Table of Content

10 July 2023, Volume 34 Issue 13

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Study on Unbalanced Meshing Loads of Planetary Gear Transmission under Heavy-load Conditions

TAN Jianjun, LI Hao, YANG Shuyi, ZHU Caichao, SONG Chaosheng, SUN Zhangdong

2023, 34(13):  1513-1524.  DOI: 10.3969/j.issn.1004-132X.2023.13.001

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 To study the gear tooth load distribution affected by the multi-flexible body deformations of planetary gear transmission under heavy-load conditions， a coupled dynamics modeling method of planetary gear transmission that taken into account the structural flexibility and dynamic contact of gear pair was proposed. Taking a certain type of megawatt-class wind turbine gearbox planetary gear train as the research object， according to the ring gear， carrier， and their boundary characteristics， the finite element reduction theory was used to establish the correlations between the ring gear teeth， carriers coupling points and the corresponding elastic supports， and the dynamic load-contact of the gear pair was used as the interface coordination condition to couple these components， to establish the planetary gear transmission coupling dynamics model. The phenomenon of unbalanced meshing loads and the effects of structural parameters on the meshing characteristics were analyzed. The results show that the comprehensive bending moment acting on the planet gear and the asymmetric structural deformations of the carrier pin are the main causes of the unbalanced meshing loads， and the resonance of the system will aggravate this phenomenon. In the resonance region， the dynamic meshing stiffness differs greatly from the static meshing stiffness. Increasing the carrier pin stiffness and the helix angle may improve the meshing condition and reduce the system vibration in the resonance region. But in low-speed region, that is not good for system vibration absorption. Increase of the rigidity of the carriers connecting plate may keep the systems vibration state in the low-speed region， and reduce the system vibration in the resonance region. 

Friction Power Loss Analysis and Efficiency Test of High Reduction Hypoid Gears

WEI Bingyang, GU Dewan, WANG Yongqiang, YANG Jianjun,

2023, 34(13):  1525-1532.  DOI: 10.3969/j.issn.1004-132X.2023.13.002

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 Aiming at the problems of complex topological surfaces of high reduction hypoid（HRH）gears， the HRH gear tooth surface model and ease-off surface were constructed by dual equitangent conjugate method， and the curvature parameters of tooth contact points， enrolling speed and kinematics parameters of roll ratio were obtained analytically. Using the contact line differential element method， coordination equations of tooth stiffness， load and deformation were established， and LTCA was carried out to obtain the distribution law of tooth surface loads and contact stresses. Combined with EHL friction factor empirical formula， the problems of instantaneous contact area distortion and the parameters calculation of EHL were solved. The distribution rules of oil film thickness， friction coefficient and friction power consumption on tooth surfaces were analyzed. The LTCA， friction power loss analysis and meshing efficiency calculation models were verified by transmission efficiency tests. 

Effect of Constrained or Unconstrained Branches on Kinematics and Stiffness Performance of PMs —Design，Analysis and Optimization of Two Novel Three-translation PMs with Partial Motion Decoupling Being Examples#br#

SHEN Huiping, LI XiaLI Ju, LI Tao, MENG Qingmei, WU Guanglei

2023, 34(13):  1533-1549.  DOI: 10.3969/j.issn.1004-132X.2023.13.003

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Two novel three-translation PMs of two branch chains with zero coupling-degree and partial motion decoupling were designed. They contained the same branch Ⅰ as a mixed branch， while branch Ⅱ was a constrained branch or an unconstrained branch respectively. Firstly， the main topological characteristics of the two mechanisms were analyzed， and their topological analytical expressions were given. Secondly， the forward and inverse position solutions， singularity， velocity and acceleration of the moving platforms， and workspaces of the two mechanisms were solved in turn. Then， the stiffness was calculated and analyzed. Finally， the comparative analyses of the kinematics and stiffness performance of the two PMs show that the PM 1 with the constraint branch chain has the advantages of large working space and good stiffness performance， which is the preferred PM. Meanwhile， the conceptual design of the application scenario of the PM 1 for the transmission， sorting and transfer of workpiece materials between trucks and yards or warehouses was given. 

Experimental Study of Thermal Deformation and Wear Characteristics of Spherically-assembled Mechanical Seals for Turbo Pumps

LI Yongfan, SONG Yong, HAO Muming, ZHUANG Suguo, ZHOU Rui, LI Tianzhao, WANG Chenyin, REN Baojie, LI Xiaozu

2023, 34(13):  1550-1558.  DOI: 10.3969/j.issn.1004-132X.2023.13.004

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Normal-pressure kerosene-lubricated spherically-assembled mechanical seals for turbo pumps were regarded as targets，  and the formation mechanism of face wear was analyzed through experimental tests. An experimental cell was designed to test the 9-point temperature matrix of the metal ring crosssection and the axial displacements of the graphite ring seat at 3 positions. The temperature rising and displacement evolutions under two spring-force conditions were obtained，  and the worn faces were observed by optical microscope and measured for the radial profile. The results show that the wear depth is the largest at the inner diameter，  and there is no wear within a certain width near the outer diameter； the axial and radial temperature gradients of the seal ring continue to increase with speeding up； taper of the sealing gap caused by thermal coning of seal rings in two conditions are approximately 2.5 mrad and 7.5 mrad respectively. For this type of seal，  configuration of hydrodynamic grooves on the face may improve the serious wear caused by hydrostatic lubrication effect lacking via achieving activated pumping lubrication. 

Experimental Study of Laser Assisted Water Jet Micromilling of Single Crystal β-Ga2O3 Substrates

TIAN Long, HUANG Chuanzhen, LIU Dun , YAO Peng , LIU Hanlian, LIU Xuefei

2023, 34(13):  1559-1567.  DOI: 10.3969/j.issn.1004-132X.2023.13.005

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 Gallium oxide （β-Ga2O3） was a new type of high performance semiconductor material. Due to the characteristics of easy cleavage， high brittleness， poor thermal conductivity and anisotropy， the micro cracks would be easily generated in traditional precision machining and laser machining, which greatly restricted the applications of gallium oxide single crystal. Laser-assisted water jet machining might combine the advantages of high efficiency and high precision of laser machining and no thermal damages of water jet machining， which might realize the near thermal damage free machining of hard and brittle materials， thus a good application prospect was obtained in the field of semiconductor wafer processing. All-factor experimental study of laser assisted water jet micro-milling of single crystal β-Ga2O3 substrates was carried out herein. Results show that the processing parameters have significant influences on the depth and the surface roughness of the bottom of the micro-groove. By optimizing the processing parameters， the micro-groove with low surface damage， flat bottom and low surface roughness （Ra<1 μm） may be obtained by the laser assisted water jet machining. 

Research on Friction and Wear Behaviors of Al7.8Co20.6Cr12.2Fe11.5Ni40.7Ti7.2 High-entropy Superalloy

LI Guangjun, DUAN Hong, XU Lei, KAN Chen, LIU Zhongliang, GAO Xiaodong

2023, 34(13):  1568-1575.  DOI: 10.3969/j.issn.1004-132X.2023.13.006

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Al7.8Co20.6Cr12.2Fe11.5Ni40.7Ti7.2 high entropy superalloy was prepared by vacuum arc melting in argon atmosphere. The microstructure and mechanics properties of the alloy were characterized. The friction and wear properties of the high entropy superalloy in nitric acid and at high-temperature environments were evaluated. Results show that the microstructure of the high-entropy superalloy is mainly composed of dendrites. The Vickers hardness， yield strength， compressive strength and fracture toughness of the high entropy superalloy are as 422±8 HV0.2， 991±32 MPa， 2121±197 MPa and 49.5±0.1 MPa·m0.5，  respectively. The high entropy superalloy has better corrosion resistance than that of 0Cr17Ni7Al in nitric acid. The friction coefficient and wear rate of the high-entropy superalloy in nitric acid are lower than those in dry sliding. The main reason is that the formation of oxide film on the worn surface reduces the friction coefficient and improves the wear resistance in the high temperature friction processes. In high-temperature environments， the temperature has a significant effect on the friction coefficient. The friction coefficient and wear rate decrease with the increasing temperature and the oxygen contents of the worn surfaces at different temperatures have significant difference， as the oxygen contents increase with the temperature increases.

Energy-efficient Job Shop Scheduling with Variable Lot Splitting and Sublots ntermingling Based on Multi-objective Hybrid Evolutionary Algorithm

XIE Fawu, LI Lingling, LI Li, HUANG Yangpeng

2023, 34(13):  1576-1588,1598.  DOI: 10.3969/j.issn.1004-132X.2023.13.007

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 For solving the lot streaming job shop scheduling， a strategy was presented integrating variable sublots splitting and sublots intermingling， and a multi-objective optimization model of lot streaming scheduling was established to minimize the energy consumption and makespan. An improved multi-objective hybrid evolutionary algorithm was presented. In order to balance the global and local searching ability of the algorithm， the population updating mechanism of the Jaya algorithm was incorporated into the decomposition based multi-objective evolutionary algorithm. Considering the scheduling characteristics of variable lot splitting and sublots intermingling， a local searching strategy was designed integrating lot splitting/merging with critical path. The performance of the proposed algorithm and the state-of-the-art algorithms were compared under a set of instances of different scales. Experimental results show that the proposed algorithm has good performance on the convergence and distribution of Pareto solution sets. Moreover， the proposed variable lot splitting and sublots intermingling strategy may effectively reduce the energy consumption and makespan. 

Time-optimal Trajectory Planning of 6-RUS Parallel Robots Based on Grid Search Algorithm

LIU Dongcai, DONG Guangyu, DU Yuhong, LI Wenpeng,

2023, 34(13):  1589-1598.  DOI: 10.3969/j.issn.1004-132X.2023.13.008

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Aiming at the problems of uneven reproducing trajectory and low trajectory planning efficiency of 6-RUS parallel painting robots， a trajectory planning method of optimal time of 6-RUS parallel painting robots was proposed based on optimizing the position of Bézier curve nodes. Firstly， the preprocessed trajectory was discretized to grid points， the node parameters were updated and the arc length of Bézier curve was optimized， and the path of small line segment was further fitted to obtain the optimal geometric path. Then， the optimal velocity corresponding to different coarse grid points and the solution time were calculated， and the appropriate coarse grid points were selected. The paths between grid points were further densified by small steps， and the forward and backward maximum velocity were iteratively solved. The maximum feasible velocity curve of the path was searched to obtain the optimal running time of the 6-RUS parallel robots. Finally， the experiments were carried out on a self-developed 6-RUS parallel robot platform. The results show that under the same teaching trajectory， the path length of the improved Bessel curve algorithm herein is as 8.12 m， which is better than that of traditional Bézier curve and G2CBS（G2 continuous cubic Bézier spiral）aigorithm. Meanwhile， the improved time-optimal path parameterization algorithm herein was used for the optimized teaching path. The solution time of the optimal velocity curve of the algorithm herein is as 416.4 ms， which is 244.7 ms less than that of TOPP-RA algorithm. Moreover， the time-optimal trajectory planning time of the algorithm herein is also better than that of TOPP-RA algorithm. The method improves the solving speed of the optimal velocity， shortens the track reproduction time of 6-RUS parallel robots， and improves the working efficiency. 

Research on Multiple Arc Erosion Properties of Cu-Diamond Composites

WANG Fei, FENG Yi, LI Xinchao, LIU Zhuhan

2023, 34(13):  1599-1604.  DOI: 10.3969/j.issn.1004-132X.2023.13.009

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 Cu-Diamond composites with uniform diamond distribution and good bonding with copper matrix were prepared by vacuum hot-press sintering method （diamond volume fraction of 5%）. After multiple arc erosion of Cu-5vol.% Diamond composites in air atmosphere， the eroded surfaces were observed and analyzed using field emission scanning electron microscopy （SEM） and three-dimensional laser confocal microscopy （3D LSCM）， and the composition after erosion was analyzed using energy dispersive spectrometer （EDS） and X-ray photoelectron spectroscopy （XPS）. The results show that after 100 times of arc erosion at a high voltage of 9 kV， the copper in the eroded area of the composites melts and sputters， and is oxidized to CuO and Cu2O. At the same time， the diamond particles substantially improve the resistance of the composite to arc erosion. 

Multi-axis Fatigue Life Analysis Method for Welded Structures of Transmission Intermediate Shafts

CAO Leilei, KANG Fanjun, GUO Chengchen, SONG Xuding, LYU Wenche

2023, 34(13):  1605-0610,1627.  DOI: 10.3969/j.issn.1004-132X.2023.13.010

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The transmission system of heavy-duty vehicles had the characteristics of large speed ratio and large torque. The welded structures of transmission intermediate shafts carried complex working loads， and multiaxial fatigue failure was easy to occur at the weld seams. In order to evaluate the fatigue life more accurately and effectively， a fatigue life analysis method for the welded structures of transmission intermediate shafts of heavy-duty vehicles was proposed based on the multi-axial structural stress method. First， the finite element model with weld details for the welded structures of transmission intermediate shafts was built. Then， the time history of the structural stress components at the fatigue hazard points of the welds was solved， the load path was synthesized on the structural stress planes to obtain the equivalent stress range of the non-proportional loading path. Finally， the fatigue life was determined by combining the main S-N curve. This method was used to evaluate the fatigue life of the weld roots and weld toes of the welded structures of transmission intermediate shafts， and the results were compared with those of the fatigue bench tests. Results show that the predicted damage location and fatigue life are both in good agreement with the experiments， and the differences between the fatigue life of the weld roots and toes are consistent with the multi-axial fatigue test results in the existing literature， which indicating that the proposed multi-axial structural stress method is reliable for the fatigue life assessment of the welded structures of transmission intermediate shafts. 

Research on Mode Switching Analysis and Control of New Hydraulic Mechanical Dual-flow Transmissions

XIA Guang, WEI Zhixiang, TANG Xiwen, ZONG Huayu, WANG Shaojie

2023, 34(13):  1611-1627.  DOI: 10.3969/j.issn.1004-132X.2023.13.011

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 A new type of HMT system was studied， and the structure and working characteristics were analyzed. Then， the mathematical model and AMESim model of the HMT mode switching processes were established， and the transmission mode switching processes were analyzed to obtain the influencing factors of the HMT transmission mode switching characteristics. Aiming at the power cycle problems in the HMT mode switching processes， a HMT mode switching stratege was proposed considering power cycle. Aiming at the speed fluctuation problems in the HMT mode switching processes， a mode switching control method was proposed based on motor output torque compensation. Simulation and experimental results show that the HMT transmission mode switching strategy considering the power cycles may effectively reduce the cycle powers， and the mode switching control based on motor output torque compensation may effectively reduce wide ranges of vehicle speed fluctuation. 

Research on Injury of Occupants with Different Postures in Rear End Impacts during Automatic Driving

WU Hequan, BIAN Chuhong, HU Lin, GONG Chuangye

2023, 34(13):  1628-1637.  DOI: 10.3969/j.issn.1004-132X.2023.13.012

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In order to explore the injury risk of occupants under different postures in automatic driving， the THUMS model was used to explore the biomechanical response of occupants in different postures. Firstly， the effectiveness of the THUMS occupant restraint system model was verified by comparing kinematics response of the cadaveric test. Based on this， the THUMS manikin posture was adjusted to be the standard occupant attitude under the E-NCAP specification and attitudes of 120°， 150° and 180° respectively. Then， four models of rear end impact with different seat angles were built， and two rear-impact acceleration waveforms （medium speed of 4.88g and high speed of 6.44g） under E-NCAP protocols were applied to them. Through the comparison of eight groups of simulation tests， it is found that in the rear end impact， the risk of injury to the passengers in the standard posture and 120°sitting posture are relatively low. The strain value of cervical interspinous ligament decreases with the increase of occupant tilt angle. In 150° and 180° postures， there are risks of pulling the anterior longitudinal ligament of the neck. The safety belt may restrain the passengers in all four postures. The lower limbs of the passengers deflect with the pelvis as the center. The ribs and the internal organs are not damaged.