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    A High-dimensional Uncertainty Propagation Method Based on Supervised Dimension Reduction and Adaptive Kriging Modeling
    SONG Zhouzhou1, 2, ZHANG Hanyu1, 2, LIU Zhao3, ZHU Ping1, 2
    China Mechanical Engineering    2024, 35 (05): 762-769,810.   DOI: 10.3969/j.issn.1004-132X.2024.05.001
    Abstract1298)      PDF(pc) (3068KB)(192)       Save
     High-dimensional uncertainty propagation currently faced the curse of dimensionality, which made it difficult to utilize the limited sampling resources to obtain high-precision uncertainty analysis results. To address this problem, a high-dimensional uncertainty propagation method was proposed based on supervised dimension reduction and adaptive Kriging modeling. The high-dimensional inputs were projected into the low-dimensional space using the improved sufficient dimension reduction method, and the dimensionality of the low-dimensional space was determined by using the Ladle estimator. The projection matrix was embedded into the Kriging kernel function to reduce the number of hyperparameters to be estimated and improve the modeling accuracy and efficiency. Finally, the leave-one-out cross-validation error of the projection matrix was innovatively defined and the corresponding Kriging adaptive sampling strategy was proposed, which might effectively avoid large fluctuations of model accuracy in the adaptive sampling processes. The results of numerical and engineering examples show that, compared with the existing methods, the proposed method may obtain high-precision uncertainty propagation results with fewer sample points, which may provide references for the uncertainty analysis and design of complex structures. 
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    A Sequential Simulation Method for Dynamic Uncertainty Analysis of Rigid-flexible Coupling Systems under Interval Process Excitations
    LIU Yanhao, NI Bingyu, TIAN Wanyi, JIANG Chao
    China Mechanical Engineering    2024, 35 (05): 770-783.   DOI: 10.3969/j.issn.1004-132X.2024.05.002
    Abstract1074)      PDF(pc) (9281KB)(118)       Save
    For the dynamic problem of rigid-flexible coupling systems under dynamic uncertain excitations, an interval process model-based sequential simulation method was proposed for uncertainty analysis, which aimed to obtain the upper and lower bounds of the system dynamic responses such as structural vibrations and mechanism kinematics, by sequential sampling of the interval process and the rigid-flexible coupling dynamics simulations. The construction and numerical solution of the dynamic equation of the rigid-flexible coupling systems with central rigid body and flexible beam were introduced. Aiming at the dynamic analysis of rigid-flexible coupling systems under uncertain dynamic excitations, the interval process model and the interval K-L expansion were introduced to quantify and represent the dynamic uncertainty efficiently, and a sequential simulation method was proposed to solve the upper and lower bounds of the dynamic responses of the system mechanism motions and structural vibrations. The method used a sequential simulation strategy to identify the interval process parameter sample sets that contributed to the upper or lower bounds of dynamic responses in the cur rent simulation sequence, and served as the local encrypted sampling center in the next simulation sequence, which might effectively avoid the inefficient convergence problem caused by excessive invalid sampling simulations when calculating the upper and lower bounds of dynamic response in direct Monte Carlo simulation. Finally, three examples were given to verify the effectiveness of the proposed method. The results show that the sequential simulation method has better computational efficiency and accuracy than that of the direct Monte Carlo simulation method for solving the upper and lower bounds of the rigid-flexible coupling systems large overall motions and vibration responses.
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    Heat Exchange Micro-tube Vibration Analysis and Reliability Evaluation Methods for Diaphragm Micro-channel Pre-coolers
    WANG Zheng, MA Tongling, WANG Bowen, GU Meidan
    China Mechanical Engineering    2024, 35 (05): 869-876,885.   DOI: 10.3969/j.issn.1004-132X.2024.05.012
    Abstract1034)      PDF(pc) (3506KB)(56)       Save
    For the problem of heat exchange micro-tube vibration reliability of diaphragm micro-channel pre-coolers which was one of the key components of pre-cooled air breathing combined cycle engines, the method and mathmatical model for calculating the natural vibration characteristics of heat exchange micro-tubes were developed, and the vibration modes and their mechanism of heat exchange micro-tube with the action of high speed air flow were studied. Then, the vibration modes including the vortex shedding excitation vibration, the turbulent buffeting vibration and the elastic excitation vibration were taken into account, and the reliability evalutating model of pre-coolers with heat exchange micro-tube vibration failure mode was derived. The pre-cooler heat exchange micro-tube vibration reliability of change rules were revealed. The results show that the natural vibration frequency of heat exchange micro-tube is affected by the parameters including outside diameter, pipe wall thickness, adjacent support plate spacing, material properties and so on, and the vibration modes of heat exchange micro-tube have the characteristics of sine function. Three important vibration modes including the vortex shedding excitation vibration, the turbulent buffeting vibration and the elastic excitation vibration those may happen in the heat exchange micro tubes of pre-cooler with the action of high speed air flow. And with the increasing of flow velocity of cooled working fluid, the heat exchange micro-tube vibration reliability of pre-coolers decreases firstly, and then increases and approaches a certain value. In order to avoid the resonance of heat exchange micro tubes, the structural parameters may be designed rationally with the operating profile and the flow and heat transfer characteristics may be also taken into account.
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    High Dimensional Multioutput Uncertainty Propagation Method via Active Learning and Bayesian Deep Neural Network
    LIU Jingfei1, JIANG Chao2, NI Bingyu2, WANG Zongtai3
    China Mechanical Engineering    2024, 35 (05): 792-801.   DOI: 10.3969/j.issn.1004-132X.2024.05.004
    Abstract884)      PDF(pc) (4472KB)(98)       Save
    An uncertainty propagation method was proposed based on active learning and BDNN for solving the high dimensional multioutput problems existed in practical engineering. Since the multiple output responses corresponded to the same input variables, the efficient one-step sampling was implemented and the initial training dataset was established. BDNN was utilized for initially establishing the surrogate model for high dimensional multioutput problem. Because BDNN might provide the uncertainty estimation for multiple predictive output responses simultaneously, an active sampling strategy was proposed for high dimensional multioutput problem. Then, Monte Carlo sampling(MCS) method and Gaussian mixture model were combined for computing the joint probability density function of multiple output responses. The results show that proposed method may avoid the repeated computing processes for different output responses individually, and make full use of the internal relationship among multiple output responses for implementing active learning. Therefore, the efficiency for solving high-dimensional multioutput problems may be improved to some extent. Finally, several numerical examples were utilized to validate the efficiency of the proposed method. 
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    Research on Reliability-based Design Optimization of Larger-caliber Artillery Ammunition Coordinator Mechanisms
    YAN Lijun1, LI Guangqi1, LIU Qin2, GAO Jingzhou1, SONG Huabin1, LUO Xiaoping1
    China Mechanical Engineering    2024, 35 (05): 877-885.   DOI: 10.3969/j.issn.1004-132X.2024.05.013
    Abstract866)      PDF(pc) (3107KB)(75)       Save
    In order to improve the coordination engagement efficiency while maintaining the high reliability of the coordination engagement action, a reliability optimization design of ammunition coordinators was carried out. Considering the main geometric dimensions, manufacturing errors, elastic deformation of important components and other factors, a parametric rigid-flexible coupled dynamic model of ammunition coordinators was established, the failures of the coordination engagement action for coordinators were reproduced through the parametric dynamics analysis, then the performance function corresponding to the coordination failure mode and the reliability optimization design model of the coordinators were built. In order to improve the efficiency and accuracy of solving the coordinator reliability optimization design model, a new Kriging model adaptive update strategy was constructed and combined with SQP method and performance measure approach(PMA)/ reliability index approach(RIA), and the coordinator mechanism reliability optimization design method was proposed. The results show that the coordination efficiency of the coordinators is greatly improved under the conditions that the coordination engagement reliability meets the requirements, and the validity and engineering value of the proposed reliability optimization design method are also verified.
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    Accelerated Test Verification and Evaluation of Storage Reliability Statistical Model of Polyurethane Sealing Elements for Electrical Connectors
    QIAN Ping, CHEN Chi, CHEN Wenhua, WU Shanqi, GUO Mingda
    China Mechanical Engineering    2024, 35 (05): 886-894.   DOI: 10.3969/j.issn.1004-132X.2024.05.014
    Abstract763)      PDF(pc) (4553KB)(57)       Save
     In order to address the issues of life evaluation for polyurethane sealing elements used in electrical connectors during prolonged storage conditions, the underlying mechanism behind cohesion failure and boundary failure that contributed to performance degradation of these seals was analyzed. The reliability statistical model of polyurethane sealing elements for electrical connectors, established at the mechanism level, was validated at a statistical level by comprehensively applying particle swarm optimization algorithm and regression analysis, AD test and goodness of fit test methods to the comprehensive stress accelerated degradation data of temperature and humidity on polyurethane sealing elements. The validity of the failure mechanism analysis was confirmed through SEM and EDS techniques. Ultimately, the developed model was employed to assess the reliable lifespan of polyurethane adhesive seals for electrical connectors under the  storage environment.
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    An Estimation Method of Failure Probability Function Based on AK-MCS-K
    SONG Haizheng1, 2, ZHOU Changcong1, 2, LI Lei1, 2, LIN Huagang1, 2, YUE Zhufeng1, 2
    China Mechanical Engineering    2024, 35 (05): 784-791.   DOI: 10.3969/j.issn.1004-132X.2024.05.003
    Abstract693)      PDF(pc) (4039KB)(96)       Save
    An efficient method for solving the failure probability function was proposed to address the difficulties of solving the failure probability function in reliability optimization design, such as complexity and large amount of computation. The basic idea of the proposed method was to utilize the adaptive Kriging method to construct a local surrogate model of the full space of input variables at the failure boundary. The local surrogate model was then combined with the Monte Carlo simulation method to calculate the failure probability of the structures under the specified distribution parameter samples. The functional relationship between the sample points of the distribution parameters and the structural failure probability was then fitted by the Kriging method. Finalization of the implicit function of the failure probability function expressed in terms of the Kriging model. In order to test the accuracy and efficiency of the proposed method, two examples were given to compare the computational results of the proposed method with those of the existing methods for solving failure probability functions. The results of examples show that the proposed method is suitable for solving complicated functional function problems and significantly reduces the amount of computation while satisfying the accuracy requirements.
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    Reliability Modeling and Analysis of Micro Accelerometers under Multi-load Environments
    GUAN Cunhe1, 2, XU Gaobin1, 2, JIANG Jingqi1, 2, WANG Huanzhang1, 2, CHEN Xing1, 2, MA Yuanming1, 2
    China Mechanical Engineering    2024, 35 (05): 860-868.   DOI: 10.3969/j.issn.1004-132X.2024.05.011
    Abstract644)      PDF(pc) (3137KB)(71)       Save
    A reliability estimation model for micro-electro-mechanical system(MEMS) micro accelerometer was proposed based on the total probability theory under a multi-load environment, addressing issues related to sensitive structural fractures and material fatigue degradation. The model combined homogeneous Poisson processes and Wiener degradation processes to characterize the number of impact loads acting on the micro accelerometers within a unit time and the fatigue degradation process of the device under vibrational loads. The model accomplished reliability modeling for the micro accelerometers under generalized extreme impacts, generalized δ- impacts and generalized mixed impact conditions. The reliabilities of the three models were compared and analyzed with time, and the results of reliability calculations from the generalized mixed impact model offer more valuable insights. Furthermore, a parameter sensitivity analysis of generalized mixed impact model shows that impact intensity and impact times have significant influences on the reliability of micro accelerometers.
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    Research Status and Development Trends of Large Wind Turbine Main Shaft Sliding Bearings
    ZHU Caichao1, ZHANG Ronghua1, SONG Chaoshen1, TAN Jianjun1, YANG Liang2
    China Mechanical Engineering    2024, 35 (10): 1711-1721.   DOI: 10.3969/j.issn.1004-132X.2024.10.001
    Abstract553)      PDF(pc) (4422KB)(364)       Save
    The pace of large wind turbine units was accelerating, and the reliability of core components was increasingly important for wind turbine operations. Sliding bearings had the advantages of high load capacity, long life, easy maintenance, scalability and small size, and they had advantages and great potential for the reliable replacement of wind turbine main bearings key components produced at home. The problems of main shaft rolling bearings in high-power wind turbines and the advantages of using sliding bearings on the main shaft were analyzed herein. The technical methods and application status of wind turbine main shaft sliding bearing design, materials, lubrication, and experimental verification were present in detail, and the existing problems of high-power wind turbine main shaft sliding bearings and future development trends were summarized. It is expected to provide reference for the digital design and industrial development of high-power wind turbine main bearings.
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    A Topology Optimized Design Method for High-performance Structures with Fluid-thermal-mechanics Coupling
    LI Rongqi, YAN Tao, HE Zhicheng, MI Dong, JIANG Chao, ZHENG Jing
    China Mechanical Engineering    2024, 35 (03): 487-497.   DOI: 10.3969/j.issn.1004-132X.2024.03.011
    Abstract485)      PDF(pc) (5000KB)(601)       Save
    The rapid advancement of topology optimization and additive manufacturing technology provided efficient methods for designing and manufacturing high-performance complex equipment. However, current topology optimization techniques for high-performance structures only considered the design of thermal-mechanics coupling or fluid-thermal coupling, and were mostly limited to simple structures. The design under the combined effects of fluid-thermal-mechanics fields was not considered, which restricted the enhancement of structural performance. This paper tackled the challenge of designing high-performance complex structures under multi-physics fields, encompassing fluid-thermal-mechanics interactions. A topology optimization method was proposed to enhance the ability to withstand temperature of intricate structures. Firstly, the governing equations of flow field, temperature field and structural displacement field were introduced to provide a unified description of the fluid-solid materials within the computational domain. Secondly, the topology optimization model was formulated with fluid-thermal-mechanics coupling. The objective function was set to minimize the average temperature, while flow energy dissipation and structural compliance served as constraint functions. Sensitivity analysis of design variables was carried out by using a combination of the variational method and Lagrangian function. Finally, the established topology optimization model was applied to the structural design of a turbine, resulting in a structure suitable for additive manufacturing with excellent heat dissipation performance and well-balanced flow channel distribution.
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    Review for Research of Fatigue Life Prediction of Welded Structures under Complex Loads and Extreme Environments
    DONG Zhibo1, WANG Chengcheng1, LI Chengkun1, LI Junchen2, ZHAO Yaobang2, LI Wukai2, XU Aijie2
    China Mechanical Engineering    2024, 35 (05): 829-839.   DOI: 10.3969/j.issn.1004-132X.2024.05.008
    Abstract347)      PDF(pc) (6000KB)(169)       Save
    The welded joints were susceptible to defects and stress concentration, rendering them vulnerable areas for fatigue crack initiation and propagation under fatigue loads. In comparison to homogeneous materials, the microstructure and stress localization in each of regions for the joints further complicated the fatigue issue in welded structures. Unlike ideal experimental conditions, the actual service environments of welded structures were intricate, it was necessity to consider the coupling characteristics between environmental factors and welded structures when predicting welded structure fatigue life. Therefore, the internal factors influencing welded structures were summarized and analyzed while reviewing existing life prediction models from perspectives encompassing complex loads and extreme service environment. Combining the latest research progresses, the recommendations were proposed to enhance fatigue life assessment methods for the welded structures.
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    Robust Control of High-pressure Pneumatic Pressure Servo Systems
    ZHANG Dijia1, 2, GAO Luping2, ZHOU Shaoliang2, GAO Longlong2, LI Baoren2
    China Mechanical Engineering    2024, 35 (07): 1141-1150.   DOI: 10.3969/j.issn.1004-132X.2024.07.001
    Abstract320)      PDF(pc) (7020KB)(222)       Save
    Parameter uncertainty and unmodeled dynamics of HPPS restricted the improvement of the control accuracy. An adaptive robust control method was proposed and applied to control the HPPS based on RISE. This paper considered the influencs of HESV control performance on the high-precision control of HPPS, and a cross-comparison test was designed. The results show that the HESV position control method may avoid sinusoidal signal distortions and reduce steady-state pressure jitter, and the HPPS pressure control method may improve the response speed and dynamic tracking capability of the systems.
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    Review on Management at Mechanical Design and Manufacturing Discipline of National Natural Science Foundation of China in 2023
    YE Xin, HUANG Zhiquan, ZHANG Junhui,
    China Mechanical Engineering    2024, 35 (04): 571-579.   DOI: 10.3969/j.issn.1004-132X.2024.04.001
    Abstract304)      PDF(pc) (8141KB)(235)       Save
     The applications, evaluations, and funding of several types of projects that were classified into the talent and exploratory funding categories at mechanical design and manufacturing discipline (division Ⅱ of engineering science) of the National Natural Science Foundation of China in 2023, as well as the research progresses and findings of the executing and finished projects were reviewed. Specific measures of mechanical design and manufacturing discipline were illustrated, such as the reform of scientific fund, talent cultivation, and future research. Finally, a short prospect of the work in 2024 was introduced.
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    Dual-resource Constrained Flexible Machining Workshop Inverse Scheduling Problem
    WEI Shupeng, TANG Hongtao, LI Xixing, YANG Guanyu, ZHANG Jian
    China Mechanical Engineering    2024, 35 (03): 457-471.   DOI: 10.3969/j.issn.1004-132X.2024.03.008
    Abstract291)      PDF(pc) (13436KB)(166)       Save
    In order to improve the efficiency and stability of machining workshops in dynamic production environments, an inverse scheduling problem model of flexible machining workshops was established considering machine and worker constraints. The model aimed to minimize makespan, machine energy consumption and inverse deviation index by adjusting workpiece scheduling, worker work, and machining parameters. Aiming at the problem characteristics, an improved differential evolution algorithm was proposed. In the algorithm, a hybrid double-layer encoding method was designed to reduce the search difficulty. Two initialization methods were proposed to improve the population quality based on dispatching rules. In order to strengthen and balance the global and local search, adaptive genetic operations and neighborhood search strategies were designed based on elite selection. The Hamming distance was improved, and a crowding operator was proposed to reflect the true diversity of the population. In the experiment, 33 test instances were constructed and the proposed algorithm was compared with the other 7 algorithms to verify the performance. Finally, the real inverse scheduling cases of a hydraulic cylinder production workshop in two different dynamic environments were analyzed. The results show that the proposed algorithm may effectively reduce the makespan by 4.2 % and the machine energy consumption by 20.2 % with a little change in the original schedule.
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    Study on Force Model and Surface Integrity of Cylindrical Grinding 18CrNiMo7-6 Steels
    WANG Dong, CHEN Lei, ZHANG Zhipeng
    China Mechanical Engineering    2024, 35 (03): 381-393.   DOI: 10.3969/j.issn.1004-132X.2024.03.001
    Abstract272)      PDF(pc) (8185KB)(440)       Save
     In order to accurately and effectively control the influences of grinding parameters on grinding force and surface integrity, a three-stage grinding force theoretical model was established based on the plastic deformation, indentation theory and shear strain effect between abrasive particles and materials by analytical method. The brown corundum grinding wheels were selected for grinding experiments to explore the effects of grinding parameters on grinding force and the effects of grinding parameters and grinding force on surface integrity. The optimal processing parameters for cylindrical grinding were obtained through orthogonal experiments of cylindrical transverse grinding. The results show that the average prediction errors of normal and tangential grinding forces in the cylindrical grinding force model are 5.56% and 7.08%, respectively. The radial feed speed of the grinding wheel has the greatest impact on grinding force, followed by grinding width, and the influences of workpiece speed and grinding wheel particle size are relatively small. The radial feed speed and grinding width of the grinding wheel have a significant impact on residual stress, and the particle size of the grinding wheel has the greatest impact on surface roughness. As the grinding force increases, the surface roughness value continuously increases, and the residual stress firstly decreases and then increases. The maximum residual stress value along the depth direction firstly increases and then decreases. Within the parameters taken in the experiments, the distribution range of residual stress is basically 20~40 μm. The optimal combination of processing parameters is a radial feed speed of 0.15 mm/min for the grinding wheel, a workpiece speed of 120 r/min, a grinding width of 10 mm, and a grinding wheel particle size of 80.
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    A GPU-accelerated High-efficient Multi-grid Algorithm for ITO
    YANG Feng, LUO Shijie, YANG Jianghong, WANG Yingjun,
    China Mechanical Engineering    2024, 35 (04): 602-613.   DOI: 10.3969/j.issn.1004-132X.2024.04.004
    Abstract262)      PDF(pc) (8284KB)(179)       Save
     An efficient multi-grid equation solving method was proposed based on the h-refinement of splines to address the challenges posed by large-scale ITO computation and low efficiency of traditional solving methods. By the proposed method, the weight information obtained through h-refinement interpolation between coarse and fine grids was used to construct the interpolation matrix of the multi-grid method, thereby enhancing the accuracy of mapping information for both coarse and fine grids and improving computational efficiency. Additionally, a comprehensive analysis of the multi-grid solving process was conducted, culminating in the development of an efficient GPU parallel algorithm. Numerical examples illustrate that the proposed method outperforms existing methods, demonstrating speedup ratios of 1.47, 11.12, and 17.02 in comparison to the linear interpolation multi-grid conjugate gradient method algebraic multi-grid conjugate gradient method, and pre-processing conjugate gradient method respectively. Furthermore, the acceleration rate of GPU parallel solution surpasses that of CPU serial solution by 33.86 times, which significantly enhances the efficiency of solving large-scale linear equations.
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    State-of-the-Art of Cutting Technology and Applications of PTFE
    NI Jing, CUI Zhi, HE Lihua, FU Xin, ZHU Zefei
    China Mechanical Engineering    2024, 35 (03): 498-514.   DOI: 10.3969/j.issn.1004-132X.2024.03.012
    Abstract258)      PDF(pc) (16200KB)(137)       Save
    PTFE, with the excellent physical and chemical properties, be came an important material in producing key parts in the fields such as electronic communication, aerospace, et al. Compared with the molding and sintering processes, the cutting technology might be used to manufacture PTFE parts with complex structures more efficiently. However, PTFE had the characteristics of strong toughness, high resilience, poor thermal conductivity, and large linear expansion coefficient. So, the machining quality of PTFE parts was difficult to be guaranteed. In some special cases, the high surface cleanliness of the PTFE parts was also required, which presented new challenges to the cutting technology of PTFE materials. Firstly, the machinability of PTFE was summarized based on the basic mechanics, physical and chemical properties. Secondly, the cutting removal mechanism of PTFE was analyzed based on the polymer cutting theory and research methods. Then, the cutting technology of PTFE such as turning, milling, and drilling was presented. Finally, the applications of PTFE cutting technology was discussed. The problems in the existing researches in terms of material property research, basic cutting theory research, and cutting technology exploration were summarized. And the research trend and focus were prospected.
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    Research on Dynamic Modeling and Decoupling Methods of Planetary Gear Trains in Wind Turbine Gearboxes with Journal Bearings
    TANG Hao, TAN Jianjun, LI Hao, ZHU Caichao, YE Wei, SUN Zhangdong
    China Mechanical Engineering    2024, 35 (04): 591-601.   DOI: 10.3969/j.issn.1004-132X.2024.04.003
    Abstract257)      PDF(pc) (13916KB)(141)       Save
    In the dynamic modeling of planetary gear trains, the influences of nonlinear oil film forces or linear stiffness damping forms on system dynamics characteristics were often considered. The former had high simulation accuracy but high computational costs, and the latter had high computational efficiency but ignores the time-varying effects of oil film forces and journal sleeve eccentricity, resulting in limited simulation accuracy. Therefore, a 2MW wind turbine gearbox was taken as the research object herein. A time-varying linear stiffness damping model of the journal bearing was established, and a calculation method for the additional eccentricity correction force of the journal bearing considering the time-varying eccentricity of the journal sleeve was proposed. Then, the time-varying linear stiffness damping model was coupled with the additional eccentricity correction force by using the coordination relationship between the carrier-pin and planet. Finally, a dynamic model of the planetary gear trains in wind turbine gearboxes using journal bearings was established, and the effects of operating conditions and bearing parameters on the calculation accuracy and dynamic system responses were compared and verified through experiments. The results indicate that the fluctuation of dynamic meshing force in gear pairs may cause periodic changes in the stiffness damping coefficient and additional eccentricity correction force of journal bearings. The proposed model may effectively predict system responses, especially planetary gear vibration responses, under stable and transient operating conditions. Reducing the width-diameter ratio and gap, increasing input torque may improve the system's load sharing performance.
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    Vibration and Lubrication Characteristics of Railway Vehicle Axle Box Bearings under Wheel-rail Excitation
    MA Qiaoying, YANG Shaopu, LIU Yongqiang,
    China Mechanical Engineering    2024, 35 (04): 580-590.   DOI: 10.3969/j.issn.1004-132X.2024.04.002
    Abstract244)      PDF(pc) (12680KB)(234)       Save
    An axle box bearings coupled with a railway vehicle model was developed based on Hertz contact and elastohydrodynamic lubrication theory. The effects of wheel-rail excitations on the vibration and oil film stiffness characteristics of axle box bearings were investigated. MATLAB/Simulink and UM were used to establish the bearing dynamic model and the railway vehicle model, respectively. The coupling relationship between the two was realized through the interaction force. The typical fault forms of bearings and wheelsets were simulated, and the impacts of these faults on bearing vibration and lubrication characteristics were analyzed in detail. The results show that lubrication may effectively reduce bearing vibrations. The partial bearing faults may increase the oil film stiffness, and bearing faults and wheel flats have a significant impact on lubrication. In addition, wheel-rail excitations reduce the vibration ratio of the bearing outer ring while increasing the vibration of other vehicle components and little effects on the vibrations of the car body.
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    Study on Influences of Ni Content, Nitriding Hardening Depth, and Shot Peening on Bending Fatigue Performance of 42CrMo Gears
    WU Zhongrui, CHEN Difa, WU Jizhan, YANG Yudian, LIU Huaiju
    China Mechanical Engineering    2024, 35 (03): 394-404.   DOI: 10.3969/j.issn.1004-132X.2024.03.002
    Abstract243)      PDF(pc) (9652KB)(595)       Save
     Single tooth bending fatigue tests were conducted on 42CrMo gears with different combinations of Ni content, nitriding hardening depth, and shot peening. The effectiveness of different process combinations on improving the bending fatigue limit of gears was investigated, providing process guidance for gear fatigue resistance manufacturing. Additionally, the contribution of surface hardness, nitriding hardening depth, surface residual stress, and Ni content to the bending fatigue limit of gears with different process combinations was analyzed using the random forest algorithm. A multiple regression model considering surface hardness, nitriding hardening depth, surface residual stress, and Ni content was established to predict the bending fatigue limit of gears. Comparing the predicted values with experimental values, the maximum error is controlled within 7.80%, providing a theoretical basis for the rapid and low-cost assessment of gear bending fatigue limit in engineering applications.
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    Design of Twisting Climbing Wheeled Inspection Robot for Mining Wire Ropes
    TANG Chaoquan, TONG Binghang, TANG Wei, ZHANG Gang, WANG Siyuan, TANG Hongwei, LIU Bei, ZHOU Gongbo
    China Mechanical Engineering    2024, 35 (10): 1732-1739.   DOI: 10.3969/j.issn.1004-132X.2024.10.003
    Abstract242)      PDF(pc) (6279KB)(193)       Save
    In response to the unmanned inspection requirements of mining wire ropes, a rope-twisting climbing inspection robot was designed and developed. Compared to traditional axial climbing robots, which required approximately 91.5% of the driving force. When carrying a load of 3 kg, the robot may overcome obstacles with a height 0.6 mm higher than that of axial climbing robots. With an obstacle height of 3 mm, the maximum load capacity exceeds that of axial climbing robots by 0.4 kg. Climbing experiments were conducted under simulated deep mine conditions with wire rope vibrations. The results show that the climbing robots exhibite stable climbing performance when the wire ropes are stationary, achieving a maximum climbing speed of 8.25 m/min and capable of continuous climbing for 500 m. Under low-frequency large-amplitude vibration conditions, the climbing speed of the robot is higher than that when stationary, while under high-frequency small-amplitude vibration conditions, slight fluctuations in climbing speed are observed due to wire rope vibrations.
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    Research on Two-level Fusion Strategy of Unmanned Driving Perception Information Target-decision under Tunnel Environments
    WANG Maosen, BAO Jiusheng, XIE Houkang, LIU Tonggang, YIN Yan, ZHANG Quanli
    China Mechanical Engineering    2024, 35 (03): 427-437.   DOI: 10.3969/j.issn.1004-132X.2024.03.005
    Abstract241)      PDF(pc) (4400KB)(249)       Save
    Based on the special driving environment in the tunnel and the perception requirements of unmanned driving, appropriate sensors and hardware were chosen to build a test vehicle and a perception system of multi-sensor fusion of millimeter-wave radar and camera. A two-level information fusion algorithm of “target-decision” was proposed based on YOLOv4 target-level information fusion algorithm and improved D-S evidence theory. Finally, a verification test of perception information two-level fusion was carried out in the urban road tunnel environments. The results show that in the tunnel environments, compared with the single camera or the millimeter-wave radar sensing results, the target-level fusion result based on the association of the camera and the millimeter-wave radar sensor to perceive the ROI area may improve the recognition accuracy by 9.51%, making up for the shortcomings of a single sensor in the tunnel environment perception technology. Based on the target-level fusion perception results, using the improved D-S evidence theory algorithm to perform decision-level fusion, compared with the single target-level fusion results, the false detection rate is reduced by 3.61%, which significantly improves detection accuracy. By adopting the multi-sensor sensing information target-decision-making two-level fusion strategy, it may meet the reliable sensing requirements of unmanned vehicles in the special tunnel environments, and provide theoretical and technical support for promoting the applications of unmanned controlled technology.
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    Research on Road Uneven Obstacle Recognition Method for Intelligent Vehicles
    ZOU Junyi, LIU Chang, GUO Wenbin, YAN Yunbing, RAN Maoping
    China Mechanical Engineering    2024, 35 (06): 951-961.   DOI: 10.3969/j.issn.1004-132X.2024.06.001
    Abstract232)      PDF(pc) (19223KB)(147)       Save
    For intelligent vehicles, if the sensing device might accurately and quickly detect the concave and convex obstacles on the roads ahead of the vehicles, the important preview information might be provided for the control of the chassis system such as the suspension of the vehicles, and finally realized the improvement of the comprehensive performance of the vehicles. Therefore, based on improved YOLOv7-tiny algorithm a recognition method was proposed for typical positive and negative obstacles such as bumps(speed bumps) and pits on the road surfaces. Firstly, the SimAM module was introduced in the three feature extraction layers of the original YOLOv7-tiny algorithm to enhance the networks ability to perceive the feature map; secondly, a smoother Mish activation function was used in the Neck part to add more nonlinear expressions; again, replacing the nearest proximal upsamping operator with the up-sampling operator to enable the network to aggregate contextual information more efficiently; and lastly, the WIoU was used as the localization loss function to improve the convergence speed as well as the robustness of the network. The offline simulation experimental results show that compared with the original model, the improved model improves the average accuracy by 2.5% for almost the same number of parameters with an intersection ratio of 0.5 between the predicted and real frames. The improved model is deployed to a real vehicle, and the real-vehicle experiments verify that the model may effectively detect the obstacles appearing on the road in front of the vehicles, indicating that the proposed algorithmic model may accurately provide the pre-precedent information for obstacle detections.
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    Effect of Heat Treatment on Temperature and Stress Distribution during Laser Cladding of 316L Steels
    LI Yanle, PAN Zhongtao, QI Xiaoxia, CUI Weiqiang, CHEN Jian, LI Fangyi
    China Mechanical Engineering    2024, 35 (04): 666-677.   DOI: 10.3969/j.issn.1004-132X.2024.04.010
    Abstract226)      PDF(pc) (11351KB)(85)       Save
    In order to study the control effectiveness of different heat treatment processes on the residual stress of laser cladding, a thermo-mechanics coupling model was established by using ANSYS finite element analysis software. The temperature and stress fields during the laser cladding of 316L stainless steel were simulated under the conditions of preheating(22~900 ℃) before cladding, annealing treatment(200~1000 ℃) after cladding and combined heat treatment before and after cladding. The results show that preheating has the greatest influence on the temperature of molten pool. The temperature of the molten pool increases with the increase of the preheating temperature. Annealing treatment has the best effect on improving the residual stress of laser cladding, and the residual stress is reduced by about 50% at 800 ℃. Comparatively, followed by preheating and annealing treatment, the residual stress is reduced by about 35%. In addition, preheating treatment may also effectively adjust the residual stress, with a reduction of 20% at 500 ℃. 
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    Elliptic Cycloid Tool Path Optimization of Impeller Rough Machining Based on Parameter Mapping
    HAN Feiyan, GU Zhicheng, ZHAO Yipeng, ZHANG Chuanwei
    China Mechanical Engineering    2024, 35 (03): 438-444,456.   DOI: 10.3969/j.issn.1004-132X.2024.03.006
    Abstract223)      PDF(pc) (17907KB)(174)       Save
    In order to improve the opening groove processing efficiency of complex curved blade passages, a cycloid tool path planning method for surface rough machining was proposed. Firstly, the processable area of the passages was parameterized. Then, a mathematical model of key parameters for elliptical cycloid tool path, with the optimization goal of minimizing machining time, was established in the parameter domain. The best short-axis length of the ellipse and the cycloid step that satisfied the machining requirements were solved by the interval narrowing method, then the cycloid tool path could be determined in the parameter domain accordingly. Afterwards, the trajectory of the parameter domain was mapped to the physical domain to obtain the cutting path. Finally, the efficiency of the proposed trajectory planning method was evaluated with an example of calculation of elliptical cycloidal open rough machining trajectory for an impeller, whose calculation time is 19.4% faster than the traditional line cutting method. In addition, the simulation results of cycloidal channel opening and line cutting show that the machining efficiency of the proposed method is 22.4% higher than that of the traditional line cutting method under the same parameter setting. The practical results of cycloidal milling show that the shape of impeller runner cut is consistent with the cycloidal track, whose surface residue meets the rough machining requirements. This paper provides a new trajectory planning method for rough machining of impeller flow channels to improve the machining efficiency, which is a substitution for the traditional line cutting method. 
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    Optimal Design of Slip Oil Pump Impeller Structures Based on NSGA-Ⅱ
    SUN Yongguo, JIN Xin, XUE Dong, SHAN Jianping, SHI Xiaochun
    China Mechanical Engineering    2024, 35 (03): 559-569.   DOI: 10.3969/j.issn.1004-132X.2024.03.018
    Abstract223)      PDF(pc) (6468KB)(225)       Save
    Slip oil pumps often needed to operate stably at high altitude and under low pressure conditions, which often led to cause problems such as insufficient oil supply and reduced efficiency. In order to get the best performance of the pump to meet the design requirements, this paper taken the impeller of a helicopter oil pump as the research object and to optimise the structure. The efficiency and lift of two typical working conditions at high altitude were selected as the optimisation targets, and the NSGA-Ⅱ was used to optimise the geometric parameters of the oil pump impellers, and the efficiency and lift of the oil pump before and after the optimisation were compared and analysed. CFD fluid simulation and experimental methods were used to verify the optimisation results. The results show that: the selected optimization parameters have a greater impact on the performance of the slip oil pumps, near the optimized slip oil pump vane positions the flow is more smooth, the high and low pressure areas of the excessively smooth, the energy loss is smaller, and the possibility of cavitation is reduced. The optimized slip oil pump design point lift increases 2.6 m, the efficiency increases 2.86%.
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    Research on Compound Wave Propulsion Performance Improvement for Bionic Fish Robots
    LUO Zirong1, XIA Minghai1, YIN Qian2, LU Zhongyue1, JIANG Tao1, ZHU Yiming1
    China Mechanical Engineering    2024, 35 (11): 1901-1908.   DOI: 10.3969/j.issn.1004-132X.2024.11.001
    Abstract223)      PDF(pc) (8473KB)(180)       Save
    Motivated by the profound impacts of longitudinal and transverse waves of earthquake, a novel underwater bionic propeller that utilized longitudinal and transverse compound wave patterns was proposed and designed. A kinematic model incorporating the composite waves was theoretically established, alongside the development of a physical prototype and testing platform. The propulsion performances of the propeller were systematically compared and analyzed through CFD simulations as well as prototype tests under varying amplitudes of longitudinal wave superposition. Simulation results show that both the thrust and velocity generated by the undulating fin may be significantly enhanced, with mean thrust increasing by 27.6% and peak thrust exceeding 200%. Experimental results reveal that under a frequency of 2 Hz with a longitudinal-wave amplitude of 20°, the steady-state average velocity achieved by the propeller reaches 0.761 m/s, which is approximately 14.7% greater than that of without longitudinal wave. This paper demonstrates that composite wave bionic fins exhibit superior thrust and velocity performance compared to single sinusoidal wave configurations, thereby offering an innovative propulsion mechanism for advancing high-performance bionic fish robots.
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    Study and Application of Roller Replacement Robots with Non-stopping for Belt Conveyors
    TIAN Liyong1, TANG Rui1, YU Ning1, YANG Xiuyu1, 2, QIN Wenguang3
    China Mechanical Engineering    2024, 35 (05): 938-949.   DOI: 10.3969/j.issn.1004-132X.2024.05.019
    Abstract220)      PDF(pc) (15549KB)(125)       Save
    In view of the problems of frequent replacement of belt conveyor rollers, heavy manual replacement tools, high labor intensity and low shutdown replacement efficiency, taking the belt conveyor in the main adit of Wangjialing Coal Mine as the research object, the roller replacement robots with non-stopping were studied according to roadway parameters and roller replacement processes, and the overall research plan of the robots was formulated. Based on the functional analysis method and the theory of roller replacement with non-stopping, the 3D solid model of the robots was established by using SolidWorks software, and the parameters of the walking mechanism, attitude adjustment platform, telescopic support platform and disassembling manipulator were optimized. The finite element analysis of the support platforms and belt lifting mechanisms was carried out by ANSYS Workbench software. The telescopic support platform adopted a sliding rail structure, and the stresses of the sliding rail under the cantilever and lifting rated load are as 15.647 MPa and 66.395 MPa respectively. The maximum deformation and displacement occur under the rated load. The displacement is as 1.0742 mm. Belt lifting mechanism adopted shear fork structure, the rated lifting maximum stress is as 152.82 MPa, the maximum displacement is as 0.7331 mm. According to the design parameters, the robot prototype was processed with the power of 64 kW diesel engine as the power, and the crawler was driven by the hydraulic motor. The speed range is as 3~8 km/h. The attitude adjustment platform may realize the lifting height 0~357 mm, the pitch angle ±15°, the roll angle -4°~7°, the rotation angle -10°~20°, the transverse movement range 0~400 mm, the longitudinal movement range 0~ 350 mm, the multi-stage telescopic mechanism adopted the combined slide to achieve the platform 0~2.1 m telescopic. Using a five-degree-of-freedom manipulator may disassemble and assemble rollers in different positions. Through the ground and underground tests, the robot prototype walking, attitude adjustment, lifting belt, disassemble roller functions were verified experimentally. The results show that the robots may pass well in the narrow tunnel of the main tunnel, and the maximum height of the lifting belt of the telescopic support platform is as 241 mm when the conveyor is not stopped, which provides enough operating space for the robots to disassemble and assemble the rollers under different positions to meet the design performance requirements. The study of roller replacement robots with non-stopping for belt conveyor provides a new way for the maintenance of coal mine belt conveyor.
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    Fusion Research of Trajectory Tracking Energy-saving Control of Unmanned Hybrid Vehicles
    LIU Junling, FENG Ganghui, ZHANG Junjiang, YANG Kai
    China Mechanical Engineering    2024, 35 (04): 678-690.   DOI: 10.3969/j.issn.1004-132X.2024.04.011
    Abstract218)      PDF(pc) (9354KB)(153)       Save
    In order to further improve unmanned hybrid vehicles trajectory tracking accuracy and energy consumption economy, this paper proposed a trajectory tracking energy-saving control fusion strategy. Firstly, the vehicle kinematics model was established, and the trajectory tracking control of the vehicle was carried out by using the model predictive control strategy. Then, with velocity as the interactive variable, a three-stage dynamic programming energy-saving control strategy was proposed. In this way, the optimal economic function was optimized online to reduce the total cost of energy consumption of the vehicles. Finally, the independent pure pursuit trajectory tracking algorithm and the power following energy-saving control were selected for comparison strategies. The results show that the proposed trajectory tracking energy-saving control fusion strategy improves the trajectory tracking effectvieness and reduces the total cost of vehicle energy consumption. The trajectory tracking errors are reduced 70.47%. The total cost of energy consumption decreases 4.52% and 25.10% in pure electric drive mode and hybrid drive mode, respectively.
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    Integrated Casting Triangular Beam Lightweight Improving with Multi-performance Constraints of Body Systems
    SU Yonglei, ZHANG Zhifei
    China Mechanical Engineering    2024, 35 (04): 691-699.   DOI: 10.3969/j.issn.1004-132X.2024.04.012
    Abstract218)      PDF(pc) (6363KB)(195)       Save
     An optimization method of integrated casting structures was constructed systematically, and based on the super-element model of body system, body casting part lightweight improving with multi-performance constraints was realized. Firstly, complex body systems were reduced, the sub-system division principle and method were proposed for continuous body structure. Super-element reduction of the sub-system was conducted to ensure analysis accuracy and improve calculation efficiency, laying the foundation for rapid optimization. Secondly, performances of casting structures and body systems were considered simultaneously, the compromise programming methods were used to normalize static and dynamic sub-targets and construct the comprehensive objective function, weight coefficients of sub-targets were obtained by analytic hierarchy process(AHP), and then multi-model topology optimization was carried out to determine position distribution of reinforcements. Furthermore, designability and manufacturability were considered simultaneously, parametric definition of variable thickness drawing surface of casting structure was carried out, manufacturing constraints were applied during optimization processes, and then thickness parameter design was completed based on combined surrogate model. The results show that, under the premise of ensuring the analysis accuracy, reduced body system models improve computing efficiency greatly, and save 97.3% of computing resources. Casting triangular beam lightweight may be achieved while improving related performance by conducting structure optimization, which indicates correctness and practicability of the proposed method. 
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    Design and Analyses of a Novel Two-axis Flexure Hinge with Elliptical Transverse Cross-sections
    WEI Huaxian1, 2, ZHAO Yongjie2, YANG Nan2, WANG Fengtao2, NIU Xiaodong2
    China Mechanical Engineering    2024, 35 (08): 1348-1357.   DOI: 10.3969/j.issn.1004-132X.2024.08.002
    Abstract217)      PDF(pc) (12837KB)(150)       Save
     Two-axis flexure hinges with orthogonally-collocated notches comprised rectangular transverse cross-sections which increased the stress concentration on the sharp edges. In addition, such effects could not be avoided through notch optimization. Consequently, a novel kind of two-axis flexure hinge with elliptical transverse cross-sections was developed herein. Firstly, the parametric model of the flexure hinges with circular notches was established. Then, the compliance and stress models of the flexure hinges were developed based on the Castiglianos second theorem. The analytical models were verified through finite element analyses and the parametric simulations were performed to evaluate the characteristics of compliances and stress concentration. Finally, the compliances of a flexure specimen were tested through experiments. The results show that the ETC flexure hinges have two-dimensional anisotropic compliances. The sharp-edge structures are avoided. Therefore, the stress concentration effects are reduced and the motion capability is increased. Compared to exiting two-axis flexure hinges with identical notch profiles but rectangular transverse cross-sections, the motion capability of the ETC type flexures hinges is increased by 47.9%. The ETC type two-axis flexure hinges expand the design spaces of the primary flexure structures.
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    Research Progresses of Mechanical Dressing for Arc Diamond Grinding Wheels
    CHEN Bing1, QING Guangye1, GUO Ye1, DENG Zhaohui2
    China Mechanical Engineering    2024, 35 (08): 1331-1347.   DOI: 10.3969/j.issn.1004-132X.2024.08.001
    Abstract216)      PDF(pc) (13816KB)(145)       Save
    The arc diamond grinding wheels had unique arc profile and commonly used for precision and ultra-precision grinding of optical components made from difficult-to-cut materials such as ceramics, optical glass, and cemented carbide. However, during the grinding process of optical elements, the interaction between the grinding wheel and the workpiece surface caused the abrasive grains on the grinding wheel to be squeezed and damaged. Then, this led to issues such as grinding wheel blockage, wear, reduction in size and shape accuracy, ultimately affecting the surface roughness, shape accuracy, and damage thickness of the optical elements after grinding. To address these problems, dressing the arc-shaped diamond grinding wheel was an effective solution. Among the various dressing methods, mechanical dressing remained the primary approach in production due to the high dressing efficiency and ease of implementation. This paper provided a comprehensive review of the mechanical dressing methods for arc diamond grinding wheels. The truing mechanism and characteristics of different methods were explored, the evaluation method for truing effectiveness was analyzed, and a future outlook for the mechanical truing of arc diamond grinding wheels was presented.
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    Design of Lane Keeping Assist Systems Based on Improved Preview Control Model
    LIANG Yongbin, FU Guang, LIN Zhigui, HE Zhicheng, ZHANG Jialuo, CHEN Tao
    China Mechanical Engineering    2024, 35 (03): 548-558.   DOI: 10.3969/j.issn.1004-132X.2024.03.017
    Abstract212)      PDF(pc) (8767KB)(255)       Save
    To address the issues of low robustness, consistency in vehicle manufacturing, and severe road surface interference in LKA system of torque control, a LKA system was designed based on angle control by using neural network technology, Autofix algorithm, and preview feedback control theory, through expected trajectory decision-making and following PID control algorithm. A hardware-in-the-loop simulation test platform was built to verify the effectiveness and accuracy of the design of the angle based lane protection systems through virtual simulation based on Carsim/Veristand/ MATLAB. Based on GB/T 39323—2020, CN-CAP—2021, Euro-NCAP—2022 and the testing requirements of the car retention systems based on real-road commissioning and user concern scenarios, the simulation and comparison with real-road scenarios show that the angle-controlled LKA system has better lane keeping capability, stability, adaptability and robustness than that of the torque-controlled LKA system in the same usage scenarios.
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    Remaining Useful Life Prediction for Lithium-ion Batteries Based on Health Indicators and Hybrid Bi-LSTM-NAR Model
    XIA Ran, SU Chun
    China Mechanical Engineering    2024, 35 (05): 851-859.   DOI: 10.3969/j.issn.1004-132X.2024.05.010
    Abstract210)      PDF(pc) (5202KB)(65)       Save
    In order to accurately predict the remaining useful life of lithium-ion batteries and reduce the risk of battery operations, a novel model was proposed for online remaining useful life prediction of lithium-ion batteries. On the basis of historical operation data of lithium-ion batteries, six types of health indicators were extracted to characterize the degradation of batteries. The random forest(RF) algorithm was adopted to evaluate and screen the health indicators. The generalized regression neural network(GA-GRNN), which was optimized by genetic algorithm, was used to estimate the residual capacity of the battery. Then, a hybrid model combining bidirectional long short-term memory(Bi-LSTM)network model and nonlinear autoregressive(NAR) neural network(hybrid Bi-LSTM-NAR model)was used to predict the remaining useful life for lithium-ion batteries. A case study was conducted with the NASA open data. The results show that by way of screening the indicators, the accuracy of capacity estimation and remaining useful life prediction of lithium-ion batteries are ensured. Compared with the prediction results of existing methods, the prediction accuracy of the proposed hybrid prediction model is improved effectively.
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    Research on Optimal Pose Set Planning Method under Physical Constraint Robot Kinematics Calibration
    JIANG Jiguang, HOU Jue, SU Chengzhi, BA Qijiao, TIAN Aixin, XU Mingyu
    China Mechanical Engineering    2024, 35 (03): 472-480.   DOI: 10.3969/j.issn.1004-132X.2024.03.009
    Abstract208)      PDF(pc) (5499KB)(195)       Save
    In the processes of kinematics calibration of industrial robots under physical constraints, the calibration accuracy was affected by the selection of the pose set, which in turn was constrained by the calibration devices. To solve these problems, an optimal pose set planning method was proposed based on sampling interval evaluation combined with pose set optimization. Firstly, the robot kinematics model and the distance constraint calibration model were established, and the robot system parameter error constraint equation and error Jacobian matrix were calculated. Secondly, the workspace of robot was divided into spatial grids and evaluate each grid interval using Latin hypercube sampling combined with observable indicators to obtain the optimal sampling interval. Finally, based on offline data, the calibration accuracy prediction model was established based on offline data and search for the optimal pose set within the optimal sampling interval. By planning and verifying the optimal pose set for the ZhongRui RT-608 robot, the results show that the average fitting sphere radius after calibration is 0.3947 mm based on the optimal pose set, which is 57.98% lower than that of the random pose set.
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    Vibration Mimicking Fish Body Wave and Flow Distribution of Underwater Flexible Structure with Resonant Actuation of Macro Fiber Composites
    WEN Zhiwei, LOU Junqiang, CHEN Tehuan, CUI Yuguo, WEI Yanding, LI Guoping
    China Mechanical Engineering    2024, 35 (03): 405-413.   DOI: 10.3969/j.issn.1004-132X.2024.03.003
    Abstract207)      PDF(pc) (12167KB)(129)       Save
    This paper utilized the unique underwater vibration properties of smart flexible structures to explore the body wave motion of carangiform fish, greatly impacting the prototype design and analysis of next-generation underwater vehicles. The second-order vibration mode shape of MFC-actuated flexible structures was employed to mimic the fish body wave motion of carangiform fish. The multiple normalized mode shapes of the MFC-actuated flexible structures were obtained using the assumed mode method, and the actual underwater second-order mode shape of the MFC-actuated structures was obtained experimentally. This verifies that the second mode shape of the flexible structures approximates the fish body wave of the carangiform fish. The distributions of the instantaneous velocity streamlines and concentrated pressure regions were revealed using CFD. Streamlines both for the inflow and outflow of the oscillating structure surfaces were observed from the simulation. The results show that:the flow directions before and after the node on the flexible structure second-order resonant states were opposite. Meanwhile, two pairs of high and low concentrated pressure regions are always on both sides of the oscillating structures. And the distributions of the high and low pressure regions are opposite before and after the node. In summary, positive pressure gradients always exist across the flexible structures, and the forward pressure component provides suggestive thrust for the oscillating flexible structures. Meanwhile, the lateral forces before and after the node induced by the pressure are in the opposite direction and are partially canceled out. Consequently, the lateral stability of the oscillating structures was enhanced. These results may benefit the design and performance improvement of underwater bionic propulsors and robotic fish.
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    Research on Driving Style Classification and Recognition Methods Based on Driving Events
    QIN Datong, CHEN Moji, CAO Yuhang, GAO Di
    China Mechanical Engineering    2024, 35 (09): 1534-1541.   DOI: 10.3969/j.issn.1004-132X.2024.09.002
    Abstract204)      PDF(pc) (6584KB)(113)       Save
    Aiming at the problems that, based on data statistical characteristics, the classification and recognition method of driving style was easy to ignore the diversity of driving style during driving, a classification and recognition method of driving style was proposed based on driving events, spectral clustering and random forest. Experiments were designed to collect driving data, and the data were preprocessed to extract turning events and braking events. After standardization and dimensionality reduction, the spectral clustering algorithm was used to cluster the driving style of turning events and braking events respectively. The entropy weight method was used to obtain the driving style weights of each driver, and the accuracy of five machine learning algorithms was compared for driving style recognition. Results show that the accuracy of driving style recognition is as 92.73% based on random forest, which significantly improves the accuracy of driving style recognition.
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    Study on Tearing of CFRP Thin Circular Tubes Machined by Ultrasonic Vibration Assisted Grinding
    KANG Renke, LU Bingwei, CHEN Kailiang, LI Shengchao, DAI Jingbin, DONG Zhigang, BAO Yan
    China Mechanical Engineering    2024, 35 (03): 524-533,540.   DOI: 10.3969/j.issn.1004-132X.2024.03.014
    Abstract203)      PDF(pc) (17635KB)(115)       Save
    Aiming at the problems of tear damages in the ultrasonic vibration assisted grinding processes of CFRP composite thin tubes with unclear causes, ultrasonic vibration assisted grinding tests were carried out on M55J and T300 composite thin tubes, and the effects of ultrasonic amplitude, feed rate and spindle speed on grinding force and tear size were investigated. Through the force analysis of grinding processes and the calculation of the maximum thickness of undeformed chips, the formation reason of tear position and the change law of tear size were analyzed. The results show that the grinding force decreases with the increase of ultrasonic amplitude, increases with the increase of feed rate, and has little correlation with spindle speed. Tear is easy to appear on the inner walls of CFRP composite tubes, and the length and height decreases with the increase of ultrasonic amplitude, increases with the increase of feed rate, and decreases with the increase of spindle speed. 
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    Numerical Simulation of Die Wear of Automobile Covering Parts Based on Dynamic Wear Model
    ZHAO Yanjie, ZHANG Shuangjie, MU Zhenkai, WANG Wei, YAN Huajun, MA Shibo, ZHANG Yonghui
    China Mechanical Engineering    2024, 35 (03): 515-523.   DOI: 10.3969/j.issn.1004-132X.2024.03.013
    Abstract200)      PDF(pc) (7871KB)(108)       Save
    In order to predict the service life of automotive cover dies, the Archard wear model was optimized to establish a dynamic wear model. The model coupled the dynamic wear coefficient and the surface hardness change curve. This model converted the wear coefficient K into a dynamic wear coefficient that varied with contact pressure and relative slip velocity, the surface hardness was converted into a dynamic hardness curve that varied with the depth of wear. Then, the Python language was used to develop the ABAQUS software for a second time, and the dynamic wear model was coupled to the finite element simulation, and the wear calculation of the die of automotive covering parts considering the wear coefficient and the depth change of the hardened layer was realized. By comparing and analyzing the dynamic wear evolution law of the typical positions of the convex and concave die during the forming processes, and taking the maximum wear depth of the die as the failure criterion, the service life of the stamping die of the aluminum alloy cover is 635 428 times. The main wear of the die was concentrated near the die clamping line and at the large rounded corner, and these positions need to be repaired and debugged in actual production, which may extend the service life of the die effectively.
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    Study on Damage Mechanism of Water Jet Guided Laser Cutting of CFRP
    CHEN Zhongan, BAO Binying, ZHANG Guangyi, CHAO Yang, , WANG Yufeng, YAO Zhehe, JIAO Junke, ZHANG Wenwu,
    China Mechanical Engineering    2024, 35 (04): 700-710.   DOI: 10.3969/j.issn.1004-132X.2024.04.013
    Abstract193)      PDF(pc) (27678KB)(166)       Save
    After water jet guided laser machining, CFRP exhibited thermal damages on the cut groove surfaces and cross-sections, which was an important factor affecting the materials mechanics properties and reducing the service performance. To address these issues, the influences of machining parameters on the geometric and surface morphology of grooves were analyzed, and the formation mechanism of surface and cross-sectional thermal damages was investigated herein. The results indicate that high laser power, low pulse frequency, and low cutting speed may effectively increase the depth of the grooves. The interaction between the laser and the material, as well as the flushing action of the water jet, are the main reasons for the formation of thermal damages on the groove surface. In the cutting experiment of 2 mm thick CFRP, it is found that the width of the heat affected zones in the cross-sections is related to the arrangement of the fibers. The heat affected zone width is the largest for 0° carbon fibers, followed by 45° and 135° carbon fibers, which have similar widths, and the width is the smallest for 90° carbon fibers. In addition, increasing the water jet velocity is beneficial for suppressing the expansion of the thermal affected zones. When the water jet velocity is increased from 80 m/s to 120 m/s, the maximum width of the thermal affected zones decreases by 35.7%.
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