China Mechanical Engineering

Study on Absolute Linear Time-grid Displacement Sensors with Multi-frequency Magnetic Field Coupling

YANG Jisen1, 2, 3, YUAN Junsong1, 3, XIU Fu1, 3, LIU Jiacheng1, 3, ZHANG Xiaolong1, 3

2025, 36(05): 889-897. DOI: 10.3969/j.issn.1004-132X.2025.05.001

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Aiming at the problems of mutual crosstalk among magnetic fields affecting the measurement accuracy of the sensors and reducing the signal-to-noise ratio when the excitation frequency of two code channels of a dual-row planar magnetic field sensor was the same， a multi-frequency magnetic field coupled absolute linear time-grid displacement sensor design scheme was proposed， which achieved the solution to the problems of eliminating the crosstalk of the magnetic fields among the code channels while solving the absolute displacement. The sensor was divided into fixed scale and dynamic scale， both using double-layer alternating structure， fixed scale using two columns of incremental code channel combination， divided into fine and coarse machines， the pairs of poles of two rows of excitation coils were two integers of the reciprocal relation， the absolute displacement measurement was realized by using the pairs of poles within the displacement difference. Precision machine measurement channel and rough machine measurement channel were input different frequencies of the excitation current signals at the same time， the precision machine was input the 1 MHz high-frequency current signals， the high-frequency excitation current signals might effectively enhance the inductive signals， improve the signal-to-noise ratio of the electrical processing system. Through the method of outlier frequency reduction， the sensor resolution was improved， which effectively solved the problems that it were difficult to reconcile the signal-to-noise ratio enhancement of the signals by increasing the frequency of the excitation signals and the high resolution of the sensors. Theoretical validation and error analysis of the sensors were carried out through electromagnetic simulation analysis. Finally， the experimental platform was built to carry out prototype experiments， and the experimental results show that the absolute sensor structure with multi-frequency magnetic field coupling effectively eliminates the magnetic field crosstalk between the fine and coarse machines， and the signal-to-noise ratio of the sensors is improved， with measurement errors are less than ±17.34 μm in the measurement range of 140 mm.

Research on Precision Control of Large Deployable Antennas Driven by Fusion of Data and Model

JIANG Donglei1, ZHAO Qiangqiang1, WU Tengfei1, MA Jia2, JIA Kang1, HONG Jun1

2025, 36(05): 898-910. DOI: 10.3969/j.issn.1004-132X.2025.05.002

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In order to improve the surface precision of large deployable planar antennas efficiently and accurately by adjusting the truss system, the surface precision prediction and accuracy verification were realized from two aspects of finite element simulation analysis and photogrammetry. According to the principle of mechanics of materials and temperature equivalence theory, the simulation model of plane antenna surface precision was constructed. A rapid measurement system of surface accuracy was established based on photogrammetry. The variable confidence Gaussian process model was established by combining the finite element simulation samples and the photogrammetry measured samples, and the precision was optimized and adjusted by Bayesian optimization. The accurate prediction and on-site rapid adjustment of large planar antenna precision were realized, which may provide simulation analysis model support for forward precision evaluation and inverse optimization adjustment of large planar antennas.

Research on Double Layer Sliding Mode Control of Large Scale Discrete Systems under High Frequency Time Varying Loads

JIA Cunde1, 2, 3, KONG Xiangdong1, 2, 3, LI Shaoguang1, 2, 3, LI Junfei4, ZHANG Junyong1, 2, 3, FENG Junxue5, AI Chao1, 2, 3, JIANG Wenguang1, 2, 3

2025, 36(05): 911-922. DOI: 10.3969/j.issn.1004-132X.2025.05.003

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To address the insufficient robustness in controlling large-scale discrete high-order systems during the drilling processes of rotary drilling machine under high-frequency load mutations, a double-layer sliding mode control(DLSMC) strategy was proposed based on distributed control principles. For pressure control applications, the proposed sliding mode control scheme demonstrated faster response speed and smaller errors compared to traditional PID and adaptive control methods. A controlled comparative analysis was implemented through paired borehole testing in geologically homogeneous formations, systematically evaluating drilling dynamics under controller-active and controller-absent configurations. The results show that the uncontrolled system experiences approximately 15 instances of power head rotational speed dropping to 0, 10 torque fluctuations with amplitudes around 100 kN·m, and 3 jamming incidents during drilling. In contrast, the controlled system maintains stable power head rotational speed and torque without any jamming occurrences. These findings validate the effectivenesses of the anti-jamming control strategy and provide a foundation for intelligentization of complete drilling systems.

Thread Extension Stress Analysis of Bolts under Pre-tensioning Conditions

GUAN Jiaoyue1, GAO Yuan1, AI Yanting1, TIAN Jing1, YAO Yudong2

2025, 36(05): 923-932. DOI: 10.3969/j.issn.1004-132X.2025.05.004

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It was difficult to accurately determine the thread stresses on the bolts under pre-tensionsing conditions， which might lead to strength fracture and premature loosening of the threads， and the reliability of the bolt joints was compromised. Currently， the contact state of the thread surfaces was usually described by stresses under an absolute coordinate system. However， the simulated stress direction was at an angle to the actual thread surface. The analysis results were not intuitive. Therefore， a thread mathematical model was derived and the extended stress analysis method of thread contact surfaces was proposed. Then， the finite element model of bolt joints was established for the structural characteristics of bolts. And the accuracy of the model was verified by tests. Finally， the extended stress analysis method was applied to study the thread surface stress and the distribution characteristics of bolts. The results show that the maximum error between the simulated preload and the testing preload is only 5.78%, where the accuracy of the simulation model is demonstrated. The extension stress analysis method may reflect the continuity and monotonicity of the stress distribution on the thread surfaces, and the method also reflects the optimal preload. The decreasing rate of the stress on the same layer thread is inversely proportional to the stress. From the stress analysis， the reason why the stresses on the thread are mainly concentrated in the first three turns is illustrated. The thread extension stress analysis method proposed herein is more intuitive and accurate. The paper may provide theoretical support for the anti-loosening analysis and reliability analysis of bolts.

Research on Liquid Film Vaporization and Structural Optimization of End Faces for Diffuser Self-pumping Mechanical Seals

RAO Yuan1, SUN Jianjun1, WEN Lan2

2025, 36(05): 933-941，953. DOI: 10.3969/j.issn.1004-132X.2025.05.005

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For the issues of liquid film vaporization in the diffuser self-pumping mechanical seals, a fluid film vaporization calculation model was established based on the Mixture two-phase flow model, viscosity-temperature equation, saturation vapor pressure-temperature relationship. The main regions and reasons were investigated for the phase transition of the liquid films between the sealing interfaces under medium and high temperature conditions. Through uniform experimentation and the NSGA-Ⅱ algorithm, the optimal sealing face structural parameters were obtained at a temperature of 393 K. The results show that phase transition mainly occurs on the inner diameter side of the sealing faces and the diffuser grooves. As the temperature of the medium increases, the vapor phase volume fraction increases and the viscosity of the medium decreases, the pumping effect weakens, and both the areas of the high and low pressure regions decrease. Under the premise of ensuring the stable operations of the seals, the optimal solution of the ratio of stiffness to leakage is as 257.17 GN·h/(m·L), and the sealing face structural parameters of helix angle β, sealing dam length wd, spiral groove length wg, spiral groove depth hg and diffuser groove width wk are as 34.4°, 5.2 mm, 8.9 mm, 43.3 μm and 5 mm respectively. These research results provide guidance for the optimization of sealing face structure design, control of liquid film phase transition, and enhancement of the sealing performance of the diffuser self-pumping mechanical seals.

Wheel Polygonal Wear On-board Quantitative Diagnostic Method Based on Frequency Response Function

XU Wentian1, LIANG Shulin1, CHI Maoru1, CAI Wubin2, TAO Gongquan1, WU Xingwen2

2025, 36(05): 942-953. DOI: 10.3969/j.issn.1004-132X.2025.05.006

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Wheel polygonal wear posed a significant challenge to the safety of high-speed trains in China， and the accuracy of current on-board wheel polygonal wear monitoring was inadequate. Traditional double integration methods for diagnosing wheel polygonal wears had limitations， primarily due to their inability to effectively mitigate interference from rail surface roughness and lacked of consideration for the impact of natural modal resonances in the wheel-rail system. Addressing these issues， a frequency response function-based quantitative diagnostic method was proposed for the wheel polygonal wears. A comb filter was utilized to mitigate the impacts of rail roughness， isolating the “pure” wheel polygon response components， then the frequency response function was employed to adjust for inherent modal influences， allowing for a quantitative assessment of polygonal order and roughness level from axle box vibrations. It is verified by simulations and measured data， compared with the double integration methods， the proposed method may achieve better diagnosis results across all polygonal orders， the average estimated errors of wheel roughness grade are less than 3.5 dB， which is significantly lower than the maximum estimated error of 14 dB for the quadratic integral methods. The results show that the proposed method has broader adaptability and enhanced accuracy， and has certain scientific and engineering values.

Precise Regulation of Differential Pressures at Port of Load-sensitive Multi-way Valves Based on ADRC Algorithm

LEI Xingmao1, DING Haigang1, 2, WANG Simin3, YANG Chengcheng1, PANG Zhizhen1

2025, 36(05): 954-962，973. DOI: 10.3969/j.issn.1004-132X.2025.05.007

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Load-sensitive multi-way valve was the core component for the hydraulic system of construction machinery， the pressure compensator was used to keep the differential pressure of the valve ports constant， but the differential pressure was susceptible to the spool opening and load changes， resulting in low accuracy of the main valve flow rate control.Therefore， a new type of load-sensitive multi-way valve differential pressure continuous control method was proposed， a proportional solenoid was used to push the spools of the compensator valves， and ADRC algorithm was used to control the proportional solenoid thrusts and realize the closed-loop control of differential pressures of the main valves， so as to accurately control the flow rate.Firstly， the working principle of the system was introduced and a mathematical model was established， then a simulation model was established based on AMESim-MATLAB joint simulation platform， and a test bench was built for experimental validation， the characteristics of the valve differential pressure maintenance and the main valve flow rate regulation were analyzed under the conditions of load changes and main valve opening degree changes. The results show that compared with the load changes， the changes of the main valve opening degree have a greater impact on the differential pressures. A new type of valve port differential pressure control structure and method may accurately control the load-sensitive multi-way valve differential pressures， so as to achieve the effectiveness of precise control of the flow rate， and may actively regulate the differential pressures without changing the main valve opening degree， so as to achieve the flow rate for the further regulation.

Research on Mechanism of Nano-surface Generation in Diamond Cutting Single-crystal Nickels

ZHENG Jiangfeng1, 2, 3, ZHANG Guoqing1, 2, 3, HAN Junhong1, 2, 3, LAI Zhihui1, 2, 3

2025, 36(05): 963-973. DOI: 10.3969/j.issn.1004-132X.2025.05.008

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To study the surface generation mechanism of single-crystal nickel ultra-precision machining， a molecular dynamics simulation model of diamond cutting single-crystal nickel was established， and the influences of different parameters on single-crystal nickel nano machining were obtained through the analysis of the results. Then， the diamond cutting experiments were carried out on single-crystal nickels， and white light interferometer and scanning electron microscope were used to characterize the cutting surfaces and chip morphologies. The cutting parameters of single crystal nickels were optimized from both of theoretical and experimental. The results show that the cutting depth is positively related to the surface quality of single-crystal nickels in a certain range. The negative rake of the tool is conducive to the improvement of the surface quality， but it may bring burrs. Single-crystal nickels are not amorphous during diamond cutting processes. The type of dislocations is dominated by Shockley dislocations， and a small amount of Hirth， Stair-rod and Frank dislocations coexist. The ［1-10］ crystal direction of the （110） crystal plane has the smallest subsurface damage， which is the best crystal direction. The study may provide certain references for optimizing the ultra-precision machining technology and improving the machining accuracy of single-crystal nickels.

A Robot Stiffness Identification Method Considering Weakly Rigid Joint Transmission Chain Structures and Flexible Rod Structures

GUO Wanjin1, 2, 3, 4, LI Ru1, WANG Libin1, HAO Qinlei1, CAO Chuqing2, ZHAO Lijun2, 4

2025, 36(05): 974-985. DOI: 10.3969/j.issn.1004-132X.2025.05.009

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To solve the stiffness identification problem for a 3T2R highly dexterous robot with weakly rigid joint transmission chain structures and flexible rod structures, a robot stiffness identification method was proposed. Firstly, the structural characteristics of the compact and cost-effective hybrid robot configuration design and the motion characteristics for adjusting the high dexterity of operational postures were analyzed. The robot Jacobian matrix was constructed, and the end deformation model of the robot was established to analyze the influences of weakly rigid joint transmission chain structures and flexible rod structures on the robot end deformations. Then, considering the effects of weakly rigid joint transmission chain structures and flexible rod structures, along with the robotic structural characteristics of weak rigidity and large deformation, robot joint stiffness identification was carried out，and the variable stiffness modeling was completed for the mobile joint 3. Experimental results indicate that the proposed method increases the stiffness of joints 3, joint 4 and 5 by 146.59%, 30.18% and 36.07% respectively, compared to conventional stiffness identification methods. The error rates between the measured and theoretical calculation values of the overall end deformations are in 4%~6% at six selected robot poses. The capability of the proposed robot stiffness identification method was verified.

Multi-tool Optimization Milling Method for Complex Cavities Based on Tool Allowable Loads

HAN Feiyan, ZHAO Yipeng, LI Hongyang, ZHANG Hao, WANG Che, PENG Xianlong, ZHANG Chuanwei

2025, 36(05): 986-994. DOI: 10.3969/j.issn.1004-132X.2025.05.010

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For 2.5D complex cavity CNC rough milling， the existing tool combination selection methods might not adequately consider the actual allowable loads of the tool， and the cutting load changed abruptly when machining with a contour-parallel tool path， which was easy to lead to chipping and tool breakage， affecting the safety and efficiency of rough milling. Therefore， a multi-tool optimization milling method was proposed for complex cavities based on tool allowable loads. An optimization model for milling efficiency with tool allowable loads as the constraint was established， and the optimal tool combination was selected from the available tool sets based on genetic algorithm. According to the selected tool combination， an adaptive machining area division method for complex cavities and a trochoidal and contour-parallel hybrid tool path generation method for multi-tool machining were given. A 2.5D complex cavity rough milling as the object of case analysis， under the tool allowable load constraints the optimal tool combination was selected and the combination of trochoidal and contour-parallel tool path was generated. Finally， the machining comparison results with the trochoidal milling method of NX software shows that the machining efficiency of the proposed method is improved by 25.9%， and the changes of machine loads are smooth during the machining processes， which verifies that the proposed multi-tool optimization milling method is feasible and effective.

Research on Spindle Structure Design with Stiffness-Strength Constraints

SHANG Xin1, CHEN Yu2

2025, 36(05): 995-1007. DOI: 10.3969/j.issn.1004-132X.2025.05.011

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Aiming at the problems that the spindle structure was mainly designed by people based on their experience, the design results had a great correlation with human experience and might not fully consider the thermal influences and other factors, so it was difficult to realize the intelligent design. By defining the geometrical structure functions of the spindle structures, establishing the strength constraints and stiffness constraints of the spindle structures, realizing the stiffness-strength coupling analysis of the spindle structures, and ultimately the expandable mathematical model was established for the design of the spindle structures. According to the established mathematical model of spindle structures, the spindle profile shape curve that meet the rigid-strong coupling requirements was obtained through numerical solving, and then, combined with the assembly requirements, the curve was transformed into a straight line profile that was easy to be processed by using the method of segmented straight line fitting, so as to obtain the straight line profile of each segment for the spindle, and to complete the design of the spindle structures based on the rigid-strong coupling. Finally, the spindle structure design of a vertical machining center was taken as an example to verify the correctness and feasibility of the proposed method, which provides an intelligent basis for spindle structure design.

Numerical Rolling Tests of Actual Measured Tooth Surfaces for Oversized Face Gears

LI Guangjun1, 2, MA Jing1, 2, DUAN Hong1, 2, HU Xiwen1, 2, XU Lei1, 2, MAO Shimin3, PENG Xianlong4

2025, 36(05): 1008-1017. DOI: 10.3969/j.issn.1004-132X.2025.05.012

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The reactor was the key equipment for the spent fuel reprocessing，and the oversized face gear drive was the core technology of the reactor.After obtaining the actual measured tooth surfaces of the face gear，the actual measured tooth surfaces were fitted into the non-uniform rational B-spline（NURBS） surfaces，numerical rolling tests were performed for the B-spline surface in mesh with the tooth surfaces of the mating cylindrical pinion，and modification design for the tooth surfaces of the cylindrical pinion was carried out according to the contact patterns and transmission errors of the numerical rolling tests， aiming to solve the reduced meshing performance problems which raised from not easy to control the machining precision of the oversized face gear tooth surfaces.A double crowning model of the cylindrical pinion was established，the spline surfaces fitted by the actual measured tooth surface coordinates of the face gear was constructed，and the model of numerical tooth surface meshing contact analysis was given.Numerical examples show that the meshing of the actual measured tooth surfaces of the face gear and the double crowned surfaces of the cylindrical pinion was capable of obtaining perfect and stable contact patterns and transmission errors.The results respectively obtained from the numerical rolling tests and experimental rolling tests are consistent，which proves that the double crowning of the pinion surfaces may compensate the machining errors of face gear tooth surfaces，and the numerical rolling test for face gear drives is feasible.

Chatter Identification Method for Heavy-duty Robotic Milling Systems Based on Variational Mode Filtering and Attention Mechanism

LIANG Zhiqiang1, 2, CHEN Sichen1, DU Yuchao1, LIU Baolong1, 2, GAO Zirui1, YUE Yi3, XIAO Yubin4, ZHENG Haoran1, QIU Tianyang1, LIU Zhibing1

2025, 36(05): 1018-1027,1073. DOI: 10.3969/j.issn.1004-132X.2025.05.013

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A method was proposed for identifying chatters in heavy-duty robotic milling systems by integrating variational mode filtering with fixed parameters, envelope filtering and an attention mechanism network identification. Initially, variational mode filtering theory was applied to eliminate non-chatter signal components in the high-frequency ranges by optimally selecting a quadratic penalty. Then, to swiftly identify the current machining conditions, the envelope filtering method was employed, leveraging signal time domain distribution and the frequency domain mapping law to remove the spindle speed-related signal components in the low-frequency ranges. Subsequently, a network identification model incorporating an attention mechanism was developed to identify preprocessed multi-temporal short-term signal segments for machining condition identification, followed by verification experiments on heavy-duty robotic milling systems. Experimental analysis results demonstrate that by eliminating non-chatter signals in the high-frequency ranges and spindle speed-related components in the low-frequency ranges, the accuracy of regenerative chatter identification is significantly enhanced, achieving an identification accuracy of 98.75%. Compared with alternative identification methods, the proposed method may effectively identify regenerative chatters during heavy-duty robotic milling processes, thus offering valuable technical support for future online chatter suppression of heavy-duty robotic milling.

Research on Constant Force Control System of Robot Bonnet Polishing Based on Fuzzy Impedance Control

LI Lucheng, WANG Zhenzhong, HUANG Xuepeng

2025, 36(05): 1028-1034. DOI: 10.3969/j.issn.1004-132X.2025.05.014

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In order to keep the contact force constant during the bonnet polishing processes， a fuzzy impedance control robot bonnet polishing constant force control system was designed which might adjust the damping coefficient in real time， and the simulations of the robot bonnet polishing constant force control system were carried out. The simulation results show that the system has good contact force convergence. The polishing experiments of planar and curved optical components and the contrast polishing experiments of force/position actuators were carried out. The experimental results show that the system may realize the constant control of the contact forces during the bonnet polishing， and the force fluctuation ranges may be controlled within 3 N. The control system may effectively control the fluctuation ranges of the contact forces in the field of robot bonnet polishing， and ensure the consistency of surface precision for the machined workpieces.

Research on Information Completeness Checking Technique of 3D Model for MBD

LIU Quanquan1, FANG Xifeng1, CHENG Dejun1, ZHANG Shengwen1, LUO Lanzhen2, KONG Junlong1

2025, 36(05): 1035-1043. DOI: 10.3969/j.issn.1004-132X.2025.05.015

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Aiming at the problems of non-standard information labeling, difficult diagnosis of structural differences, lack of dimensional redundancy and low efficiency of manual detection for 3D model information, a holistic completeness check method was proposed. By calling the application programming interface(API)functions of the 3D computer-aided design(CAD) software, secondary development of the inspection modules was carried out to complete the inspection and correction of 3D model information for MBD technology. Automatic capture of the basic direction view of the MBD model was realized through secondary development of CAD software, and then OpenCV library was called through Python to compare the newly captured view with the existing model view in the database by using the image SSIM, and the most similar model view image was obtained. The structural difference areas between two images were extracted and highlighted through image subtraction operation. Finally, the sizes of the 3D model were classified according to the classification rules, and the size completeness check was completed by DFS algorithm combined with the size redundancy missing check rule. The feasibility of the proposed method was verified by taking a cabin car product as an object.

Time-optimal Trajectory Planning of Robotic Arms Based on MIPSO Algorithm

WANG Guirong, NI Zhiqiang, ZHOU Kun, WANG Binrui

2025, 36(05): 1044-1053. DOI: 10.3969/j.issn.1004-132X.2025.05.016

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For the tasks of industrial robots finishing their work in the quickest possible time while meeting kinematics limitations， a time-optimal trajectory planning scheme was designed. Firstly， the robotic arms were modeled and analyzed， the kinematics equations were established. A 3-5-3 polynomial function was introduced as the research foundation of trajectory planning， and a time-optimal objective function was constructed under kinematics restrictions. Then， based on the improvement and optimization of the standard particle swarm optimization algorithm， a MIPSO algorithm was proposed by using tent chaotic mapping to initialize the population. Additionally， dynamically varying learning factors， nonlinearly decreasing modified inertia weights， and mutation operations in genetic algorithms were introduced. Finally， various algorithms were employed to optimize the robotic arms operating time， and the comparative results reveal that the MIPSO algorithm achieves a greater level of solution accuracy. The optimal time obtained from the solution is applied to the physical robotic arms， and the joint motion curves obtained are continuous without abrupt changes， which verifies the feasibility of the proposed scheme.

A Cylinder Liner Defect Detection Method Based on Improved YOLOv8n

LUO Liang1, 2, LANG Xiao1, ZU Guoqing2, ZHANG Nong1, YANG Lin3, SHEN Xiongwei4

2025, 36(05): 1054-1064. DOI: 10.3969/j.issn.1004-132X.2025.05.017

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Honing texture defects of the cylinder liners were the important quality indicator of an engine. Widely used manual quality inspection, however, owned problems of low detection accuracy, low efficiency, and manual uncertainty, as well as manual errors, and related automation detection research mightn not identify different types of defects. Therefore, a cylinder liner defect detection method was proposed based on an improved YOLOv8n model, which might accurately identify seven types of honing mesh defects. Firstly, the seven types of honing defects were defined based on geometric feature parameters.Then, the SC-C3 module was designed based on lightweight convolutional SCConv to reduce computational parameters of the model. Simultaneously, the channel prior convolutional attention(CPCA) mechanism was introduced to enhance the feature extraction ability of network. Finally, the Wise-IoU loss function was used to lower negative impacts of low-quality samples. The results show that the proposed detection method may effectively identify and distinguish composite defects under complex mesh backgrounds. The detection models mAP@0.5(mean of average precision of IoU is as 0.5) reaches 96.7%, and frame per second(FPS) approaches 476 frames/s. Moreover, the proposed model improves recognition accuracy by 2% and reduces computational load of 0.7 GFLOPs(Giga floating-point operations per second) compared to those of the YOLOv8n model. The paper provides an automated high-speed high-precision solution for detecting surface defects on cylinder liners.

Cross-domain Fault Diagnosis of Bearings Based on Joint Subdomain Contrast Alignment

YANG Kang1, CHEN Xuejun1, 2, ZHANG Lei3, LIU Feng3

2025, 36(05): 1065-1073. DOI: 10.3969/j.issn.1004-132X.2025.05.018

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The fault data of bearings exhibited significant distribution discrepancies under varying operating conditions， relatively low diagnostic accuracy was resulted in practical fault detection models. Additionally， most existing research on cross-domain bearing fault diagnosis primarily emphasized inter-domain alignment and intra-class comparison， while neglecting the influences of interactions between subdomains. Therefore， a cross-domain fault diagnosis method of bearings was proposed based on joint subdomain contrast alignment. In order to highlight the fault features， the bearing vibration signals were transformed into time-frequency graph by short-time Fourier transform， and the fault features were obtained by inputting them into the feature extraction module. Domain adaptation methods achieved cross-domain recognition by transferring knowledge learned from the source domain to the target domain. During the domain adaptation processes， a joint subdomain contrast alignment strategy was used to bring samples from the same subdomain closer together while separating samples from different subdomains， which aligned the subdomain distributions of the same class samples among the source and target domains， thereby enhancing the models generalization ability in the target domain. Resnet34 was used as the feature extraction network on the model architecture， and the maximum mean difference was used at the output of the network to align the global distribution of the source domain and the target domain. Compared with the classical domain adaptation methods， the experimental results on the bearing fault data set of Case Western Reserve University shows that the cross-domain fault diagnosis method of bearings based on joint subdomain contrast alignment has better feature transfer ability.

Establishment and Influences of Critical Wrinkling Criterion of Sheet Metals Considering Thickness Stress

DU Bing1, 2, LI Yang1, 2, LIU Fenghua1, 2, DONG Mingxin1, 2, WAN Yufan1, 2, ZHONG Qingshuai1, 2

2025, 36(05): 1074-1082. DOI: 10.3969/j.issn.1004-132X.2025.05.019

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Wrinkling instability was one of the main technical challenges affecting the precise plastic forming of thin-walled parts. The stress state in the thick direction had a great influence on the forming limit of the sheet metals during the sheet forming processes. In view of the above problems， the wrinkling instability of sheet metals in plastic forming processes was studied under different thickness stress conditions. The Buckle-Dynamic algorithm in ABAQUS software was combined with solid element modeling to establish a numerical analysis model of liquid-filled compression of fan-shaped parts， and the accuracy of the simulation algorithm was verified by tests. According to the wrinkling bifurcation theory and numerical analysis results， a method was adopted for defining the critical wrinkling time of the plates considering the thickness stress， and the critical wrinkling limit curve was established under the compression conditions of the plates. The influences of thickness stress on the compression wrinkling behaviors， wrinkle resistances and the positions of critical wrinkling limit curve in space of fan-shaped parts were discussed. The results show that the applications of thick stress may improve the wrinkle resistances of the sheets and improve the forming quality， which provides useful reference and experimental basis for the selection of sheet metal forming parameters and the trial production of typical parts.

Influence Law and Mechanism of Geometric Parameters on Wrinkling Characteristics of Hollow Aluminum Profiles in Stretch-Bending#br#

LIU Zhiwen1, 2, LEI Chong1, SUN Kaibo1, OUYANG Basheng1, LI Luoxing2, LIU Xiao3, LI Fazhi1

2025, 36(05): 1083-1093. DOI: 10.3969/j.issn.1004-132X.2025.05.020

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Based on the plate and shell theory， the expression of wrinkling energy and external force work functions of hollow aluminum profiles in stretch-bending were derived. Combined with the energy criterion， the theoretical prediction model of wrinkling was established for hollow profiles in stretch-bending and the accuracy of model was verified by bending experiments. The formation mechanism of wrinkling defects in stretch-bending of hollow profiles was revealed and the influences of geometric parameters on wrinkling limit and morphology were quantitatively studied. The results show that the theoretical predictions of the number and height of wrinkling under three different bending radii are in good agreement with those of the experimental ones. The maximum differences are as 1.2 and 0.55 mm， respectively， with relative errors of 16.93% and 11.28%， respectively. The growth rate of external force work in the bending stages is greater than that of wrinkling energy. With the increase of bending time， the external force work is greater than the wrinkling energy， resulting in the appearance of wrinkling instability. With the increase of thickness-to-height ratio and thickness-to-width ratio of the profiles， the wrinkle ratio and wrinkling number decrease， while the wrinkling limit and wrinkling height increase. With the increase of the aspect ratio， the wrinkle ratio and wrinkle height increase， while the wrinkling limit and wrinkling number decrease. The wrinkling limit might be increased by adding inner reinforcement rib in the profile cavities， while the wrinkling number increases and the wrinkling height decreases.

Influences of Differential Lubrication on Forming Quality for 5A02 Aluminum Alloy T-shape Tubes

XU Yong1, 2, 3, ZHANG Chi1, XIE Wenlong2, 3, XIA Liangliang4, YANG Baocheng2, 3, ZHANG Shihong2, 3, HUANG Xinyue5, WANG Shengcheng5

2025, 36(05): 1094-1102,1131. DOI: 10.3969/j.issn.1004-132X.2025.05.021

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In order to improve the forming quality of T-shape tubes, a method of differential lubrication was proposed by using hydroforming. The advantages of differential lubrication were verified by finite element simulation compared with traditional lubrication. Based on the fluidity of materials, the tensile stress and compressive stress of axial and circumferential elements of T-shape tubes were extracted during deformation. The influences of the area of the differential lubrication zones on the forming quality were analyzed. The results show that compared with the traditional lubrication method, the differential lubrication may effectively reduce the wall thickness thinning rate of the sides and tops of the T-shape tubes. Differential lubrication also may reduce the amount of side feed to reduce the risk of wrinkling. With the increasing of lubrication area in the bulging zones, the axial tensile stress of the arm element is gradually reduced, and the thinning rate of the arm sides of the T-shape tubes is reduced. With the increasing of the artificial roughing areas in the non-bulging zones, the axial compressive stress of the T-shape tubes sidewall element decreases, but the circumferential tensile stress increases gradually, and the material is more likely to flow to the transition zone of T-shape tubes, avoiding material accumulation in the middle of the tubes, thus reducing the risk of wrinkling. The research may provide technical support and theoretical reference for the forming of T-shape tubes.

Study on In-plane Shear Behavior and Interaction Mechanism of Flexible Elastic Composite Lattice Structures

NIU Guofa1, JI Xiaogang1, 2, WANG Wei1, WANG Guangyang1

2025, 36(05): 1103-1110. DOI: 10.3969/j.issn.1004-132X.2025.05.022

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The shear behavior and interaction mechanism of composite lattice structures were studied under in-plane shear loads by tests and numerical simulations. The damage failure courses and failure modes of matrix body centered cube(BCC) structures were analyzed experimentally. Using BCC cell structure as matrix, the influences of the diameter of chimeric structures on shear strength and shear modulus of composite structures were investigated by means of chimeric structure. Finally, the reliability of finite element analysis was verified by face centered cubic(FCC) structure tests, and the interaction mechanism of FCC-BCC structures was explored under in-plane shear loads. The testing results show that the mosaicism amang structures enhances the bearing capacity of the composite lattice structures, and influences the strains of the composite structures. The ultimate shear strength of FCC-BCC and simple cube-body centered cube(SC-BCC) are as 159% and 80% higher than that of the matrix respectively when the diameter size of the structural rods are both 0.45 mm.

Research on Applicability of Multi-functional Inter-vehicle External Vestibule Diaphragm in High-speed EMUs

ZHAO Cangpeng, DAI Liangcheng, CHI Maoru, GUO Zhaotuan, ZENG Pengcheng, SUN Baokai

2025, 36(05): 1111-1122. DOI: 10.3969/j.issn.1004-132X.2025.05.023

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In order to enhance the inter-vehicle coupling, high-speed EMUs were usually equipped with inter-vehicle longitudinal dampers at the car end. However, the large size and high cost of these dampers were in contradiction with the demands for lightweight, easy-to-operate, high-performance and achievable vehicle-end coupling systems in future high-speed EMUs. In response, a multi-functional inter-vehicle external vestibule diaphragm device was proposed, which had the functions of the traditional external vestibule diaphragm to reduce noise and air resistance and to protect against rain and snow as well as had the characteristics of stiffness and damping that might replace the inter-vehicle longitudinal dampers, playing the role of inter-vehicle vibration damping. The numerical simulation model of the sub-unit structure of the multi-functional inter-vehicle external vestibule diaphragm was established based on the operating principle, and the number of the sub-units when the multi-functional inter-vehicle external vestibule diaphragm might be equivalent to the damping function of the inter-vehicle longitudinal dampers was determined by comparing the dynamic characteristics parameters of the sub-units with those of the inter-vehicle longitudinal damper under the same working conditions. Finally, the dynamic co-simulation of the numerical simulation model of the multi-functional inter-vehicle external vestibule diaphragm and the high-speed EMUs dynamic model were carried out by using Simulink. The influences on the dynamic performance of the vehicles without an inter-vehicle damping device, equipped with the inter-vehicle longitudinal dampers and equipped with the multi-functional inter-vehicle external vestibule diaphragm were compared. The results show that compared with the inter-vehicle longitudinal dampers, the multi-functional inter-vehicle external vestibule diaphragm may further reduce the amplitude of yaw angle displacement of the carbody and the amplitude of lateral vibration acceleration of the carbody, suppress the yaw vibration of the carbody more efficiently, and further improve the lateral ride quality of the vehicle running.

Multi-objective Torque Coordination Control for Distributed Drive Electric Vehicles Based on Nonlinear MPC

KAN Xiaobo1, ZHAO Youqun1, LI Danyang1, LIN Fen1, HE Kunpeng1, 2, YOU Qingshen2

2025, 36(05): 1123-1131. DOI: 10.3969/j.issn.1004-132X.2025.05.024

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The control objectives for yaw stability in current distributed drive electric vehicles were relatively simplistic. To address this issue， a multi-objective torque coordination control strategy was proposed based on nonlinear MPC. The upper-level controller was a nonlinear MPC speed and yaw moment controller based on a 7-degree-of-freedom vehicle model. And the lower-level controller focused on both of achieving stability and economic efficiency through multi-objective torque coordination. The road adhesion utilization and hub motor power loss were considered in the objective function to achieve dynamic and coordinated distribution of torques. Finally， using the CarSim/Simulink joint simulation platform， the proposed method was compared with traditional control methods under the double lane change conditions and driving cycle conditions for low adhesion coefficient. The simulation results indicate that the proposed control strategy enables better tracking of the vehicles sideslip angle and yaw rate to their ideal values， thereby enhancing vehicle stability compared to that of conventional methods. Additionally， motor energy loss is reduced and vehicle economic efficiency is improved.

Research on Processing Parameter Optimization of Rail Repair by Abrasive Waterjet

ZHENG Yan

2025, 36(05): 1132-1141. DOI: 10.3969/j.issn.1004-132X.2025.05.025

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In order to improve the efficiency and repair quality of abrasive waterjet repairing rails and reduce energy loss， the orthogonal experiments on abrasive waterjet repairing rails were carried out on Chinas U71Mn 60 kg/m heavy rail， based on central composite design（CCD） response surface method. The repair quality regression model of rails was established， the influences of each processing parameter on the repair quality was studied. The results show that the nozzle feed rate has the more significant effect on the profiles， the surface roughnesses of cutting ground zones and the surface roughnesses of deformation ground zones than that of waterjet pressure. And two sets of processing parameter optimization combinations are obtained under different applicable conditions， one focuses on the repair quality， the other focuses on efficiency of repairing. It is found that the errors of the predicted values and the experimental values of the profiles， the surface roughnesses of the cutting ground zones and the surface roughnesses of the deformation ground zones are less than 6%， and the average error is less than 4%. It is proved that the model may effectively predict the surface roughnesses of the cutting surfaces， which lays a theoretical foundation for the practical applications of abrasive waterjet repairing rails.

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