Table of Content

10 January 2019, Volume 30 Issue 01

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Performance Tests of Engine Electromagnetic Valvetrains

CHEN Huitao;CHANG Siqin;FAN Aimin

2019, 30(01):  2-8. 

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To test the flexible control and operation stability of valve motions by the self-developed moving coil EMVT, a test platform was constructed based on digital signal processor (DSP) as the core controller and the performance tests were carried out. And a control system scheme was proposed for practical applications of EMVT, a hardware-in-the-loop simulation platform was constructed based on dSPACE platform and controller area network (CAN) bus. The test results show that the EMVT may achieve a minimum transition time for value opening and closing is as 2.7 ms and the average value seating velocity is as 0.028 m/s, which meet the requirements of rapid response and valve soft landing, and the EMVT has the characteristics of low powers, each valve may be controlled individually. The EMVT may realize the flexible adjustment of the valve timing, the valve opening duration, the valve transition time and the valve lift, and may ensure stable operations for a long time at low, middle and high engine speeds. The feasibility of the proposed control system scheme is validated by the hardware-in-the-loop simulation.

Leader-follower Joint Optimization of Product Family Architecting Design and Supplier Selection

DU Gang;GUAN Jinliang;XIONG Yixuan;MA Yujie

2019, 30(01):  9-17. 

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The problems of joint optimization between product family architecture design and supplier selection was studied, and an interaction evaluation mechanism was proposed based on leader-follower strategy. According to the leader-follower decision-making mechanism, the leader-follower joint bilevel planning optimization model was established, the product family architecture design was the leader and the supplier decision was the follower. The product family architecture design was decided by upper level of the model that was targeted at the utility-cost ratio; the suppliers of module selection were decided by lower level of the model that aimed to costs. The two-level nested genetic algorithm was constructed to solve the problem, and the coding processing strategy with product family characteristics was added. The model and genetic algorithm were explained in the case of passenger car chassis.

Simulation Analysis and Experimental Validation of Micro-feature Grinding for High-elastic Alloy Steel 3J33 with Considering Hardness

XU Luyao;LI Beizhi;YANG Jianguo

2019, 30(01):  17-21. 

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Aiming at the problems of machining difficulty and experimental complexity of high-elastic alloy steel 3J33, a simulation study was carried out in the machining processes. Based on the elastic-plastic mechanics, grinding mechanism and finite element analysis, considering hardness for single grain grinding thin rib a residual stress simulation model was established by professional metal cutting simulation software AdvantEdge. Simulation analyses and comparisons of the residual stresses of different hardnesses for thin ribs were conducted when grinding and verified through the experiments. Finally, the reliability of the optimized simulation model was verified.

Structural Strength Analysis of Bogie Frames Considering Parameter Uncertainty

ZHI Pengpeng1;LI Yonghua2;CHEN Bingzhi2

2019, 30(01):  22-29. 

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Considering the uncertainty of engineering design parameters, the structural strength analyses of bogie frames were carried out based on the D-optimal design and reliability theory. According to the UIC 510-3-1994 standard, the structural strength analysis of frames was made to determine the larger forces of the parts. The parametric model of the frame was established by APDL language, and the design parameters were designed by D-optimal experiments, and then the structural strength of frames was calculated.The least square method was utilized to fit the test data, meanwhile, the polynomial response surface function was established, and the variance analysis was done to test the accuracy of the response surface. Based on the high precision response surface function, the Monte-Carlo Latin hypercube sampling method was adopted to analyze the structural strength reliability of the frames. The results show that the changes of design parameters have great influences on the structural strength, and the interaction of design parameters is minimal. Structural reliability of the bogie frames is as 0.984 3, which shows the influences of uncertain parameters on the structural strength and safety of frames. The response surface method based on D-optimal design has high efficiency and may provide reference for the uncertainty analysis of other complex structures.

Study on Fabrication of Lyophobic PCD by Pulsed Fiber Laser

CUI Ｗei;HAO Xiuqing;CHEN Xinwen;XIAO Sinong;LI Liang

2019, 30(01):  30-37. 

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In view of PCD surfaces, an economic, efficient and controllable method on fabrication of microstructure by laser processing was proposed herein, combined with low surface energy treatment technology, the characteristics of the surface might be regulated effectively. First of all, micro grooves and micro conical convexes were formed on the surface of PCD by using laser surface texturing method. And the effects of single pulse energy and scanning speed on the microstructure morphology and characteristic size parameters were analyzed. Then, the laser textured PCD surfaces were treated with fluorination, and the influences of the surface microstructure of PCD on the hydrophobicity and lipophobicity were analyzed. The results show that with the increases of single pulse energy or the decreases of the scanning speed, the parameters of groove depth, the ridge spacing and surface roughness increases. After low surface energy treatment, the contact angles of water are in the range 93°~149°and 102°~134° respectively, which realize the control on different wettability of PCD surfaces. In addition, the formation mechanism of microstructure on PCD surfaces was analyzed, and the influences of microstructure on hydrophobicity and lipophobicity were discussed.

Geometrical Characterization Test of Serrated Chips under High-pressure Cooling

WU Mingyang;YU Yongxin;CHENG Yaonan;LI Lubin;ZHAO Xu

2019, 30(01):  38-45. 

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The theoretical models of geometrical characterization were analyzed, including segmented degree, serration frequency and serration step pitch. The cutting tests of GH4169 nickel-based superalloy was carried out with PCBN tools under high-pressure cooling，and the chips were prepared and polished to analyze the morphology and geometrical characterization of serrated chips under different conditions of cutting parameters and coolant pressures. The change laws of geometrical characterization of serrated chips were analyzed under different cutting parameters. The experimental results show that with the increases of cutting speeds, feed rates and cutting depths, the segmented degree and the serration step pitch of chips increase, on the contrary, the serration frequency of chips decreases. With the increases of coolant pressures, the segmented degree of chips decreases, the serration frequency of chips increases, and the serration step pitch firstly increases and then decreases. The chip breaking ability of the chips is improved under high pressure cooling, and the chip breaking effectiveness further improves as the coolant pressure increases.

Study on Cycle's Energy Losses of Vehicle Gasoline Engines for CDA

HU Maoyang;CHANG Siqin;LIU Liang;LU Jiayu;XU Yaxuan

2019, 30(01):  46-52. 

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Under conditions of CDA, the cycle's energy losses and friction losses had great differences under different valve strategies and control parameters. Based on EMVT, energy losses of three valve strategies including trapped exhaust gas, trapped fresh air and keeping exhaust valve open were analyzed. The simulation results show that reducing the trapped gas of deactivated cylinder helps to reduce energy losses, and the energy losses for the exhaust valve open strategy decreases with the increase of lift. Lastly, the CDA strategy with the minimum energy losses to improve the fuel economy and the CDA valve strategy with the maximum energy losses to improve the shift quality were achieved.

Automatic Parking Path Planning for Dead Zone Avoidance Based on Entry Baselines

LI Maoyue;CHEN Yue;XU Guangqi

2019, 30(01):  53-63. 

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In order to avoid the existence of the parking dead zones， a trajectory calculation algorithm of the automatic advance to the forward horizontal line was put forward. To reduce the required length of parking spaces， the method of reversing the entry baselines from the forward line was studied. By means of interpolation spline theory and geometric mathematics， the external parking path and function of the car were determined by several fixed points that must be passed， and the function was unique. Therefore， the feedback processes and correction of the systems in automatic parking were reduced. Through the simulation and verification of the experimental vehicles， the correctness of the route planninges was proved. The movement simulation of the parking process was carried out by CarSim software， and the trajectory line was analysed. The results show that the method may effectively avoid the parking dead zones and reduce the demands for parking length.

Optimization Method of Partitioned Complex Surface CNC Milling for Minimum Energy Consumption and High Efficiency

ZHAO Junhua1;LI Li1;LI Lingling1;LI Congbo2

2019, 30(01):  64-71. 

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Traditionally, the workpiece complex surfaces were machined by a specific cutting parameters and toolpath. In fact, the dynamic curvatures of complex surfaces had major impacts on energy consumption and machining time. The workpiece complex surfaces were partitioned into several patches according to the characteristics of surface curvatures and by using fuzzy clustering algorithm. Then for each patch, a set of orthogonal experiments were designed to determine the optimal cutting parameters and toolpaths aiming to minimize the machining time and energy consumption. Finally, the effectiveness of the proposed method was demonstrated through comparison of the partitioned complex surface milling and the traditional whole complex surface milling.

Contribution of Chip Deformations and Crushes to Tool Failures in High-speed Dry Gear Hobbing

LI Benjie;CAO Huajun;YANG Xiao;ZHOU Jin

2019, 30(01):  71-78. 

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In allusion to the chip deformations and chip crushes in high-speed dry gear hobbing, a simulation model of high-speed dry gear hobbing was built based on DEFORM-3D herein. Through the simulation of high-speed dry gear hobbing under different process parameters, the visualization of material removal processes in high-speed dry gear hobbing was achieved, and the mechanism of chip deformations and the tool wear conditions of dry hobs were obtained. Combined with experiments, the simulation results were further validated by comparing the chip geometry and tool damage types obtained from simulation and experiments respectively. This study may provide a reference for parameter optimizations and tool life extension in high-speed dry gear hobbing.

Finite Element Simulations of Temperature Fields and Stress Fields in Laser Cladding Repair Processes of Milling Cutter Disks

SHU Linsen1,2;WANG Jiasheng1

2019, 30(01):  79-84. 

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In order to determine whether thermal stress cracking would occur during laser cladding repair processes of milling cutter disks， the three-dimensional temperature fields and stress fields of the milling cutter disks were simulated.The three-dimensional repair model of milling cutter disks was established based on the characteristics of the damage failures. The grid model and boundary conditions of the repaired milling cutter disks were established by using hexahedral structured meshing method. The laser cladding processes of milling cutter disks were reappeared by combining the live and death element technology with the ANSYS APDL self-programming technology. The researches showed that, the high temperature gradient and geometrical constraints resulted in high residual thermal streses in the repaired areas.The maximum residual thermal stress is as 384 MPa. The applications show that the milling cutter disks do not crack after repaired, and the repair effectiveness is good, which verifies the correcteness of the simulation.

G Code Preprocessing Optimization Algorithm for 3D Printers

YU Daoyang

2019, 30(01):  85-89. 

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In order to break the limitations of the original file processing mode of the existing 3D printer control systems, a method of preprocessing the G codes on the PC side in advance was proposed. In the program preprocessing processes, the forward control and speed planning of multiple segments were carried out at the same time. After finishing the preprocessing, the output data were sent to the 3D printers for executing printing. The methods reduce the loads of the 3D printer processors and obtain more optimized calculation results through PC-side preprocessing. Finally experimental measurement data prove that, the G code preprocessing methods save the processing time of the printer processors and improve the printing quality compared with the traditional G code processing methods.

Analysis and Optimization of HBP Temperature Field for FDM Rapid Forming Machines

LYU Ning;ZHENG Jian;ZHAO Xin;XU Wei

2019, 30(01):  90-95. 

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Through the temperature field acquisition and simulation of HBP, the heat transfer principles of HBP were analyzed, and the reasons and methods of temperature exchange between HBP and the outside world were obtained. A new HBP was proposed, which could realize temperature compensation and temperature balance. The simulation models of the surface temperature differences between two kinds of HBP at different ambient temperatures were established, the actual model printing work was completed for two kinds of HBP, and the dimensions of the molded parts were measured and analyzed. Finally, the surface temperature of HBP after optimization is more balance according to the experimental results, which may effectively suppresses the warping deformations of the molded part.

Frame Weldment Fatigue Life Prediction of Electric Dump Trucks Based on Modified Strain Energy Density Method

MI Chengji1,2,3;GU Zhengqi1,3;JIAN Haigen1;ZHANG Yong1,3;LI Wentai1;YU Bing1

2019, 30(01):  96-104. 

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In consideration of non|completely closed and crossed stress|strain responses for welded structures under complicated loadings, a modified strain energy density calculation method was proposed to account for plastic strain energy density being out of closed loop. The butt joints were designed and made to conduct research on mechanical performances and fatigue tests. The Ramberg|Osgood equation parameters were obtained, and a fatigue damage model was constructed based on total strain energy density. The frame element finite model of electric dump truck was built and the non|linear finite element analyses of frame weldments were conducted on simulating multi|loading steps. Combined the method herein and stress|stain response obtained from the numerical simulation, several strain energy density parameters of dangerous points were calculated to estimate the fatigue life of frame weldments according to the fitted fatigue damage model. The calculated results show well agreement with the real failure positions and cracking time.

Hardness Indentation Size Effect Analysis of 316L Austenitic Stainless Steels during Cold Working

XUE He;LI Kai;WANG Shuai;ZHAO Kuan

2019, 30(01):  105-112. 

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The 316L austenitic stainless steel hardness ISE in the cold working processes was analyzed by the theory combined with the test method, and the true hardness obtained by the theoretical model was compared with the test hardness. The results show that the 316L austenitic stainless steel exhibits positive ISE phenomenon under different tensile rates. Through the analyses of three common theoretical models, it is found that the modified proportional specimen resistance(MPSR) model may more accurately describe the ISE phenomenon of 316L austenitic stainless steels under cold working processes, and the true hardness values under 0,15%,30%,40% stretching rates obtained by this model are as 159.16 MPa, 228.07 MPa, 259.72 MPa and 282.54 MPa respectively. The obtained hardness was verified, and the results satisfy the linear theoretical relationship. Then, it is found that the Vickers hardness of 316L stainless steels after different static uniaxial stretching is almost no ISE phenomenon under the 9.8 N indenter load.