Table of Content

25 September 2022, Volume 33 Issue 18

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Research Progresses on Surface Integrity of Bearing Grooves

WANG Dongfeng, YUAN Julong, WANG Yanshuang, CHENG Yongjie, LYU Binghai

2022, 33(18):  2143-2160.  DOI: 10.3969/j.issn.1004-132X.2022.18.001

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Improving the surface integrity of bearing grooves was an important solution to solve technical problems such as low reliability life, high friction power consumption and unstable vibrations and noises of bearings. On the basis of comprehensive research of generalized surface integrity by domestic and foreign scholars, the definition and connotation of characteristic parameters of bearing groove surface integrity were proposed, and the significance of characteristic parameters and the influence mechanism on bearing performance were expounded. The influences of different processing processes such as forging, turning, heat treatment, grinding and ultra-precision on the surface characteristic parameters of bearing raceways were analyzed in details, and the corresponding control measures were given. The new technologies, new processes, and new methods for improving surface integrity were briefly introduced. Finally, the summary and prospect of improving the surface integrity of bearing grooves were made to provide some references for improving the contact fatigue lifes of bearings.

Simulation and Experimental Research about Temperature Fields of PDMS Cooled by Liquid Nitrogen Jet Impingement

LIU Xu, SUN Yuli, ZHANG Guiguan, QIAN BingkunG, AO Hang, ZUO Dunwen

2022, 33(18):  2161-2171.  DOI: 10.3969/j.issn.1004-132X.2022.18.002

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In order to explore the changes and distributions of the temperature of PDMS sample being impacted and cooled by the liquid nitrogen jet during the cryogenic micro-abrasive air jet machining the PDMS microchannels, this paper proposed a systematic research method of temperature that composed of temperature measurement experiments, Becks inverse estimation method fitting and APDL temperature field simulation. The errors between the final simulation results and the temperature measurement ones are only 1.735%. The simulations find that it will take 5.747 s for the surfaces to reach the obvious embrittlement temperature -147 ℃. PDMS may not reach a machinable embrittlement state at the moment of contact with liquid nitrogen， so it is necessary to pay attention to the pre-cooling time before machining. The simulation data was used to fit the cooling rate of PDMS to -147 ℃, and the cooling rate was used as a reference to predict the pre-cooling time required in the actual machining. By comparing the cooling rate, it is found that the cooling rate in the depth range of 0~100 μm from the surface of the PDMS specimen is 22.054% faster than that in the depth range of 0~1500 μm, and the cooling rate of the aluminum alloy workbench is about 22.311% higher than that of the adiabatic workbench.

Anti-vibration Design for Compressor Pipelines of Inverter Air Conditioners Based on Particle Damping

ZHANG Hongquan, XIAO Wangqiang

2022, 33(18):  2172-2182，2189.  DOI: 10.3969/j.issn.1004-132X.2022.18.003

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In order to solve the vibration problems of compressor pipelines of the inverter air conditioners, the dynamics analysis of pipelines was simulated by finite element method. The frequency conversion experiments were carried out at measured points range from 35 to 72 Hz. Energy consumption model of the particle dampers was established based on pipelines. In regard to the optimal design parameters, the influences of particle material, particle size and filling rate on the energy consumption were analyzed by the discrete element method. The vibration experiments of pipelines were performed and the experimental data indicate that when particle materials of iron base alloy, particle size of 2 mm and damper filling rate of 90% are adopted, the acceleration response of the intake pipe decreases evidently with B-type particle dampers in 45°way and the reduction of measured points is 36.57%, 30.15%, 45.79% respectively. The acceleration response of the exhaust pipe also decreases evidently with A-type particle dampers in horizontal way and the reduction of measured points reaches to 40.87%, 62.04% and 50.42% respectively. Eventually, the variation trend of the acceleration response in the tests was compared with the analysis results of the energy consumption model. The comparison results verify the feasibility of the energy consumption model of particle dampers for pipelines.

A Kinematic-parameter Calibration Method of Robots Based on Tool Coordinate

GAO Wenbin, CHU Yajie, YU Xiaoliu,

2022, 33(18):  2183-2189.  DOI: 10.3969/j.issn.1004-132X.2022.18.004

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To solve the problems that the error model contained the product of the orientation errors and the position vectors, which affected the accuracy of parameter calibration and recognition, when the pose errors of robot end-effectors were represented in the basic frame. A pose error calibration model of robots based on the POE including joint constraints was established where the tool frame was used as the reference frame, so as to avoid the influences of the product of orientation errors and the position vectors on the accuracy of parameter calibration and recognition. The UR5 robot was used as the calibration object, and the LeciaAT960-MR laser tracker was used as the measuring equipment to perform the parameter calibration tests. The test results show that the mean value of norms of the position errors and orientation errors of UR5 robot after calibrations are reduced by 91.07% and 89.16% respectively.

Investigation of Deformation Mechanism and Suppression Method of Weak Stiffness Components by Magnetorheological Finishing

PAN Bo, KANG Renke, HE Zengxu, LI Kailong, ZHANG Yunfei, HUANG Wen, GUO Jiang

2022, 33(18):  2190-2196.  DOI: 10.3969/j.issn.1004-132X.2022.18.005

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 Weak stiffness components were sensitive to the stress, and it was hard to guarantee the flatness after machining. To solve this problem, A MRF process was proposed to improve the flatness. The deformation mechanism of the components was clarified, and the residual stress relaxation was considered as the main cause of the deformations, which was predicted by an established model. The simulation results show that the deformations are about 9.5 μm by single-side machining, while the deformations are about 0.7 μm by turning over machining. Thus, the machining strategy by turning over was proposed based on the simulation deformation results. Experiments were conducted to verify the simulation. The results reveal that serious deformations happen by single-side machining, while the deformations recover by turning over machining, and the flatness converged efficiently. By the turning over machining strategy, the flatness peak and valley(PV)  value reduce from 4.6 μm and 5.9 μm to 2.0 μm respectively on a 200×2 mm weak stiffness flat component of copper. 

Experimental Research and Analysis on Torsional Fatigue Strength of Engine Crankshafts

CONG Jianchen, NI Peixiang, SUN Jun, LYU Shijie

2022, 33(18):  2197-2204.  DOI: 10.3969/j.issn.1004-132X.2022.18.006

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The factors of affecting crankshaft torsional fatigue strength and the causes of various torsional failure were analyzed by torsional fatigures test of crankshafts， and the corresponding improvement measures were put forward. It was pointed out that with the increase of engine explosion pressure， the torque of crankshafts increases accordingly， which leads to the increase of crankshaft torsional fatigue failures. The main torsional failure locations include pin journal oil hole， crank arm and pin journal bottom center of the crankshafts. The causes of failure are related to structural design， raw materials， machining， heat treatment and so on. The oil holes of pin journal are the most common part of torsional fatigue failures， and the crack sources are generally about 8～10 mm from the inner walls of oil holes to the journal surfaces. The torsional fatigue strength of crankshafts is more affected by induction hardening on the journal surfaces. The torsional fatigue strength of crankshaft reduces about 30% by surface induction hardening. The torsional fatigue strength of surface hardening crankshafts is increased more than 25% by polishing the internal surfaces of the oil holes. 

Study on Turning Performance of GCr15 Steels with Nanofluids Prepared by Composites of MWCNTs and Oleic Acid

GUAN Jiju, GAO Chao, XU Zhengya, DING Yunpeng, LI TeXU Xuefeng

2022, 33(18):  2205-2214，2226.  DOI: 10.3969/j.issn.1004-132X.2022.18.007

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 In view of the problems that cutting fluids were not easy to penetrate into the cutting areas for lubrication, it was proposed to prepare nanofluids using multi-walled carbon nanotube(MWCNTs) composites filled with OA as additives. The nanofluids were easier to penetrate into the cutting areas, and the composites might release OA during cutting processes to enhance lubrication. The thermophysical properties of the nanofluids were tested, and the performance of the nanofluids in cutting GCr15 steels under minimal quantity lubrication(MQL) conditions was evaluated. The cooling and lubrication mechanism of the composites in the cutting processes was analyzed. The results show that nanofluids prepared by the composites are significantly improved in terms of dispersion stability, heat transfer and wettability. Compared with ordinary emulsion, the cutting force, cutting temperature and surface roughness are reduced by 15%, 25%, 16%, respectively, and the and tool life is enhanced by 22% when turning with composite nanofluids.

An Energy Efficiency Optimization Model of Fused Filament Fabrication 3D Printing Based on Support Vector Regression

BAO Hong, YANG Jing, KE Qingdi, LI Hongzhen, YAO Yongzheng,

2022, 33(18):  2215-2226.  DOI: 10.3969/j.issn.1004-132X.2022.18.008

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The fused filament fabrication 3D printing energy efficiency was predicted and optimized based on response surface method and support vector regression model. Firstly, the Taguchi method was used to design the six factor three level orthogonal test, based on the response surface method, three factors that had a significant impact on processing energy efficiency were obtained, namely layer height, printing speed and hot bed temperature. Then, the prediction model of processing energy efficiency was established by support vector regression method, and compared with BP neural network method, the results show that the modeling and prediction performance of support vector regression method is better. Finally, the optimization model aiming at processing time and energy efficiency was established, and NSGA-Ⅱ, MOEA/D, SPEA2 and MOPSO were used to solve the model respectively, the Pareto front of the four algorithms was analyzed and compared, the results show that NSGA-Ⅱ performs best in solving this problem, the optimization results obtained by NSGA-Ⅱ algorithm were compared with the experimental results, which reflects the effectiveness and rationality of the optimization results of NSGA-Ⅱ algorithm.

Analysis of a Full Hydraulic Power Steering System with Integrated Power Regeneration Module

ZHOU Xin, LI Geqiang, LEI Xianqing, XU Zengjian

2022, 33(18):  2227-2233.  DOI: 10.3969/j.issn.1004-132X.2022.18.009

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Heavy trucks using full hydraulic power steering system experience load suddenly changed during bumpiness or sharp turns， the system would suffer pressure shocks, losses of hydraulic energy, serious hydraulic component damages and even system collapse. To solve the problems, a power regeneration module was introduced, which was integrated into the full hydraulic power steering system to collect and re-utilize the energy and reduce the pressure impacts. Based on AMESim, mathematical models with power regeneration were established for full hydraulic power steering system with and without load feedbacks. To study the dynamic characteristics of power regeneration, and the module was tested with a heavy truck under different road conditions. Both of the simulation and test results show that the power regeneration module has good effectiveness, may effectively absorb pressure shocks in the processes of heavy load transportation, and may also smoothly release hydraulic pressure. 

Experimental Study of Micro Scale Mechanics Behavior of Cleavable Gallium Oxide Crystals

XU Yameng, ZHOU Hai, ZHANG Jiequn, REN Xiangpu, ZHANG Chunwei

2022, 33(18):  2234-2240.  DOI: 10.3969/j.issn.1004-132X.2022.18.010

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In order to explore the free cutting direction and critical cutting depth of single crystal gallium oxide crystal ultra-precision machining，the (100) crystal plane and (010) crystal plane of the single crystal gallium oxide was divided into 24 equal parts at equal angles, and nanoindentation tests with Berkovich diamond indenter were conducted, nanoindentation scratch with Cube diamond indenter tests were conducted. The critical depth of cut for brittle-plastic transformation is the largest at 120° of the (100) crystal plane, which is about 623 nm, and the critical load of brittle-plastic transformation is 29.4 mN. The critical depth of cut for brittle-plastic transformation is the cargest at 105° of the(010) crystal plane, which is about 686nm, and the critical load of brittle-plastic transition is 20.0 mN. Gallium oxide crystals have strong anisotropy, and the (010) plane anisotropy is relatively strong. Comparing the variation trends of hardness, elastic modulus, fracture toughness and relative brittle-plastic transition critical depth of cut with direction, combined with the scratch test results in various directions, it may be seen that the (010) plane of gallium oxide crystal is an easy-to-process crystal plane, and the 105° direction is the easy machining direction.

Recession of Elastic Modulus and Prediction of Springback for 7075 Aluminum Alloy Sheets

YANG Zhuoyun, FAN Bocheng, LI Xiaoyi, ZHANG Zilu, DONG Guojiang,

2022, 33(18):  2241-2248.  DOI: 10.3969/j.issn.1004-132X.2022.18.011

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The recession of elastic modulus happening in the plastic deformation of sheet metals had a big influence on the springback prediction in sheet metal forming processes. To study the recession law of elastic modulus for 7075 aluminum alloy sheets, the conventional cyclic loading experiments were used and a new bending-unloading experiment with the assistance of DIC strain measuring system was designed to test the elastic modulus. The testing results show that the elastic modulus has a significant decline with the growth of plastic deformations and the recession law of elastic modulus is influenced by the stress states during deformation. The recession laws obtained by two experiments were applied to the springback simulation of forming processes for a beam with shape C. The comparison between the results of simulations and experiments shows that the analysis results of springback from the recession law of cyclic loading experiments are better than that from the bending-unloading experiments. The prediction accuracy of the four springback angles is increased by 42%,7%,40% and 200% separately.

Simulation Analysis and Experimental Study of Stiffness Characteristics of Aero-engine Spline Couplings

LI Lunxu, CHEN Guo, YANG Mohan

2022, 33(18):  2249-2257.  DOI: 10.3969/j.issn.1004-132X.2022.18.012

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Focusing on aero-engine low-pressure rotor spline couplings, the nonlinear characteristics of bending stiffness and the mechanism were analyzed, a solid finite element model of spline coupling considering gear surface contacts was established, the static stiffness experiments of the spline couplings were carried out. Through simulation and experiments, the nonlinear variation law of the structural stiffness of spline couplings was studied, and then the influence laws of fit clearance, tightening moment and torque on bending stiffness were discussed. The research results show that, due to the different contact states and stress conditions of the positioning surfaces, the bending stiffness variations of the spline couplings were mainly divided into two stages, which had piecewise nonlinear characteristics. The bending stiffness of the spline couplings is sensitive to the fit clearances of the positioning surfaces, and reducing the fit clearances of the positioning surfaces may effectively improve the bending stiffness of the structures; tightening moment has little influence on the bending stiffness, and under low load conditions, torque has an obvious effect on the bending stiffness. 

Three Dimensional Dynamics Behaviors of Rod-cone Collisions with On-orbit Re-placement Units

YOU Bindi, CAO Qian, YU Xiangjie, LIU Zhaoxu, LIU Yuqiang, LIU Xiaomeng, ZHAO Yang

2022, 33(18):  2258-2267.  DOI: 10.3969/j.issn.1004-132X.2022.18.013

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To study the contact collision dynamics of the ORU and the target spacecraft during the positioning guidance processes, taking the target spacecraft and ORU equipped with rod-cone positioning and guiding structure as the research object, a three-dimensional collision dynamics model(NE-CR-LN(Newton-Euler cone-rod Lankarani-Nikravesh) three-dimensional contact dynamics model) was developed for the positioning guidance processes of the spacecrafts and the ORU, taking into account the structural characteristics of the positioning guidance mechanisms and the actual positioning processes, and the cone-rod collision detection equation was derived in three-dimensional space was derived. The model applied the method of vector analysis, considering the characteristics of the cone-rod guidance system, four different contact conditions were divided. The model simulation results are compared with LS-DYNA simulation ones and literature models to verify the correctness of the NE-CR-LN dynamics model. According to the simulations and dynamic analysis results of ORU in contact and collision processes with typical working conditions, the actual collision regularity may be predicted by the NE-CR-LN three-dimensional contact dynamics model.