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  • NIU Wenchao, SUN Zhaoyang, SHENG Zhongqi, YU Jiancheng, ZHAO Baode, ZHAO Wentao,
    China Mechanical Engineering. 2023, 34(22): 2647-2658. https://doi.org/10.3969/j.issn.1004-132X.2023.22.001
    In order to study the influencing factors and influencing laws of the wing sail mast root stress, a numerical calculation model of the root stress of the wing sail masts was proposed based on the equivalence principle, and the accuracy of the proposed model was verified by finite element calculation. Based on the numerical calculation model of mast root stress, it was derived that there were 4 external parameters and 3 body parameters which affect the mast root stresses, the external parameters contain autonomous sailboat rolling period , rolling amplitude, rolling angle and deflection angle of wing sails. The body parameters contain mast center of gravity height, wing sail mass and the eccentric distance of wing sail. Based on the numerical calculation model, the influences of the above factors on the root stress of the masts were analyzed, and it is found that the stress values have a decreasing negative quadratic power function relationship with the rolling period , which is proportional to the rolling amplitude, the wing sail center of gravity height, the eccentric distance and wing sail mass, and the change curve of stress values with deflection angle coincides with the sinusoidal curve, and the stress value curve shows a sinusoidal waveform in one roll cycle. Finally, a method of adding stiffeners to optimize the structure was proposed for the stress concentration in the roots of the mast, and it was verified by the finite element calculation and the experimental analysis of turntable shaking. It is found that this method may reduce the stress value of the roots effectively during the working processes of the wing masts.
  • LI Jie, MA Chao, WANG Xiaoyan
    China Mechanical Engineering. 2023, 34(22): 2693-2703,2710. https://doi.org/10.3969/j.issn.1004-132X.2023.22.006
    In order to study the mechanism and the change law of the belt discharge torque of the friction plates under the no-load condition of the wet clutchs at high linear speed, a belt was established based on the hydrodynamics model considering the influences of the surface tension of the lubricating oil film and the oil-gas two-phase flow at high linear speed. The mathematical model of the drag torque was used to establish the volume fraction of air and oil two phases flow simulation for the oil film with an exhaust gap to analyze and verify the change of the oil film. The analysis of the model shows that the oil-gas two-phase flow of the friction plate produces part of drag torque at high linear speed, which is the main reason for the recovery of drag torque. Drag torque tests was did in high-speed belt-row test system for friction components. The influences of direction, lubricating oil temperature, flow rate, belt-row gap, and friction plate size on drag torque were analyzed.
  • YE Xin, HUANG Zhiquan, ZHANG Junhui,
    China Mechanical Engineering. 2024, 35(04): 571-579. https://doi.org/10.3969/j.issn.1004-132X.2024.04.001
     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.
  • WU Zhifeng, GAO Jianxiong, XU Rongxia, ZHU Pengnian
    China Mechanical Engineering. 2023, 34(22): 2659-2664,2673. https://doi.org/10.3969/j.issn.1004-132X.2023.22.002
     In order to study the evolution law of fatigue damage of metal components, a non-uniform damage accumulation model and life prediction theory were established considering the interaction of loads. First, a non-uniform fatigue damage model was proposed based on residual life under constant amplitude loading. Secondly, the loading sequence effect was expounded, and it was proved that the proposed load loading sequence effect might be considered in the non-uniform damage model. Then, the interaction among loads was verified, and it was proposed that there was mutual influence between adjacent two-level loads, the load interaction factor was defined and introduced, and a new equivalent damage model was established. Finally, combining the non-uniform damage model with the new equivalent damage model, a non-uniform damage model was constructed under multi-level variable amplitude loads. Life prediction was carried out with the test data of 30NiCrMoV12 steel and Al-2024-T45 alloy under two-level loading. By comparing with various models, it was verified that the proposed model may predict fatigue life well. The proposed model has a certain reference value for the damage evolution law of metals. 
  • YI Jun, YI Tao, CHEN Bing, DENG Hui, ZHOU Wei,
    China Mechanical Engineering. 2023, 34(22): 2711-2720. https://doi.org/10.3969/j.issn.1004-132X.2023.22.008
     The rough surface modeling method was employed to establish the surface topography model of a straight groove structured grinding wheel, considering the influences of structural characteristic parameters on the continuity of the grinding wheel surface through actual measurements. Based on the kinematics relationship between the grinding wheel and workpiece, as well as the trajectory equation of cutting edge, a prediction model for workpiece surface topography after grinding was formulated. Grinding experiments were conducted using both electroplating CBN and brazing CBN straight groove structured grinding wheels. The results show that relative errors between predicted Ra values and experimental ones are below 10%, while relative errors between predicted Rz values and experimental ones are below 12%, thereby validating the accuracy of the prediction model. Furthermore, the influences of various structural parameters on the surface topography of the workpiece were investigated. When the groove width of the grinding wheel remaines constant, an increase in the intermittent ratio of the grinding wheel resultes in an elevation of workpiece surface roughness. Conversely, when the intermittent ratio is held constant, variations in groove width have a minimal effect on workpiece surface roughness. Additionally, it is observed that roughness of the grinding wheel itself is a significant factor determining ground workpiece surface roughness. Among the three characteristic parameters of the grinding wheel surface topography investigated herein, it is observed that the skewness of the grinding wheel surface height exerts the most significant influence on the ground workpiece surface roughness.
  • ZHANG Dingge, WANG Liyong, LI Le, ZHANG Jinle
    China Mechanical Engineering. 2023, 34(22): 2665-2673. https://doi.org/10.3969/j.issn.1004-132X.2023.22.003
    In order to meet the demands of real time monitoring of load characteristics and the demands of health management of the special vehicle integrated transmission system under actual complex conditions, by using the matrix analysis method and numerical solution method of planetary transmission mechanisms, and taking the real vehicle sensor data as the model input, a dynamic model of integrated transmission system was established to rapidly and continuously solve the transmission output speed and torque under time-varying conditions. The kinematic matrix, differential equation and torque balance equation of the planetary transmission mechanisms were constructed. The fast continuous solution method of the dynamic model under time-varying conditions and the method for solving road load under the conditions of missing road load information were proposed. The calculated transmission output speed and torque were compared with the bench test results under the three typical conditions of launching, shifting and acceleration. The results show that the dynamic model may realize the dynamic simulation calculation of the output characteristic of the integrated transmission under the conditions of missing road load information. It provides support for real-time monitoring, dynamic control and intelligent operation and maintenance of special vehicle integrated transmission systems. 
  • ZHANG Xiao, CHI Maoru, XIE Yuchen, WANG Huansheng, CAI Wubin, DAI Liangcheng
    China Mechanical Engineering. 2023, 34(22): 2746-2757. https://doi.org/10.3969/j.issn.1004-132X.2023.22.011
    According to the research of the dynamics of Chinese-Russian variable-gauge trains, it was found that a single wheel tread might not be suitable for multiple types of rails, resulting in issues such as low conicity shaking, low critical speed, and poor wear performance. Based on the wheel-rail contact relationship, vehicle dynamics theory, and a reverse design recursive algorithm for wheel treads, a method for designing balanced and adaptable wheel treads for multiple types of steel rails was proposed. Based on this approach, the LMAopt wheel tread was obtained by optimizing the LMA treads. When the LMAopt treads were matched with Russian P65 steel rail, the low conicity shaking phenomenon is effectively suppressed, lateral ride index is improved, and the critical speed of the vehicle is increased by 22%. When matched with Chinese CHN60 steel rail, the dynamics performance is comparable to the LMA tead. The wear performance of the LMAopt profile under the influences of both types of steel rails is also improved, ensuring better dynamics performance throughout the service life of the vehicles. In conclusion, the LMAopt tread is a more suitable optimized wheel tread for variable-gauge trains.
  • YANG Feng, LUO Shijie, YANG Jianghong, WANG Yingjun,
    China Mechanical Engineering. 2024, 35(04): 602-613. https://doi.org/10.3969/j.issn.1004-132X.2024.04.004
     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.
  • TAO Liang, TANG Yu, QI Wenjie, ZHANG Dashan, LU Rui, ZHANG Xiaolong
    China Mechanical Engineering. 2023, 34(22): 2737-2745. https://doi.org/10.3969/j.issn.1004-132X.2023.22.010
    In light of the issue that the tread depth of passenger car tires was shallow and the conventional identification of wear characteristics were not obvious based on acceleration time-domain signals. This paper aimed to explore the classification and estimation of tire wear through the analysis of frequency-domain features of internal tire acceleration. Firstly, an intelligent tire test system was built by self-developed special rim assembly and data collector, and a three-axis accelerometer was arranged in the tire inner liner. The acceleration values were obtained by wired method, and the sampling frequency was 50 kHz. Secondly, based on the built test system, the typical tire pure rolling test was carried out on the Flat Trac bench, and the data was analyzed to clarify the parameters of the classification algorithm and construct the data set. The test tires included new tire, semi-grinding tire and full-grinding tire. The data analyses show that the circumferential acceleration Ax and radial acceleration Az of tires with different wear degrees are significantly different in the frequency domain of 5 kHz. Therefore, the vibration amplitude of Ax and Az in the frequency domain of 5 kHz was extracted at an interval of 10 Hz as the feature point, and the frequency domain data sets FDAx and FDAz were established respectively with vertical load, speed and tire pressure. Finally, the random forest algorithm was used to train and predict the two data sets respectively. When the number of decision trees and the minimum number of leaves are 20 and 20 respectively, the model classification effectivenes is the best. The results show that the average classification accuracy of the frequency domain data set FDAz is 95.1543%, which is higher than that of the data set FDAx. Compared with the time domain data sets TDAx and TDAz constructed by extracting Ax and Az time domain features from the same experimental data, the classification accuracy is increased by 16.18% and 10.08% respectively. At the same time, the feature values of the FDAz data set are optimized to obtain the optimal model classification accuracy and real-time performance when the feature frequency band and the number of feature points are within 1000 Hz and 100, respectively. The research shows that it is feasible to identify the degree of tire wear based on the frequency domain signals of the acceleration in the tire, which provides an effective means for the identification of the degree of tire wear of passenger cars.
  • JIA Zhixin, ZHANG Kaiyue, WANG Jin
    China Mechanical Engineering. 2023, 34(22): 2684-2692. https://doi.org/10.3969/j.issn.1004-132X.2023.22.005
    In order to improve the efficiency of EDM PCD, the spark discharge was promoted by mixing iron powders into kerosene working fluid. The mechanism of PCD in EDM of mixed iron powders was analyzed. The effects of iron powder concentration, peak current, pulse width, pulse and servo voltage on workpiece MRR and machining surface roughness were studied by experiments, and the reasons were analyzed. The experimental results show that kerosene mixed with a certain concentration of iron powders may improve the MRR of EDM PCD. The MRR increases with the increase of peak current, increases first and then decreases with the increase of pulse width, increases first and then decreases with the increase of pulse, and decreases with the increase of servo voltage. The surface roughness of EDM PCD is less affected by the concentration of iron powder, peak current, pulse width, pulse interpulse and servo voltage. The optimal combination of electrical parameters is obtained by orthogonal test: peak current 20 A, pulse width 125 μs, pulse interpulse 75 μs and servo voltage 27.5V.
  • HOU Caisheng, LI Jinhu, LIU YuMA Hui
    China Mechanical Engineering. 2023, 34(22): 2704-2710. https://doi.org/10.3969/j.issn.1004-132X.2023.22.007
     In view of the problems of low compression ratio and small displacement volume of equal wall thickness profiles, the gas force of the variable wall thickness profile changed greatly and it was difficult to machine and measure, a design method of asymmetric equal wall thickness profiles was proposed using base circle involute. Using this method, the fully engaged asymmetric scroll teeth with equal wall thickness were established, and the calculation formula of the working chamber volume was derived. The dynamic change processes of the axial, tangential and radial gas forces exerted on the orbiting scroll tooth were obtained with the spindle angles. The results show that compared with the traditional scroll profiles with equal wall thickness and variable wall thickness profile, the displacement volume of the newly constructed asymmetrical scroll profiles with equal wall thickness is increased by 25.99% and 7.82% respectively, and the compression ratio is increased by 19.70% and 2.04% respectively. While the variation range of the axial, tangential and radial gas forces is significantly reduced. It also shows that the asymmetric scroll profiles with equal wall thickness may give better consideration to the advantages of the traditional profiles, and has more superiorities in volume performance and dynamic performance. 
  • TANG Yang, ZHANG Wudi, ZHANG Yulin, WANG Yuan,
    China Mechanical Engineering. 2023, 34(22): 2758-2771. https://doi.org/10.3969/j.issn.1004-132X.2023.22.012
    The problems such as setting failure and tube wall damage were easy to occur in the deceleration and setting processes of pipeline plugging robot slips. Aiming at the ploughing effectiveness and hard contact phenomenon of slip in the deceleration and setting processes, the force of the slip deceleration and setting and the damage factors of pipe wall were analyzed. The finite element simulation model of slip deceleration and setting processes was established, and the influences of structural parameters such as slip tooth apex angle, tooth inclination angle and tooth number on the bearing performance and tube wall damage characteristics were analyzed. Four kinds of slips with the optimal combination of the key structural parameters of tooth apex angle, tooth dip angle and tooth number were obtained by using the method of multi-factor orthogonal experimental analysis. The simulation experiments of slip deceleration and setting processes were designed and built. Four kinds of slips with optimal combined structural parameters were processed, and the experimental test of friction between slip and tube wall during slip deceleration and setting was completed. Through the comparative analysis of the results of the pressure bearing performance and the damage degree of tube wall obtained by simulation and experiments, the optimal structural parameter combination of slip is optimized as tooth apex angle θ=65°, tooth dip angle γ=60°, and tooth number m=18.
  • ZHAO Yu, LI Yanting, WU Zhenyu, ZHOU Di, HU Jie
    China Mechanical Engineering. 2023, 34(22): 2721-2736,2757. https://doi.org/10.3969/j.issn.1004-132X.2023.22.009
    Aiming at the challenges of multi-mode, high dimension and nonnormality of industrial process data, a multi-mode online monitoring method was designed herein based on covariance tests considering time constraints. Firstly, the covariance matrix of the data to be detected was estimated using a cross-validated linear shrinkage estimation method. Secondly, the sparse principal eigenvalue test statistic was calculated based on the estimated covariance matrix. Subsequently, an EWMA(exponentially weighted moving-average) control chart with sliding window was designed based on the sparse principal eigenvalue test statistic: the MSPEWMA control chart, and the final test statistic was obtained by combining the mode transition constraints. Through Monte Carlo simulation, the performance of the MSPEWMA control chart under different conditions(variable dimension, drift size, control sample size, transition constraint parameters, and observation data distribution) was investigated. The results show that the newly proposed control chart has better monitoring results under large drift and non-normal conditions compared with other control charts based on covariance tests. Finally, the effectiveness of the method was demonstrated using real SCADA data of wind turbines.
  • LI Yanle, PAN Zhongtao, QI Xiaoxia, CUI Weiqiang, CHEN Jian, LI Fangyi
    China Mechanical Engineering. 2024, 35(04): 666-677. https://doi.org/10.3969/j.issn.1004-132X.2024.04.010
    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 ℃. 
  • JU Chun, LIU Jia, YANG Shengqiang, ZHANG Jingjing, ZHAO Xuhui,
    China Mechanical Engineering. 2023, 34(22): 2674-2683,2692. https://doi.org/10.3969/j.issn.1004-132X.2023.22.004
    Aiming at the structural difficulties of the thin thickness of the leading and trailing edges of the blades and the sharp change of the curvature, the least square method was used to fit the ellipse of the discrete points of the blade section including the leading and trailing edges and part of the blade body. By setting the three error constraints of the average distance, maximum distance and subtraction of slope, the boundary of the leading and trailing edges was identified. The elastic tool flag wheel suitable for the leading and trailing edge polishing was selected, and the polishing model of the flag wheel was simplified. Starting from the polishing of a single abrasive particle, the relationship between the compression of the flag wheel and the polishing force during the polishing processes was explored. Based on the Hertz contact theory and the improved equal chord height error method, the step spacing was determined. Finally, the blade was clamped by the robot, and the comparison experiments of lateral polishing and longitudinal polishing were carried out by means of flag wheel polishing. Both polishing methods may ensure that the values of surface roughness are less than 0.4 μm and the profile errors are less than 0.08 mm, which may meet the dimensional accuracy and surface quality requirements of the blades.
  • ZHANG Jinyang, XU Weichun, WANG Xiaohan, JIANG Xiaohui, GAO Shan
    China Mechanical Engineering. 2024, 35(04): 624-635. https://doi.org/10.3969/j.issn.1004-132X.2024.04.006
    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.
  • HAN Xiaohui, LIN Sen, FANG Xifeng, WANG Zhenzhong, SUN Zhaogang, YU Feilong, LI Lei, MA Yunwu, LI Yongbing,
    China Mechanical Engineering. 2024, 35(04): 721-730. https://doi.org/10.3969/j.issn.1004-132X.2024.04.015
    Rivet coating was a key factor influencing the formation and mechanics performances of riveted joints. The SSFR processes were used to join 6005A-T6 and 6A01-T5 aluminum alloy sheets herein. Three types of rivets including non-coated, Zn coated, and ZnNi coated were utilized to study the evolution laws of riveting force, energy input, and formation of the SSFR joints. Moreover, the remaining thickness of the coating layers at different positions in the joints and the diffusion of coating elements at the rivet/sheet interfaces was analyzed, and the influences of the rivet coating on the tensile-shear and cross-tension performances of the joints were investigated. The results indicate that the coating reduces the energy input generated by rivet rotation, thereby reducing the heat-affected zones of aluminum alloy materials. However, the decrease in energy input is not conducive to the formation of solid phase bonding between aluminum alloy materials in the rivet cavity, resulting in a decrease in the tensile-shear and cross-tension performances of the joints. Compared with Zn coating, the ZnNi coating has stronger wear resistance, and the remaining thickness still exceeds 40% after the stirring friction caused by high-speed rotation of rivets, which helps to improve the corrosion resistance of joints.
  • ZHANG Meng, ZHANG Songlin, LIU Yuwei, LIU Shicheng, FAN Pengju
    China Mechanical Engineering. 2024, 35(04): 656-665. https://doi.org/10.3969/j.issn.1004-132X.2024.04.009
     In view of the ubiquitous problems in tunable diode lasers, such as small tuning range of output optical frequency without mode hopping, low scanning frequency and complex structure, the dynamic characteristics of the internal piezo-based actuated systems of tunable diode lasers were studied. Based on the design goals of improving rotation accuracy and reducing axis offset, a multi-leaf parallel star-shaped flexible mechanism structure was proposed. After that, based on the Lagrange equation and Duhamel integral, the differential equation of motion and the vibration equation of the piezo-based actuated systems were respectively established.Then, the dynamics model of the flexible mechanisms was established and the structural parameters were optimized. Finally, a test platform was built to explore the mechanical response characteristics of the piezo-based actuated systems and the tunable range of tunable diode lasers. The experimental results show that the first-order natural frequency of piezo-based actuated systems is as 2187 Hz. The maximum axis offset of the flexible mechanisms is as 0.947 mm. In the mode-hop-free tuning performance tests of tunable diode lasers, a mode-hop-free tuning range of 103.5 GHz is achieved at a tuning frequency of 20 Hz. 
  • TANG Hao, TAN Jianjun, LI Hao, ZHU Caichao, YE Wei, SUN Zhangdong
    China Mechanical Engineering. 2024, 35(04): 591-601. https://doi.org/10.3969/j.issn.1004-132X.2024.04.003
    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.
  • SU Yonglei, ZHANG Zhifei
    China Mechanical Engineering. 2024, 35(04): 691-699. https://doi.org/10.3969/j.issn.1004-132X.2024.04.012
     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. 
  • WANG Xin, DAI Liangcheng, YANG Dongxiao, LUO Yun, CHI Maoru, GUO Zhaotuan, ZENG Pengcheng
    China Mechanical Engineering. 2024, 35(04): 742-751. https://doi.org/10.3969/j.issn.1004-132X.2024.04.017
    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.
  • HUANG Yun, HUANG Jianchao, XIAO Guijian, LIU Shuai, LIN Ouchuan, LIU Zhenyang
    China Mechanical Engineering. 2024, 35(01): 2-26. https://doi.org/10.3969/j.issn.1004-132X.2024.01.001
    The abrasion resistance of currently prepared superhydrophobic surfaces is generally poor, which limite the applications in various fields. Studied results found that micro-nano structure and low surface energy were the key factors to achieve superhydrophobic properties. Firstly, based on the mechanism of superhydrophobic surface, the superhydrophobic surface texture was summarized, aiming to solve the wear-prone challenge of micro-nano structures by optimizing the surface texture. Secondly, the superhydrophobic surface processing technology was summarized, and measures to reduce surface energy were analyzed in terms of cost and efficiency which might provide ideas for expanding the superhydrophobic surface processing system. Then, the means of analyzing the abrasion resistance of superhydrophobic surfaces were concluded in detail and the methods of improving the abrasion resistance of superhydrophobic surfaces were described. Finally, the future development prospects of abrasion resistant superhydrophobic surfaces was prospected, with a view to promote the large-scale applications of superhydrophobic surfaces in engineering.
  • CHANG Boyan1, 2, GUAN Xin1, JIN Guoguang1, 2, LIANG Dong1, 2
    China Mechanical Engineering. 2024, 35(07): 1156-1167. https://doi.org/10.3969/j.issn.1004-132X.2024.07.003
    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.
  • WANG Dongfang1, JIANG Cheng1, GONG Boyue2, LI Wenlong1
    China Mechanical Engineering. 2024, 35(07): 1263-1268. https://doi.org/10.3969/j.issn.1004-132X.2024.07.014
    Turbine nozzles were crucial components in aircraft engines, and the throat area was a key parameter that directly affected the engines power performance. In response to the issues of low efficiency and inaccurate estimation in existing measurement methods for the throat area, a new method for three-dimensional measurement point processing and accurate calculation of the throat area for aircraft turbine nozzles was proposed. Comparative experiments between the proposed method and the CMM method were conducted on a multi-blade turbine nozzle sample. The experimental results show that the throat areas obtained by the proposed method are more accurate, and the results of multiple measurements and calculations have high consistency.
  • YANG Yixiao, SUN Dan, LAN Kexin, ZHAO Huan, FENG Yuzhong, ZHANG Jieyi,
    China Mechanical Engineering. 2024, 35(04): 636-645,690. https://doi.org/10.3969/j.issn.1004-132X.2024.04.007
    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.

  • LI Yingchun, NIE Aonan, YANG Mingxuan, ZHU Dingkang, QIU Ming, YANG Gengsheng
    China Mechanical Engineering. 2024, 35(04): 646-655. https://doi.org/10.3969/j.issn.1004-132X.2024.04.008
     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. 
  • PENG Wenfei, ZHANG Cheng, LIN Longfei, HUANG Minghui, YU Feng
    China Mechanical Engineering. 2024, 35(04): 711-720,751. https://doi.org/10.3969/j.issn.1004-132X.2024.04.014
    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.
  • QI Maofu, SUN Yuantao, TIAN Chunlei, FENG Jiaqi
    China Mechanical Engineering. 2024, 35(04): 752-759. https://doi.org/10.3969/j.issn.1004-132X.2024.04.018
    In order to reduce the shear force of 850 ton cold shears, the shearing mechanism and characteristics of the cold shear were studied, the effects of shear parameters such as shear clearance, blade inclination, shear velocity, blade width and blade overlap on shear force were analyzed by orthogonal test. Variance, range and significance were used as the indexes of influencing factors, and the priority of them were given to optimize the shear parameters and reduce the shear force. The experimental verification of the cold shear before and after the optimization of shear parameters were carried out in the workshops which show that the errors between the measured and simulated values of the shear force of the cold shear before and after optimization were within 5%, which verifies the reliability of the simulation analysis. By setting the optimal shear parameters and shearing the same steel bar, the maximum shear force of the upper shear blade is reduced by 5.84 kN, about 13%. The maximum shear force of the lower shear blade is reduced by 4.77 kN, about 9.7%. Feedbacks from workshops show that the optimization greatly prolongs the period of blade broken and blunt and improves the blade life and shearing efficiency. The results are of great significance for improving the economy and production efficiency of the equipment, and may be applied to the engineering design of the same type of cold shears.
  • LIU Junling, FENG Ganghui, ZHANG Junjiang, YANG Kai
    China Mechanical Engineering. 2024, 35(04): 678-690. https://doi.org/10.3969/j.issn.1004-132X.2024.04.011
    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.
  • NI Jing, CUI Zhi, HE Lihua, FU Xin, ZHU Zefei
    China Mechanical Engineering. 2024, 35(03): 498-514. https://doi.org/10.3969/j.issn.1004-132X.2024.03.012
    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.
  • MA Qiaoying, YANG Shaopu, LIU Yongqiang,
    China Mechanical Engineering. 2024, 35(04): 580-590. https://doi.org/10.3969/j.issn.1004-132X.2024.04.002
    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.
  • CUI Haitao, QIAN Chunhua
    China Mechanical Engineering. 2024, 35(01): 67-73,82. https://doi.org/10.3969/j.issn.1004-132X.2024.01.006
    In phase TMF tests on nickel-based high-temperature alloy GH4169, a commonly used material for engine hot end components, under conditions of 200450 ℃ and 400650 ℃ is conducted. Considering the micro damage strain energy of polycrystalline materials in the elastic stages under the condition of TMF, a TMF life prediction model suitable for polycrystalline materials was proposed, model parameters were determined by combining the TMF test data. Three superalloys, GH4169, IN718, DD8, were used to evaluate the TMF life prediction ability of this model. The prediction accuracy of the life model is higher than that of the Manson-Coffin model and Ostergen model commonly used for TMF life prediction.
  • PENG Yuxin1, 2, 3, LIU Sheng1, 2, 3, HU Xinbin1, 2, 3
    China Mechanical Engineering. 2024, 35(07): 1290-1298. https://doi.org/10.3969/j.issn.1004-132X.2024.07.017
    By adding Ni interlayers to steel plates, the reliable connections between 6061T6 aluminum alloy plates and 08Al steel plates were successfully realized, and the mechanical properties of aluminum/steel spot welding joints were significantly improved. The results show that the thickness and distribution of Ni intermediate layers on steel plates may be controlled by using the prefabricated Ni intermediate layer processes, and the formation of Al-Fe brittle intermetallic compounds may be reduced. Compared with adding Ni foil intermediate layers directly, the prefabricated Ni intermediate layer processes may effectively increase the nugget diameter. The maximum tensile sheer force of aluminum/steel resistance spot welding joints with laser cladding Ni layer on steel plates is 35.5% higher than that without intermediate layers.
  • CHEN Zhongan, BAO Binying, ZHANG Guangyi, CHAO Yang, , WANG Yufeng, YAO Zhehe, JIAO Junke, ZHANG Wenwu,
    China Mechanical Engineering. 2024, 35(04): 700-710. https://doi.org/10.3969/j.issn.1004-132X.2024.04.013
    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%.
  • LI Rongqi, YAN Tao, HE Zhicheng, MI Dong, JIANG Chao, ZHENG Jing
    China Mechanical Engineering. 2024, 35(03): 487-497. https://doi.org/10.3969/j.issn.1004-132X.2024.03.011
    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.
  • CHEN Yuan1, XIONG Dianfeng1, LI Yuntang1, GAO Yongcao2, LI Chuancang2, WANG Bingqing1, JIN Jie1
    China Mechanical Engineering. 2024, 35(07): 1178-1187. https://doi.org/10.3969/j.issn.1004-132X.2024.07.005
    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.
  • 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. https://doi.org/10.3969/j.issn.1004-132X.2024.05.011
    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.
  • ZOU Junyi, LIU Chang, GUO Wenbin, YAN Yunbing, RAN Maoping
    China Mechanical Engineering. 2024, 35(06): 951-961. https://doi.org/10.3969/j.issn.1004-132X.2024.06.001
    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.
  • KONG Yankun1, DENG Wei1, JIN Guozhong2, LEI Jilin1, CHEN Liqiong3, JIA Dewen1
    China Mechanical Engineering. 2024, 35(06): 1103-1111,1119. https://doi.org/10.3969/j.issn.1004-132X.2024.06.016
     A comparative analysis was conducted on the fracture splitting processing performance of two types of high-strength connecting rods, 36MnVS4 and 46MnVS5, which were made from non-quenched and tempered materials. The reasons that affected the quality of connecting rod cracking were explored, and the boundaries for connecting rods cracking processing were optimized. The impacts of the connecting rod structures on the fracture-splitting processing performance were analyzed as well. The distribution characteristics of principal stresses and plastic strains at the roots of the cracking grooves were analyzed, and the crack initiation positions for connecting rods made of different materials were determined. The crack propagation processes of the connecting rods were simulated using the finite element software ABAQUS and FRANC3D, and a comparative analysis was conducted. The loading speed for the cracking processing of the 36MnVS4 materials was optimized. The impacts of the connecting rod structures on the cracking performance were analyzed.The results indicate that under the same boundary conditions, the cracking performance of 46MnVS5 material is better, with the tendency to have a unique crack initiation position, low notch sensitivity, good fracture brittleness, faster crack propagation speed, and higher required crack load. At a loading speed of 25 mm/s, the cracking performance of 36MnVS4 material improves. Connecting rod structures with smaller theoretical fracture surface area exhibit relatively better cracking performance.
  • ZHANG Dijia1, 2, GAO Luping2, ZHOU Shaoliang2, GAO Longlong2, LI Baoren2
    China Mechanical Engineering. 2024, 35(07): 1141-1150. https://doi.org/10.3969/j.issn.1004-132X.2024.07.001
    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.