston assembly-cylinder liner systems of internal combustion engines exhibit obvious effects in reducing friction, wear resistance and energy-saving. However, because of the wide variety of coating materials, developing a unified industrial standard and norms as well as industrial applications are difficult. The dynamics characteristics, synergistic effect of surface texture, surface coating, and lubrication are complex in the piston assembly-cylinder liner systems of internal combustion engines. In the future, thorough considerations of friction reduction and wear resistance mechanisms of various surface technologies coupling under multi-field conditions and further improvement of surface composite theory and technology system for piston assembly-cylinder liner systems are necessary, to provide a technical guidance for the green and efficient development of internal combustion engines. 3 tabs, 14 figs, 111 refs.More>

2022, 22(1): 24-41. doi: 10.19818/j.cnki.1671-1637.2022.01.002

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Status and future trend of wheel/rail system

SHEN Gang, MAO Xin, MAO Wen-li, DONG Qiang-qiang, YIN Xiang-qin

Abstract: The current engineering problems, present progress in research, and engineering treatment methods of existed traditional steel wheel rail type wheel/rail system were summarized. The formation and propagation mechanisms of rail corrugation and wheel out-of-roundness were analyzed, and innovative suggestions for addressing the tread hollow wear problems of high-speed trains were made. A personalized optimal strategy was formulated based on the systematic novel idea of obtaining safe and economical railway conditions through the profile design, wear evaluation, and wear control of wheel/rail system. For current rail grinding and wheel reprofiling, a summary and a discussion of future trends were presented. Based on a discussion of wheel/rail system detection methods, suggestions were made to avoid excessive detections, and the future development trend of wheel/rail system was predicted. Analysis results show that the mechanisms of rail corrugation and wheel out-of-roundness are both the coupling of parametric excitation and wheel/rail tangential wear of wheel/rail system. The wear on the hump zone is higher than that of the concave zone together with the coupling phase of variable normal force and tangential wear. In the case of the tread hollow wear of high-speed trains, the trouble seems to be caused by the inlaying wear on the very small wheelset/track interaction on the straight track with high speed and super large-radius curved track, which can be based on the copy-type wear of wheel and rail treads during the highly stable wheelset/track lateral movement. The cause of wheel flange wear of low-speed trains appears to be the flange guiding action together with the large lateral creep force on the radius of the sharp curved track. The hollow wear of the tread does not easily form. Various rail and turnout problems are usually related to the load bearing and impact. Its fatigue failure is mainly the low-frequency high-stress fatigue failures. With the increase in the running speed and axle load, the limitation of optimization on the wheel and rail side reaches its maximum. Thus, only through systematic optimization between wheel and rail can their potential be realized and the application value of the rail system be maintained. 7 tabs, 14 figs, 60 refs.More>

2022, 22(1): 42-57. doi: 10.19818/j.cnki.1671-1637.2022.01.003

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Experiment on out-of-plan mechanical behavior of CFST X-type arches

WEI Jian-gang, XIE Zhi-tao, YANG Yan, WU Qing-xiong, CHEN Bao-chun, PING Jian-chun

Abstract: To investigate the effects of non-conservative forces on the out-of-plane stability of concrete filled steel tubular (CFST) X-type arches, the structural spatial mechanical behaviors of CFST X-type arches were analyzed via experiment and finite element analysis. Based on a prototype bridge, the structural spatial mechanical behaviors of a CFST X-type arch with hangers were tested to elucidate the failure mechanisms of the arch model. A finite element model of a standard CFST X-type arche was created based on the experimental data and the actual structural engineering parameters. The conservative and non-conservative forces from hangers were considered respectively in models with or without tie hangers. The effects of arch rib inclination, rise-span ratio, and width-span ratio on the out-of-plane ultimate bearing capacities of CFST X-type arches considering the non-conservative force from hangers or not were analyzed. Based on a finite element model for combined material and geometric nonlinearities and in terms of load and displacement ratios, the improvement in the spatial mechanical behaviors of arch rib due to the non-conservative force was quantitatively analyzed under different parameters. Research results indicate that during the spatial mechanical process, the displacement of the CFST X-type arch is symmetrically distributed about the crown section, and the strain distribution is also highly symmetric. Therefore, the arch model has good overall stability and low sensitivity to initial geometric defects during the spatial mechanical process. The arch model ultimately failed due to an out-of-plane extreme point instability. The arch rib mainly bears compression and out-of-plane bending moment, and the out-of-plane bending moment is the main controlling factor for the stability and ultimate bearing capacity of the arch model. The out-of-plane ultimate bearing capacity of CFST X-type arches initially increases and then decreases with the increasing arch rib inclination, rise-span ratio, and width-span ratio. The arch model reaches its maximum ultimate bearing capacity when the arch rib inclination is 9°, the rise-span ratio is 0.25, and the width-span ratio is 0.03. The non-conservative force should be considered when calculating the out-of-plane ultimate bearing capacity of CFST X-type arches, as the omission of the force will lead to a 22% underestimation of the out-of-plane ultimate bearing capacity. 1 tab, 21 figs, 32 refs.More>

2022, 22(1): 58-69. doi: 10.19818/j.cnki.1671-1637.2022.01.004

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Internal force state of long-span continuous rigid-frame bridge with high-rise piers and its effect on seismic response

SHI Yan, LI Jun, QIN Hong-guo, LI Ping, ZHENG Guo-zu, WANG Dong-sheng

Abstract: An analysis model was established to study the effects of actual construction process and concrete shrinkage and creep on the internal force state of continuous rigid-frame bridge to determine the differences in seismic responses of the main bridge under different internal force states. The model was established taking a long-span continuous rigid-frame bridge with high-rise pier as the background, through MIDAS/Civil, and the effects of each construction factor on the internal force state of the main bridge were discussed. Based on the equivalent load method, the calculation formulas of internal force equivalent loads were proposed for continuous rigid-frame bridges. The internal forces of the main bridge were decomposed. Several simple internal force equivalent loads were used for equivalence, followed by the summation using the superposition principle to obtain the equivalent internal force state corresponding to the actual situation. The nonlinear dynamic analysis model of the completed bridge was established through the OpenSees, and the internal force equivalent loads corresponding to different internal force states were applied to enable the positioning of the corresponding equivalent internal force states. Forty groups of typical near-fault ground motion records with velocity pulse effect were selected as the input. The nonlinear dynamic time-history analysis of the completed bridge was carried out under different internal force states. Analysis results show that with the prestress of the main bridge ignored, the maximum bending moment of the main girder is overestimated by about 2.8 times, and the maximum bending moments of the top and bottom of the main pier are overestimated by about 3.5 and 2.0 times, respectively, with the bending moment in reverse direction to the actual situation. Therefore, the influence of prestress on the internal force state of continuous rigid-frame bridge cannot be ignored. The maximum error between the peak value of the equivalent internal force of the main girder and that of the target internal force near the pier-beam consolidation is less than 5%. Under the action of near-fault ground motions, the drift angle of main pier, curvature ductility factor, and maximum strain of reinforcement in plastic hinge area all display decreasing trends with the increase of concrete shrinkage and creep, especially detectable along the longitudinal direction of the bridge. The proposed calculation method of equivalent internal force loads can provide a reference for the seismic design and performance evaluation of continuous rigid-frame bridges in high intensity areas. 4 tabs, 12 figs, 30 refs.More>

2022, 22(1): 70-81. doi: 10.19818/j.cnki.1671-1637.2022.01.005

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Multi-dimensional seismic fragility analysis method of bridge system based on Nataf transformation

LI Jia-lu, REN Le-ping, HU Wei

Abstract: In the framework of multi-dimensional performance limit state theory, the correlation of seismic response parameters of bridge components was considered, and an improved multi-dimensional seismic fragility analysis method of bridge system was proposed by introducing Nataf transformation. Taking a three-span V-shaped continuous girder bridge as an example, the nonlinear dynamic analysis model of the bridge system was established by using OpenSees software, 20 seismic waves were selected from the strong earthquake database of Pacific Seismic Research Center for the incremental dynamic analysis, and the maximum response samples of the bridge structure under earthquake were obtained. The maximum likelihood estimation method was used to obtain the statistical parameters of the bridge component's seismic demand probability model. Combined with the defined bridge component damage index, the seismic fragility of the example bridge multi-dimensional system was analyzed by using the proposed method. Analysis results show that on the basis of considering the correlation between the seismic response parameters of the components and the performance limit states, the proposed method can calculate the fragility of the bridge system without relying on the joint probability density function between the seismic response parameters of the components. When constructing the multi-dimensional limit state equation, the influence deviation of the bridge component failure mode ranking on the multi-dimensional seismic fragility of the bridge system is less than 3%, so the component failure mode ranking has little influence on the fragility analysis result. In any damage state, with the increase of the correlation coefficient between the ground peak acceleration and the limit state, the ratios of the failure probability of the bridge system and the transition pier under the action of earthquake gradually decrease and approach 1, the correlation between the performance limit states of different bridge components becomes weaker, and the area of the system failure domain becomes smaller, resulting in that the failure probability of the bridge system reduces, and the multi-dimensional fragility of the bridge system is closer to the evaluation result when the performance indexes are independent of each other. When the multi-dimensional performance indicators are used, their correlation cannot be ignored, otherwise it will lead to the overestimation of the seismic performance of the bridge structure. 4 tabs, 6 figs, 30 refs.More>

2022, 22(1): 82-92. doi: 10.19818/j.cnki.1671-1637.2022.01.006

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Axial compression test of masonry short columns with ultra-high performance mortar

HUANG Qing-wei, LIAO Miao-xing, CHEN Bao-chun, LU Shao-bin, LIU Jun-ping, LI Cong, HUANG Wen-jin, HUANG Xin-yi

Abstract: To improve the mechanical properties of masonry columns, a new masonry column with UHPM (UMC) based on the ultra-high performance mortar (UHPM) was proposed. Axial compression test were carried out on two groups of UMC with fired brick and concrete brick. By comparing with the conventional masonry columns (MC), the stress mechanism and failure mode of UMC were discussed. The applicability of formula for calculating the axial compression bearing capacity of masonry columns in the current specification to UMC was evaluated, and the prediction formula for the axial compression bearing capacity of UMC was proposed. Analysis results show that the whole stress process of UMC and MC is similar, which both experience the stress stage before cracking, cracking development stage and failure stage. The initial cracking load of UMC is much higher than that of MC, where, the values of UMC with fired brick and concrete brick are 2.36 and 2.45 times than those of MC, respectively, and both are greater than the ultimate load of MC. Both the UMC and MC lost their bearing capacity due to the block failure. The failure mode of MC shows obvious brittleness, and the cracks mainly develop at the interface between the mortar and the block. However, the failure of UMC shows good ductility, and the crushing degree of block is much larger than that of MC. Compared with MC, mortar in UMC is no longer a weak part, and the UHPM plays a constraint role on the lateral deformation of the block, which can significantly improve the bearing capacity of the masonry column. The compression bearing capacities of UMC with fired brick and concrete brick are 1.74 and 2.00 times that of MC, respectively, indicating that the application of UHPM in masonry structure is quite feasible. The strength calculation formula for MC in the current specification will overestimate the bearing capacity of UMC. The proposed UMC strength calculation formula for UMC takes into account the strength of block and the constraint effect of UHPM on the block. 8 tabs, 9 figs, 25 refs.More>

2022, 22(1): 93-102. doi: 10.19818/j.cnki.1671-1637.2022.01.007

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Field test on soft ground with liquefiable silt interlayer reinforced by jet-grouted mixing piles

ZHANG Ding-wen, LIU She-chuan, LIN Wen-feng, SHI Hong-bin, MAO Zhong-liang

Abstract: For the engineering projects involving the reinforcement of soft ground with liquefiable silt interlayer, the applicability and effect of reinforcement using jet-grouted mixing piles were investigated on-site. The pile-forming quality and core strength of jet-grouted mixing pile were measured and analyzed by investigating the core samples obtained by drilling and static loading test. The data pertaining to ground surface settlement, deep horizontal displacement, pile load sharing ratio, pile-soil stress ratio, and excess pore water pressure were monitored under embankment load at a typical section of the soft ground during and after reinforcement. The reinforcement effect and stress characteristic on soft ground with liquefiable silt interlayer reinforced by the jet-grouted mixing piles were analyzed. Analysis results show that jet-grouted mixing piles can be successfully driven into the soft ground with liquefiable silt interlayer. The unconfined compressive strength of the pile core reaches 2.5 MPa at 28 d, which is nearly twice as high as the value of the core of conventional mixing pile. Under the embankment load, the jet-grouted mixing piles can effectively reduce the foundation settlement and the deep horizontal displacement at the toe of the slope, and improve the embankment stability. The pile-soil differential settlement is relatively small, the pile-soil stress ratio is 5-10, and the pile load sharing ratio is less than 50% in the jet-grouted mixing pile reinforced foundation, demonstrating the advantageous characteristic of the composite foundation. Composite foundation is divided into flexible pile composite foundation and rigid pile composite foundation. The design methods of the two are very different. The jet-grouted mixing piles studied in this paper is suggested to be designed as flexible pile composite foundation. Therefore, the soft ground with liquefiable silt interlayer reinforced by the jet-grouted mixing piles demonstrates satisfactory effect and can be used in practical engineering. 2 tabs, 12 figs, 30 refs.More>

2022, 22(1): 103-111. doi: 10.19818/j.cnki.1671-1637.2022.01.008

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Vibration propagation law within over-track buildings above throat area of metro depot

WANG Yi-min, TAO Zi-yu, ZOU Chao, CHEN Ying

Abstract: Relying on a metro depot with over-track buildings in Shenzhen, the vibration acceleration responses during trains passing on different tracks in the throat area were measured on-site at the ground floor, platform transfer floor, and the over-track 4-storey steel-framed structure. The propagation laws of environmental and structural vibrations caused by train operations in the throat area were analyzed. Research results show that there exists energy loss when the train-induced vibration propagates from the surrounding soil to the foundation through the soil-structure dynamic interaction. The measured acceleration amplitude at the foundation bottom of the structure is significantly smaller than that at the adjacent ground surface. In the process of train-induced vibration propagation from the surrounding soil to the structure, the high-frequency component above 50 Hz attenuates more rapidly. The soil-structure coupling loss can be up to 27-34 dB. Therefore, the influence of soil-structure coupling loss should be considered when using the foundation bottom inputs to predict the train-induced vibration responses within the over-track buildings at metro depots based on the substructure method. The vibrations at the foundation bottom of the platform columns should be used as the vibration input of the model. The structural designs of over-track platform and transfer floor can help to reduce the upward propagation of the train-induced vibration to some extent. The acceleration level attenuation amplitude is 3-6 dB. The train-induced vibration propagates upward through the platform columns in the form of axial wave and spreads horizontally through the transfer beams and floor slabs in the form of bending wave. The vibration energy has multiple paths to propagate toward the over-track building and superpose. The vibration difference among measuring points on the platform transfer floor is within 8 dB. The vibration propagation law between floors in the over-track building depends on the impedance ratios of beam to vertical load-bearing structure and floor slab to vertical load-bearing structure. Increasing the impedance of the beam or floor slab helps to reduce the upward propagation of vibration. The train-induced vibration frequency within the 4-storey steel-framed structure has three peaks at 6.3, 12.5, and 40.0 Hz, respectively. It is related to the natural frequency of the structure and the dynamic characteristics of the excitation. 3 tabs, 10 figs, 32 refs.More>

2022, 22(1): 112-121. doi: 10.19818/j.cnki.1671-1637.2022.01.009

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Dynamics characteristics of rack railway guiding equipment

CHEN Zai-gang, TANG Liang, YANG Ji-zhong, CHEN Zhi-hui, ZHAI Wan-ming

Abstract: The coupled dynamics finite element model of the vehicle-rack railway guiding equipment (RRGE) was established by using the large finite element commercial software ABAQUS. The whole process of vehicle passing through the RRGE was simulated, and the dynamic interaction between the vehicle and the RRGE was analyzed. Considering the influences of different parameters, the dynamic performance response laws such as the vibration response, structural stress and dynamic contact force of rack railway guiding equipment were studied. Research results indicate that as the increase of the supporting spring preload, the rotating speeds of the gear increase to the value that matching the train speed more promptly. And generally the vibrations and dynamic stress of the synchronous section increase, while both the vibrations and dynamic stress of the entry section and the vibration of the calibration section decrease. The reasonable supporting spring preload should be determined by considering the effect of structural stress and vibration level comprehensively. For the calculation scenarios in this paper, the reasonable supporting spring preload is recommended to be 3 kN. The vibration speed, the root mean square of the vibration speed, the vibration acceleration, and the root mean square of the vibration acceleration reach their maximum values (e.g. 5.66 m·s^-1, 1.31 m·s^-1, 5 657.82 m·s^-2, 479.36 m·s^-2) under the condition that the supporting spring preload is 1 kN. As the increase of the initial rotating speed of the gear up to the train speed, the vertical vibration of the synchronous section varies little in general, and the longitudinal vibration decreases, indicating that it is better to set the initial rotating speed of the gear equal to the train speed. The impact force acting to the RRGE structure from the gear increases with the increase of train speed, therefore, the reasonable train speed passing by the RRGE should be determined by considering the factors comprehensively such as the impact vibration and the operation efficiency. For the calculated speeds of 5 and 10 km·h^-1, it is recommended that the reasonable train speed passing by the RRGE should be 5 km·h^-1 or less. 5 tabs, 15 figs, 30 refs.More>

2022, 22(1): 122-132. doi: 10.19818/j.cnki.1671-1637.2022.01.010

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Calculation methods of stress factor in welding seam quality grade evaluation of EMUs aluminum alloy car body

LU Yao-hui, LI Zhen-sheng, YIN Xiao-chun, SONG Cheng-yu, LIU Xi, LU Chuan

Abstract: The finite element analysis model of the aluminum alloy welded car body for a type of electric multiple units (EMUs) was established. The welding seam was simplified modeling, and the difference between the welding seam and the actual existence was corrected in the calculation of the equivalent structural stress. The loads on the car body were analyzed based on BS EN 12663-1:2010. Nine fatigue load cases of car body were determined by the Box-Behnken orthogonal matrix design. A multi-axial load was applied to the finite element model of car body, and the stress distribution of the four long welding seams on the car body side wall were analyzed. Six concerned points for stress factor calculations were identified. The stress factors of welding seams on the car body side wall were calculated by using the nominal stress method and the equivalent structural stress method. Two stress analysis methods were compared and analyzed. Analysis results show that the allowable stress ranges of the two stress analysis methods are different at 1.0×10⁷ cycles, with a nominal stress of 16.40 MPa and an equivalent structural stress of 26.61 MPa. The nominal stress ranges of the six concerned points are all smaller than the equivalent structural stress ranges, and the obtained stress factors of the nominal stress and equivalent structural stress are 0.33, 0.25, 0.50, 0.49, 0.76, 0.62 and 0.23, 0.24, 0.39, 0.45, 0.61, 0.48, respectively. For the concerned points of the same welding seam, the stress factors obtained by the nominal stress method are greater than the values obtained by the equivalent structural stress method. The nominal stress method has a large dispersion, which leads to a large stress factor. The structural stress method has a clearer physical meaning, and the calculated stress factor is more reasonable. 2 tabs, 8 figs, 30 refs.More>

2022, 22(1): 133-140. doi: 10.19818/j.cnki.1671-1637.2022.01.011

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Dynamic performance test of medium and low speed maglev vehicle-bridge coupled system

LI Miao, MA Wei-hua, GONG Jun-hu, LIU Wen-liang, GAO Ding-gang, LUO Shi-hui

Abstract: To investigate the vibration characteristics of medium and low speed maglev vehicle-bridge coupled system, field dynamics tests were carried out at Shanghai Lingang Medium and Low Speed Maglev Test Base, the effects of vehicle speed and structural form of the bridge on the dynamic response of the coupled system were studied. The levitation frames with mid-set suspension was adopt by the test vehicle, while the test bridges were 25 m simply-supported with concrete and steel structures. Modal tests were performed to clarify the natural vibration characteristics of the two bridges. The acceleration of the vehicle-bridge coupled system and the vertical dynamic displacement signals of the bridge under different operating conditions were extracted. The key dynamic indicators of the vehicle-bridge coupled system such as the vertical and lateral Sperling indexes, dynamic coefficients, and rotation angle of the beam end were calculated, the dynamic response characteristics of the coupled system were analyzed in detail, and the vibration level of the system was evaluated. Research results show that the vertical first-order natural frequencies of the concrete bridge and steel bridge are 7.32 and 7.72 Hz, respectively, and the key dynamic indicators of these two bridges meet the requirements of relevant standards. The maximum acceleration of the concrete bridge and steel bridge are less than 0.2 and 1.4 m·s^-2, respectively. When the vehicle is operating at 5 km·h^-1, the amplitude of vertical dynamic response of the steel bridge is approximately 7.6 times that of the concrete bridge. In the speed range tested, the lateral Sperling index of vehicle is less than 2.5, indicating excellent lateral operation stability when the vehicle is running on the concrete bridge and steel bridge. The peak of the vertical natural frequency of the vehicle's air-spring suspension system reaches its maximum when the vehicle speed is 25 km·h^-1, and the vertical Sperling indexes reach 2.687 and 3.340 when the vehicle passes through the concrete bridge and steel bridge, respectively. The test results can provide valuable references for the optimal design and numerical model validation of medium and low speed maglev vehicle-bridge coupled system. 1 tab, 19 figs, 26 refs.More>

2022, 22(1): 141-154. doi: 10.19818/j.cnki.1671-1637.2022.01.012

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Spectrum analysis of hunting motion of flexible bogies in high-speed EMUs

GAN Feng, DAI Huan-yun, LUO Guang-bing, YANG Zhen-huan, LI Tao

Abstract: In order to analyze the spectrum of bogie hunting motion of high-speed EMUs at different operating speeds, a free wheelset hunting motion model was deduced, and three first-order differential equations related to the longitudinal velocity, lateral velocity and yaw angular velocity were established. A hunting motion model of the flexible bogie was established, and a 9- degree of freedom hunting motion equation related to the degrees of freedom of lateral displacement and shaking-head of wheelset and frame was given. Combined with the parameters of vehicle suspension and the measured wheel-rail contact relationship, and together with the hunting motion equation of free wheelset, the hunting wavelengths and frequencies of frame under different initial lateral displacements of wheelset were solved. Taking the wheel tread profile measured in one wheel repair cycle of a certain type of EMUs as an example, the variation law of the frame hunting wavelengths and frequencies under different mileages after wheel repair were analyzed. Analysis results show that some measuring points have obvious vibration frequencies of 2.9, 14.9 and 33.6 Hz, and these frequencies increase linearly with the vehicle speed. 33.6 Hz comes from the frequency when the vehicle passes through the CRTS Ⅱ track plate; 14.9 Hz comes from the wheel rotation frequency when running at 350 km·h^-1. When the initial lateral displacement of the wheelset is 3 mm and the equivalent conicity is 0.14, the calculated hunting frequency of the frame is 3.0 Hz, which is close to the measured lateral vibration frequency of the frame of 2.9 Hz. And then the accuracy of the differential equation is verified. With the increase of the mileage after the wheel repair, the equivalent conicity under the same wheelset lateral displacement continues to increase, the hunting wavelength of the frame continues to decrease, and the hunting frequency also increases. After 206 000 km after wheel repair, the maximum hunting frequency is close to 8 Hz when the wheelset lateral displacement is 1 mm. 1 tab, 18 figs, 32 refs.More>

2022, 22(1): 155-167. doi: 10.19818/j.cnki.1671-1637.2022.01.013

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Formation mechanism and progression pattern of eccentric wear of high-speed train wheels

KANG Xi, CHEN Guang-xiong, YANG Pu-miao, ZHU Qi, SONG Qi-feng

Abstract: To investigate the generation mechanism of the eccentric wear of high-speed train wheels, a high-speed wheel-rail finite element model was established based on the results of a field test and multibody dynamics-based simulation, and the impacts of residual static unbalance of wheels on wheel-rail normal contact forces were analyzed by transient dynamic simulation. The field test was performed on the operational speed of a multiple-unit train with a maximum operational speed of 250 km·h^-1 to determine the average speed of the train travelling in a uniform speed interval. Based on the viewpoint that the periodic fluctuations of frictional work result in uneven wheel-rail wear, the impacts of residual static unbalance of wheels on wheel-rail contact forces were analyzed, and the causes of the eccentric wear of wheels were explored. The residual static unbalance was simulated by adjusting the material density in the specific area on the wheel plate in the wheel-rail finite element model to investigate the relationship between the eccentric wear and the level of residual static unbalance. By recompiling the node coordinates in the finite element model to investigate the progression pattern of the eccentric wear of wheels, the eccentric wear of the actual wheel tread contour was simulated. Simulation results show that when the high-speed train travels at a uniform speed of 237 km·h^-1, the residual static unbalance of the wheels causes the wheel-rail system to vibrate at around 24 Hz, resulting in the periodic changes in wheel-rail normal contact forces and 1-order out-of-roundness wear of the wheel tread (that is, the eccentric wear of the wheels). With the progression of the wear, the vibrations at about 48 Hz and 72 Hz are stimulated in the wheel-rail system, which causes 2- or 3-order polygonal wear of wheels. When the maximum radial runout value of the worn wheel tread is greater than 0.15 mm, the vibration intensity is the greatest at 72 Hz within the frequency range of 0-150 Hz, resulting in the rapid progression of the 3-order polygonal wear of wheels. The formation of 1-order out-of-roundness wheels can be attenuated by reducing the amount of residual static unbalance of wheels. 2 tabs, 11 figs, 29 refs.More>

2022, 22(1): 168-176. doi: 10.19818/j.cnki.1671-1637.2022.01.014

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Gearbox fault diagnosis method based on convergent trend-guided variational mode decomposition

JIANG Xing-xing, SONG Qiu-yu, ZHU Zhong-kui, HUANG Wei-guo, LIU Jie

Abstract: From the perspective of the center frequency, the decomposition characteristics of different initial center frequencies in the variational mode decomposition algorithm were deeply analyzed. Making use of the decomposition characteristics, the initial center frequencies used in the variational mode decomposition were reasonably updated, without the prior knowledge, the entire analysis frequency band of the signal was adaptively decomposed. According to the kurtosis criterion, the fault component with the most abundant fault information was selected from the decomposed sub-signals. Envelope analysis was performed on the optimal fault component which has been processed by the balance parameter optimization and sparse code shrinkage. Based on the decomposition characteristics of variational mode, a complete gearbox fault diagnosis method was constructed based on the convergent trend-guided variational mode decomposition, and the diagnosis method was applied to the early local damage fault identification of gears in automobile transmission gearboxes and fault diagnosis of gearboxes in contact fatigue testing machines. Research results show that there is a convergent trend phenomenon in the variational mode decomposition algorithm. With the gradual increase of the initial center frequency, the convergent center frequency of the extracted mode has a specific convergent relationship with its corresponding initial center frequency. The proposed method can decompose the vibration signal adaptively without the prior knowledge of parameters. In experiment 1, the kurtosis of the fault component obtained by the proposed method is 3.056, and the kurtosis of the fault component after optimization is 24.812. The maximum kurtosis of the fault component in the traditional variational mode decomposition with two different ways for initializing the center frequency is 2.830 and 2.421, respectively. The fast spectral kurtosis analysis method fails to extract the fault component. In experiment 2, the kurtosis of fault component obtained by the proposed method is 3.467, and the kurtosis of the fault component after optimization is 19.780. The maximum kurtosis of the fault component in the traditional variational mode decomposition with two different ways for initializing the center frequency is 3.231 and 3.361, respectively. The fast spectral kurtosis analysis method fails to extract the fault components. The proposed method can enhance the transient characteristics and fault characteristic frequencies, and is more accurate and superior in the gearbox fault diagnosis. 22 figs, 30 refs.More>

2022, 22(1): 177-189. doi: 10.19818/j.cnki.1671-1637.2022.01.015

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Adaptive optimal energy management strategy of fuel cell vehicle by considering fuel cell performance degradation

WANG Ya-xiong, YU Qing-gang, WANG Xue-chao, SUN Feng-chun

Abstract: To improve system efficiency and reduce the risk of working life reduction caused by the adverse operation conditions of fuel cell, an adaptive Pontryagin's minimum principle (PMP) energy management strategy with the fuel cell performance degradation consideration was proposed for the fuel cell/supercapacitor hybrid power system in the city bus. The off-line PMP energy distributions of the fuel cell/supercapacitor hybrid power system in five different driving conditions were analyzed, and the relation between the initial value of the costate variable and the difference of state variable of the energy management system, i.e., the state-of-charge difference of the supercapacitor, between the beginning and the end, was obtained. The corresponding relation between the initial value of the costate for online PMP and state-of-charge could be interpolated. Integrating with the normal equation of the PMP, the instant costate variable was obtained, and thus the adaptively updating costate variable in the online PMP leading to keep up state-of-charge could be formulated. Choosing the fuel cell performance degradation, the power change rate, number of start-stop, and maximal power of the fuel cell as the constraints of the energy management system, the fuel cell power change rate was further formulated as a penalty term in the cost function of the adaptive PMP to meet the energy management constraints as well as achieve better fuel economy. The controller hardware-in-the-loop (HIL) simulation test was carried out to validate the practical efficacy of the proposed energy management strategy.Research results show that, under the bus condition SC03 and New York City cycle condition (NYCC) that are different from the costate variable formulation used typical operation conditions, the adaptive PMP energy management can make the terminal state-of-charge approach the target value, and compared with the off-line PMP, the losses of fuel economy are only 1.27% and 0.94%, respectively. Under the China bus driving cycle (CBDC) comprehensive test condition that is different from the operation conditions used for the costate determination and cost function weighting adjustment, the proposed adaptive optimal energy management strategy can implement the energy distributions of fuel cell and supercapacitor under the provided constraints, and the fuel economy can keep up 90.76% compared with the off-line optimization. Under the CBDC and NurembergR36 test conditions, the average errors between HIL and numerical simulations are less than 5%. Consequently, the proposed adaptive optimal energy management strategy considering the performance degradation of fuel cell can implement the high operation of the hybrid power system with the potential of a long working life. 9 tabs, 13 figs, 29 refs.More>

2022, 22(1): 190-204. doi: 10.19818/j.cnki.1671-1637.2022.01.016

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Coordinated scheduling model of arriving aircraft at large airport

JIANG Yu, LIU Zhen-yu, HU Zhi-tao, WU Wei-wei, WANG Zhe

Abstract: The problem of coordinated scheduling of arriving aircraft at large airports was studied to reduce the total delay and taxi times of arriving aircraft. The minimum weighted sum of runway sequencing time span and total delay time, the fewest number of flights assigned to remote gates, and the shortest taxi time of arriving aircraft were taken as the objective functions, respectively. A forward coordinated scheduling model for the systems of runway, gate, and taxiway was constructed. A gate re-adjustment model was used to perform the reverse optimization of the taxiway by adjusting the gate assignments of aircrafts with long taxi times. A genetic algorithm (GA) with improved gene coding was designed to prevent the generation of unfeasible solutions and to improve efficiency. Simulation results show that, compared with the first-come-first-serve strategy, the improved GA reduces the runway sequencing time of arriving aircraft by 20 s and the total delay time by 21% from 254 350 s to 199 760 s, respectively. Compared with the ant colony optimization, the improved GA reduces the total delay time by 20 060 s (9%) and produces a smoother iteration curve. After 12 iterations of the improved GA, all arrival aircrafts can be assigned to bridge gates. The total taxi time of 18 arriving aircrafts decreases by 9% from 4 575 s to 4 145 s, and only 3 taxi conflicts occur. 11 aircrafts choose the shortest routes, and only 3 aircrafts have extra taxi time of more than 40 s. After gate adjustment, the total extra taxi time decreases by 58 s or 27%. Therefore, the proposed coordinated scheduling model for arriving aircraft can improve the operational efficiency of large airports and provide decision-making support for airfield resource management. 5 tabs, 11 figs, 31 refs.More>

2022, 22(1): 205-215. doi: 10.19818/j.cnki.1671-1637.2022.01.017

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A flight phase identification method based on airborne data of civil aircraft

WANG Bing, ZHANG Ying, XIE Hua, LI Jie

Abstract: To resolve the flight phase identification errors in the airborne quick access recorder (QAR) trajectory data of civil aircraft, a method of flight phase re-identification was proposed based on the aerodynamic configuration and vertical movements of aircraft. This method comprises four steps: preprocessing of QAR data, identification of vertical movements, construction of a flight state characteristics model, and re-identification of flight phases. A DBSCAN-based local traversal clustering method was used to cluster the trends of pressure altitude to classify vertical movements, and a valid minimum state persistence time was set to eliminate the local flutter in the pressure altitude data. Considering aircraft-to-aircraft differences in flap position and control, fluctuations in airfield QFE, and inaccuracies in the airspeed indicator during low-speed taxiing, a flight-state characteristics model suitable for all types of aircraft and based on state parameters, such as flap switch position, landing gear position, ground speed, and vertical movements, was constructed. The model was used to divide the QAR data into flight state characteristic segments. The relationship model between each flight phase and flight state characteristics was established, and all flight state feature segments were identified as corresponding flight stages combined with landing gear air-ground logic. Three typical sample flights are used as examples, calculation results show that all the flight phases (including go-arounds) are correctly identified and divided, and are also fully consistent with the flap and landing gear states of the aircraft. The flight phase identification error in raw QAR data fields is solved effectively. The flight phases of QAR tracks of 272 268 flights are re-identified, and the success rate is 99.7%. The average durations of non-clean configuration flight phases, such as take-off, initial climb, approach, and landing, are 0.6, 1.9, 6.1 and 4.0 min, respectively, and the average altitudes from the ground are 54, 3 680, 6 030 and 2 500 ft, respectively, which are consistent with the actual flight operation behaviors. Therefore, the flight-phase re-identification method can be applied to numerous flights and provide technical support in analyzing the characteristics of civil aircraft flight phases. 5 tabs, 8 figs, 25 refs.More>

2022, 22(1): 216-228. doi: 10.19818/j.cnki.1671-1637.2022.01.018

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Effects of lidar location on retrieval of aircraft wake vortex characteristic parameter

ZHUANG Nan-jian, ZHAO Li-ya, GU Run-ping, WEI Zhi-qiang

Abstract: To improve the accuracies of wake vortex detection and retrieval of lidar in range height indicator mode, an algorithm for solving the optimal location of airport lidar based on the vortex core region segmentation was proposed. The influence of the lidar lateral and longitudinal installation positions on the accuracy of wake vortex retrieval was studied. Considering the effects of wake vortex dissipation and descent, a simulation model of lidar dynamic echo data was established. The radial distance formula of the wake vortex region segmentation was deduced, and the wake vortex core positions were determined according to the velocity extreme points after the region segmentation. After the detection time difference was corrected, the vortex core positions were substituted into the induced velocity equation. The simultaneous equations were constructed using the radial velocity of the characteristic point near the vortex core, and the relative error of the wake vortex circulations was solved. The calculation process for the lidar optimal location was designed based on the porportion of aircraft types at the airport. According to the operational data at a domestic airport for one week, data of five typical aircraft types were extracted to analyze the impact of airport lidar location, and the optimal lidar location of the airport was determined. Research results show that the lateral distance of the lidar location has a great influence on the retrieval accuracy, and there is an optimal lateral distance, which is about 10 times the aircraft wingspan. Approximately 200 m near the optimal lateral distance is a pretty good selection range, and the detection accuracy within this range does not change much. There is a minimum value for the selection of longitudinal distance, which is positively correlated with the descent speed of the wake vortex. For the typical large civil aviation aircraft, the value is about 800 m. When the longitudinal distance is greater than the minimum value, its change basically does not affect the wake vortex detection accuracy. The best location area for the airport lidar is a long strip area where the lateral position is near the optimal lateral distance, and the longitudinal distance is greater than the minimum value. It can be seen that the algorithm for solving the optimal location of the airport lidar is effective, and can be applied to the wake vortex detection experiment or the lidar location decision analysis of the dynamic wake separation system. 2 tabs, 11 figs, 31 refs.More>

2022, 22(1): 229-239. doi: 10.19818/j.cnki.1671-1637.2022.01.019

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A study on shipowners' selection preferences in response to global sulfur restrictions based on revealed preference data

BAI Xi-wen, HOU Yao, YANG Dong

Abstract: A decision-making modeling framework for the shipowners' emissions reduction plan based on the revealed preference (RP) data was established, and the selection mechanism for the shipowners' practically feasible plan for reducing the sulfur emissions was empirically investigated. Based on the AIS data and the data from other related databases, 11 factors from ship particulars, shipowner characteristics, and external market conditions were comprehensively considered. The limitations of existing literatures focusing on economic factors and ignoring non-economic factors were overcome, and the shipowners' selection of countermeasures under sulfur restrictions was systematically analyzed. Analysis results show that the 11 factors considered in this study, which exhibit varying degrees of effects, contribute to the interpretation of the shipowners' energy selection. In terms of the modified effect sizes, the factors are sequentially presented: the time period away from the implementation of the global sulfur restrictions (3.957), the deadweight tonnage (2.270), the ship age (1.711), the company size (1.579), the price difference per ton of the fuel (1.456), the freight rate index (1.442), the environmental awareness index (1.353), the speed of the ship (1.243), the voyage length (1.172), the proportion of sailing distance in the emission control area (1.127), and the trading route diversity (1.108). With regards to the shipowners' selection of an energy plan, the time period away from the implementation of the global sulfur restrictions and the deadweight tonnage significantly affect their decisions, and the modified effect sizes are more than 2.0. The five factors (i.e., the ship age, the company size, the price difference per ton of the fuel, the freight rate index, and the environmental awareness index) moderately affect their decisions, and the modified effect sizes are within 1.3-1.8. The other four factors related to the shipowners' operation patterns marginally affect their decisions, and the modified effect sizes are less than 1.3. 3 tabs, 30 refs.More>

2022, 22(1): 240-249. doi: 10.19818/j.cnki.1671-1637.2022.01.020

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Vehicle-following model in mixed traffic flow considering interaction potential of multiple front vehicles

ZONG Fang, WANG Meng, ZENG Meng, SHI Pei-xin, WANG Li

Abstract: The mixed traffic flow consisting of automated vehicle (AV) and regular vehicle (RV) was analyzed. Based on the full velocity difference (FVD) model, a vehicle-following model for two types of vehicles (AV and RV) in mixed traffic flow was constructed by considering the factors of the headway, velocity, velocity difference and acceleration difference of multiple front vehicles and one rear vehicle. By introducing the molecular dynamics, the model also quantitatively expressed the influence degree of a surrounding vehicle on the host vehicle. According to the data collected from the vehicle-following field test mixed with AVs and RVs, the model parameters were globally optimized to obtain the highest accuracy. The stability of traffic flow for the vehicle-following model and FVD model was compared, and the influence of velocity on the stability of traffic flow was analyzed. Numerical simulation was designed to simulate the common traffic scenarios including urban areas and expressways, and the accuracy of the proposed model was analyzed. Simulation results indicate that the stability of traffic flow improves by considering the information from surrounding multiple vehicles, and the small velocity can reduce the stability. The proposed model can respond to the behaviours of the whole platoon in advance and simulate the dynamics characteristics of AVs better. In urban areas, compared with the FVD model, the average maximum error and average error of RV for the proposed model reduce by 0.18 m · s^-1 and 13.12%, respectively, and the accuracy improves by 4.47%. In expressways, compared with the adaptive cruise control (ACC) model provided by PATH Laboratory, the average maximum error and average error of AV for the proposed model reduce by 7.78% and 26.79%, respectively, and the accuracy improves by 1.12%. In addition to providing model basis for AV-following control and queue control in mixed traffic flow, the proposed model can be utilized in vehicle-following behavior simulation for AV and RV. 1 tab, 7 figs, 38 refs.More>

2022, 22(1): 250-262. doi: 10.19818/j.cnki.1671-1637.2022.01.021

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Centralized ramp confluence cooperative control method with special connected and automated vehicle priority

WANG Qiu-ling, ZHAO Xiang-mo, XU Zhi-gang, ZHU Zhang-yuan, GUAN Wen-ying

Abstract: To ensure that the special vehicles pass quickly and smoothly in the confluence area of typical Y-type ramps in unmanned driving environment, a cooperative control method was studied by considering the priority to special vehicles for the centralized control scenario of fully connected and automated vehicle (CAV). The confluence sequence arrangement in the controlled area was determined using games. By considering the task priority attribute of special CAV and characteristics of vehicles, attributes related to the acceleration-associated lane priority of special CAV, the time-associated vehicle type priority, and the acceleration change rate-associated vehicle stability priority were designed separately, and a joint characterization of these attributes was performed using the cost function. The confluence sequence arrangement with the special CAV was transformed into an optimal sequence set solution, and the optimal confluence sequence was determined using the income matrix method of two-person cooperative game. Based on the sequencing results, the Pontryagin's maximum principle was applied to determine the vehicle trajectory control, and the optimal analytical solution for the longitudinal trajectory was obtained when the cost was at the minimum, to achieve the cooperative control while prioritizing the special CAV. Through the case calculation, Python was used to simulate and verify the cooperative control method giving priority to the special CAV, and the respective fuel consumptions and transit times with no control strategy and using the first-in-first-out strategy were compared. Research results show that 86% of vehicles can travel at the maximum speed to smoothly pass through the confluence area, and the cooperative control method can effectively guarantee the priority of special CAV. Compared with cases without control strategy and under the first-in-first-out strategy, the cumulative fuel consumptions under the cooperative control decrease by 11.8% and 16.1%, respectively, and the overall fleet passing time is shorter than those obtained with the two traditional confluence strategies. There are corresponding thresholds for the maximum speed limit, initial speed, and controlled area length to enable the special CAV to pass quickly. These values can serve as references in the confluence area design. 3 tabs, 7 figs, 31 refs.More>

2022, 22(1): 263-272. doi: 10.19818/j.cnki.1671-1637.2022.01.022

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Collision avoidance virtual simulation of intelligent vehicle embedded with multiple control models

TONG Qiu-hong, CHAI Guo-qing, ZHAO Hua-dong, GAO Yue, ZHANG Yong, REN Jin-tao, FENG Ming-ming

Abstract: In view of the high cost and risk involved in the driving safety distance monitoring and collision avoidance tests of intelligent vehicles and the difficulty in visualizing the test results, virtual simulations were conducted for the safety distance monitoring and collision avoidance of an intelligent vehicle. The virtual simulation technology based on the Visual Studio 2015, 3Dmax, and Unity3D was used to conduct the driving safety distance monitoring and collision avoidance virtual simulation tests on an autonomous car equipped with multiple control models in the virtual braking control system. The collision avoidance effects of different braking models were tested. Models for a virtual full vehicle and its braking system were established based on the dynamic performance and braking dynamics characteristics of electric vehicles. A virtual environment including a virtual test road model and a test scene was established based on the pavement adhesion coefficient and different road materials. Simulation models were developed for the test electronic devices to realize the multiple virtual controllers embedding. The embedding and simulation effects of the basic model and a back propagation (BP) neural network were studied. The design effects of the virtual software and hardware were correlated with the simulation test process through the design interface, and the animation rendering was used to directly display visually. Meanwhile, the memory optimization was applied to enable the virtual simulation test to be conducted in the server through the web access. Actual vehicle tests were conducted to verify the simulation system, and the actual vehicle test data were compared with the simulation results using the two models. Research results indicate that, at a low velocity, the relative error between the safety distance calculated by the basic model and that measured by the actual vehicle test is 2.49%, while the relative error between the safety distance calculated by the BP neural network and that measured by the actual vehicle test is 2.07%. At a high velocity, because of the sensor instability, the relative error between the safety distance calculated by the basic model and that measured in the actual vehicle test is 10.03%, while the relative error between the safety distance calculated by the BP neural network and that measured in the actual vehicle test is 10.35%. Therefore, the simulation system can enable a high-risk collision test to be conducted in a virtual environment. 6 tabs, 16 figs, 32 refs.More>

2022, 22(1): 273-284. doi: 10.19818/j.cnki.1671-1637.2022.01.023

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