Table of Content

10 May 2019, Volume 30 Issue 09

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Fatigue Properties of Knitted\|dapped Metal Rubbers under High Temperature Environment

LI Tuo1;BAI Hongbai1,2;XUE Xin2;WU Yiwan2

2019, 30(09):  1009-1017. 

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Fatigue property tests of knitted-dapped metal rubbers were performed with tension compression type composite test installation under the control mode of displacement. The fatigue properties of knitted-dapped metal rubbers under different amplitudes in room temperature (25 ℃) and high temperature (300 ℃)were researched. The damage evolutional processes were analyzed with average stiffness, equivalent viscous damping coefficient, and their damage factors. The results indicate that the fatigue damage forms of knitted-dapped metal rubbers are as abrasion, fracture of wires and plastic deformations. The fatigue processes include stiffness strengthening processes and stiffness attenuation processes, while the attenuation of mechanical properties mainly happen in the later stages. The increase of amplitudes and the rise of temperatures, which will clearly increase the accumulated damages of the specimens, both may shorten operating lifes of the materials.

Lane Keeping Model Prediction Control and Vehicle Stability Control on Low Adhesion Coefficient Roads

WANG Xuanyao1,2,3;CHENG Yi1;CHENG Yu1;YE Youdong1,2

2019, 30(09):  1018-1025. 

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A lane keep model prediction control algorithm was proposed. The relationship between the peak value of secondary low pass filtering of steering wheel angle and lateral acceleration and the degree of vehicle instability were analyzed by double lane change（DLC） on low adhesion coefficient roads, the fuzzy logic control algorithm was determined based on the measured signals such as steering wheel angle, lateral acceleration, yaw rate and velocity, and a lateral stability controller was designed. In order to prevent the stability controller's false start on low velocity and not serious instability conditions, an unstable index fuzzy control algorithm was determined. In order to avoid coefficient of vehicle stability rapidly declining, a retainer of coefficient of stability was designed. The CarSim/Simulink simulation results show that the designed steering and vehicle stability controllers have better lane keeping ability and stability on low adhesion coefficient roads.

An Improved Fast Algorithm for Solving Intersections of Lines and NURBS Curves and Surfaces Using Interval Analysis with Affine Transform

CHI Baotao1,2;ZHANG Jianming1,2;JU Chuanming1,2

2019, 30(09):  1026-1033. 

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An improved geometric method was presented for efficiently computing intersections between a line and a NURBS curve in parametric space or a line and a NURBS surface using interval arithmetic with affine transform. Combined with the subdomain decomposition algorithm based on the curve or surface curvatures, the appropriate preliminary iterative intervals could be determined quickly. In comparison with conventional interval iterative algorithms, the proposed method was superlinearly convergent which could overcome the conservatism of conventional interval arithmetic to some extents. In addition, the method prossessed the ability to relax requirements for initial iterative intervals, greatly to reduce numbers of unnecessary iterations and to promote the performance and efficiency of interval arithmetic. Based on the numbers of intersection points and the computational accuracy, this method could be applicable to the intersection problems of the inner and outer loop or domain. Numerical examples demonstrate the validity, accuracy and efficiency of the proposed method.

Research on Transmission Performances of Wind Turbines with Differential Speed Regulation

RUI Xiaoming;YIN Wenliang

2019, 30(09):  1034-1040. 

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Aiming at the newly-proposed wind turbines with differential speed regulation, the kinematics principles, total power flow and mechanical efficiency of the transmission system were studied. On the basis of completing the triaxial dynamics of the wind turbine transmission systems, a 1.5 MW simulation model of wind turbines with differential speed regulation was established. Afterwards, the correctness of the built simulation model was verified via experiments. Finally, the transmission performances of the proposed wind turbines were studied with the 1.5 MW simulation model. The simulation results show that the overall transmission system efficiency of the proposed wind turbines is high enough under different wind speed conditions which may be up to 0.951. The power required for speed regulation is quite small and only accounts less than 15.47% of that outputs by synchronous generator, while the maximum steady-state errors of the output speed are all less than 1.23%. The transmission performances of the proposed wind turbines are able to meet the requirements for practical applications well.

Research on Load Distribution Characteristics for Web-flange Splice Structures

LI Binbin1,2;ZHAO Youkun1;LIU Jie1

2019, 30(09):  1041-1048. 

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The multi-bolted web-flange splices were studied in terms of evaluating the load distribution among bolt rows of two simply supported types, i.e., four-point bending and three-point bending, as well as the effects of different simply supported types on the bolt-transferred loads. Firstly, the stress distribution of bolted regions which were located on the splice plates and the upper flanges, was preliminarily estimated by means of the strain gauge electric testing technique. Then, three-dimensional finite element models were constructed with ABAQUS software to simulate and analyze the behaviors of the load distribution among bolt rows. The results reveal that the load distribution characteristics of four-point bending specimens are obviously different from those of three-point bending specimens. For four-point bending specimens, the load distribution of bolt rows on splice plates or the upper flanges is almost symmetrical. But what is different about three-point bending specimens is that the asymmetrical structures along the length direction of specimens result in an asymmetry of load distribution. Besides, whether the four-point bending specimens or the three-point bending specimens, the load distribution of unilateral bolt rows located on splice plates is “bathtub-shaped” with the edge rows carrying more amount of load than the inner ones. Furthermore, for bolt rows located on upper flanges, the nearer to the butt surface of two I-beams, the smaller the bolt-transferred load will be and vice versa.

Thermal Error Modeling of CNC Machine Tools Based on State Space Model

MIAO Enming1;LYU Xuanxuan2;WEI Xinyuan2;SONG Xianjin2;DONG Yunfei2

2019, 30(09):  1049-1055,1064. 

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In order to reduce the influences of thermal error changes caused by machine tool operating parameters changes on prediction accuracy of the models, the state space modeling algorithm was proposed, which might automatically adjust the models according to the changes of machine tool operating parameters, so that the models had good adaptability to the changes of machine tool operating parameters. The prediction accuracy of the thermal errors for the machines under different conditions were compared by experiments. And the thermal error compensation experiments of plane cutting were carried out on the Leaderway V-450 CNC machine tool based on state space model. The experimental results show that compared with the traditional thermal error modeling algorithm, the prediction accuracy of the proposed algorithm is improved by 58.12%, the robustness is also improved effectively, and the actual thermal error compensation effectiveness is significant.

Surface Quality of Aramid Fiber Composites with Ultra-low Temperature and Micro-milling

SHI Wentian;HAN Dong;LIU Yude;HOU Yanjun

2019, 30(09):  1056-1064. 

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The micro-milling comparison machining tests were carried out under normal temperature and liquid nitrogen ultra-low temperature environments for aramid fiber composites， the machining surface quality and milling force data were obtained under different parameters and environments. The results show that the ultra-low temperature milling environments may modify the processing materials, reduce the strength, toughness and other properties, making it easy to cut, reducing the occurrence of wire drawing defects, fiber chip breaking thoroughly, and helping to obtain a more excellent surface topography. The ultra-low temperature environment suppresses the generation of ablation defects completely, improves the surface quality of the machined surfaces, and the surface roughness of milled surfaces may reach 2 μm or less. Compared with the normal temperature environments, ultra-low temperature processing may maintain a good milling surface quality at a high feed rate, and may improve the processing efficiency to a certain extent while ensuring the processing quality. The milling forces drop significantly and the tool surface wear is less. The ultra-low temperature processing environments improve the milling performance of the aramid fiber composites and improve the milling surface quality.

Study on Precipitation Behaviors of Second Phase Particles in Twin-roller Strip Vibratory Cast-rolling Processes of 20CrMn Steels

WANG Haijun1,2;SUN Minghan1;ZHU Zhiwang1;DU Fengshan1,2;XU Zhiqiang1,2

2019, 30(09):  1065-1071. 

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The vibration and non-vibration cast-rolling experiments of 20CrMn steels were carried out on a twin-roller strip vibratory cast-rolling mill. The obtained slabs were subjected to tensile test, fracture morphology observation and energy spectrum.The results show that the vibration may suppress the formation of large-sized particles and promote uniform precipitation of small-sized particles, thereby improving the mechanics properties of the strips.Combined with the preliminary second-phase particle dynamics analysis,the mechanism of the influences of vibration on the precipitation of the second phase particles in the strips were proposed as follows.The vibration disturbs the molten steels in the molten pool areas to make the alloy elements evenly distributed, thereby inhibiting the precipitation of the large-grain crystal phase in the solidification stages of the molten steels due to local enrichments, and promoting the desolvation and precipitation in the form of small-sized second phase particles in the rolling stages. The alloying elements are distributed in the small-sized second phase particles which have obvious reinforcing effects on the matrix, improving the use efficiency of the alloying elements and greatly strengthening the comprehensive mechanics properties of the cast-rolling slabs.

Study on Discrete Noises and Blade Distribution Characteristics of Vehicle Axial Fans

ZHONG Yinhui1;LI Yinong1,2;GAO Feng1

2019, 30(09):  1072-1080,1089. 

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Aiming at the problems that discrete noises of the axial fans were so big that affected total SPL(sound pressure level) and sound quality of automobiles，a theoretical and simulation model of the relationships between discrete noises and blades distribution characteristics were established by using harmonic correlation theory，and the relationships among the number of blades，the distribution characteristics of the unequal interval and fluxes，efficiency，noise were obtained separately combined with numerical calculations and simulation analyses. The results indicate that 7 blades fan has the best comprehensive performance in flow，efficiency and noise，and the best adjustment angle as 2.406 rad may achieves the effectiveness of optimal noise reduction to different numbers of equal interval blades based on unequal interval theory，and has no obvious effects on the flux and efficiency as well，which is proved by simulations and experiments. Based on the above research，a new method of reducing the discrete noises under the premise of satisfying the flow and efficiency is advanced，which provides references for the studies of the structure distribution characteristics of the blades.

Modification Method of Cycloidal Gears Based on Contact Stress Equalization

DING Guolong1;QIN Yuan1;MING Tingbo1;ZHAO Daxing1;YU Yunqing2

2019, 30(09):  1081-1089. 

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Based on the traditional combination modification methods, a cycloid gear modification method involving with contact stress equalization was proposed after comprehensively analyzing the transmission accuracy and tooth surface contact stress. Firstly, the working sections with the minimum pressure angle of the cycloidal gear transmission were used as the intervals for the shaping amount modification. Secondly, required backlashes were analyzed and a reasonable range of corner modification was selected; Then, with the angle modification as the target profile, approximation was made by combinion of equidistant and displacement modification, and finally was used to determine the corresponding equidistant and distance modification amount. The variances of contact stress distribution among teeth meshing at the same time in the optimum interval were obtained after the modification amounts were brought into the equation of the cycloidal transmission. Finally, with the objective of minimizing the variance of contact stress distribution among teeth meshing at the same time, the optimum angular modification and corresponding combined modification were searched within the range of angular modification. The simulation and test results show that this method may improve the transmission accuracy, the forced conditions of the tooth surfaces and prolong the services life of cycloidal gears, compared with the traditional methods.

A Battery Equalization Strategy Based on Reasoning Model of C-F

LIU Zhengyu1,2;WANG Xuesong1;TANG Wei1;YAN Peng1

2019, 30(09):  1090-1096. 

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A battery equalization strategy on the basis of the reasoning model of C-F was proposed，based on the analysis of the advantages and disadvantages of terminal voltage balancing strategy, combined the bidirectional Cuk equalizer which was simple to control balancing circuit and equalization energy， for the inconsistency of voltage, capacity and internal resistance of lithium-ion batteries in group use. To solve the problems of the inconsistency in use of lithium-ion batteries, individual imbalance degree of state of charge (SOC) and terminal voltages were defined. Overall imbalance degree was derived by using C-F model, and the difference of batteries was reduced by controlling the magnitude and direction of the equalization current of the topology circuit. Experimental results show that, this method may effectively reduce the difference of  terminal voltages and SOC of individual battery in the discharging and charging processes, and improve the efficiency of energy utilization.

Recognition Methods of Small Amplitude Hunting in High-speed Trains Based on S-transform

NING Jing;RAN Wei;CHONG Chuanjie;CHEN Chunjun

2019, 30(09):  1097-1102,1110. 

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For the problems that the existing high-speed train monitoring methods did not consider the non-stationary characteristics of vibration signals of the high-speed trains, which caused the trains to lose the hunting stability, based on S-transform a method was proposed to process the high-speed train bogie signals and then extract the features. The LS-SVM was utilized to train and identify the features. The results show that the recognition accuracy of the features based on S-transform is 100%, which is much better than that of the wavelet-transform-based method. Therefore, the proposed method may predict the running states of the high-speed trains in time and ensure the operation security of the trains.

Mold CNC Machining Recommendation Systems Based on Local Features

WANG Wei;WANG Huachang;CHEN Songwei;LI Jianjun

2019, 30(09):  1103-1110. 

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To realize the effective reuse of the existing CNC process design results, a model of CNC process recommendation system was proposed based on local feature matching. Combined with the geometric semantic informations, such as the size and so on, the 3D polar radius moments of the local features were used, to establish the machining geometric features. And the CNC process informations of the typical local features were efficiently organized and expressed, to construct the CNC process case database. In addition, a similarity measure method was designed based on the comprehensive weighing of the machining geometric features, to achieve the local feature retrieval and the accurate matching of the machining features. The CNC process instance reuse method was defined according to the matching degree and the users' process demands, to generate applicable CNC process recommendations.

Multilevel Bionic Modelling and Optimization Techniques

YU Changjiang;DAI Ning;LI Dawei;CHENG Xiaosheng

2019, 30(09):  1111-1118. 

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Aimmed at the non-coexistence problems between high hardness and high fracture of the objects produced by additive manufacturing methods. Inspired by the multilevel structures in nature, a multilevel lattice structure modeling methodology was proposed. Firstly, a family of multi lattices with specific mechanical properties was established. Secondly, different lattices were filled in multistage space. Isosurface geometry modeling algorithm was used to achieve transitional connection between the lattices and gradient design . Thirdly, the FEA (finite element analysis) results were used to actuate the porosity and size of lattice structures by using image mapping method. An object which could satisfy biomechanics properties was obtained through multiple iterations. Finally, the experimental results validate this method may well control the elastic modulus and impact toughness. Moreover, this method was applied to the design of teeth, and achieves good results.

Review on ICE Remanufacture with Additive Repair Technology

LI Fangyi1，2;LI Zhen1，2;WANG Liming1，2;LI Jianfeng1，2;LI Yanle1，2;LU Haiyang1，2;SHANG Jiantong1，2

2019, 30(09):  1119-1127,1133. 

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The principles and characteristics of additive repair technology were described, such as laser cladding, cold welding, thermal spraying and brush plating, etc. Also research progresses and applications of additive repair technology in crankshafts, connecting rods and cylinder blocks were maninly introduced and summarized, and the future research foci on laser cladding, cold welding, thermal spraying and brush plating were pointed out. The development trend of additive technology of remanufacturing for ICE was prospected.