China Mechanical Engineering

Recognition Applications for Air Fuel Ratio Faults of Gasoline Engines Using Sparse Representation Classification Based on Optimization of Dictionary Coherence

WU Shili1;TANG Zhenmin1;LIU Qi2

2017, 28(23): 2773-2778,2784.

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Sparse representation classification directly took fault samples as atoms which would result in higher coherence of classification dictionary. Thus, accuracy of sparse classification would be affected. A new optimization algorithm was proposed to improve effectiveness of sparse classification by effectively reducing the coherence of classification dictionary herein. Firstly, the representative atom of each sub-dictionary was obtained by affinity propagation clustering algorithm. Secondly, all the sub dictionaries consisted of representative atoms were optimized based on polar decomposition and subspace rotation methods. The experimental results of an engine show that, the novelty classification algorithm achieves high accuracy of recognition for five common faults in idle and 2000r/min operating conditions using the dictionary with lower coherence.

Effects of Pipe Pressures on Longitudinal Mode Guided Wave Propagations

CAI Haichao1;XU Chunguang2;WANG Dongfeng3;SHANG Zhendong1

2017, 28(23): 2779-2784.

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In engineering applications, the internal walls of pipelines tended to have mediums, which might produce pressures on the pipeline walls. When the ultrasonic guided wave technique was revealed to detect these pipelines, medium pressures whether or not to have effects on the propagation characteristics of ultrasonic guided wave were a very important problem. Liquid medium pressures in the pipelines were studied herein on the influences of ultrasonic guided wave propagation through numerical simulation method, guided wave attenuation properties in the different excitation frequencies and medium pressures were analyzed, and pressure pipeline experimental system was set up. The experimental results show that the ultrasonic guided wave propagation in the pipes does not change with the changes of inside pressures.

Research on Torsional Fretting Wear Behaviors of Material in Hub Bearings

ZHOU Mingzhuo1;ZHANG Gengpei2;LU Wenlong1;ZHANG Po1;LIU Xiaojun1;PENG Heping3

2017, 28(23): 2785-2791.

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The torsional fretting wear behavior researches of CuNiAl against 42CrMo4 in a controllable pitch propeller of dynamic positioning system were carried out on flat-on-flat contact under various angular displacement amplitudes simulating sea waves. The fretting wear appearances were discussed combined with the micro-examinations of the wear scar with scanning electron microscope and ultra-depth three-dimensional microscope， and the rule of torsional fretting wear behavior researches of CuNiAl against 42CrMo4 was investigated. The results indicate that with the increase of the angular displacement amplitudes the fretting running regimes change from partial slip regime to gross slip regime, corresponding to the decrease of the friction coefficients. And the damages of the torsional fretting become more and more severe while delamination tend to be the major wear mechanism at the same time. The mixed fretting regime should be avoided on account of the crack propagation which goes against the life time of the hub bearings.

Dynamics Properties and Experimental Investigations for Light Manipulators with Elastic Restraint Joints

LIU Yufei1,3;ZHANG Xi2,3;LI Wei3;XU Dezhang1

2017, 28(23): 2792-2799.

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The dynamics properties of flexible manipulator systems with elastic restraint joints were investigated. Firstly, an elastic restraint model with the linear restraints was established, and then, the frequency equation was subsequently derived. Secondly, based on the established elastic restraint model and Hamilton principle, the vibration displacement equation was derived. Finally, the dynamics properties of the flexible manipulator elastic restraint systems were analyzed using theoretical simulation and experimental approach, and the influence mechanism of elastic restraints on the dynamics were revealed. The results show that the established model may describe the elastic restraints of joints, particularly for higher order modes. Moreover, in the defined elastic restraint regions, the relationship of the frequency and the restraint stiffness has the characteristics of power function, and the fitting errors for the first two order frequencies are small than 0.08% and 0.45%, respectively, and the analysis errors for the vibration displacements are as 2.38%, which were verified experimentally.

Kinematic and Mechanics Characteristic Analysis of 3-RSR/SP Parallel Vehicle-borne Antenna Mechanisms

HOU Yulei;ZHAO Yajie;ZHOU Zhiyu;ZENG Daxing;YANG Yandong

2017, 28(23): 2799-2808.

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A new 3-RSR/SP parallel vehicle-borne antenna mechanism was presented. Based on the screw theory, the number of degree of freedoms (DOFs) of the mechanisms was analyzed and found alterable under different states. The static equilibrium equations and the deformation equations of compatibility of the mechanisms were set up, and the relation curves among the forces acted on the mechanism components and the poses of the mechanisms were plotted. The driven torques of the proposed mechanisms are smaller than those of 3-RSR parallel mechanisms, which indicates that the middle limbs of the proposed mechanisms have the effects static unloading functions. Considering the actual working status of the vehicle-borne antennas, the dynamics models of the mechanisms were established by using the Lagrange equation when the base was fixed and moving respectively. The changing curves of the mechanism's driven torques corresponding to the two conditions were plotted, which indicate that the base movement has obvious influences on the driven torques. The proposed mechanisms broaden the applications of the parallel mechanism in the antenna fields, and the performance analysis will possess certain reference values for further developments of the prototypes.

Investigation on Splitting-merging Micromixers Based on Chaotic Mixing

SHI Dongdong;LI Jinbeiqi;WANG Ruijin;ZHU Zefei

2017, 28(23): 2809-2816.

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Three trypes of micromixers, Smale, Helical and Baker micromixers, were built based on chaotic theory. In order to illustrate mixing mechanism and mixing effects, numerical simulations were carried out at various Reynolds numbers. Corresponding experiments were conducted to verify the numerical results. The results show the good agreements between numerical results and experimental results. Baker micromixers have more excellent mixing effects at low Reynolds numbers than that of Smale micromixers，because more-folds of interface areas between two streams caused by lamination expedite mixing. However, the mixing effects of Baker micromixers were not a patch on that of Smale at high Reynolds numbers. The reasons should be that, more convective mixings owing to more bending channels in Smale micromixers intensify mixing effects besides the lamination being slightly inferior to Baker micromixers. The mixing effects in Helical micromixers are not so satisfied because of no lamination at low Reynolds numbers, and somewhat improved at high Reynolds numbers.

Semi-physical Simulation of SAW CIDTs

CHEN Zhijun;ZHONG Yueyun;CHEN Tao;PENG Fuqiang;CHEN Zhaoxing

2017, 28(23): 2816-2820.

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In order to test the correlation properties of the physical CIDT devices more conveniently and flexibly, a semi-physical simulation method of the SAW CIDT was proposed based on ADS software. This method abstracted the physic devices by their S-parameters from actual tests and established the virtual excitation signal generating circuits in the ADS. By using the transient simulation function of the ADS, the different responses of the physical devices to the various excitation signals were studied. Compared with the theoretical simulation by the MATLAB and the experimental results by the reader, the semi-physical simulation by the ADS was confirmed to be feasible to study the correlation properties of the CIDTs.

Research on Injury Risks of 3 Year-old Children Using Numerical Simulations of Side Impacts in UN R129

HAN Yong1,2,3;PAN Di1;TIAN Fengyi1;WANG Fan1,2;HUANG Hongwu1,2;MIZUNO Koji4

2017, 28(23): 2821-2828.

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According to the side impact conditions of UN R129 children restraint system, 2 kinds of simulation test methods were developed and the feasibility was verified. Based on the validated test method, the numerical simulation of side impacts in 3 different restraint systems (five-point-car seat belt, five-point-ISOFIX and shield-car seat belt) with Q3 child FE dummy model was adopted. The kinematic response of the child occupants and the physical parameters of head, neck and thorax were analyzed. The results show that the child occupant kinematics is different in various types of CRS. The injury physical parameters of child head in the ISOFIX CRS are the highest. Chest acceleration (3ms) and neck bending moment value of child occupants in the ISOFIX CRS and shield CRS are much higher than children's injury tolerance limit. The chest and neck of a child occupant in a side impact are subjects to high injury risks.

Gait Planning of a Hexapod Robot Based on Multi-dimensional Space Coupled

AI Qinglin;RUAN Huixiang;CHEN Jiaoliao;YING Shenshun

2017, 28(23): 2829-2838.

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The existing algorithms to compute the body workspace were not suitable for the gait planning of a hexapod robot on the uneven terrains. To overcome this problem, a calculation method of the body workspace of a hexapod robot was introduced based on multi-dimensional space coupled herein. Then, the method was applied to the gait planning on the unseven terrains. Three subspaces of the body and the boundary equation of these subspace were presented, and then, these subspaces were coupled to get the body workspace. Based on the body workspace, in order to obtain the relationship among the postures of the body and the joint angles of standing legs, the algorithm of the body postures was solved. The simulation and experimental results show that compared with the existing planning methods the gait planning introduced herein may guarantee the footend reaching the desired foot point precisely and reduce the rangeability of the attitude angles of the body, which may ensure the hexapod robot walking on the uneven terrains stably.

Toolpath Generating Method and Simulation Based on Space-filling Curves

SUI Xiulin;CHEN Xiaoqi;JIAO Yan;LIAN Chong

2017, 28(23): 2839-2845,2852.

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In view of grids for space-filling curve were regular rectangles, and toolpath constructed on space-filling curve had defects such as frequent turns, tediously long lengths, long generation time, etc. A tool path generation algorithm was proposed based on space-filling curve. T-spline surfaces were regarded as modeling surfaces for generating grids with irregular rectangles, and a loop planning was performed. And then an improved Hamiltonian algorithm was used for generating tool path preliminarily. At last, the whole tool paths which could be obtained based on optimized corner by using an improved fillet algorithm. A simulation system was developed to verify the tool paths generation algorithm, and the algorithm was also tested by the actual machining. The results show that the algorithm is effective and feasible, and it will reduce lengths and time costs of tool-path's generatons.

Measuring Pirinciples and Measuring Device Design of Joint Stiffness of Car Bodys

CHEN Shaowei1;CHEN Tao1;TANG Yi1;NIE Jiquan2;ZHU Denghong3

2017, 28(23): 2846-2852.

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The necessity and the measurement principles of car body joints were briefly introduced. Aiming at the gap of measuring device of body joints in domestic currency situation, a set of joint stiffness measuring device for multiple platform car body was designed, and the main features of the design device were analyzed. Finally, the stiffness of the joints of the body was measured by the device, and the finite element analysis numerical values were compared with the measured value, and the errors were analyzed.

Design and Applications of a QZS Absolute Displacement Sensor

HE Jianfeng;DENG Zhaoxiang;TUO Jiying

2017, 28(23): 2853-2858.

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A QZS absolute displacement sensor was designed here in. The structural parameters of the QZS systems were first analyzed to ensure that the system was staying at stable equilibriums. Given the different incentives, the precisions and response speeds of the QZS sensors were measured. Moreover, shortages of the QZS sensors were studied and potential solutions were discussed. The QZS sensor was applied to the Stewart platform for speed feedback. Applying the harmonic balance method, the frequency responses of the platform were obtained in the direction of z axis, around the x axis and y axis. The QZS sensors are shown to be a useful devices for absolute displacement measurements in the direction of z axis, around the x axis and y axis.

Torque Coordination Control during Mode Transitions for a HybridShip

ZHU Jianyun1,2;CHEN Li1,2;PENG Cheng1,2

2017, 28(23): 2859-2867.

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During the mode transitions of the hybrid ships, unexpected torque fluctuations, intensive shaft jerk and clutch over wear tended to occur. A new torque coordination control method of MRC was proposed to address these problems. Dynamics models were built, followed by the reference model. The MRC algorithm was derived. The results show that compared with the conventional method, MRC may reduce power interruption and shafting dramatic impacts effectively. At the same time, the clutch friction loss is reduced evidently. Further, sensitivity analysis illustrates the effects of the external disturbances and the actuation noises on the transition performance.

Dynamic Tracking Performance Analysis of Differential Gear Trains

XU Lin;LIU Kai;CUI Yahui;MENG Peiyuan

2017, 28(23): 2868-2874,2879.

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The speed, torque and power of three DGT's basic components were analysed, and the concepts of sensitivity and contribution were studied. The parameters and rules that affected the sensitivity and the contribution were analyzed, and corresponding expressions were obtained in the end. In order to verify the speed sensitivity calculation method the tests were completed. The research results show that, sensitivity of speed and contribution torque of three basic components are only associated with the characteristic parameters of DGT, contribution expressions of speed and power are determined by the characteristic parameters and speed matching relationship of differential gear systems. Sensitivity and contribution reflect the dynamic tracking performances of DGT，and provide guidances for selection and design of DGT.

Testability Evaluation of Complex Equipment Based on Multi-source Informations

ZHANG Lei;LIANG Deqian;CHA Chendong

2017, 28(23): 2875-2879.

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Aiming at the problems of classical evaluation methods and traditional Bayesian evaluation method, a testability evaluation method was proposed based on multi-source information fusions for small sample problem of current complex equipment testability evaluations. The reliability and credibility of multi-source informations were comprehensively considered, and the problems of the reliability of multi-source informations on the testing level of complex equipment were solved, as well as the problems that small sample field test informations were submerged due to different characteristics of multi-source informations and field test informations when the fusions were solved after the posterior distributions. Finally, the testability evaluation of a certain type of fire control system was taken as an example, and compared with the classical evaluation method and the traditional Bayesian evaluation method. The results show that the testability evaluation method based on mult-source information fusions is more reasonable and has more advantages when dealing with field test informations for small samples.

Effects of Compound Technology of FSW and Heat Treatment on Microstructures and Properties of 2219 Aluminum Alloys

LI Xiaoxia1，2;HUANG Liang1，2;LI Jianjun1，2;WANG Zeyu1，2

2017, 28(23): 2880-2888.

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The effects on microstructures and properties of 2219 aluminum alloys under different aging temperatures and time were investigated. According to the mechanics properties of 2219 aluminum alloys, three compound technologies were compared, including FSW-solid solution-aging, solid solution-FSW-aging and solid solution-aging-FSW. The results show that the tensile strength and elongation rate of the alloys are as 386MPa and 24.8% respectively after aging at 180℃/6h. It is also found that the very fine θ″ precipitates appear inside the grains, no second phases and dislocation on grain boundaries. The best mechanics properties of 2219 aluminum alloys are achieved by the compound technology of FSW-solid solution-aging, the tensile strength and elongation rate of the alloys are as 380MPa and 15.4% respectively. The abnormal growth of grains is found in the joints, and the heat affected zones in the FSW joints are the weak areas of mechanics property. It is also found that the dimples on tensile fracture are more lager and deeper, and second-phase particles appear at the bottom.

Study on Dynamic Compressive Mechanics Behavior of TC17 Titanium Alloy at High Temperature and High Strain Rates

NIU Qiulin1,3;CHEN Ming2;MING Weiwei2

2017, 28(23): 2888-2892,2897.

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The dynamic mechanics behaviors of TC17 titanium alloy were studied under the conditions of high temperatures and high strain rates by using SHPB experimental system. The stress and strain behaviors of the materials were tested, and the effects of the experimental temperatures, strain rates and strains on the dynamic mechanics properties were analyzed. The experimental results show that when the strain rate is as 3000s-1, TC17 titanium alloy exhibits obvious strain hardening effects, but the strain hardening effects are weakened at high temperatures and high strain rates. TC17 titanium alloy has strain rate strengthening effect, but during the temperature increase processes, the strain rate sensitivity decreases firstly and then increases with the temperature increase. The effects of temperature on the dynamic compressive mechanics behaviors of TC17 titanium alloy are very obvious, and the temperature sensitivity factor increases with the temperature increase.

Effects of Laser Ablation on Corrosion Resistance of Adhesive-bonded Aluminum Joint

ZHU Chuanmin1,2;LYU Shanshan1,2;MEI YU1,2;LIN Jianping1,2

2017, 28(23): 2893-2897.

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Physicochemical properties of surfaces were analyzed after laser-treated for aluminum 5052. And lap-shear strength and failure mode of adhesive joints were tested under salt spray environments. The results show that the residual strength of adhesive-bonded laser ablated aluminum alloys increases by 40% after salt spray environments, and the failure mode transferres to cohesive failure from interfacial failure. The values of surface roughness are improved from 0.09μm to 1.17μm, and a concavo-convex porous structure formed by laser ablation. It shows that the adhesive may penetrate into the substrates so that the interface is enhanced. Also, more oxygen elements are found on the surfaces after laser ablation which may improve the corrosion resistance of aluminum substrates.

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