Table of Content

25 May 2020, Volume 31 Issue 10

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Study on Fluid-Solid Coupling of Deformation Characteristics of Piston Bush in Water Hydraulic Pumps

NIE Songlin1;LI Shuo1;YIN Fanglong1;ZHOU Xin1;HU Zhen2

2020, 31(10):  1135-1141. 

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To realize the efficient sealing of piston pair within water hydraulic pumps and automatically compensate the wear gaps, an automatic compensation structure for piston pair gaps was proposed. The fluid-solid coupling simulation technology was used to study the deformation characteristics of piston bushs under the coupling of inner annular fluid and outer annular clearance fluid pressure with different piston bush thicknesses and ring groove widths. The simulation results show that, under the same working pressure, fluid boundary conditions and annular groove width, the deformation of piston bush gradually decreases with the increase of piston bush thickness. And the piston bush was made of engineering plastic PEEK. When the piston bush thickness is unchanged, the deformation of piston bush increases gradually with the increase of ring groove width. In addition, a test system for automatic clearance compensation of piston pair was established and preliminary tests were carried out. The experimental results are basically consistent with the simulation data.

Design and Kinematic Characteristics Analysis of an Intermittent Rotation Mechanism Based on Non-circular Gears

LIN Chao1;XIA Xiguang1;XING Qingkun2;LIU Wensi1

2020, 31(10):  1142-1148. 

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Aiming at the transmission performance defects of existing intermittent rotating mechanisms, an intermittent rotating mechanism was proposed based on non-circular gears. Firstly, the transmission and indexing principles of the intermittent rotating mechanisms were analyzed. Then, the mathematical model of the mechanisms was established, and the matching design method of the core components, the non-circular gear pairs, were detailed. Finally, the theoretical analysis of the mechanism’s transmission performance was carried out from the perspective of kinematics. Combined with a design example, a virtual prototype of the mechanisms was established by MATLAB and SolidWorks software. The kinematics simulation was carried out in ADAMS software. The comparison between the simulation results and the theoretical oness shows that the indexing angle errors of the mechanisms are about 0.74%, which verifies the correctness of the design theory and theoretical analysis of the kinematics characteristics.

Structural Optimization of Mould Electromagnetic Stirrer for Blooms

ZHANG Jing;MA Liang;ZHAO Dengfei

2020, 31(10):  1148-1154. 

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In order to improve the flow of molten steel in mould, the influences of electromagnetic stirrer structure on distribution of electromagnetic field, flow field, and temperature field in mould were studied with finite element method and finite volume method. The results show that the electromagnetic forces produced by the new electromagnetic stirrer at 400 A and 3 Hz are more uniform than that produced by traditional electromagnetic stirrer at 500 A and 3 Hz. The disturbance of molten steel is stronger in the mould, which is helpful to increase the heat transfer efficiency, formulate initial solidified shell and equiaxed crystal, thus improves quality of blooms.

Robust Design of Hydrostatic Bearings on Precision Grinding Machine Rotary Tables

WANG Jianlei1;WANG Yunlong1;MEN Chuanhao1;CUI Yahui1;CHEN Runlin1;WANG Xiaohu1;JIA Qian2

2020, 31(10):  1155-1161,1168. 

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Concerning that the performance simulation data was inconsistent with the measured data of the rotation errors of precision grinding machine rotary table hydrostatic bearing and to improve the design level of the rotary table hydrostatic bearings, a robust design method of hydrostatic bearings was proposed herein. The method considered the changes of bearing structure parameters in the bearing life cycle and analyzed the law of change about radius clearance, oil cavity size, threshold ratio and lubricating oil viscosity in 4 stages about design, machining, assembly and service, the effect of radius clearance on bearing performance at 4 stages was mainly studied and the robust design procedure of the rotary table hydrostatic bearings was given. The method was illustrated by a robust design example of a rotary table static pressure radial bearing and the design results were compared with the traditional design. The contrasting indices were stiffness, bearing capacity and temperature rise of bearing in 4 stages, which had direct impacts on bearing rotation accuracy. The results show that after the robust design, during the life cycle, the variations of the stiffness and bearing capacity of the hydrostatic bearings are 10%~27%, and the variation of temperature is 0.5%~16%, which is more stable than traditional design.

Lithium Battery Parameter Identification and SOC Online Joint Estimation Based on Combined Model

LIU Zhengyu1,2;LI Panchun1;ZHU Chengcheng1;YOU Yong1

2020, 31(10):  1162-1168. 

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Aiming at the hysteresis effects between open circuit voltage and SOC and the influences of noise in charge and discharge current and terminal voltage during SOC estimation, a Frisch scheme double filter (FSDF) method was proposed based on combined model. Firstly, a new model was established by using first-order RC equivalent circuit model combined with Preisach discrete model. Then the Frisch algorithm was used to estimate the noise variances of the input and output of models to filter out some of the input and output noises. Finally, the extended Kalman filter combined with the unscented Kalman filter was used to implement real-time parameter update and the battery cell SOC estimation. Experiments show that the FSDF method has higher accuracy and better robustness than that of the other methods such as Frisch scheme recursive least squares-unscented Kalman filter.

Research on Quality Control of Abrasive Flow Precision Machining Nozzles Based on Large Eddy Simulation Smagorinsky Model

LI Junye1;LU Hui1;SU Ningning1;ZHANG Xinming1;ZHANG Hongwei2

2020, 31(10):  1169-1174. 

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In order to study the influence mechanism of the flow field distribution, formation of eddies and existence of eddies on the nozzle holes by solid-liquid two-phase abrasive flow machining, the abrasive flow machining was used to polish variable diameter nozzle and the process was calculated with the Smagorinsky sub-grid model of the large eddy simulation. The numerical simulations show that the collision and shear actions between the abrasive particles and the wall increase with the increase of fluid velocity, and the velocity of the same section has a varied velocities, which are accompanied by the existence of eddies. According to the experimental results, the surface quality of the nozzle holes after the solid-liquid two-phase abrasive flow machining is improved significantly. The value of surface roughness Ra at the large holes decreases from 1.24 μm to 0.542 μm and at the small hole decreases from 1.21 μm to 0.437 μm. The conclusions show that the solid-liquid two-phase abrasive flow machining technology may effectively improve the inner surface quality of the machined nozzle holes. There is a velocity difference in the same cross section during machining, the existence of the velocity difference is conducive to the formation of eddies. The presence of eddies is helpful to improve the shearing effect of the abrasive flow machining processes and is beneficial to obtain a high-quality surface of the nozzle holes.

Mechanical-hydraulic Co-simulation of Vibration Characteristics for Forging Hydraulic Presses

WANG Feixue1,2;YAO Jing1;HU Futai1,2;ZHENG Yongjiang1,2;ZANG Xinliang1,2

2020, 31(10):  1175-1182,1189. 

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Considering the flexibility of mechanical equipment, using the co-simulation technology of AMESim, ADAMS and ABAQUS, the elastic dynamics co-simulation model of the forging hydraulic presses was established. The vibration characteristics of the forging hydraulic presses were studied under the unloading impacts of the hydraulic systems. Two conditions of equal load and partial load were discussed, and the influences of forging force, system pressure and eccentric load on vibration characteristics were analyzed. The results show that with the increase of forging force and eccentric load, the impact vibration increases correspondingly; with the same eccentric load, the vibration in Y direction is greater than that in X direction; the system pressure has little effect on the vibration. A verification experiment was been completed in the laboratory, and the experiment verifies the correctness of the co-simulation model.

Hysteresis Modeling Method of Pneumatic Muscles Based on KP Model

XIE Shenglong1;LI Tiefeng2;WANG Binrui1;CHEN Dijian1

2020, 31(10):  1183-1189. 

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In order to identify the hysteretic nonlinearity of motion processes on PM, KP model and polynomial model were used to model the displacement/pressure hysteresis of PM based on the displacement/pressure hysteresis characteristics experiments of PM. The unknown parameters in the two models were identified by recursive least square (RLS) method, and the effects of the number of KP operators and the order of polynomial on the accuracy of the two models were studied. The parameter identification results show that the KP model is better than that of the polynomial model in modeling accuracy, the modeling accuracy of KP model increases significantly as the number of operators increases and modeling accuracy of polynomial model increases with the increase of polynomial order.

Parking Line Parking Slot Recognition and Decision Planning of Automatic Parking Systems Based on Information Fusion

JIANG Wuhua1;XIN Xin1;CHEN Wuwei1;XIE Youhao2

2020, 31(10):  1190-1196. 

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A parking space recognition method was proposed based on information fusion by integrating distance and visual informations. Firstly, the coordinates of the corners of parking space in overhead image were captured by camera. Then the lateral distances of the vehicle body from the corners of the parking space were obtained by using the plane ranging model based on inverse perspective transformation. Finally, the parking line parking plane model was established by combining ultrasonic sensor and vehicle mileage information. The plane model determined the coordinates of the center point of rear axle of vehicle and the relative initial yaw angle to realize the recognition of the parking line parking slot. Based on the identified parking information, path planning and simulation analysis were carried out and verified by the real vehicle tests. Results show that the parking identification method of the vehicle may effectively realize the identification of parking line parking space, and the planned path is reasonable and feasible.

Optimization of Pressure Linearity of Energy-saving Reduction Circuits of CVT at Low Temperature

LUO Wei1;ZENG Hongyang1;ZHOU Yunshan1,2;HU Xiaolan2;ZHANG Feitie1;WEI Dong2

2020, 31(10):  1197-1202,1212. 

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Aiming at the phenomenon that the pressure linearity of CVT pressure reduction circuits with energy-saving pilot proportional pressure reduction valve worsened with the decrease of oil temperature, a test design method of central combination was adopted. Amplitude and frequency of dither currents were taken as input parameters, and the pressure linearity was taken as observation target to conduct low temperature tests. According to the results of low temperature tests, response surface model was established, and then genetic algorithm was used to optimize the response surface equation. Results of low temperature tests with the simulation optimization parameters show the effectiveness of this method.

Injury Investigation in Lower Limb Caused by Automotive Shapes and Pedestrian Ages during Traffic Crashes

QU Zhidong1;XIAO Sen1;HUANG Jing2;QIE Yanchao1

2020, 31(10):  1203-1212. 

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Pedestrian traffic injuries mostly occured in lower limbs, and the degree of injury was related to the front shape of vehicles. In order to reveal the different causes of pedestrian lower limb injuries caused by front end structure of vehicles and confirm the mechanism of such injuries, models of lower limbs of different ages were established based on the characteristics of Chinese human body and bone materials. Frontal collision was simulated in combination with front structural features of vehicles, and the quantitative relationship among age, front structure of vehicles, and lower limb injuries was analysed. The results show that age differences may cause significant differences in joint injury. Meanwhile，the structures of car's front walls affect the location of pedestrians' lower limb injuries; lower ground clearance and wider front wall may cause less serious lower leg injury.

Inherent Characteristics Analysis of Fiber-reinforced Composite Plates under Bolt Looseness Boundary

SUN Hai;LI Hui;XU Zhonghao;JIA Chenqiang;LIU Yuanning

2020, 31(10):  1213-1218. 

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The inherent characteristics of the fiber-reinforced composite plates under the bolt looseness boundary were analyzed using artificial spring stiffness method. Firstly, in order to study the impacts of bolt looseness boundary, the multiple sets of spring were artificially introduced into the constraints of composite plates to simulate bolt looseness boundary of varying degrees, so that the theoretical model of the thin plates under this complex boundary was established. Then, based on the orthogonal polynomial method, a free vibration mode function of thin plates was expressed. The inherent frequency and modal shapes under bolt loosening boundary were solved by Ritz method, and the specific calculation procedure was also proposed. Finally, a vibration test system of the composite plates was set up with an embedded pressure sensor under bolt looseness boundary. The corresponding inherent frequencies and modal shapes under different bolt looseness boundaries were measured accurately. After the comparison between experimental and theoretical analyses, the results show that their modal shape results are coincidence with each other, and the errors of inherent frequencies are in the range of 0.08% and 7.54%, which are in an acceptable level. Therefore, the correctness of the proposed theoretical method was verified.

Effect of Compound Milling Path on Surface Quality

LI Shenwang1;ZHANG Fan1;XIE Lijing2

2020, 31(10):  1219-1224. 

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Compound milling was generally composed of multiple rotational motions and multiple translation motions. The compound milling path equation and the compound milling paths were obtained by homogeneous transformation matrix method. The effects of compound milling path on surface quality were researched. The results show that the surface roughness of enveloping surface of compound milling was obviously lower than that of unenveloping surface. The surface roughness of unenveloping surface of compound milling was similar to that of ordinary face mill. The feed has little effects on the surface roughness of unenveloping surface, but the surface roughness of enveloping surface increases with the increase of feed. The surface roughness Ra of the unenveloping surface and the enveloping surface decrease with the increase of cutting rate ratio k. The residual stress of compound milling is smaller than that of ordinary face mill, and the residual stress of enveloping surface in compound milling is smaller than that of unenveloping surface.

An Optimization Method of Picking Routes for Warehouses with Fishbone Layout

LIU Jiansheng;LEI Zhaofa;NIE Weihao;TU Haining

2020, 31(10):  1225-1232. 

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A picking route optimization model was established and the distance matrix for the storage location in non-traditional warehouse was constructed according to the characteristics of a non-traditional fishbone layout and considering the actual warehouse operation constraints. Meanwhile, a MPGA with an evolutional reversed operator was proposed based on the standard genetic algorithm (SGA) to overcome the premature convergence and poor local search ability of SGA. To verify the effectiveness of the algorithm, MPGA was compared with SGA and S-Shape under different order sizes, and the MATLAB software was used to simulate and analyze. Experimental results show that the MPGA has the best calculation results, and the speed of searching optimal solution is quicker than that of SGA. The proposed algorithm may be better to solve the problems of picking route optimization for the warehouse with fishbone layout and improve the intelligent level of warehousing.

Data Driven Fault Diagnosis Method Based on XGBoost Feature Extraction

JIANG Shaofei;WU Tianji;PENG Xiang;LI Jiquan;LI Zhi;SUN Tao

2020, 31(10):  1232-1239. 

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Aiming at the problems that the current machine learning methods in fault diagnosis were not possible to fully exploit the hidden fault feature informations in the data and has insufficient approximation accuracy, an implicit feature information extraction method was proposed based on XGBoost. Firstly, the loss function of the XGBoost algorithm was customized according to the fault data and the fault types, and the fault splitting tree was constructed iteratively. Secondly, the leaf node position index vector of the sample in the fault tree was extracted and the feature code was reconstructed to obtain the intelligent representation of the implicit fault informations. Thirdly, based on the characterization matrix, a machine learning algorithm such as SVM was used to establish a fault diagnosis model to realize predictive diagnosis of multiple failure modes. Finally, the proposed method was validated by taking a driver  fault diagnosis as an example. The results show that compared with the fault diagnosis model under the original features, the diagnostic model based on XGBoost extraction implicit features has higher accuracy and better robustness, which may give the order of importance of the feature variables.

Influences Law of Mechanics Properties of 3D Printing Composite Open-hole Plates

YAN Dongdong;SHAN Zhongde;ZHAN Li;FAN Congze;SUN Qili

2020, 31(10):  1240-1245. 

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In order to improve the tensile mechanics properties of 3D printing continuous carbon fiber reinforced composites, the influences of different filling paths on open-hole plates composite tensile properties were studied. The principal stress trajectory path planning method was used to print the main stress trajectory path filled open-hole plate test specimen，and the tensile properties were compared with zig-zag path filled open-hole plates and machined open-hole plates. The results show that, compared with machined open-hole plates, the tensile strength of principle stress trajectory path filled open-hole plates is 9.73% higher, and the elastic modulus is 25.58% higher. The principle stress trajectory path filled open-hole plate strain distribution before fracture is more uniform and the strain is smaller.

Thermo-stress Field Evolution of TC4 Titanium Alloy by LSF

LU Xufei1,2;MA Liang1,2;LIN Xin1,2;ZHENG Yuxiang1,2

2020, 31(10):  1246-1252. 

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LSF might achieve accurate forming of high-performance complex parts, while large thermal gradients in LSF processes provoked residual stress and distortion, and affected the geometrical accuracy and mechanics properties of fabricated parts. A situ measurement system of thermal and distortion for single side clamping of substrate was built, and the—temperature and distortion evolution of plate of multi-channel multi-layer TC4 titanium alloy parts was investigated. Influences of different scanning strategies on thermo-stress field of parts were analyzed. The research results show that the development of substrate distortion is propelled by corresponding thermal history, and the scanning strategies significantly affect the thermal distortion of LSF parts.

Extrusion Mechanism of Ceramic 3D Printer Based on Screw Pump Feeding

ZHANG Jing, ZHOU Jing, DUAN Guolin

2020, 31(10):  1252-1259. 

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The precision of micro-flow extrusion was mainly influenced by printed materials and processing parameters. In order to improve the printing precision of ceramic parts, a screw pump was adopted to transport the slurry to ensure continuous feeding of slurry and constant pressure and to realize discontinuous printing. Then, the rheological characteristics of the printing materials were analyzed, and the extrusion speed and flow were calculated according to the structure parameters of the printing platform. Finally, the mathematical model was established, and the rheological properties of the materials were matched with the motion parameters of the platform reasonably. Relevant experiments were carried out. The experimental results are consistent with the theoretical calculation ones, which verifies that the feeding mechanisms and the mathematical model may improve the printing accuracy.