China Mechanical Engineering

Vehicle Rollover Predicting Systems Based on Grey Prediction Theory

ZHAO Youqun;JIN Yingzhi;JI Lin

2018, 29(09): 1009-1016.

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In order to guarantee the high speed train operation safety， an estimation of rollover evaluation index was studied based on preview-estimate driver model，and a vehicle rollover predicting system was designed based on preview-estimate driver model.Focused on the cars with high center of gravity， a three degree-of-freedom vehicle rollover dynamic model and a driver model were built.And the preview-estimate driver model was established based on the preview-follower theory and the theory of grey prediction.According to the mechanism of rollover， the LTR that could reflect the rollover situation was introduced， and the vehicle rollover index estimation-prediction model was proposed.And the vehicle rollover prediction system was established based on the active-steering rollover prevention control strategy and estimate-prediction model of vehicle rollover index.The rollover prediction system was proposed for the simulation analysis under different working conditions， and the effectiveness of the proposed system was confirmed.

Numerical Simulation of Helical Gear Tooth Root Crack Initiation Life of High-speed EMUs

LI Xiuhong1，2;LI Gang3;REN Jiajun1;LI Wenhui1

2018, 29(09): 1017-1024.

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In order to study the tooth root crack initiation lifes for the helical gears of high-speed EMU， a three-dimensional model of helical gear pair was established using UG software，and the crack initiation positions were determined by ABAQUS.Based on the fatigue cumulative damage theory，nominal stress method and local stress-strain method were used to calculate the crack initiation lifes of the test gears respectively.High-frequency fatigue tests were performed on the test gears to obtain the crack initiation lifes.The simulation results were compared with the test ones to determine the best damage model.The tooth root crack initiation lifes of the helical gears were calculated using the determined model.The influences of factors such as loads， tooth surface roughness， residual stresses， addendum modifications on the crack initiation lifes were analyzed.The research results show that the influences of loads and tooth surface roughness on the crack initiation life are significant， the crack initiation life increases with the increase of residual compressive stresses， proper addendum modifications may improve the crack initiation lifes of the helical gears.

Product Radical Innovation Design Processes Based on Radical Trimming

YANG Bojun1，2;FENG Yanxia1，2;SUN Qun1，2

2018, 29(09): 1025-1030.

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The radical innovation of products might significantly improve the performances of the products， sharply reduce their costs and also improve the ideal levels of the system.The radical trimming method was brought into the processes of the fuzzy front end stages of product development to improve the efficiencies of radical innovation and to solve the problems of ideas， The function analyses and root cause analyses were used to determine the trimming objects and implementation of trimming.Standard solutions， evolution trends and effects etc.were used to assist functional reorganization and to generate radical innovation ideas.Based on these， the product radical innovation design process model was proposed to apply the innovation design of automatic shipment machine which verified proposed model’s feasibility and practicability.

Research and Implementation of Tooth Surface Machining Allowance Uniform Distribution Processing Technology of Non-circular Gears

HAN Jiang;GAO Ting;LI Dazhu;XIA Lian

2018, 29(09): 1031-1038.

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In order to solve the non-uniform tooth surface machining allowances of non-circular gears caused by the curvature variation of gear blank pitch curve in the multiple cutting cycles of non-circular gear machining， a tooth surface machining allowance uniform distribution processing technology for non-circular gears was proposed.Based on the principles of gear shaping， the shaping processes of non-circular gears were studied， and then the origins of the non-uniform tooth surface machining allowances of non-circular gears were analyzed.An uniform distribution processing technology shaping linkage model of non-circular gears was established， so that the tooth surface machining allowances might be distributed uniformly through the real-time adjustment of the geometric position relationship between the shaper and the gear blank.The non-circular gear shaping CAM system was developed， which was used to simulate the tooth surface machining allowance uniform distribution processing technology for non-circular gears， the simulation results show that the proposed processing technology is correct and feasible.The uniform distribution processing technology was integrated into the self-developed gear CNC system， and the actual shaping experiments of non-circular gears were conducted， the experimental results show that the proposed processing technology may uniformly distribute tooth surface machining allowances effectively.Finally， the 3D profile measurements of non-circular gear tooth surfaces were conducted， the measurement results show that the proposed processing technology may significantly improve the surface quality and machining accuracy of non-circular gears.

Study on Compiling Method of Torque Load Spectrum of Fatigue Tests for Loader Driving Axles

LIANG Jia;SONG Xuding;HUANG Zhu'an;YU Luping;LYU Pengmin

2018, 29(09): 1039-1044.

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To simulate the loader driving axle fatigue tests more realistic loader actual operation situations， a torque load spectrum compiling method of fatigue tests for loader driving axles was researched.In the compiling processes of the torque load spectrums， the loading method of former transmission shaft forword and reverse was proposed according to the actual torque characteristics of the loader driving axles.Subsequently the levels of load spectrum， the load threshold and the rotational speed of fatigue tests were determined.The results show that the equivalent effects of the theoretical treatment by the loading method of former transmission shaft forword and reverse are consistent with the actual operations of the loader， which may reduce fatigue test difficulties largely.The selection method of rotational speeds for the former transmission shafts in the fatigue tests may get the fatigue tests more realistic to simulate the actual operation of the loader.Loading an intensified fatigue test load spectrum of 11.4 h is equivalent to the actual operation of the loader for 609.2 h， which means that the fatigue test processes of driving axles are accelerated greatly.

Lightweight Design Method for Electric Vehicle Battery Boxes Made by Composite Materials

ZHAO Xiaoyu1，2;ZHANG Shuren1

2018, 29(09): 1044-1049.

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In order to reduce the qualities of electric vehicles， the bearing characteristics of electric vehicle battery boxes were analyzed， based on the design method of rigidity equivalent， composite materials were used instead of metal materials based on the design method of rigidity equivalent.The laminated structure of the battery boxes was constructed by the theory of laminated structures of composite materials， the mechanics equations of equivalent stiffness and optimization functions were established and the structure parameters of the battery-boxes were determined.In order to verify the effectiveness of lightweight， the combination method of theoretical analysis and finite element numerical analysis was used， and the stiffnesses and deformations of metal materials and composite materials were compared.The results show that the method of equivalent stiffness is a convenience method for lightweight design of auto parts， and this method also provide references to the lightweight design for plate type parts of bearing structures.

Numerical Simulation on Influences of Impact Angles of Blunt-nosed Projectile on Failure Characteristics for 2A12-T4 Aluminum Alloy Plates

HU Jing;DENG Yunfei;CUI Yanan;ZHANG Yinbo

2018, 29(09): 1050-1054,1062.

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A simulation model was established using finite element software ABAQUS， and the numerical simulations of 38CrSi steel projectile impacting 2A12-T4 aluminum alloy plates were conducted， then the influences of impact angles of projectile on the failure characteristics of target and ballistic attitude of projectile were analyzed.Based on numerical simulation and experimental results， the failure characteristics of the target were analyzed， the change laws of the dominant failure modes under different impact conditions， as well as the influences on the impact resistance of target because of that were established.The results show that with the increases of impact angles the ballistic limit velocity decreases， and then increases， and the ballistic limit reaches the minimum when the impact angle is about 15 degrees.In addition， the impact angle of projectile impacting greatly influences the failure mode of target， with the projectile angle increases， the dominant failure mode of target changes from shearing to tearing， and also increasing the degree of tearing the target.The initial impact angle and velocity of projectile have great influences on the trajectory attitude of the projectile during the impacts， especially in the vicinity of the ballistic limit velocity.

Research on Adaptive Machining of Disc Gear Form Grinding

ZHU Yue1;YAN Ping1;LI Xianguang2

2018, 29(09): 1055-1062.

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To solve the problem of the machining errors caused by the mismatch between the gear axis and the rotation axis when the location benchmark in the disc gear finishing processes was the end face and the outer circle of step surface，a new method called adaptive machining of disc gear forming grinding was proposed.The principles of adaptive machining of disc gear form grinding were introduced.The coordinates of the gears at the key positions on the worktable were collected，the actual position of axis of the central hole in the workbench coordinate system was fitted out.The axis was regarded as Z axis to establish the gear coordinate system.Then the formulae for the transformation were derived between coordinates in the gear axis coordinate system and coordinates in the workbench coordinate system and the angles that the grinding wheel needed to be adjusted in each slot cutting were calculated.The calculation and simulation results of gear machining examples show that when gear axis of the center hole is eccentric after gear clamping， the gear machining accuracy may be improved by this method.

Numerical Simulation of Dynamic Stress and Analysis of Fatigue Load Characteristics for High-speed Railway Catenary Droppers

QI Guangfeng1;ZHAO Hui1;XIAO Xiaohui1;XU Hongyan2;LI Hongmei2

2018, 29(09): 1063-1068.

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The finite model of a high-speed railway pantograph-catenary system was established to perform the dynamic simulation，then features of the droppers’ force history curves in a selected span were analyzed when the pantograph passed through at a speed of 300 km/h.Static dropper forces and maximum dropper forces under the conditions of 250 km/h and 300 km/h were analyzed respectively when the train was running with dual pantographs，then the results were gained that the maximum dropper forces of the dropper vibration of 300 km/h may be up to 2.0 times larger than that of 250 km/h at most.Stress histories of the dropper were counted by the rainflow counting method to obtain stress statistics spectrum，which consisted of stress amplitudes，stress mean and stress cycles.Using the Goodman line method，zero-mean stress conversion of the stress statistics spectrum obtained by the rainflow counting method was performed to acquire the fatigue load spectrum，which could be used for test loading and life prediction.The research results show that for the same running speed，droppers closer to the midspan are more easily to produce fatigue fractures；in terms of the midspan droppers，droppers which are passed firstly along the driving direction are more sensitive to speed， and their fatigue fractures probabilities are much higher when the running speed is higher than 300 km/h.

Space Velocity Vector Model of Real-time Non-clearance Ball Precise Transmissions

DUAN Liying1;AN Zijun1;FU Zhiqiang2

2018, 29(09): 1069-1075.

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To solve the space motion problems of ball existed in the real-time non-clearance precision ball transmissions，a modified D-H transform matrix was derived and the positions of any point on the steel balls relative to the center plate and the combined planetary plate were obtained based on differential geometry theory.A mathematical model of the relative velocity vectors of the balls relative to the center plate and the combined planetary plate was established by using the transform mechanism method and space geometric modeling method.The influences of the groove angle of the cycloid plate and numbers of ball on the velocity vector model were analyzed.The comparisons between the numerical results and the simulation results verify the reliability of the velocity vector models.

Dynamic Stiffness Chain Modeling and Forward Conceptual Design of Vehicle Body

HU Yufei;LIU Zijian;ZHONG Haolong;QIN Huan

2018, 29(09): 1076-1083,1089.

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The forward conceptual design processes of vehicle body was presented and a simplified geometric model of vehicle body was established by class A surfaces and the scheme of vehicle general layouts.The locations of 22 main cross-sections were determined.Based on the beam element theory and transfer matrix method， the dynamic stiffness chain model of the vehicle body in modal coordinate system was obtained， then taking the main cross-section properties as the design variables and the relationship between the main cross-section properties and the natural frequency of the vehicle body was established.Body lightweight was taken as the objective function， and the vehicle body static stiffness and natural frequency were taken as constraints for optimization， and using genetic algorithms to solve the optimization problems for the main cross-section properties.The feasibility of the design method of the dynamic stiffness chains was verified by comparing the results of static stiffness simulation and modal analysis with the approximate benchmark cars.

Simulation and Experiments for Seven Spindled Hybrid Coupled Hydro Pneumatic Suspension Vehicles

TIAN Wenpeng1;YI Xiaogang1;GUO Lei2;GUO Yanjun2

2018, 29(09): 1084-1089.

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A seventeen degrees of freedom dynamics model of vehicles was established based on the principles of seven spindled hybrid coupled hydro pneumatic suspension and vehicle model.A vehicle joint simulation model including Simulink model and AMEsim model was established based on Simulink platform.The time domain analog signals generated by white noise were used as simulation excitation to carry out joint simulation analysis.Combined simulation and actual road tests were carried out under the speed of 40km/h and 60km/h.The data show that the experimental results are in good agreement with the simulation results.The relative errors between the simulated data and the experimental data of the root mean square acceleration peak mean square root and power spectral density peak is less than 8%.It shows that the established simulation model has higher accuracy， which may be used as a basis for the study of vehicle characteristics.

Modeling and Optimization for Two-sided Disassembly Line Balancing Problems

ZOU Binsen;ZHANG Zeqiang;LI Like;CAI Ning

2018, 29(09): 1090-1097,1107.

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In view of the shortages that the previous disassembly line balancing problems all set the workstation in the same way but some products adopted two-sided disassembly in actual productions， a model of multi-objective two-sided disassembly line balancing problems was built.To reduce the transport path and idle time of workstations， the tasks were assigned to the sides whose workstation numbers were low prior， then considering the workstations whose remaining time was ample.A Pareto bat algorithm was put forward to solve the two-sided disassembly line balancing problems， Pareto was introduced to save the diversity of the solutions， the adoption of elitism strategy speeded up the convergence rate of the algorithm effectively， the operating efficiency of the proposed algorithm was improved by the adoption of crowded distance to external files.The effectiveness of the proposed algorithm was verified by testing the classic problems and comparing with other algorithms.The two-sided model was applied to design the disassembly lines， and the results may provide various balancing programs with high quality.

Energy Efficiency Acquisition Method for Machine Tools with Both Tool and Workpiece Axis Rotating during Machining Process

ZHANG Xicheng;LIU Fei;LIU Peiji

2018, 29(09): 1098-1107.

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It is difficult to install the cutting-force measuring instruments on machine tools with both tool and workpiece axis rotating， thus the theoretical cutting force model and the empirical formulae failed to reflect the transient changes of cutting forces during the machining processes.As a result， it is still a challenge to acquire the energy efficiency of machine tools with both tool and workpiece axis rotating.Therefore， the energy efficiency models for machine tools with both tool and workpiece axis rotating were established， and the load loss coefficient models for tool and workpiece axis were developed based on their basic data respectively.Based on these model， the methods for calculating the load loss energy， efficient energy and energy efficiency for this kind of machine tools were presented.In practical applications， the proposed method may calculate the energy efficiency only need to monitor input powers and idle powers by using power sensors.Experimental verifications show that this method may obtain the energy efficiency precisely.Application cases show that the method may be effectively employed to obtain the energy efficiency for machine tools with both tool and workpiece axis rotating， without any usage of cutting-force measuring instruments.The proposed method， which may provide some technical supports for machine tool energy efficiency prediction， monitoring and management， has a wide application prospects.

Study on Strengthening Mechanism of Excitation Magnetic Field to Stress-magnetization Coupling Effects

LIU Zhifeng;FEI Zhiyang;HUANG Haihong;QIAN Zhengchun

2018, 29(09): 1108-1114,1126.

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The stress-magnetization coupling effect was the basis of metal magnetic memory detection and other electromagnetic nondestructive testing technology.To investigate the mechanism of the excitation magnetic field to stress-magnetization coupling effect under different stress levels， a differential value ΔH， was calculated theoretically from the relationship of permeability and stress and environmental magnetic field， which was the difference between the magnetic field strength affected by stress or magnetism interactively and by them individually.It was deduced that ΔH increased with the increases of tensile stresses.A control test was conducted with a prefabricated defective 45 steel sample， and it is found that ΔH， characterized the effects of the excitation magnetic field on the stress-magnetization coupling， increases exponentially with the increases of the stresses.And the orthogonal experiment was designed to verify that the interactions between the excitation magnetic field and the stress on the magnetic signals were significant.In the loading processes， the excitation magnetic fields were the greatest impacts on the signals.These are consistent with the theoretical analyses.The results show that excitation magnetic field plays a certain role in strengthening the stress-magnetization coupling effects.

Research on Probabilistic Fatigue Lifes of CRH5 EMU Wheels at Low Temperature

YANG Liuqing;HU Ming;ZHAO Deming;ZHOU Xun SONG Hao;CHEN Wenhua

2018, 29(09): 1115-1119.

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In order to investigate the probabilistic fatigue lifes of wheels for the CRH5 EMU，this paper followed by the comparisons with three extrapolation methods of AASHO， ECCS and CPM， applied CPM method to obtain the p-c-S-N curves of ER8 steel at -40 ℃ temperature and used dynamic and finite element simulation to get probabilistic fatigue lifes of the wheels at -40 ℃.The results show that:the positions 2mm under the wheel treads are the dangerous points to initiate cracks.Besides， the fatigue lifes of wheels under low temperature are insufficient for it is of only 1 740 km under survival rate p and confidence c are 50%.It decreases 23% compared with the life under normal temperature， that is to say， low temperature has a strong impact on fatigue lifes of wheels.

Analysis of Influence Factors for Density of Compressed Powder Products during High Velocity Compaction

YU Shiwei;ZHOU Jian;ZHANG Wei;ZHANG Xuejie;LIU Kun

2018, 29(09): 1120-1126.

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The density and its uniformity were crucial parameters which affected the mechanics properties of high velocity compacted powder products.The distribution and variation of densities in powder compaction processes were obtained by using Drucker-Prager Cap model and transient explicit dynamics finite element method.Four parameters， i.e.， sidewall friction coefficient， height-to-diameter ratio， energy per unit mass and initial relative density were analyzed quantitatively to study their effects on the density and its uniformity.The sensitivity of these factors were studied by orthogonal tests.The main conclusions are drawn as following:the non-uniformity of the density mainly concentrates on the top and bottom surfaces， and the density difference increases with the compact processes.The non-uniformity of density is more obvious along the sidewall locations.The major factor that has the greatest impact on density is the energy per unit mass， while the improvement of lubrication conditions of sidewall， height-to-diameter ratio， initial relative density do not affect the density obviously.The major factors that have the greater impact on density non-uniformity are sidewall friction coefficient and energy per unit mass.The density increases with the energy per unit mass.Once the energy per unit mass reaches its critical value， the average density does not increase any more， but the density uniformity keeps improved.

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