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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 Abstract （637）      PDF（pc） （4422KB）（394）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （362）      PDF（pc） （8141KB）（278）       Knowledge map    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． Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （278）      PDF（pc） （12680KB）（237）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （257）      PDF（pc） （6363KB）（231）       Knowledge map    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.  Reference | Related Articles | Metrics | Comments（0）

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Lubrication Characteristics of Gear End Face Friction Pairs of Aviation High-speed Gear Pumps CHEN Yuan1, XIONG Dianfeng1, LI Yuntang1, GAO Yongcao2, LI Chuancang2, WANG Bingqing1, JIN Jie1 China Mechanical Engineering    2024, 35 (07): 1178-1187.   DOI: 10.3969/j.issn.1004-132X.2024.07.005 Abstract （231）      PDF（pc） （9034KB）（226）       Knowledge map    Save Aiming at the serious wear problems of gear end face friction pairs of aviation external gear pumps, a new compound texture combining Tesla valve groove type and elliptical shape was opened on the gear end faces to improve lubrication performance. Based on hydrodynamic lubrication theory and finite element simulation calculation method, a theoretical analysis model of gear textured end face friction pair lubrication was established. Pressure distribution and velocity distribution of fluid within the end face liquid films were simulated and analyzed under conditions with and without texture, and the effects of operating and structural parameters on the openness and sealing performance of gear end faces were studied. The results show that the hydrodynamic pressure generated by the texture may make the gear end face friction pairs run non-contact, which has a positive effect on reducing friction and increasing efficiency. With the comprehensive consideration of the openness and leakage control performance of gear end face friction pairs, groove depth is as 7~9 μm, height difference is as 5~6 μm, inclination angle is as 0°~10°, and shape factor is as 0.4~0.5 are the optimal structural parameters for the texture structure. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （360）      PDF（pc） （7020KB）（224）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （1364）      PDF（pc） （3068KB）（208）       Knowledge map    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.  Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （299）      PDF（pc） （6279KB）（205）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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China Mechanical Engineering    2024, 35 (05): 1-.   Abstract （192）      PDF（pc） （110765KB）（191）       Knowledge map    Save Related Articles | Metrics | Comments（0）

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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 Abstract （311）      PDF（pc） （8284KB）（186）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （282）      PDF（pc） （8473KB）（184）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （403）      PDF（pc） （6000KB）（178）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （242）      PDF（pc） （27678KB）（172）       Knowledge map    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%. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （265）      PDF（pc） （9354KB）（164）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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Research on Thermal Characteristics of Auxiliary Bearing in AMBs and Friction Reduction Design LI Yingchun, NIE Aonan, YANG Mingxuan, ZHU Dingkang, QIU Ming, YANG Gengsheng China Mechanical Engineering    2024, 35 (04): 646-655.   DOI: 10.3969/j.issn.1004-132X.2024.04.008 Abstract （212）      PDF（pc） （8283KB）（164）       Knowledge map    Save  The rotor of the AMBs and the auxiliary bearing might produce huge impacts， vibrations and friction heat during the rotor falling which was easy to make the auxiliary bearing fail. The thermal characteristics during the vertical rotor drop on auxiliary bearings were studied， and the main factors leading to the auxiliary bearing failure during the rotor falling were analyzed herein. Subsequently， a method of reducing friction was proposed to deposit solid lubricating film(GLC) on the key surfaces of auxiliary bearings by magnetron sputtering technology， and the rotor drop tests of coated and uncoated auxiliary bearings were performed. The results show that the maximum temperature of the auxiliary bearing is as 210.60 ℃ at a drop speed of 20 000 r/min， which appear in the high-speed rubbing stage between the rotor and the inner ring end face of the bearing. The temperature is higher than the tempering temperature of bearing steel of 160 ℃， which will lead to the failure of the bearing burn. The surface appearance of the channel and end face of the self-lubricating auxiliary bearings coated with GLC film is obviously better than that of the uncoated ordinary auxiliary bearing after the drop tests. The hardness decrease of the inner ring end face caused by friction and heating is lighter， the trajectory of the center of mass and axial displacement are more stable， and the temperature rise is lower. The GLC films play a key role in self-lubrication， wear resistance and friction reduction， the service life and service reliability of the auxiliary bearings are improved. It also provides an idea and method to solve the problems of auxiliary bearing failures easily in AMBs.  Reference | Related Articles | Metrics | Comments（0）

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China Mechanical Engineering    2024, 35 (09): 0-.   Abstract （58）      PDF（pc） （364KB）（163）       Knowledge map    Save Related Articles | Metrics | Comments（0）

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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 Abstract （281）      PDF（pc） （12837KB）（156）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （261）      PDF（pc） （13816KB）（155）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （296）      PDF（pc） （19223KB）（152）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （315）      PDF（pc） （13916KB）（151）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （267）      PDF（pc） （15549KB）（146）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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A Review of Mechanics Property Studies of Retracting and Releasing Cables for Marine Exploration Equipment WAN Buyan1, 2, PENG Fenfei1, 2, 3, JIN Yongping1, 2, LIU Deshun1, 2, PENG Youduo1, 2 China Mechanical Engineering    2024, 35 (09): 1521-1533.   DOI: 10.3969/j.issn.1004-132X.2024.09.001 Abstract （235）      PDF（pc） （8520KB）（144）       Knowledge map    Save The retracting and releasing cables were the only link between the submarine exploration equipment and the ship, had the functions of power, information transmission and load-bearing, and were widely used in all kinds of launch and recovery systems. The safety and reliability of retracting-releasing cables were of the core functional requirements. Therefore, conducting experiments on mechanics properties of retracting-releasing cables was the foundation of retracting-releasing cable research. Starting from the types and failure modes of ocean winches and retracting-releasing cables, the state of experimental studies of the mechanics properties of retracting-releasing cables was systematically summarized, and an outlook on future research directions was provided. Firstly, the functions of ocean winches and retracting-releasing cables were categorized, followed by a detailed analysis of the forms and reasons for their failures. Secondly, the operating conditions, mechanics performance requirements of retracting-releasing cables, and experimental researchs current status were described. Lastly, the research directions for the mechanics properties of retracting-releasing cables in ocean detection equipment were discussed, including the impact and mechanism of extreme operating environments on mechanics properties of synthetic retracting-releasing cables, the behavior and mechanism of synthetic retracting-releasing cable damage under multiple load couplings, and the technology and integrated simulation devices for retracting-releasing cable mechanics properties. Reference | Related Articles | Metrics | Comments（0）

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Design and Parameter Optimization of Slicing Machines Based on New Rotary-straight Line Reciprocating Mechanisms HU Fuqing, SUN Jianghong, SUN Yingjie, SUN Yutong, MA Chao, ZHOU Fuqiang, China Mechanical Engineering    2024, 35 (04): 614-623，635.   DOI: 10.3969/j.issn.1004-132X.2024.04.005 Abstract （232）      PDF（pc） （12049KB）（140）       Knowledge map    Save Aiming at the problems of low slicing efficiency and quality of the existing pastry slicing machines, the design analysis and parameter optimization of a slicing machine was carried out based on the new rotary-linear reciprocating mechanisms. Firstly, the design of the slicing mechanisms and the calculation of the length-diameter ratio and speed of the elliptical guide rail was carried out. Secondly, the kinematics and the statics analyses were carried out, then, based on the simulation analysis of different aspect ratios and rotational speed dynamics, the cubic polynomial fitting equation of the mean and root mean square value of the cutter acceleration was constructed as the objective function. The NSGA-Ⅱ genetic algorithm was used to optimize the long and short diameter multi-objective parameters, and the rotational speed was selected. Finally, a prototype was built to complete the comparative experiments of different speeds and the performance tests of corn cake slices. The results show that the optimal long and short diameters and rotation speeds are as 190 mm, 120 mm and 20 r/min respectively. After optimization, the cutter efficiency is increased by 75%, the maximum and average errors of the cutter feeding acceleration are reduced by 26% and 49% respectively, and the maximum and arerage errors of retract acceleration are reduced by 60% and 63% respectively. The corn cake section is neat and beautiful, which verifies the feasibility of the design. Reference | Related Articles | Metrics | Comments（0）

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China Mechanical Engineering    2024, 35 (07): 0-.   Abstract （76）      PDF（pc） （350KB）（137）       Knowledge map    Save Related Articles | Metrics | Comments（0）

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Study on Influences of Milling Process Optimization on Residual Stress Distribution for Machining Nickel-based Superalloys ZHANG Jinyang, XU Weichun, WANG Xiaohan, JIANG Xiaohui, GAO Shan China Mechanical Engineering    2024, 35 (04): 624-635.   DOI: 10.3969/j.issn.1004-132X.2024.04.006 Abstract （215）      PDF（pc） （19741KB）（134）       Knowledge map    Save The distribution of machining residual stress of nickel-based superalloys had a significant influence on the product quality. To achieve the control method of residual stress, the effects of processing parameters, tool parameters and mechanics-thermal coupling on the residual stress distribution of nickel-based superalloys were studied by means of simulation and experiments. It is found that the change of cutting depth will affect the radial and tangential residual stresses at the same time, and the change of feed rate per tooth mainly affects the residual stress in the feed direction. When the rotating speed increases, the temperature field becomes stronger, the materials are softened, the milling forces are decreased, and the thermal stress is gradually increased. The optimal proportioning scheme is obtained by the method of parameter combination proportioning. Taking the machining of engine blade parts as an example, the method based on parameter optimization may effectively control the residual stress of Nickel-based superalloys. Reference | Related Articles | Metrics | Comments（0）

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Dynamic Performance Analysis of High-speed Double Deck EMUs with Inter-car Rolling Damping Devices WANG Xin, DAI Liangcheng, YANG Dongxiao, LUO Yun, CHI Maoru, GUO Zhaotuan, ZENG Pengcheng China Mechanical Engineering    2024, 35 (04): 742-751.   DOI: 10.3969/j.issn.1004-132X.2024.04.017 Abstract （152）      PDF（pc） （7243KB）（130）       Knowledge map    Save Double deck EMUs were equipped with amplifiers for secondary lateral damping to mitigate the vibrations caused by primary hunting behaviour. However, increased secondary lateral damping could negatively impact the lateral ride quality of the vehicles. In order to solve the problem of poor lateral ride quality in high-speed double deck EMUs, a mathematical model of the inter-car rolling damping devices was created by taking into account the working principle of the damper as well as the rolling and yaw state of the carbody, and the simulation models of the damper established in AMEsim software were verified with the bench tests. Finally, the key parameters of the inter-car rolling damping devices were optimized by establishing a co-simulation model between the inter-car rolling damping device and the vehicle model, without changing the existing suspension parameters of the vehicles. The simulation results show that the device may effectively improve the lateral ride quality of the double deck EMUs without affecting the vertical ride quality of the vehicles and ensure the safety of curve operations. Reference | Related Articles | Metrics | Comments（0）

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Research on Geometric Parameter Constraints of Swing Roller Movable Tooth Transmission Systems WEI Rui1, JIN Herong1, 2, 3, YANG Zeyu1, CHEN Tao1, YI Yali1 China Mechanical Engineering    2024, 35 (10): 1722-1731,1739.   DOI: 10.3969/j.issn.1004-132X.2024.10.002 Abstract （214）      PDF（pc） （9450KB）（126）       Knowledge map    Save Aiming at the problems such as long dimensional chain and weak structure of key components for the traditional swing movable tooth transmission, a new type of swing roller movable tooth transmission configuration and the tooth profile design method and parameter selection strategy were proposed. The swing roller movable tooth transmission mechanism was equivalent treated, and the equivalent connecting rod vector transfer model was constructed by topological analysis. According to the principle of conjugate meshing, the conjugate tooth profile vector equations of wave generator and ring gear were derived. Based on the constraint conditions of avoiding motion interference and top cutting of tooth profiles, the selection strategies of swing coefficient and base circle radius of the wave generator were developed with the transmission pressure angle as the evaluation basis. The tooth profile design and performance analysis were carried out according to the optimized parameters and the two groups of comparison parameters. The results show that the designed swing roller movable teeth transmissions have continuous tooth profiles and are able to run without stalling. Under the same load conditions, the peak value of engagement force of the wave generator and movable teeth with the optimized parameters is 37.09% and 28.28% lower than that of the comparison groups, which verifies the effectiveness of the design strategy. The research may provide theoretical reference for the tooth profile design and parameter selection of swing roller movable teeth transmission. Reference | Related Articles | Metrics | Comments（0）

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Rolling Bearing Fault Diagnosis of Wind Turbines Based on Frequency Domain Group Sparse Model with Graph Regularization Constraints LI Jimeng, WANG Ze, SHI Qingxin, MENG Zong China Mechanical Engineering    2024, 35 (11): 1909-1919.   DOI: 10.3969/j.issn.1004-132X.2024.11.002 Abstract （186）      PDF（pc） （11269KB）（126）       Knowledge map    Save Due to effects of the non-stationary operations, noisy working environment and strong electromagnetic interference for the wind turbines, the fault impulses of rolling bearings were submerged by strong noise, and the weak features were difficult to accurately identify. To solve the above problems, a frequency domain group sparse model with graph regularization constraints was proposed, which might effectively extract fault features of rolling bearings without periodic prior knowledge. Firstly, vibration signals were converted into graph signals to construct the graph regularization constraints, and the structured information was utilized to guide the penalty strength to improve the accuracy of sparse reconstruction. Secondly, the frequency domain group sparse model with graph regularization constraints was constructed, the method was given to determine the shrinkage threshold of the in-group components, and the objective function was simplified with the proximal mapping to optimize the solution. Finally, the parameters of the model were optimized by using the constructed comprehensive index and the moth flame optimization algorithm, and rolling bearing faults were identified by the envelope spectrum analysis of the reconstructed signals in the time domain. Numerical simulation and experimental results demonstrate that the proposed method has good anti-noise performance and may effectively extract weak fault features of rolling bearings under strong noise interference. Reference | Related Articles | Metrics | Comments（0）

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Experimental Study of Matching of Brush Seal Friction Pairs Based on Frictional Heating Effects YANG Yixiao, SUN Dan, LAN Kexin, ZHAO Huan, FENG Yuzhong, ZHANG Jieyi, China Mechanical Engineering    2024, 35 (04): 636-645，690.   DOI: 10.3969/j.issn.1004-132X.2024.04.007 Abstract （173）      PDF（pc） （13759KB）（125）       Knowledge map    Save The frictional heating effects caused by the interaction between brush seal wire and rotor coating directly affected the sealing performance and service life of brush seals. The theory of frictional heating effects between brush seal frictional pairs was analyzed. The experimental device of frictional heating effects between brush seal frictional pairs was designed and built. Six brush seal experimental parts with different structural parameters and brush wire materials and four frictional turntables with different coating materials were designed and processed. The effects of working condition parameters, structural parameters and different frictional pair materials on the frictional heating effects of brush seals were studied experimentally. By comparing and analyzing the maximum temperature of brush seals and the wear morphology and wear amount of frictional pairs before and after wear, the matching relationship between brush wire and rotor coating material was obtained. The results show that the maximum temperature of brush seals increases rapidly and then tends to be stable with the increase of friction time, and increases with the increase of interference. When the interference increases from 0.3 mm to 0.4 mm, the average maximum temperature of brush wires rises to 39.96 ℃. The maximum temperature increases with the increase of the brush thickness and decreases with the increase of the rear baffle protection height. When the brush wire material is cobaltbased superalloy GH605, the best rotor coating material is WC; when the brush wire material is nickelbased superalloy GH4169, the best rotor coating material is ZrO2.These two matching materials may produce lower friction heat under the same working conditions, and the wear resistance is higher than that of other matching materials. Reference | Related Articles | Metrics | Comments（0）

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Research on CNC Milling Machine Cutting Power Prediction Model Considering Tool Wear Based on VMD-SSA-LSTM WANG Qiulian1, OU Guixiong1, XU Xuejiao1, LIU Jinrong1, MA Guohong2, DENG Hongbiao2 China Mechanical Engineering    2024, 35 (06): 1052-1063.   DOI: 10.3969/j.issn.1004-132X.2024.06.011 Abstract （239）      PDF（pc） （11485KB）（125）       Knowledge map    Save Traditional researches of cutting process powers required complex cutting power models and often neglected the influences of tool wear, so a CNC milling machine cutting power prediction model considering tool wear was designed based on VMD, SSA, and LSTM neural network. This model did not require the deconstruction of the energy consumption mechanism during the operation of CNC milling machines, and achieved high-precision prediction of cutting process powers based on historical experimental data. Firstly, artificial intelligence machine vision technology was used to analyze and process images of the tool wear, obtaining digital features of the worn tools and determining the maximum wear. Then, the VMD-SSA-LSTM model was established, which considered tool wear in the prediction of CNC milling machine cutting powers. VMD was used to decompose the operational data of CNC milling machines, and then the SSA algorithm optimized the hyperparameters of the LSTM neural network. The decomposed milling machine data components were input into the LSTM neural network, and the predicted values of each component were summed to obtain the cutting power prediction value. Taking face milling as an example, the proposed prediction model was compared and analyzed against BP neural networks, LSTM neural networks, and traditional models, which validated the effectiveness and superiority of the proposed model. Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （1121）      PDF（pc） （9281KB）（123）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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China Mechanical Engineering    2024, 35 (05): 0-.   Abstract （180）      PDF（pc） （372KB）（122）       Knowledge map    Save Related Articles | Metrics | Comments（0）

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Geometric Design and Performance Analysis of Multi-closed-loop Deployable Honeycomb Mechanisms with Thick Panels CHANG Boyan1, 2, GUAN Xin1, JIN Guoguang1, 2, LIANG Dong1, 2 China Mechanical Engineering    2024, 35 (07): 1156-1167.   DOI: 10.3969/j.issn.1004-132X.2024.07.003 Abstract （257）      PDF（pc） （14153KB）（122）       Knowledge map    Save A new type of space mechanisms with single-closed-loop was proposed according to thick-panel origami teory, and the mobility was analyzed by using screw theory. The degree of freedom of mechanism was reduced to 1 by the introduction of Myard constraint and Sarrus constraint, and the corresponding deployable units were obtained with the names of Myard deployable honeycomb unit and Sarrus deployable honeycomb unit. M-type honeycomb mechanism and S-type honeycomb mechanism were proposed based on kinematic analysis and planar mosaic array of deployable honeycomb units. The influence regularity of various factors on folding ratio was analyzed, and the deployable honeycomb units  were optimized with the rising of folding ratio index. The results show that M-type honeycomb mechanism may achieve flat surface, and S-type honeycomb mechanism may achieve higher folding ratio index. Reference | Related Articles | Metrics | Comments（0）

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State-of-the-art and Trend of High Loading Capacity Plastic Gear Drives LIU Huaiju, LU Zehua, ZHU Caichao China Mechanical Engineering    2025, 36 (01): 2-17.   DOI: 10.3969/j.issn.1004-132X.2025.01.001 Abstract （181）      PDF（pc） （15004KB）（121）       Knowledge map    Save Focusing on the loading capacity and applications in power transmission of plastic gears, the failure modes and loading capacity under the current materials and technology levels were introduced. The strengthening measures for improving loading capacity of plastic gears were elaborated from the application of new materials, lubrication improvement, collaborative design, and so on. The applications and potential of plastic gears scenarios in power transmissions such as automobile engines, vehicle reducers, and aeroengine accessory gearboxes were introduced, which has important reference significance for promoting the development of high load plastic gear technology and applications. Reference | Related Articles | Metrics | Comments（0）

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Research Progresses on Reliability Analysis and Optimal Design of Automobile Structures ZHANG Lei1, 2, 3, SUN Xuetao1, 2, CHEN Jie1, 2, SUN Yuanbo3, GUO Jiajia1, 2, ZHENG Jie1, 2 China Mechanical Engineering    2024, 35 (11): 1948-1962，1970.   DOI: 10.3969/j.issn.1004-132X.2024.11.006 Abstract （200）      PDF（pc） （2504KB）（120）       Knowledge map    Save In order to study the reliability of automobile structures, the uncertainty of mechanical structure analysis and design was summarized, and the uncertainty of design variables and parameters of automobile structures was analyzed from three aspects: structural parameter uncertainty, material performance parameter uncertainty and load uncertainty. The research progresses of probabilistic reliability analysis and non-probabilistic reliability analysis methods were reviewed and summarized. The applications of reliability analysis method in automobile structures were listed. The mathematical model and algorithm of reliability were sorted out, and the applications of reliability optimization design in lightweight and crashworthiness of automobiles were studied, and the development trends of reliability analysis and optimization design of automobile structures were presented.  Reference | Related Articles | Metrics | Comments（0）

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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 Abstract （272）      PDF（pc） （6584KB）（120）       Knowledge map    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. Reference | Related Articles | Metrics | Comments（0）

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Study on Dynamic Mechanics Characteristics and Fatigue Life Prediction of Single PCPs ZU Haiying, SUN Jinshan, YE Weidong, LI Daqi China Mechanical Engineering    2024, 35 (08): 1358-1365.   DOI: 10.3969/j.issn.1004-132X.2024.08.003 Abstract （159）      PDF（pc） （6691KB）（120）       Knowledge map    Save Aiming at the rubber fatigue failures of the stator of conventional production PCPs, the fatigue test of stator rubber material under 50 ℃ oil immersion condition was carried out with GLB120-27 type single PCP as the research object, the fatigue performance parameters of rubber material were obtained, and the fatigue life prediction model was established. The dynamic mechanics characteristics of PCPs were analyzed by finite element method with ABAQUS software. Based on the stress-strain response results obtained by numerical simulation and the stress-strain fitting expression of stator rubber materials in uniaxial tensile tests, the range of strain energy release rate at fatigue danger points was calculated. The fatigue life prediction of PCPs under different interference conditions was studied by using the established fatigue life prediction model. The results show that the fatigue life decreases exponentially with the increase of interference. Compared with the average working life of a single PCP in recent 5 years, based on crack propagation method the fatigue life of the stator rubber may meet the requirements of engineering prediction accuracy. Reference | Related Articles | Metrics | Comments（0）

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Research Progresses on Incremental EMF Technology for Thin-walled Components CHENG Xiao1, LI Rui2, ZOU Guisheng2, LIN Junfeng1, 3, YU Haiping1, 3 China Mechanical Engineering    2024, 35 (12): 2092-2105.   DOI: 10.3969/j.issn.1004-132X.2024.12.001 Abstract （567）      PDF（pc） （12617KB）（119）       Knowledge map    Save With the development of Chinas high-end manufacturing industries, the demands for thin-walled components in many industrial fields such as aerospace were increased dramatically. The high-speed forming characteristics, traditional EMF was successfully applied to the production of thin-walled components of some key lightweight materials. However, due to the limitations of forming coil and discharge equipment, it was difficult to process large-scale and complex structure parts. In the past decade, incremental EMF technology was developed and gradually applied to the large thin-wall components processing, where a large number of research results were emerged. On the basis of briefly describing the principle and characteristics of EMF technology, the existing incremental EMF technology was divided into two categories according to the processing form: incremental electromagnetic composite forming and incremental electromagnetic direct forming. The research status of each processes was expounded from the aspects of basic principle, technical scheme and application results. Thus the main problems existing in the incremental EMF technology were analyzed, then the future development prospects and research direction of the incremental EMF technology were prospected. Reference | Related Articles | Metrics | Comments（0）

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Friction Reduction Mechanism of MoSe2/Graphene-Stainless Steel Self-lubricating Materials YAN Songshan1, XIAO Zhengli1, MAO Ya1, HU Rui2 China Mechanical Engineering    2024, 35 (07): 1151-1155.   DOI: 10.3969/j.issn.1004-132X.2024.07.002 Abstract （211）      PDF（pc） （9756KB）（116）       Knowledge map    Save In order to overcome the shortcomings of high friction coefficient and easy wear of stainless steel friction pair parts， based on the through-hole characteristics of powder metallurgy stainless steel porous matrix and the super sliding effect of heterojunction nano lubricants, a two-step preparation process of vacuum impregnation and hydrothermal synthesis were used to preduce MoSe2/graphene-stainless steel self-lubricating materials. The tribological properties and friction reduction mechanism of the composites were studied. The results indicate that the MoSe2/graphene lubricants in the matrix pores form a uniform lubricating film on the friction surfaces under the dragging effect during the friction processes, and significantly reduce the friction coefficient and wear rate of the friction pairs. At room temperature, load of 40 N, and speed of 100 r/min, the friction coefficient drops to 0.106, and the wear rate drops to 6.45×10-5 m3/(N·m). Compared with the stainless steel matrix, the friction coefficient and wear rate are reduced by 86% and 93% respectively.  Reference | Related Articles | Metrics | Comments（0）

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Modeling and Prediction of Central Damages in Cross Wedge Rolling Based on Continuous Damage Mechanics PENG Wenfei, ZHANG Cheng, LIN Longfei, HUANG Minghui, YU Feng China Mechanical Engineering    2024, 35 (04): 711-720,751.   DOI: 10.3969/j.issn.1004-132X.2024.04.014 Abstract （210）      PDF（pc） （9476KB）（112）       Knowledge map    Save Due to the cumulative central damage behavior in cross wedge rolling, it was prone to form central porosity defects, thus it was of great significance for high-performance manufacturing of cross wedge rolling shaft parts to accurately predict the formation conditions of central damages. The hot tensile tests were conducted under different conditions to obtain the main factors that affected material damages. Subsequently, the coupled damage constitutive models considering temperature, strain rate and stress triaxiality were proposed based on continuous damage mechanics. Furthermore, experiments on cross wedge rolling with different area reduction were conducted to calibrate the material fracture threshold of the damage constitutive model and verify the prediction accuracy of the damage model. The models were used to predict the influence laws of area reduction, spreading angle, and forming angle on central damage, which provided references for parameter selection. The results show that temperature, strain rate and stress triaxiality all significantly affect material damage behavior, and the established coupled damage constitutive models may effectively predict the evolution processes of central damages in cross wedge rolling. The central damages of cross wedge rolling are inversely proportional to the forming angle, and is directly proportional to the spreading angle and area reduction. The degree of influence of each parameters, from small to large, is in order of area reduction, spreading angle, and forming angle. Reference | Related Articles | Metrics | Comments（0）