Table of Content

25 March 2024, Volume 35 Issue 03

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Study on Force Model and Surface Integrity of Cylindrical Grinding 18CrNiMo7-6 Steels

WANG Dong, CHEN Lei, ZHANG Zhipeng

2024, 35(03):  381-393.  DOI: 10.3969/j.issn.1004-132X.2024.03.001

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 In order to accurately and effectively control the influences of grinding parameters on grinding force and surface integrity, a three-stage grinding force theoretical model was established based on the plastic deformation, indentation theory and shear strain effect between abrasive particles and materials by analytical method. The brown corundum grinding wheels were selected for grinding experiments to explore the effects of grinding parameters on grinding force and the effects of grinding parameters and grinding force on surface integrity. The optimal processing parameters for cylindrical grinding were obtained through orthogonal experiments of cylindrical transverse grinding. The results show that the average prediction errors of normal and tangential grinding forces in the cylindrical grinding force model are 5.56% and 7.08%, respectively. The radial feed speed of the grinding wheel has the greatest impact on grinding force, followed by grinding width, and the influences of workpiece speed and grinding wheel particle size are relatively small. The radial feed speed and grinding width of the grinding wheel have a significant impact on residual stress, and the particle size of the grinding wheel has the greatest impact on surface roughness. As the grinding force increases, the surface roughness value continuously increases, and the residual stress firstly decreases and then increases. The maximum residual stress value along the depth direction firstly increases and then decreases. Within the parameters taken in the experiments, the distribution range of residual stress is basically 20~40 μm. The optimal combination of processing parameters is a radial feed speed of 0.15 mm/min for the grinding wheel, a workpiece speed of 120 r/min, a grinding width of 10 mm, and a grinding wheel particle size of 80.

Study on Influences of Ni Content, Nitriding Hardening Depth, and Shot Peening on Bending Fatigue Performance of 42CrMo Gears

WU Zhongrui, CHEN Difa, WU Jizhan, YANG Yudian, LIU Huaiju

2024, 35(03):  394-404.  DOI: 10.3969/j.issn.1004-132X.2024.03.002

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 Single tooth bending fatigue tests were conducted on 42CrMo gears with different combinations of Ni content, nitriding hardening depth, and shot peening. The effectiveness of different process combinations on improving the bending fatigue limit of gears was investigated, providing process guidance for gear fatigue resistance manufacturing. Additionally, the contribution of surface hardness, nitriding hardening depth, surface residual stress, and Ni content to the bending fatigue limit of gears with different process combinations was analyzed using the random forest algorithm. A multiple regression model considering surface hardness, nitriding hardening depth, surface residual stress, and Ni content was established to predict the bending fatigue limit of gears. Comparing the predicted values with experimental values, the maximum error is controlled within 7.80%, providing a theoretical basis for the rapid and low-cost assessment of gear bending fatigue limit in engineering applications.

Vibration Mimicking Fish Body Wave and Flow Distribution of Underwater Flexible Structure with Resonant Actuation of Macro Fiber Composites

WEN Zhiwei, LOU Junqiang, CHEN Tehuan, CUI Yuguo, WEI Yanding, LI Guoping

2024, 35(03):  405-413.  DOI: 10.3969/j.issn.1004-132X.2024.03.003

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This paper utilized the unique underwater vibration properties of smart flexible structures to explore the body wave motion of carangiform fish, greatly impacting the prototype design and analysis of next-generation underwater vehicles. The second-order vibration mode shape of MFC-actuated flexible structures was employed to mimic the fish body wave motion of carangiform fish. The multiple normalized mode shapes of the MFC-actuated flexible structures were obtained using the assumed mode method, and the actual underwater second-order mode shape of the MFC-actuated structures was obtained experimentally. This verifies that the second mode shape of the flexible structures approximates the fish body wave of the carangiform fish. The distributions of the instantaneous velocity streamlines and concentrated pressure regions were revealed using CFD. Streamlines both for the inflow and outflow of the oscillating structure surfaces were observed from the simulation. The results show that:the flow directions before and after the node on the flexible structure second-order resonant states were opposite. Meanwhile, two pairs of high and low concentrated pressure regions are always on both sides of the oscillating structures. And the distributions of the high and low pressure regions are opposite before and after the node. In summary, positive pressure gradients always exist across the flexible structures, and the forward pressure component provides suggestive thrust for the oscillating flexible structures. Meanwhile, the lateral forces before and after the node induced by the pressure are in the opposite direction and are partially canceled out. Consequently, the lateral stability of the oscillating structures was enhanced. These results may benefit the design and performance improvement of underwater bionic propulsors and robotic fish.

Analysis of Surface Gradient Decarburization in Automotive Front Axle Bending Based on n-Order Shear Deformation Theory

YUAN Rongfu, WU Min, HU Zeqi, FENG Wei, WANG Rongcheng, XU Jin,

2024, 35(03):  414-426.  DOI: 10.3969/j.issn.1004-132X.2024.03.004

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During the hot forging and heat treatment processes of the automotive front axle, decarburization occured on the surfaces of the material, leading to change in the mechanics properties of the decarburized layer with varying depths. This phenomenon significantly impacted the bending performance of the front axle under load. A segmented function was used to create a graded variation in surface functionality on both sides of the axle, resulting in a simply supported sandwich beam with uniform internal properties. The bending behavior of the beam under two-point loading was investigated using the n-order shear deformation theory. The displacement field control equation was derived using the principle of virtual work, The Navier analytical method was used to obtain the bending behavior of a beam under simply supported boundary conditions, and compared with examples in the literature. The results indicate that the n-order shear deformation theory has good accuracy and reliability. The deflection and rotation of the beam increase with the increase of the decarburization index k, and reach quasi-steady state at k≈10. When the depth of decarburization is greater than 5 mm, the stress caused by the bending of the beam is more strongly influenced by the  thickness of the decarburized layer than by the height change. When the depth of decarburization on both sides is asymmetric,  the physical neutral surface migrates. The bending deflection and rotation of the beam decrease with the increase of thickness and width, but the change in beam thickness has a greater impact.

Research on Two-level Fusion Strategy of Unmanned Driving Perception Information Target-decision under Tunnel Environments

WANG Maosen, BAO Jiusheng, XIE Houkang, LIU Tonggang, YIN Yan, ZHANG Quanli

2024, 35(03):  427-437.  DOI: 10.3969/j.issn.1004-132X.2024.03.005

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Based on the special driving environment in the tunnel and the perception requirements of unmanned driving, appropriate sensors and hardware were chosen to build a test vehicle and a perception system of multi-sensor fusion of millimeter-wave radar and camera. A two-level information fusion algorithm of “target-decision” was proposed based on YOLOv4 target-level information fusion algorithm and improved D-S evidence theory. Finally, a verification test of perception information two-level fusion was carried out in the urban road tunnel environments. The results show that in the tunnel environments, compared with the single camera or the millimeter-wave radar sensing results, the target-level fusion result based on the association of the camera and the millimeter-wave radar sensor to perceive the ROI area may improve the recognition accuracy by 9.51%, making up for the shortcomings of a single sensor in the tunnel environment perception technology. Based on the target-level fusion perception results, using the improved D-S evidence theory algorithm to perform decision-level fusion, compared with the single target-level fusion results, the false detection rate is reduced by 3.61%, which significantly improves detection accuracy. By adopting the multi-sensor sensing information target-decision-making two-level fusion strategy, it may meet the reliable sensing requirements of unmanned vehicles in the special tunnel environments, and provide theoretical and technical support for promoting the applications of unmanned controlled technology.

Elliptic Cycloid Tool Path Optimization of Impeller Rough Machining Based on Parameter Mapping

HAN Feiyan, GU Zhicheng, ZHAO Yipeng, ZHANG Chuanwei

2024, 35(03):  438-444，456.  DOI: 10.3969/j.issn.1004-132X.2024.03.006

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In order to improve the opening groove processing efficiency of complex curved blade passages, a cycloid tool path planning method for surface rough machining was proposed. Firstly, the processable area of the passages was parameterized. Then, a mathematical model of key parameters for elliptical cycloid tool path, with the optimization goal of minimizing machining time, was established in the parameter domain. The best short-axis length of the ellipse and the cycloid step that satisfied the machining requirements were solved by the interval narrowing method, then the cycloid tool path could be determined in the parameter domain accordingly. Afterwards, the trajectory of the parameter domain was mapped to the physical domain to obtain the cutting path. Finally, the efficiency of the proposed trajectory planning method was evaluated with an example of calculation of elliptical cycloidal open rough machining trajectory for an impeller, whose calculation time is 19.4% faster than the traditional line cutting method. In addition, the simulation results of cycloidal channel opening and line cutting show that the machining efficiency of the proposed method is 22.4% higher than that of the traditional line cutting method under the same parameter setting. The practical results of cycloidal milling show that the shape of impeller runner cut is consistent with the cycloidal track, whose surface residue meets the rough machining requirements. This paper provides a new trajectory planning method for rough machining of impeller flow channels to improve the machining efficiency, which is a substitution for the traditional line cutting method. 

Molecular Dynamics Study on Tribological Mechanism of Spherical Nanoparticles on Nickel-based Alloy Grinding Interfaces under Nanofluid MQL

ZHANG Yu, WANG Dexiang, GUO Feng, LI Xinming,

2024, 35(03):  445-456.  DOI: 10.3969/j.issn.1004-132X.2024.03.007

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This paper aimed to study the anti-friction and anti-wear mechanism and to further reveal the formation mechanism of lubrication film generated by nanofluid on the grinding interfaces through molecular dynamics simulations. 1-butyl-3-methylimidazolium tetrafluoroborate (［BMIM］BF4 ionic liquid) was used as the base fluid of nanofluid. And spherical nanoparticles made of alumina and copper were taken as representatives of high-and low-hardness nanoparticles respectively. The results show that boundary lubrication layer is formed on the grinding interfaces in NMQL grinding of nickel-based alloy. Copper nanoparticle occurs a series of tribological behaviors on the grinding interfaces, such as compression, shear, spread and separation, because of the far lower hardness than that of abrasive grains and nickel-based alloy workpiece. A layer of solid lubricating film was finally formed by copper nanoparticle, which may reduce the contact areas between abrasive grain and workpiece, resulting in lowered tangential grinding force by 4.6 percent compared with MQL grinding. Alumina nanoparticle maintains the initial spherical nanostructure during grinding due to their higher hardness than that of nickel-based alloy workpiece. Three tribological behaviors, i.e. sliding, rolling and polishing, occur on the grinding interfaces. The polishing scratches may enlarge the wet areas of ionic liquid, and hence may reduce the contact areas between abrasive grain and workpiece. The rolling behavior of alumina nanoparticle that moves like rolling balls may transform the sliding friction between abrasive grain and workpiece into rolling friction. Tangential grinding force is therefore reduced by 6.6 percent compared with MQL grinding.

Dual-resource Constrained Flexible Machining Workshop Inverse Scheduling Problem

WEI Shupeng, TANG Hongtao, LI Xixing, YANG Guanyu, ZHANG Jian

2024, 35(03):  457-471.  DOI: 10.3969/j.issn.1004-132X.2024.03.008

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In order to improve the efficiency and stability of machining workshops in dynamic production environments, an inverse scheduling problem model of flexible machining workshops was established considering machine and worker constraints. The model aimed to minimize makespan, machine energy consumption and inverse deviation index by adjusting workpiece scheduling, worker work, and machining parameters. Aiming at the problem characteristics, an improved differential evolution algorithm was proposed. In the algorithm, a hybrid double-layer encoding method was designed to reduce the search difficulty. Two initialization methods were proposed to improve the population quality based on dispatching rules. In order to strengthen and balance the global and local search, adaptive genetic operations and neighborhood search strategies were designed based on elite selection. The Hamming distance was improved, and a crowding operator was proposed to reflect the true diversity of the population. In the experiment, 33 test instances were constructed and the proposed algorithm was compared with the other 7 algorithms to verify the performance. Finally, the real inverse scheduling cases of a hydraulic cylinder production workshop in two different dynamic environments were analyzed. The results show that the proposed algorithm may effectively reduce the makespan by 4.2 % and the machine energy consumption by 20.2 % with a little change in the original schedule.

Research on Optimal Pose Set Planning Method under Physical Constraint Robot Kinematics Calibration

JIANG Jiguang, HOU Jue, SU Chengzhi, BA Qijiao, TIAN Aixin, XU Mingyu

2024, 35(03):  472-480.  DOI: 10.3969/j.issn.1004-132X.2024.03.009

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In the processes of kinematics calibration of industrial robots under physical constraints, the calibration accuracy was affected by the selection of the pose set, which in turn was constrained by the calibration devices. To solve these problems, an optimal pose set planning method was proposed based on sampling interval evaluation combined with pose set optimization. Firstly, the robot kinematics model and the distance constraint calibration model were established, and the robot system parameter error constraint equation and error Jacobian matrix were calculated. Secondly, the workspace of robot was divided into spatial grids and evaluate each grid interval using Latin hypercube sampling combined with observable indicators to obtain the optimal sampling interval. Finally, based on offline data, the calibration accuracy prediction model was established based on offline data and search for the optimal pose set within the optimal sampling interval. By planning and verifying the optimal pose set for the ZhongRui RT-608 robot, the results show that the average fitting sphere radius after calibration is 0.3947 mm based on the optimal pose set, which is 57.98% lower than that of the random pose set.

Study on Accuracy of Alumina-based Ceramics Formed by Three-head Extrusion

PENG Ziwei, WANG Yincheng, YANG Li, FAN Zitian

2024, 35(03):  481-486.  DOI: 10.3969/j.issn.1004-132X.2024.03.010

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On the basis of the self-built three-head layered extrusion equipment，the effects of extrusion head diameter d， extrusion head moving speed vs and extrusion layer height h on the surface roughness and dimensional accuracy of formed ceramics were studied. Then matching accuracy of ceramic green body samples during double-head and three-head synergistic extrusion was studied. The experimental results show that when the single-end extrusiond is as 0.41 mm, vs is as 10 mm/s, h/d is as 0.85, the roughness value of the ceramic side surface is as 24.423 μm, and the minimum dimension deviation is as 0.67%. When the double-head cooperative extrusion was formed, the positioning error of the double-head is as 1.03%, and the side surface roughness value is as 30.671 μm. When the three-head cooperative extrusion was formed, the positioning fit error of the three-head is as 1.15%, and the side surface roughness value is as 30.671 μm. Finally, alumina-based ceramic samples were prepared by double-head and three-head extrusion, and the feasibility of multi-head and multi-material cooperative extrusion was verified.

A Topology Optimized Design Method for High-performance Structures with Fluid-thermal-mechanics Coupling

LI Rongqi, YAN Tao, HE Zhicheng, MI Dong, JIANG Chao, ZHENG Jing

2024, 35(03):  487-497.  DOI: 10.3969/j.issn.1004-132X.2024.03.011

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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.

State-of-the-Art of Cutting Technology and Applications of PTFE

NI Jing, CUI Zhi, HE Lihua, FU Xin, ZHU Zefei

2024, 35(03):  498-514.  DOI: 10.3969/j.issn.1004-132X.2024.03.012

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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.

Numerical Simulation of Die Wear of Automobile Covering Parts Based on Dynamic Wear Model

ZHAO Yanjie, ZHANG Shuangjie, MU Zhenkai, WANG Wei, YAN Huajun, MA Shibo, ZHANG Yonghui

2024, 35(03):  515-523.  DOI: 10.3969/j.issn.1004-132X.2024.03.013

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In order to predict the service life of automotive cover dies, the Archard wear model was optimized to establish a dynamic wear model. The model coupled the dynamic wear coefficient and the surface hardness change curve. This model converted the wear coefficient K into a dynamic wear coefficient that varied with contact pressure and relative slip velocity, the surface hardness was converted into a dynamic hardness curve that varied with the depth of wear. Then, the Python language was used to develop the ABAQUS software for a second time, and the dynamic wear model was coupled to the finite element simulation, and the wear calculation of the die of automotive covering parts considering the wear coefficient and the depth change of the hardened layer was realized. By comparing and analyzing the dynamic wear evolution law of the typical positions of the convex and concave die during the forming processes, and taking the maximum wear depth of the die as the failure criterion, the service life of the stamping die of the aluminum alloy cover is 635 428 times. The main wear of the die was concentrated near the die clamping line and at the large rounded corner, and these positions need to be repaired and debugged in actual production, which may extend the service life of the die effectively.

Study on Tearing of CFRP Thin Circular Tubes Machined by Ultrasonic Vibration Assisted Grinding

KANG Renke, LU Bingwei, CHEN Kailiang, LI Shengchao, DAI Jingbin, DONG Zhigang, BAO Yan

2024, 35(03):  524-533，540.  DOI: 10.3969/j.issn.1004-132X.2024.03.014

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Aiming at the problems of tear damages in the ultrasonic vibration assisted grinding processes of CFRP composite thin tubes with unclear causes, ultrasonic vibration assisted grinding tests were carried out on M55J and T300 composite thin tubes, and the effects of ultrasonic amplitude, feed rate and spindle speed on grinding force and tear size were investigated. Through the force analysis of grinding processes and the calculation of the maximum thickness of undeformed chips, the formation reason of tear position and the change law of tear size were analyzed. The results show that the grinding force decreases with the increase of ultrasonic amplitude, increases with the increase of feed rate, and has little correlation with spindle speed. Tear is easy to appear on the inner walls of CFRP composite tubes, and the length and height decreases with the increase of ultrasonic amplitude, increases with the increase of feed rate, and decreases with the increase of spindle speed. 

Research on Microfluidic Chip Fluid Dynamic Pressure Polishing Process

FU Zhenfeng, WANG Zhenzhong, WANG Biao

2024, 35(03):  534-540.  DOI: 10.3969/j.issn.1004-132X.2024.03.015

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Microstructure polishing ball was designed based on fluid dynamic pressure lubrication theory, through theoretical analysis of the microstructure in the polishing ball rotation processes to generate more fluid dynamic pressure. Fluent was used to analyze the type of microstructure and the effects of microstructure size on the dynamic pressure generated by polishing, the generated polishing force was obtained by fitting Fluents data via MATLAB. After obtaining the better parameters of microstructure, area polishing of the microfluidic chips was performed. The surface roughness of the microfluidic chip plane area is reduced from 1.330 nm to 0.658 nm, and the surface roughness of the microfluidic chip flow channel is reduced from 0.737 nm to 0.379 nm. Thus, the applications of hydrodynamic pressure polishing process to the deterministic polishing of microfluidic chips may be further explored.

Research on Energy Transfer Model and Optimisation of Operating Parameters of Vibratory Rollers

HUI Jizhuang, LUO Wei, ZHANG Zeyu, ZHANG Jun, WANG Jie

2024, 35(03):  541-547.  DOI: 10.3969/j.issn.1004-132X.2024.03.016

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 In order to improve the compaction quality of vibratory rollers, the energy transfer model of vibratory rollers and the optimisation of operating parameters were studied. Firstly, the system vibration dynamics model of “wheel-compacted material” was established based on the U-K equation, and the energy transfer model of vibratory roller was proposed in combination with energy conservation.Then, the vibration frequency and compaction speed were taken as the optimal working parameters to construct the optimisation model of road compaction quality.Finally, the feasibility and effectiveness of the proposed method were proved through case verification. The results show that: the ratio between the working frequency and the intrinsic frequency of the compacted material is kept within the range of 2～2 to avoid the effect of resonance.The initial stage of low-speed rolling, and after the material properties were stabilised, the rolling speed may be increased to ensure efficient compaction, which results in the vibration frequency in the range of 21.8～27 Hz and the compaction speed in the range of 2.36～2.91 km/s, to achieve the optimal compaction effectiveness. The proposed energy transfer model and operation parameter optimisation model lay a foundation for guaranteeing the compaction quality of vibratory rollers and provide a reference for improving the compaction quality and efficiency of vibratory rollers.

Design of Lane Keeping Assist Systems Based on Improved Preview Control Model

LIANG Yongbin, FU Guang, LIN Zhigui, HE Zhicheng, ZHANG Jialuo, CHEN Tao

2024, 35(03):  548-558.  DOI: 10.3969/j.issn.1004-132X.2024.03.017

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To address the issues of low robustness, consistency in vehicle manufacturing, and severe road surface interference in LKA system of torque control, a LKA system was designed based on angle control by using neural network technology, Autofix algorithm, and preview feedback control theory, through expected trajectory decision-making and following PID control algorithm. A hardware-in-the-loop simulation test platform was built to verify the effectiveness and accuracy of the design of the angle based lane protection systems through virtual simulation based on Carsim/Veristand/ MATLAB. Based on GB/T 39323—2020, CN-CAP—2021, Euro-NCAP—2022 and the testing requirements of the car retention systems based on real-road commissioning and user concern scenarios, the simulation and comparison with real-road scenarios show that the angle-controlled LKA system has better lane keeping capability, stability, adaptability and robustness than that of the torque-controlled LKA system in the same usage scenarios.

Optimal Design of Slip Oil Pump Impeller Structures Based on NSGA-Ⅱ

SUN Yongguo, JIN Xin, XUE Dong, SHAN Jianping, SHI Xiaochun

2024, 35(03):  559-569.  DOI: 10.3969/j.issn.1004-132X.2024.03.018

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Slip oil pumps often needed to operate stably at high altitude and under low pressure conditions, which often led to cause problems such as insufficient oil supply and reduced efficiency. In order to get the best performance of the pump to meet the design requirements, this paper taken the impeller of a helicopter oil pump as the research object and to optimise the structure. The efficiency and lift of two typical working conditions at high altitude were selected as the optimisation targets, and the NSGA-Ⅱ was used to optimise the geometric parameters of the oil pump impellers, and the efficiency and lift of the oil pump before and after the optimisation were compared and analysed. CFD fluid simulation and experimental methods were used to verify the optimisation results. The results show that: the selected optimization parameters have a greater impact on the performance of the slip oil pumps, near the optimized slip oil pump vane positions the flow is more smooth, the high and low pressure areas of the excessively smooth, the energy loss is smaller, and the possibility of cavitation is reduced. The optimized slip oil pump design point lift increases 2.6 m, the efficiency increases 2.86%.