2021 Vol. 21, No. 6

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Review
Management summary of transportation and vehicle engineering discipline in NSFC: review and prospects in 2021
WANG Zhi-zhong, PI Da-wei, WU Bing
Abstract: Transportation and vehicle engineering is a new discipline in the Natural Science Foundation of China's (NSFC) technology section. In 2021, related management team focused on the discipline development, collected and compiled One Hundred Scientific Questions on Transportation and Vehicle Engineering, and classified the discipline codes and key words. These activities helped to clarify the discipline boundaries, enhance popularity, and increase the number of applications. Using the discipline tree, field-specific seminars and demonstration meetings refined the disciplinary structure and balanced the development of various transportation systems. Efforts were made to strengthen the demand traction and problem orientation. An overall layout of major discipline projects was developed that emphasized addressing practical needs and scientific problems. Efforts were made to promote orderly sound talent team development, and get rid of the "four only" tendency. The team also endeavored to bring scientific and technological achievements from "bookshelves" to "market shelves", and accelerate the development of new disciplines. Specifically, this study includes: application, acceptance, evaluation, and funding of projects in the transportation and vehicle engineering discipline in 2021, funding areas and considerations behind the secondary code system adjustment and the definition of discipline boundaries, focus areas for future disciplinary work, the layout of key and talent projects, and discipline management work plans, such as promoting translating research advances into real productivities. In the future, the team will further deepen disciplinary surveys and research, coordinate programming key and major projects according to the research results, foster talent teams, smooth transformation mechanisms, and actively promote the implementation of innovation achievements. 6 tabs, 3 refs.More>
2021, 21(6): 1-7. doi: 10.19818/j.cnki.1671-1637.2021.06.001
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Research on dynamics of rail transit vehicle with tire running gears: state-of-arts and challenges
REN Li-hui, LI Wen, LENG Han, JI Yuan-jin, WANG Gang
Abstract: The current research progress on the dynamics of several typical rail transit vehicles with tire running gears was summarized, including straddle monorail vehicle, suspended monorail vehicle, rubber-tired track vehicle, rubber-tired tram and virtual rail vehicle. The possible research directions of future dynamics of vehicles were discussed. Research results show that the dynamics research of straddle monorail vehicles has previously focused on anti-roll stability, curving performance, and vehicle-bridge coupling vibration. The critical roll angle theory proposed according to the variation in the anti-roll stability of straddle monorail vehicles expounds the setting principles of the preloadings of stabilizers and guiding wheels, and gives the relationships of the preloadings of stabilizer and guiding wheel with running comfort and curve speed limit. The primary means increasing the speed of straddle monorail vehicle is to develop the tires with better performance and to control the vibration deterioration caused by the increase in the running speed. The studies on the dynamics of suspended monorail vehicles emphasize on the running performance and vehicle-bridge coupling vibration. The tilting characteristics and tilting stability caused by the crosswind are the unique dynamics problems of suspended monorail vehicles. The low-frequency noise of steel track beam caused by the vehicle-bridge coupling vibration remains a problem to be solved. The dynamics research on rubber-tired track vehicles has just begun in China, and the primary issue is improving the lateral ride quality of vehicles. The dynamics research of rubber-tired trams is focused on vehicle running performance and the relationship between guiding wheels and rails. Clarifying the mechanisms and influencing factors of guiding stability is difficult. As a new type of rail transit vehicle, virtual rail vehicles face many new dynamics problems, including tracking control, compatibility between mechanical structure and tracking control strategy, longitudinal force distributions, and distributed drive. Virtual rail vehicles may become a new hotspot in dynamics research of rail transit vehicles with tire running gears. 18 figs, 105 refs.More>
2021, 21(6): 8-30. doi: 10.19818/j.cnki.1671-1637.2021.06.002
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Summary of dynamics research on traction power transmission system of rail transits
CHEN Zai-gang, LIU Yu-qing, ZHOU Zi-wei, NING Jie-yu
Abstract: To promote the dynamic service performance of railway vehicle traction power transmission system and ensure the service reliability and safety, the current situation and development trend of dynamics research of traction power transmission system were analyzed, the analysis theory and research methods of gear dynamics, rolling bearing dynamics and electromechanical coupling effects were studied, and the future research focus and developing directions were discussed. Research results indicate that in the dynamics research of traction power transmission system, the lumped parameter method is mainly used for the coupling dynamics modeling, the dynamic excitations, such as gear time-varying meshing stiffness and wheel-rail excitation, are focused, and the coupling vibration characteristics between gear transmission and vehicle system are analyzed. In dynamics research of rolling bearing of railway vehicle, the dynamic characteristics of four rolling bearings, including axle box bearing, motor bearing, axle suspension bearing, and gearbox bearing, are analyzed. The research on locomotive traction motor's control strategy, harmonic torque suppression, and fault excitation mechanism and characteristics based on rotor dynamics and electromechanical coupling effect is gradually conducted. The studies of key components, such as traction motor, gear transmission, bearing, and other aspects are relatively independent, the dynamic coupling relationship among them has not been fully considered, and the dynamic interaction mechanism has not yet been revealed. Based on the previous research, the main research directions of the future are to further consider the impact of railway vehicle service environment, deeply study the dynamic characteristics, load identification, fatigue life, fault mechanism, fault diagnosis, performance evolution law and state monitoring of key parts of traction power transmission system, and explore the dynamic characteristics of new traction power transmission system. 4 tabs, 8 figs, 122 refs.More>
2021, 21(6): 31-49. doi: 10.19818/j.cnki.1671-1637.2021.06.003
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Research progress on intelligent control and maintenance technology of railway vehicle braking system
ZUO Jian-yong, DING Jing-xian
Abstract: Focusing on the microcomputer-controlled direct electro-pneumatic braking system commonly used in railway vehicle, the structural composition, working principle, and control principle of the braking system were introduced, the technical characteristics of the braking system were analyzed, and the technical development trend of the intelligent braking system was summarized and discussed. The research status and existing problems of the braking system were reviewed from the two aspects of intelligent control and intelligent maintenance. Research result shows that the braking system of the railway vehicle is a complex mechanic-electric-pneumatic(hydraulic) coupled dynamic time-varying nonlinear control system, and its service process and failure behavior have the characteristics of uncertainty, fuzziness, and small samples. In terms of braking system control technology, compared with the theoretical braking force control, the two braking control modes of speed adhesion control and deceleration control have improved control effects when dealing with external interference. Aiming at uncertain factors such as external interference, performance degradation, or latent faults in the control of the braking system, an autonomous intelligent control based on parameter identification and closed-loop feedback is the development trend of the intelligent control technology of the braking system. The core goal is to realize the self-adaptation of external interference, self-maintenance of performance degradation, and self-adjustment of latent faults. With respect to braking system maintenance technology, the operation and maintenance of the braking system mainly involve condition monitoring and fault diagnosis, and few studies exist on fault prognosis and condition assessment. Making full use of the service status information of the braking system and strengthening the research on the service behavior and evolution law of the braking system under the coupled effect of multi-source factors are the development trend of the intelligent maintenance technology of the braking system. Further research should be conducted on service performance consistency analysis and evaluation, sensor layout optimization, and remaining useful life prediction methods of the braking system. 6 figs, 90 refs.More>
2021, 21(6): 40-62. doi: 10.19818/j.cnki.1671-1637.2021.06.004
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Review on development and key technologies of permanent magnet synchronous traction system for rail transit
ZHANG Ji-min, SU Hui, REN Qiao, LI Wei, ZHOU He-chao
Abstract: To systematically analyze and summarize the technologies and development trend of permanent magnet traction system control, the advantages and disadvantages of using the permanent magnet synchronous motor (PMSM) as the traction motor in rail transit were introduced, and the applications of permanent magnet synchronous traction systems in at home and abroad were illustrated. The technologies those control high-power traction inverters at low switching frequencies and control permanent magnet synchronous traction motors were reviewed to analyze the design concepts and research methods of key technologies, such as the pulse width modulation strategies and field-weakening control. Investigations of recent research results were carried out to illustrate the advantages and limitations of various control methods, and the prospects and challenges of PMSM in the field of rail transit traction were predicted. Research results show that the built-in PMSMs are suitable for direct drive systems, and their small volumes and high efficiencies make them superior. A traction inverter usually adopts a hybrid pulse width modulation strategy. The asynchronous, synchronous, and single-pulse modulation are used in low frequency bands, middle frequency bands, and under square wave conditions, respectively. Improving the system's dynamic performance under special synchronous modulation and ensuring the smooth switching between different modulation methods are the most difficult aspects of traction inverter pulse width modulation technologies. The motor control strategy mainly focuses on three field-weakening control methods in high-speed operation areas, such as field-weakening control based on dual current regulators, field-weakening control with voltage vector angles, and field-weakening control under square wave conditions. Based on the previous research, future studies should include the sensorless technology, on-line fault diagnostics and prediction, and high-precision parameter identification of PMSMs, and the electromechanical coupling characteristics and short-circuit handling of traction drive systems are the key research directions in the future. 2 tabs, 16 figs, 68 refs.More>
2021, 21(6): 63-77. doi: 10.19818/j.cnki.1671-1637.2021.06.005
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Review on strength and environmental durability of composite adhesive structures
NA Jing-xin, WANG Guang-bin, ZHUANG Wei-min, MU Wen-long, XU Qian-hui
Abstract: In order to deepen the research on the environmental durability of composite adhesive structure, the research status at home and abroad was reviewed from the basic research of adhesives and the engineering oriented the application research of adhesive structure, and the influence of aging, fatigue and their coupling action on the strength of adhesive structure was discussed. The aging mechanism of single factor and multi-factor coupling was summarized. The prediction methods of the strength and fatigue life of adhesive structure were summarized based on the basic research, and the future research emphases and directions were prospected. Analysis results show that the effect of temperature and humidity on the mechanical properties of adhesive structure is most significant. Aging under the coupling of multiple factors is more destructive, curing shrinkage and difference in thermal expansion coefficient with temperature, and hydrolysis and plasticizing with humidity all lead to adhesive aging, and the load can accelerate the absorption of moisture and cause damage to the bonding interface, leading to the premature failure of the structure. There is a bidirectional coupling between aging and fatigue. The alternating load with time will not only affect the fatigue life of the bonded structure, but also accelerate the aging of the bonded structure, and the aging of the bonded structure in the long-term service process will reduce the fatigue performance of the structure. At present, there is still a lack of in-depth research on the aging mechanism under the coupled action of humid and thermal environment and alternating load. The cohesion model in engineering application has poor prediction effect on ductile adhesive and thick adhesive layer. Therefore, the accuracy of cohesion model should be further improved under complex stress state. The damage mechanics model should take into account the actual service condition of vehicle and add the influence of hygrothermal coupling factors to improve the service accuracy. The fatigue life prediction of the bonded structure is mostly based on semi-empirical models, and the prediction of joint fatigue behavior is limited to specific environmental condition. With the further development of adhesive technology, the effective evaluation of the service performance of the adhesive structure under complex stress states and the establishment of progressive damage model under the comprehensive effects of quasi-static, fatigue and environmental degradation will be the focus of future research. 1 tab, 8 figs, 117 refs.More>
2021, 21(6): 78-93. doi: 10.19818/j.cnki.1671-1637.2021.06.006
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Review on test methods of aerodynamic brake for high-speed train
TIAN Chun, WENG Jing-jing, WU Meng-ling, ZUO Jian-yong
Abstract: For the problem of no unified standards for aerodynamic braking test methods for high-speed trains, the relevant achievements and developments in aerodynamic brake were systematically reviewed in two aspects from aerodynamic characteristics and device functional characteristics. The effects of the shape, size, position, and spacing of wind panel on the aerodynamic characteristics and the effects of the structure, working principle, and configuration of the device on the functional characteristics were analyzed. The test requirements for the braking system performance were clarified. The impacts of aerodynamic braking on other equipments in the vehicle, operational stability of wheel-track/maglev train, and aerodynamic noise were analyzed. In addition, the test requirements for the operational impact of the aerodynamic brake were determined. The effects of object impact, average wind load, and pulsating wind load on the aerodynamic braking devices and the effect of the device installation on the structural strength of vehicle were analyzed. Furthermore, the test requirements for the structural strength of the aerodynamic brake were clarified. Analysis results show that with the application of a new composite wind panel, further detailed information regarding the bird striking test process should be recorded by using a high-speed camera. Aerodynamic load test is convenient to simulate and verify braking capacity, strength and aerodynamic noise of the device under different operating conditions. However, it is difficult to test the braking system and car body because of space and cost constraints. Field tests can verify the braking system performance, operational impact, and structural strength, but it is challenging to simulate all operating conditions, limited by weather conditions. Further investigations of the standard test methods of aerodynamic brake are required, ground wind loading test and field test simulation methods for determining different device locations, operating conditions, and fault states are explored, and the evaluation standard of test results is improved. 4 tabs, 11 figs, 55 refs.More>
2021, 21(6): 94-105. doi: 10.19818/j.cnki.1671-1637.2021.06.007
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Review on BIM technology in railway vehicle operation and maintenance
LEI Bin, WEN Yan, LI Jia-chen, CAO Zhen, PRAMOD KUMAR Gupta, MA Jian-sheng, LEI Dong-bo, LIU Yang
Abstract: Based on the relevant research at home and abroad, the research status of building information modelling (BIM) technology in the field of rail vehicle operation and maintenance in recent years were summarized, and the theoretical, technical and applied research results in this field were summarized. Research results show that the application research framework of BIM technology in railway vehicle operation and maintenance includes three levels: theory, technology, and application. Theoretical research focuses on the vehicle modeling, database establishment, operation, and maintenance. Technical research concentrates on the three-dimensional CAD, platform construction, digital management, and vehicle component monitoring. Application research is mainly reflected in the daily operation, maintenance, and value of trains. However, there are some deficiencies in previous results, owing to the late start of related research. In terms of theory, the modeling and database establishment of railway vehicles are imprecise, and the integrity of the life cycle operation and maintenance is insufficient. In terms of technology, model sharing, software collaboration, information management, and vehicle monitoring require further investigation and improvement. For applications, researches on the visualization, cost management, and software development of railway vehicle operation and maintenance need to be specific, specialized, and refined to all levels. Collaborative design and data standardization among BIM multiple disciplines should be strengthened in future research. Integration with new information technology should be achieved, an intelligent and comprehensive management platform should be built, and a deep secondary development of BIM software will be realized. A complete BIM railway vehicle operation and maintenance system should be developed by combining the theory, technology, and application. The BIM-based visual management system should be improved.Moreover, the integrated management of all service objects, data, and business functions in railway vehicle operation and maintenance should be strengthened, and the efficiencies of railway vehicle operation and maintenance need to be improved. A research foundation and theoretical basis for the railway vehicle operation and maintenance are provided to ensure the safe operation of railway vehicles. 2 tabs, 16 figs, 76 refs.More>
2021, 21(6): 106-123. doi: 10.19818/j.cnki.1671-1637.2021.06.008
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Road and railway engineering
Design method of rail grinding profile in frog area of high-speed railway
LIN Feng-tao, WU Tao, YANG Yang, PANG Hua-fei, ZOU Liang, WENG Tao-tao, WANG Song-tao, DENG Zhuo-xin
Abstract: For the critical section of a rail in the frog area with top widths of 20, 35 and 50 mm of the core rail as the research object, the rail profile reconstruction method was developed to analyze the frog area based on the NURBS curve theory. Several types of data points on the rail profile of the key section were set as design variables, and the reduction of the removal amount of grinding material and derailment coefficient were taken as the objective, and the geometric characteristics of the rail profile and the rolling contact fatigue reduction of the rail were used as constraints, the economic grinding profile of the rail in the frog area of No.18 turnout was designed. The wheel-rail contact finite element model and vehicle-track coupling dynamic model were established, and the wheel-rail contact stresses and dynamics indexes were calculated. Analysis results show that the optimized grinding profile contact points are evenly distributed and have good wheel-rail contact geometric characteristics. The removal amount of the rail grinding material decreases by 17.2 % in section 2. The Mises stresses of each section decrease by 8.7%, 8.3%, and 11.5%, respectively, and the wheel-rail contact stresses decrease by 12.9%, 15.8%, and 18.0%, respectively. When the train reversely passing turnout branch, wheel-rail lateral force and lateral vibration acceleration of the car body decrease by 10.3% and 15.6%, respectively, the derailment coefficient and the wheel-load reduction rate decrease by 8.1% and 10.6%, respectively, and the fatigue index decreases by 12.2%. Therefore the optimized profile not only ensures train operation safety, but also improves train operation stability and the service life of the rail in frog areas. 5 tabs, 14 figs, 26 refs.More>
2021, 21(6): 124-135. doi: 10.19818/j.cnki.1671-1637.2021.06.009
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Wear detection method of CL60 railway wheel and U75V rail steel based on nonlinear ultrasound
CAI Zhi-chao, CHEN Lan, LI Hao, QIN Tao, SHEN Ming-xue
Abstract: With an aim to resolve the difficulty of the characterization of the change process of early wheel/rail rolling wear by non-destructive measurement, a nonlinear ultrasonic technology was proposed to detect and evaluate CL60 wheel and U75V rail specimens with different wear degrees. The Murnaghan model was established based on the surface wear characteristics of wheel/rail specimens. A finite element simulation of nonlinear ultrasonic was used to simulate different degrees of friction damage based on the plastic deformation layer thickness. The change law of the relative nonlinear coefficient and its causes in the process of wheel/rail friction damage, were analyzed. Experimental results indicate that the early wear of wheel/rail can result in the formation of a plastic deformation layer on the material surface, and with the aggravation of plastic deformation, the material damage appears mainly through microcracks. With an increase in the wheel angular acceleration, the relative sliding time between wheel and rail is shorter, the plastic deformation layer is thinner, and the CL60 wheel wear is more serious than the U75V rail wear. When the wheel angular accelerations for the CL60 wheel specimens are 10, 250, and 1 500 r·min-2, respectively, the corresponding relative nonlinear coefficients are 12.19, 8.43, and 5.68, respectively. When the wheel angular accelerations for the U75V rail specimens are 10, 250, and 1 500 r·min-2, respectively, the corresponding relative nonlinear coefficients are 7.57, 6.09, and 5.04, respectively. Compared with the CL60 wheel specimens, the nonlinear coefficient of the U75V rail specimens changes more slowly. Therefore, the relative nonlinear coefficient and plastic deformation layer thickness are positively correlated, and the nonlinear effect caused by microcracks is stronger than that of the plastic deformation layer, resulting in a high increase in the relative nonlinear coefficient. Thus, the wear stage of a material can be determined by the change in the relative nonlinear coefficient of the material. 2 tabs, 15 figs, 30 refs.More>
2021, 21(6): 136-146. doi: 10.19818/j.cnki.1671-1637.2021.06.010
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Road properties of completely weathered phyllite composite improved soil
ZHAO Xiu-shao, ZHAO Lin-hao, WANG Zi-yao, FU Zhi-tao, GENG Da-xin, RAO jiang-long, CHEN Zi-xi
Abstract: In order to make full use of completely weathered phyllite as subgrade filler, the combined improvement schemes were designed, in which red clay blending ratio was 0, 20%, 40%, 60%, and 100%, respectively, and cement content is 0, 3%, and 5%, respectively. The tests of boundary moisture content, shear strength and unconfined compression of the improved soil were carried out, and the road performances of the improved soil were analyzed. The test results of the improved soil show that the liquid limit of the improved soil is lower than 40% when cement content is 3% or 5%, and all improved soils comply with the liquid limit control requirement of the design of railway earth structure (less than 40%). The cohesion of the improved soil increases with the increase of red clay blending ratio and cement content. The internal friction angle of the improved soil increases first and then decreases with the increase of red clay blending ratio, and increases with the increase of cement content. But both shear indexes increase slightly when cement content is more than 3%. The calculation results of ultimate bearing capacity of the improved completely weathered phyllite subgrade show that the ultimate bearing capacity of the subgrade with 5% cement is only 725.3 kPa, and the value of the subgrade with 40% red clay is 2 198.3 kPa, being 2.34 and 7.10 times that of the completely weathered phyllite subgrade, respectively. Therefore, the improvement effect of red clay is better than that of cement. Analysis results show that the rational mixing scheme is that red clay blending ratio is 40% and cement content is 3%. Under the scheme, when the curing age is 28 days, the calculated value of the ultimate bearing capacity of the improved completely weathered phyllite subgrade is 4 247.7 kPa, and the liquid limit of the improved completely weathered phyllite is 32.7%. Microscopic mechanism analysis results show that red clay particles are smaller than fully weathered phyllite particles. When red clay blending ratio is greater than 40%, red clay can surround the point-to-point contact of phyllite particles, and increase the contact points and contact area, which greatly improves the ultimate bearing capacity of the improved soil subgrade. The test results of unconfined compressive strength show that the 7-day unconfined compressive strength of the improved soil in the optimized scheme is 487.25 kPa, which meets the requirement of the design of railway earth structure. 2 tabs, 17 figs, 30 refs.More>
2021, 21(6): 147-159. doi: 10.19818/j.cnki.1671-1637.2021.06.011
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Transportation vehicle engineering
Sensitivity analysis of high-speed train wheel vibration influenced by vehicle-track coupling
XIAO Qian, CHENG Yu-qi, LUO Jia-wen, ZHOU Sheng-tong, ZHOU Qian-zhe, CAO Tao-ying
Abstract: A random simulation model for one trailer of the CRH2 EMU was established based on the multi-body dynamics software UM under considering the randomness of the primary and secondary suspension parameters of the vehicle and track parameters. The optimal Latin hypercube experimental design method was used to extract the random samples of the parameters, the multi-objective optimization software iSight was used to select the random samples, and the UM was used to analyze the samples. Under the limitation of limited experimental design samples and simulation data, a polynomial chaos expansion surrogate model was built by combining the minimum angle regression, low-order interactive truncation and leave-one-out cross-validation to achieve the polynomial chaos expansion in order to reach the best approximate accuracy. The Sobol method was used to analyze the global sensitivity of polynomial chaos expansion surrogate model to study the influence of the random coupling action of vehicle and track parameters on the wheel vibration characteristics under the straight line and curve working conditions. The key factors were studied and the coupling action of multi-parameters was considered. The results show that the polynomial chaos expansion method can fit an accurate surrogate model based on the existing samples and calculate the Sobol sensitivity coefficient with an average error (less than 3%) so as to analyze the effect of the coupling of various parameterss on the wheel vibration efficiently and quantitatively. The vehicle parameters, such as the lateral stiffness of the boom node, the vertical stiffness of the primary spring, the lateral stiffness of the primary spring and the damping of the secondary transverse shock absorber, have an obvious contribution to the variance of the wheel vibration response. The track parameters, such as the lateral and vertical stiffnesses of the track, have a large contribution to the variance of the wheel vibration response. There are obvious interaction effects between the various parameters. 2 tabs, 16 figs, 31 refs.More>
2021, 21(6): 160-169. doi: 10.19818/j.cnki.1671-1637.2021.06.012
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Effect of axle box rotary arm node performance on wheel-rail coupling vibration for high-speed EMUs
HOU Mao-rui, HU Xiao-yi, GUO Tao, LUO Jun, FAN Ling-ju
Abstract: To analyze the effect of axle box rotary arm node performance on the wheel-rail coupling vibration under wheel-rail short-wave irregularities such as rail corrugation and wheel polygon, the comprehensive research was conducted from three aspects, such as simulation calculation, field test, and bench test. A dynamics simulation model of a vehicle-track rigid-flexible coupling system was established to analyze the effects of rail corrugation and wheel polygon on the wheel-rail coupling vibration. The effects of new and old axle box rotary arm nodes on the axle box vibration responses under the rail corrugation and the bogie vibration responses under the high-order polygon were tested using a rolling test bench along the Wuhan-Guangzhou High-Speed Railway Line. 10 million fatigue durability tests were conducted on the type A and B axle box rotary arm nodes that have been in service for 1.2 million km, to demonstrate the fatigue reliability safety margins of the nodes. Research results show that the vibration accelerations of rails and axle box as well as the wheel-rail vertical force effectively remain unchanged with an increase in the radial stiffness of the axle box rotary arm node from 40 MN·m-1 to 200 MN·m-1, when the rail wavelength is 120 mm, the wheel polygon is of the 20th order, and the wave depths of rail corrugation and wheel polygon are both 0.04 mm. The change in the axle box rotary arm node stiffness will not significantly influence the wheel-rail coupling vibration responses under short-wave excitations such as rail corrugation and wheel polygon. With an increase in the number of fatigue test, the radial and axial stiffnesses of axle box rotary arm nodes decrease gradually. After 10 million fatigue durability tests, the appearances of the decommissioned axle box rotary arm nodes remain basically unchanged. Although the core shaft and rubber adhesive parts show slight tackle and cracking, the tackle and cracking depths are not more than 5 mm. The rubber body itself shows no cracks. In general, the performance still meets the General Technical Requirements for Rolling Stock Rubber to Metal Parts (TB/T 2843—2015). 3 tabs, 14 figs, 30 refs.More>
2021, 21(6): 170-180. doi: 10.19818/j.cnki.1671-1637.2021.06.013
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Influence of double-track embankment height on aerodynamic performance of high-speed train under crosswind
ZHU Hai-yan, WANG Yu-hao, ZHU Zhi-he, YUAN Yao, ZENG Jing, XIAO Qian
Abstract: Models for embankments with different heights and a specific type of electric multiple units (EMUs) with three vehicles, including a locomotive, an ordinary vehicle, and a caboose, were established with the help of Creo and Fluent to simulate the operation of a train at the speeds of 300 and 350 km·h-1 under the crosswind speeds of 17.10, 20.70, 24.40 and 28.40 m·s-1, respectively. The obtained aerodynamic loads of the high-speed train were subsequently applied to the dynamics model established using the Simpack to calculate the dynamics performance parameters. The pressure distributions, airflow field structures, aerodynamic forces and wind-induced safeties of the high-speed train running on the leeward side of a double-track were analyzed under different embankment heights in a crosswind environment. Considerable attention was also given to the safety of the locomotive under different operating speeds and crosswind speeds. Analysis results indicate that for the same vehicle speed and crosswind environment, as the embankment height increases, the lateral force acting on the train increases overall, and the caboose experiences an opposite lateral force under crosswinds. The locomotive is subjected to the largest lateral force, while the lift increases continuously. The ordinary vehicle is subjected to a relatively large lift, and the caboose is subjected to the greatest resistance. The pressure peak of the train in a crosswind environment is at the nose tip of the locomotive and offset to the windward side. The airflow field structure remains basically the same regardless of the embankment height. There are obvious eddy currents on the leeward side of the locomotive and the bottom bogie. However, the eddy currents at the caboose are observed on the windward side. They may be the main factor causing an opposite force acting on the caboose. As the embankment height and crosswind speed increase, the derailment coefficient, wheel axle lateral force, wheel rail vertical force and wheel load reduction rate also increase, and the wheel rail vertical force is always within the safety limit. To ensure the safety of the train under the crosswind speeds of 24.40 and 28.40 m·s-1, the speed of the high-speed train should be lower than 350 and 300 km·h-1, respectively. 2 tabs, 21 figs, 32 refs.More>
2021, 21(6): 181-193. doi: 10.19818/j.cnki.1671-1637.2021.06.014
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Dynamics performance of new type of fully automatic track inspection vehicle
CHANG Chao, LING Liang, SUN Yu, ZHAI Wan-ming, WANG Kai-yun, WANG Gui-dong
Abstract: Dynamics numerical simulations of a track inspection vehicle were performed to precisely evaluate the dynamics performance of a new type of fully automatic intelligent track inspection vehicle. The nonelliptical multipoint contact Kik-Piotrowski algorithm was adopted for the wheel-rail contact. During the vehicle system modeling process, the factors such as the nonlinear suspension force elements and geometric nonlinear characteristics of the wheel-rail contact were considered, and the influence of vehicle-mounted equipment vibration was analyzed. For the unique structure of the wheel tread surface wrapped with high-hardness polyurethane, the finite element software ABAQUS was used to establish the wheel-rail local contact model. The Mooney-Rivlin rubber model was utilized to simulate the distinct properties of polyurethane, and the wheel-rail equivalent contact stiffness was calculated. The relevant parameters in the Kik-Piotrowski algorithm were corrected based on the finite element calculation results. The coupled vehicle-track rigid-flexible model was established using the Craig-Bampton modal synthesis method and the multibody dynamics software UM. To verify the accuracy of the simulation model, the real vehicle dynamics test was carried out. The vibration responses of the inspection vehicle under the working conditions of the straight line and 300 m small-radius curve at running speed of 10-30 km·h-1 were analyzed. Research results show that when the vehicle runs normally, the vertical maximum acceleration of the middle-vision module exceeds that of the left-vision module. Moreover, the lateral maximum acceleration is lower than that of the left-vision module, and the maximum acceleration of the frame exceeds the value of the vision module. The middle part of the frame is prone to vertical bending and deformation because of the rubber cushion at the installation position of the vision module. The track inspection vehicle runs satisfactorily along a straight line and the 300 m small-radius section. When the vehicle runs at 30 km·h-1 on the 300 m small-radius curve section, the maximum wheel-load reduction rate can reach 0.92, and the vibration response of the frame is relatively large. The inspection speed in the curve section should be controlled at approximately 20 km·h-1 to ensure the safety of vehicle-mounted equipment and prevent the vehicle derailment. 5 tabs, 24 figs, 31 refs.More>
2021, 21(6): 194-208. doi: 10.19818/j.cnki.1671-1637.2021.06.015
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Numerical simulation of bearing capacity of carbody for high-speed train subjected to longitudinal impact
QIN Rui-xian, GAO Feng, WANG Tie-cheng, CHEN Bing-zhi
Abstract: The static tension and dynamic compression experiments of the aluminum alloy 6005A-T6 and 6082A-T6 used in the carbody of high-speed train were carried out, their strain rate effects within the strain rate range of 0.001-2 500 s-1 were identified, and the corresponding Johnson-Cook constitutive model was established. An explicit dynamic analysis model for the typical vehicle of high-speed train was constructed, the process of the carbody impacted by a rigid wall was simulated, and the influence of coupler stable force, impact speed, and loading condition on the bearing capacity of the carbody was investigated. The deformation evolution of the carbodies 1 and 2 for the high-speed train subjected to the impact load was analyzed, the bearing capacity of the carbody was determined by finding the critical point of stress change, and the crashworthiness of the train configured with a higher energy mode was analyzed for the performance verification. Research results indicate that the strain rate sensitivity coefficients of the 6005A-T6 and 6082A-T6 aluminum alloys are 2.9×10-3and 8.5×10-3 within the strain rate range of 0.001-2 500 s-1, respectively, so their strain rate effects are not obvious. Under the axial dynamic impact load, the strengthening effect of the strain rate has no obvious effect on the bearing capacity of the aluminum alloy carbody structure, and the inertial effect is the main reason that its bearing capacity is higher than the static limit. When the longitudinal impact load is transmitted at the coupler position, the dynamic bearing capacity limitations of the carbodies 1 and 2 are obviously higher than the maximum allowable value under the static compression. The bearing capacity of the carbody structure under the impact load can provide an upper bound for the platform force of the energy absorbing element used in the interfacial energy distribution problem of the high-speed train collision. It is recommended to enlarge the mechanical parameters' design domains of the energy absorbing components by appropriately increasing the allowable load, meeting the passive safety performance of the train considering more severe requirements. 1 tab, 22 figs, 31 refs.More>
2021, 21(6): 209-224. doi: 10.19818/j.cnki.1671-1637.2021.06.016
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Lateral load characteristics of EMUs axle box based on measured data
WANG Bin-jie, ZHAO Xin-yuan, FAN Jun, LIU Zhi-ming, LI Qiang, WANG Wen-jing
Abstract: A high-precision testing method for axle box lateral loads was investigated. The calibrated axle box was installed on the operating vehicle, and the load-time history was obtained. Combined with the operation state of the vehicle, the load characteristics under typical service conditions of the high-speed line were analyzed. The constant amplitude load spectra corresponding to the conditions of entering and exiting station, low-speed and high-speed operations were compiled. Research results show that the main factors influencing the lateral load of the axle box are vehicle running speed, curve radius, turnouts, and track irregularity. During the service, a low load dominant frequency of 2 Hz exists, and it is relatively fixed and independent of the vehicle running speed. For the frequencies higher than 5 Hz, the load dominant frequency is directly related to the running speed of the train. The variation amplitude of the axle box load on the inner rail side is slightly larger than that on the outer rail side when passing through a curve. The average load and the maximum load amplitude increase with the increasing running speed of the train. As the curve radius increases, the mean value of the lateral load gradually approaches zero, and the maximum load amplitude decreases gradually. Passing through the turnouts during entering and exiting the station will cause a fluctuation of lateral load for approximately 10 s, including the short-time impact load. The lateral track irregularity causes a couple of large fluctuations in the lateral axle box load when passing through the corresponding section. Both the fluctuation period and peak value decreases with the increasing running speed. The entrance to and exit from the tunnel have no significant influence on the lateral load. For the load spectrum results obtained under different operating conditions, the load amplitudes during entering and exiting the station are the largest, and the count of the corresponding cycles is small.The load amplitude during low-speed running is the second largest, and the count of the corresponding cycles accounts for approximately 1/3 of the total. The load amplitude during high-speed running is the smallest, and the corresponding cycle count accounts for more than 60%. 2 tabs, 26 figs, 26 refs.More>
2021, 21(6): 225-236. doi: 10.19818/j.cnki.1671-1637.2021.06.017
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Rolling bearing fault diagnosis method based on TQWT and sparse representation
NIU Yi-jie, LI Hua, DENG Wu, FEI Ji-you, SUN Ya-li, LIU Zhi-bo
Abstract: Based on the sparse representation theory, a new method of rolling bearing fault diagnosis was proposed using the tunable-Q wavelet transform (TQWT). The characteristics of the original vibration signals and early fault signals containing early fault components were analyzed, and the applications of the sparse representation model to solve the problem of fault feature extraction and fault type recognition were studied. The original signal was transformed into a set of sub-band wavelet coefficients using the TQWT. The effectiveness of extracting sparse wavelet coefficients using an iterative threshold shrinkage algorithm and the sensitivity of spectral kurtosis to fault impact signals were studied. By calculating the spectral kurtosis of each sub-band signal component and selecting the sub-band wavelet coefficient that contains obvious fault information, a fault feature extraction method for the sparse fault signal component was established. Using the sparse representation classification model of extracted fault signals, the method of rolling bearing fault-type recognition based on sparse representation was realized. Experimental results indicate that the proposed fault feature extraction method has a significant effect in eliminating interference components in the Case Western Reserve University dataset. The average diagnostic accuracy for the four types of data is 99.83%. The average diagnostic accuracy for the 10 types of data is 97.73%. Compared with the TQWT and iterative threshold shrinkage algorithm for fault feature extraction, the fault diagnosis accuracy of the proposed method improves by 11.60%, and the running time reduces by 8%. For the vibration dataset collected by the QPZZ-Ⅱ rotating machinery platform, the average diagnostic accuracy of the proposed method for the four types of data is 100%. Compared with the traditional wavelet denoising method, the accuracy of the proposed method improves by 35.67%, and the running time reduces by 7.25%. Therefore, the proposed method can effectively solve the problem of rolling-bearing fault diagnosis. 7 tabs, 7 figs, 30 refs.More>
2021, 21(6): 237-246. doi: 10.19818/j.cnki.1671-1637.2021.06.018
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Locomotive bearing fault diagnosis based on deep time-frequency features
ZHANG Long, ZHEN Can-zhuang, XIONG Guo-liang, WANG Chao-bing, XU Tian-peng, TU Wen-bing
Abstract: To address the problems such as the unsatisfactory fault feature extraction and low diagnostic accuracy of existing locomotive bearing diagnosis methods, a new method for diagnosing locomotive bearing faults was developed based on the deep time-frequency features. Dual-channel one-dimensional and two-dimensional convolutional neural networks (CNNs) were separately adopted to extract the deep features from the input one-dimensional original and two-dimensional time-frequency signals extracted by the continuous wavelet transform (CWT). A one-dimensional CNN was employed for the upper channel such that the input one-dimensional original signals could effectively reflect the global characteristics of the signals in the time domain. A two-dimensional CNN was applied for the lower channel such that the input two-dimensional time-frequency domain signals could reflect the subtle local changes in the signals from multiple angles. The upper- and lower-channel features were automatically fused in the fusion layer into a new deep time-frequency feature. Then, the extracted deep fusion time-frequency features were classified and identified by a normalized exponential function. Finally, seven types of locomotive bearing data measured in a locomotive depot were analyzed to verify the practical engineering application value of this method. Research results indicate that the average diagnosis accuracies of the proposed method for the seven types of locomotive bearing faults are as high as 100%. Compared with the one-dimensional CNN model, two-dimensional CNN model, and support vector machine (SVM) model, the average diagnosis accuracy of the proposed model increases by 0.7%, 1.9%, and 2.2%, respectively. The distribution intervals of each fault type in the deep time-frequency features are regular and orderly, and the intra-class spacing is very small. Conversely, the features extracted by the single one-dimensional and two-dimensional CNN models exhibit irregular distribution intervals for all fault types, and the intra-class spacing is large. This verifies the superiority of the proposed model in extracting deep features. Therefore, it is an effective model to address the issues in the locomotive bearing fault diagnosis. 4 tabs, 17 figs, 30 refs.More>
2021, 21(6): 247-258. doi: 10.19818/j.cnki.1671-1637.2021.06.019
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Wheel polygon state recognition method based on improved EEMD-WVD joint time-frequency analysis
SONG Ying, LIANG Lei, WANG Yue, SHI Wen-jie
Abstract: To accurately identify wheel polygon state and wheel abrasion amplitude of high-speed EMUs, a random vibration signal's joint time-frequency analysis method combing improved ensemble empirical mode decomposition (EEMD) and Wigner-Ville distribution (WVD) was presented. The correlation coefficient method and spectrum analysis were used to evaluate and filter the EEMD decomposition variables of the axle box vibration acceleration signal. Subsequently, the WVD of each intrinsic mode component was calculated for maintaining a high time-frequency resolution and effectively curbing cross-interference items. The method was applied to analyze the vibration acceleration signals of axle box caused by periodic and measured random wheel polygons. Research results indicate that the wheel polygon type can be recognized using the dominant frequency of the two-dimensional time-frequency spectrum of EEMD-WVD, and the abrasion amplitude can be evaluated using the energy amplitude distribution of the three-dimensional time-frequency-energy spectrum of EEMD-WVD, with the maximum error of 0.3%. Compared with the time-frequency analytical results by the short-time Fourier transform, wavelet transforms, and WVD method, the improved EEMD-WVD joint time-frequency analysis method dose not require parametric variation, has strong adaptability, retains the characteristics of WVD high time-frequency resolution, and effectively curbs both the modal aliasing phenomenon caused by EEMD decomposition and the cross-interference items caused by WVD distribution. The current study verifies the effectiveness and advantages of the proposed joint time-frequency analysis method, providing a novel technical approach for wheel polygon recognition and the evaluation of high-speed EMUs. 1 tab, 11 figs, 30 refs.More>
2021, 21(6): 259-268. doi: 10.19818/j.cnki.1671-1637.2021.06.020
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Remaining useful life prediction for equipment based on LSTM encoder-decoder method
ZHAO Zhi-hong, LI Qing, LI Le-hao, ZHAO Jing-jiao
Abstract: A remaining useful life (RUL) prediction model of mechanical equipment was established based on the long short-term memory (LSTM) encoder-decoder method. The acquired sensor data were preprocessed. The data sequence was coded using the LSTM encoder method. An intermediate representation of the equipment status information was obtained. The characteristic information of the equipment status was obtained in the intermediate representation of the equipment status information. The intermediate representation information was decoded using the LSTM decoder method, and the RUL was predicted using the decoded information. RUL prediction experiments of the LSTM encoder-decoder method on open C-MAPSS data sets were performed. The LSTM encoder-decoder method was compared with the LSTM method, deep-LSTM (D-LSTM) method, and other methods. The effect of the sliding window size on RUL prediction results was evaluated. Research results show that scoring function values and root mean square error (RMSE) evaluation indexes of the RUL prediction results of the LSTM encoder-decoder method are more accurate than those of the LSTM method and D-LSTM method. In the FD001 subset, the RMSEs of the LSTM encoder-decoder method, LSTM method, and D-LSTM method are 11, 12, and 16, respectively. When the sliding window size is 30, the scoring function values corresponding to the FD001-FD004 subsets of the LSTM encoder-decoder method are 164, 3 012, 372, and 4 800, and the corresponding RMSEs are 11, 20, 14, and 22. When the sliding window size increases to 40, the respective scoring function values are 305, 1 220, 408, and 4 828, and the corresponding RMSEs are 14, 16, 15, and 19. Therefore, the proposed method based on the LSTM encoder-decoder effectively predicts the RUL of mechanical equipment, and the sliding window size significantly influences the RUL prediction results. 4 tabs, 6 figs, 32 refs.More>
2021, 21(6): 269-277. doi: 10.19818/j.cnki.1671-1637.2021.06.021
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Fatigue life evaluation of bogie frame based on kernel density extrapolation for stress spectrum
WANG Qiu-shi, ZHOU Jin-song, GONG Dao, WANG Teng-fei, ZHANG Zhan-fei, SUN Yu, CHEN jiang-xue, YOU Tai-wen
Abstract: A fatigue life evaluation method based on the multi-sample kernel density stress spectrum extrapolation was proposed. The determination of optimal bandwidth and kernel function in the kernel density estimation was studied. The grey correlation analysis method was proposed to quantitatively evaluate and verify the extrapolation optimization of stress spectrum. The relationship between the relative error of fatigue life evaluation and the extrapolation multiple was discussed. To verify the correctness and feasibility of the method, taking a measurement point near the weld of the positioning mounting seat of a bogie frame at the research object, three sets of dynamic stress test data were selected to conduct the multi-sample knernel density stress spectrum extrapolation and fatigue evaluation when the wheel was in the initial, middle, and final stages, respectively. Research results show that the probability density function based on the minimum asymptotic integral mean square error has a goodness of fit. Among the four types of studied kernel functions, the correlation based on the Epanechekov kernel function is the best, and the correlation coefficient is 0.99 and 0.01%-0.12% higher than the coefficients of the other three kernel functions. The consistency based on the Circular kernel function is the best, and the grey correlation degree is 0.592 0 and 0.17%-0.32% higher than the degrees of the other three kernel functions. The assessment fatigue life based on 10-time multi-sample kernel density stress spectrum extrapolation reduces by 1.15% compared with that based on the linear extrapolation. When the stress spectrum is extrapolated to the whole life cycle, the safe operation mileage evaluated based on the kernel density extrapolation reduces by 6.45%. Therefore, the fatigue life evaluation based on the extrapolation of kernel density stress spectrum is safer, and can ensure the safe service of the vehicle structure. 4 tabs, 12 figs, 31 refs.More>
2021, 21(6): 278-288. doi: 10.19818/j.cnki.1671-1637.2021.06.022
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Operation performance prediction of C80 railway freight car braking device
LU Bi-hong, XU Chao, GUO Hong-yuan
Abstract: Based on a combination of field tests and multi-body dynamics simulations, a set of modeling and model verification methods reflecting the actual contact state of a C80 unit braking device were developed, the RecurDyn simulation analysis platform was used, and the operation performance of the braking device was analyzed and predicted using the simulation analysis and experimental methods. Research results show that the contact stress on the side near the flange of brake-shoe is high, and the stresses on the lower parts of brake-shoes 2 and 3 are high, causing a significant eccentric wear of the brake-shoe. High stress exists at the braking beam-column connection, and the maximum instantaneous contact stresses of the connection parts of the floating and fixed levers are 137 and 127 MPa, respectively. The forces on pin shafts No.12 and 15 in the C80 unit braking device are the highest. When applying brakes for empty and heavy vehicles, the combined forces on the pin shafts exceed 10 and 50 kN, respectively. During on-site maintenance, the inspection of floating lever, middle tie rod, fixed lever, braking beam-column, vertical braking lever, and their connection parts should be conducted. During dynamic operation, the braking beam moves in the reverse direction toward the vehicle, causing abnormal intermittent collision and contact between the brake-shoe and the wheel. The contact force of the wheel shoe increases with the increasing running speed, resulting in the abnormal wear of the wheel and the eccentric wear of the brake-shoe. This research proposes a new technique for predicting the operation rule and performance of railway freight car braking devices and other complex mechanisms. The proposed method can be applied in the formulation and design improvement of C80 and other braking devices of railway freight cars. 2 tabs, 13 figs, 29 refs.More>
2021, 21(6): 289-297. doi: 10.19818/j.cnki.1671-1637.2021.06.023
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Semi-active control of metro vehicle based on flexible multi-body dynamics
CHEN Zhao-wei, ZHU Guo
Abstract: To realize more accurate evaluation and more effective optimization of the running performance of metro vehicles, based on the finite element theory and substructure theory, the flexible dynamics models of critical parts, such as car body and bogie frame, were established. Based on the algorithm of semi-active skyhook control and the theory of flexible multi-body dynamics, the rigid-flexible coupling dynamics model of a metro vehicle was established considering a semi-active control suspension.The effect of random track irregularity was considered, and the influences of semi-active control suspension and structural flexibility on the running stability and ride comfort of metro vehicles were investigated. Analysis results show that compared to the traditional suspension device, the semi-active skyhook control can significantly reduce the vibration acceleration of the vehicle and decrease its variation trend, suppressing the low-frequency vibration of the vehicle obviously. Based on the parameters adopted in this study, the semi-active skyhook control decreases the vertical Sperling index and root mean square (RMS) of vertical vibration acceleration on the straight segment by 26.8% and 7.5%, respectively, and 8.8% and 4.9% for lateral vibration acceleation, respectively. The semi-active skyhook control decreases the values of vertical vibration acceleration on the curve segment by 25.1% and 5.7%, respectively, and 15.6% and 8.3% for lateral vibration acceleration, respectively. Thus, the ride comfort and running stability of the vehicle improve significantly. Under considering the structural flexibility, the vertical Sperling index and RMS of vertical vibration acceleration of the vehicle increase by 4.3% and 6.8%, respectively, compared to those under no considering the structural flexibility, and 3.0% and 3.4% for lateral vibration acceleration, respectively. Thus, the structural flexibilities of the car body and frame significantly influence the dynamic characteristics of the vehicle and should be considered in calculating and evaluating the vehicle running stability and ride comfort. 5 tabs, 21 figs, 29 refs.More>
2021, 21(6): 298-309. doi: 10.19818/j.cnki.1671-1637.2021.06.024
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Mechanism and countermeasures of coupler separation of middle locomotive for long heavy-haul trains
LING Liang, WU Jian, ZHOU Kun, ZHOU Kang, WANG Kai-yun, ZHAI Wan-ming
Abstract: A three-dimensional dynamics model of the middle locomotive-wagon system for a 20 000-ton heavy-haul train was established based on the multi-body dynamics theory. The effects of the key factors such as the initial height difference between the connected coupler and the friction coefficient of the coupler head on the coupler separation were analyzed. The formation mechanism of the middle locomotive-wagon connected coupler separation under air brake release and traction conditions was analyzed, and the corresponding countermeasures were proposed. Research results indicate that the connected couplers can remain stable under the compressive force. However, during the changing process of the coupler and draft gear system from the compressive state to the pulling state, the electric braking/traction force of the locomotive will cause a certain vertical relative movement between the couplers. After the coupler force changes to the pulling state, the self-locking force between the couplers is insufficient owing to the large initial coupler height difference and the small friction coefficient of the coupler head, causing a rapid increase in the vertical relative displacement between the couplers. If the limit of the vertical rotation angle of the locomotive coupler is too large, the vertical relative displacement between the couplers will increase dramatically with the increase in the pulling force (no less than 300 mm), thereby eventually leading to the coupler separation. When the friction coefficient of the coupler head and the limit of the vertical relative displacement of the locomotive coupler are 0.08 and 8°, respectively, the minimum initial height difference of the connected couplers and the applied ratio of the braking force inducing coupler separation under the air braking release condition are 40 mm and 40%, respectively, whereas the minimum initial height difference of the connected couplers and the applied ratio of the traction force induced to coupler separation under the traction condition are 30 mm and 50%, respectively. Meanwhile, when the initial height difference of the connected couplers is 50 mm and the applied ratio of the electric braking force is 70%, the minimum friction coefficient of the coupler head and the limit of the vertical rotation angle of the locomotive coupler resulting in coupler separation under the air braking release condition are 0.09 and 6°, respectively. Furthermore, when the initial height difference of the connected couplers is 50 mm and the applied ratio of the electric traction force is 100%, the minimum friction coefficient of the coupler head and the limit of the vertical rotation angle of the locomotive coupler resulting in coupler separation under the traction condition are 0.10 and 7°, respectively. Hence, to prevent coupler separation accidents, it is necessary to strictly limit the initial height difference between the connected couplers, appropriately reduce the electric braking force/traction of the locomotive, increase the friction coefficient of the coupler head, and limit the vertical free angle of the locomotive coupler. 9 figs, 30 refs.More>
2021, 21(6): 310-320. doi: 10.19818/j.cnki.1671-1637.2021.06.025
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Optimization design on suspension parameters of equipment mounted under car body via analytical target cascading method
HE Xiao-long, CHEN Jie, E Shi-ju, TANG Da-yong, ZHANG Li-min
Abstract: To improve the running comfort in high-speed trains and reduce the vibration of the equipment mounted under the car body, a vertical dynamics model was constructed for the vehicle-equipment system, and a frequency response function related to the vibration acceleration of vehicle system was derived. The root-mean-square of vibration acceleration of the equipment mounted under the car body was calculated using a function for the track irregularity excitation spectrum. The vertical running comfort indices were calculated for the car body reference points by applying a human comfort weighting filter function. The analytical target cascading (ATC) method was used to hierarchically decompose the vibration indices of vehicle-equipment system to construct a two-level index decomposition mathematical model for the vehicle-equipment system. An exponential penalty function strategy was used to coordinate the interlevel coupling problems in the vibration indices. A multi-objective optimization method was developed to maximize the running comfort of vehicle and minimize the vibration acceleration of equipment mounted under the car body, and an optimization model for the stiffness and damping of the equipment mounted under the car body was constructed. The efficacy of the ATC method for the parameters optimization in complex vehicle systems was investigated via a comparison with the design method of dynamic vibration absorber (DVA). Analysis results show that compared with the design method of DVA, during the operation at 300 km·h-1, the optimization by the ATC method improves the running comfort at the vehicle center by 8.5% and decreases the equipment vibration level by approximately 20%. Over the full range of operating speeds, the vibration attenuation of ATC method is twice as that of DVA design method for the vehicle center, and 4.5 dB better for the equipment. Compared with the unoptimized state, the ATC method improves the running comfort at the vehicle center by a maximum of 15% and reduces the equipment vibration acceleration by 0.18 m·h-2. Therefore, the ATC method can be used for the optimization design of structure parameters in complex railway vehicles to significantly reduce the vibration level in vehicle systems, and is also a guidance for the parameters optimization design of the equipment mounted under car body. 2 tabs, 10 figs, 30 refs.More>
2021, 21(6): 321-330. doi: 10.19818/j.cnki.1671-1637.2021.06.026
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