China Mechanical Engineering

Structure Design and Optimization of Distributing Chutes in Blast Furnace for Wear Resistance

MA Caisheng, REN Tingzhi

2017, 28(03): 253-257,266.

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The structure of distributing chute in blast furnace was designed and optimized to improve the wear resistant performance. Based on the characteristics of the burden motions and the chute wear conditions, the combination of the burden accumulation liner and the smooth liner was applied. Then the buffer effects of the piled burden layer cushions with different thicknesses were simulated by using discrete element method, and the parameters of the chute liner were optimized to match the burden charging operations. The results show that the abrasive wear is the main cause of the chute wear failure, the burden layer piled at the bottom of the chute may effectively disperse the burden impacts on the chute and reduce the abrasive wear, and plied burden thicknesses of no less than 60mm are recommended. The burden piled at the bottom of the optimized chute liner increases 32.13%, and the total burden passing through the chute may increase 15.5%.

Type Synthesis of Three-translational Hybrid Mechanisms

GE Shuyi, CAO Yi, ZHOU Rui, ZHU Jingyuan, DING Zehua,

2017, 28(03): 258-266.

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For a three translational hybrid mechanism with three degrees of freedom, an efficient synthesis methodology and a novel analysis approach were proposed from the view of fractal theory and topological graph. Firstly, the basic concept of the topology graph and the fractal theory were introduced. Secondly, the kinematic characteristics and algorithm were expounded. Thirdly, the model between the hybrid mechanism and fractal theory was established. And the procedure of methodology of type synthesis was concluded in detail, meanwhile, the three translational hybrid mechanism was synthesized. Finally, a method for analyzing the kinematic characteristics of hybrid mechanisms was proposed and applied to the synthesized structure by which the validity of the methodology proposed herein was demonstrated.

Helical Gear Shaping Technology Based on Error Compensation by Trial Cuts and Experiments

WU Zhenyu, ZHAO Daxing, ZHONG Ruiling, XU Wan

2017, 28(03): 267-272.

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A machining technology based on error compensation by trial cuts was presented for improving machining precisions of a helical gear for CNC gear shaper. Firstly, the ideal main motion curve was derived using some straight lines approaching the ideal main motion curve, where the maximum allowable step of each straight lines and the corresponding crank angles that might satisfy the demands of machining precision were calculated. Then, the deviations of the main motion curve were calculated by the helix deviations of gear trial cuts, and a new more accuate ideal main motion curve was derived. At last, the new ideal main motion curve was approached by some straight lines again in the G codes used final gear machining. The test results show that the helix deviations of machined helical gears achieve 7 level accuracy, and satisfy the demands, and which verifies the feasibility of the method presented herein.

Calculations and Analyseis on Aerodynamic Noise Characteristics of Rotating Saw Blades

TIAN Yongjun, DUAN Guolin, XIA Xiaoguang, ZHANG E

2017, 28(03): 272-278.

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In order to analyze the acoustic characteristics of the rotary tool under the fluid action, a combined simulation model was constructed based on coupled-field calculation equations. Firstly, the vibration response characteristics of the structure were extracted under the system which contained the rotating saw blades and air flow.Moreover, the vibration responses were regarded as acoustic boundary conditions to calculate acoustic radiation of the circular saw based on the boundary element method.Then, a structure acoustic coupling model was established to calculate the sound pressures. As compared with the experimental results, the coupling model may be used to noise prediction of the rotary tool.The laminar flow may turbulent flow characteristics of blade vibrations were studied in the processes of the rotating saw with around flow field and the sound radiation in time domain characteristics and laminar and turbulent characteristics with the coupled system was studied herein. Then,the characteristics of the directivity of aeroacoustic noise were studied. Finally，the influences of the size structure on the noise of the saw was determined, which provides a method for desining a low noise circular saw.

Preference Design of Large Machine Beds Based on TOPSIS Method

LI Yupeng, SUN Hongsheng, XU Yagang

2017, 28(03): 279-285,293.

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A spherical worm grinding wheel machine bed wasas research object and several bed structures were designed.The parametric models of each alternative were built and their sensitivity analyses were conducted respectively. The optimal dimensions of each alternative were obtained through multi-objective optimization. The preliminary data was obtained for decision making through finite element analysis of each optimized model. TOPSIS mathematical model of the bed was established and the best alternative was determined according to calculation results. The validity of the preference results was verified compared with analysis results of the original bed. The preference task for the bed of spherical worm wheel grinding machine was completed.

Effects of Airfoil on Flight Performance of Autonomous Underwater Gliders

XU Shixun, LIU Yuhong, ZHU Yaqiang, WANG Yanhui,

2017, 28(03): 286-293.

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Based on the NACA 4-digit airfoil, effects of the airfoil on flight performance, such as flight efficiency and static stability, were analyzed by using the method of computational fluid dynamics with the environment of commercial software ANSYS-FLUENT. Results show that appropriate airfoil may greatly improve the flight efficiency of AUGs, but the improvements to the static stability of the AUGs are not so obvious. For asymmetric airfoils, the camber and bending directions of the airfoil have great influences on both of flight efficiency and static stability. According to the present researches and combining with the engineering practices, the flexible wings with variable trailing edge were proposed to make the AUG get better flight performance, which was proved by the numerical simulation experiments. The present achievements provide theoretical guidance for the design of flexible wings of AUGs.

Calculation Method of Tooth Profile Modification Based on Mesh Node Deformations

LI Jianmin, WU Yuecheng, XUAN Haifeng, CHEN Wenhua, PAN Xiaodong, WANG Wei, ZHOU Xinteng

2017, 28(03): 294-299.

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In order to deal with the problems of gear modification, a method to calculate the displacements of the gear tooth related nodes was proposed, which was based on the finite element dynamics calculation. The elastic deformations of the teeth were obtained by extracting the displacements of the gear teeth, which were used as the gear's maximum profile.The calculation program was used to calculate the gear tooth profiles. Taking a wind power gear box for example, the maximum stress of the gear is reduced by about 20%, and the life of the gear is prolonged, and the reliability of the gear box is increased.

Research on Theoretical Model for Effective Bulk Modulus of Air-liquid Mixtures of Hydraulic Oil

TANG Donglin, WU Fan, JIA Pinyuan, ZENG Zhichun

2017, 28(03): 300-304,333.

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In order to predict the effective bulk modulus of air-liquid mixtures of hydraulic oil below the saturation pressure accurately,based on the definition of the bulk modulus and law of mass conservation,according to the air release and cavitation processes, a theoretical model for effective bulk modulus of air-liquid mixtures of hydraulic oil below the saturation pressure was proposed.The numerical calculation results show that the B-p curve of the theoretical model for effective bulk modulus of air-liquid mixtures of hydraulic oil shows good agreement with the B-p curves of published literature's theoretical model and fitted experimental data,verifing the accuracy of the theoretical model,especially the extreme low pressure region below the atmospheric pressure. The effective bulk modulus of air-liquid mixtures of hydraulic oil is more consistent to practical conditions. Furthermore, the effects of initial air content,pressure and pressure rising time on effective bulk modulus were analyzed. The results show that below the saturation pressure area,the effective bulk modulus deceases with the increasing of initial air content， and the effective bulk modulus increases in a narrow range with the increasing of the pressure rising time.

Structures and Properties of a Symmetrical Optical Fiber Bundle Differential Pressure Sensor

HU Hao, ZHONG Liqiong,

2017, 28(03): 305-309,315.

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The structures and properties of a symmetrical optical fiber bundle differential pressure sensor were studied herein. First, a kind of structures of symmetrical optical fiber bundle differential pressure sensor was put forward, which consisted of two identical structure detection probes and bridge optical paths, the detection probes adopted mechanical capsulation. Second, by theoretical studies on the sensor, a intensity modulation mathematical model was established, simulation calculations and analyses were carried out. Finally, an experimental prototype was pilot produced, and experimental researches were carried out.The experimental results of show that: under different design sizes of probes and the diaphragm, sensor has different measurement ranges, output sensitivities, detection resolutions, linearity and repeatability precisions.The results show that this symmetrical optical fiber bundle differential pressure sensor has a good detection performances,which may be able to meet needs of different detections.

Sparse Decomposition of Vibration Signals of Rolling Bearings Based on ADMM Dictionary Learning

SUN Zhanlong, TONG Qingbin

2017, 28(03): 310-315.

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In the processes of sparse decomposition, the effects of sparse decomposition would be directly affected by dictionary model construction.A dictionary learning method was proposed based on ADMM herein. In the processes of dictionary learning, the ADMM was used to update the atoms in the dictionary, which might obtain the dictionary with better structure. The method was applied to the sparse decomposition of the vibration signals of rolling bearings, shorter dictionary learning time and better sparse decomposition results might be obtained. Compared with the K-SVD dictionary learning method, the proposed method has the superiority in the sparse decomposition of bearing signals.

A Novel Collision Detection Algorithm Based on Grids Enveloping for Industrial Robot Simulations

ZHAO Liang, ZHANG Yide, HU Xuxiao

2017, 28(03): 316-321.

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To speed up the collision detection efficiency of industrial robots in the complex working environments, a novel collision detection algorithm was proposed using equal-sized cubic grids to cover the model and building tree structure of AABB in the grid. The space coordinates of these grids were stored orderly in the modeling progresses so as to determine whether there were grids intersecting in the traversal periods. Then traverse the hierarchical structure in the intersecting grids to detect collision precisely. Due to the grids had far less model data than the whole model, the detection speeds in the grids were far more fast than the traditional hierarchical bounding volume method where the building model was based on the whole model. The experimental results show that the detection efficiency in the novel algorithm is several times to dozes times (which depends on the size of grids) more than that in the traditional SOLID method for the large complex model environments.

A Rapid Identification Method for Stiffness among Ends of Multi-axis CNC Machine Tools

CHEN Guangsheng, ZHENG Qingzhen

2017, 28(03): 322-326.

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A new method to identify the static stiffnesses of ends of a multi axis machine tool(cutting tool and table) was presented based on a loaded ball bar and circular motion. A kind of special loading ball bar was designed to measure both of the forces and displacements of the instrument, and the deformation errors of CNC machine tools at different loads might be measured by the instrument. The static stiffnesses of machine tool ends were decomposed into x, y and z along the coordinate axis, and a stiffness identification model was established based on circular motions. The deformation errors of the ends of the machine under different loads were obtained by the circular motion tests, which were carried out in the machine tool oxz, oyz and oxy planes by using the ball bar. Then the stiffnesses of the machine tool were obtained by the stiffness identification model. Through the comparison of the three axis CNC milling machine stiffness tests and simulation results, the effectiveness of the method was proved by the consistency between simulation results and experimental results. The method is simple and the instrument is portable. The method is suitable for industrial field conditions where the large and heavy loading equipment were not required.

Bearing Fault Diagnosis Based on DTCWT and AWTFPSO-optimized SVM

ZHANG Shuqing, HU Yongtao, JIANG Anqi, WU Di, LU Chao, JIANG Wanlu

2017, 28(03): 327-333.

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Based on DTCWT and SVM improved by AWTFPSO, a new method of bearing fault diagnosis was proposed. The mechanical vibration signals were first processed by DTCWT and the energy entropy was extracted as the feature vector. Then, SVM optimized by AWTFPSO was introduced to bearing fault diagnosis. Comparions of different methods show that the proposed method has advantages of high speed and accuracy.

Temperature Distribution of Cemented Carbides Irradiated by Pulsed Fiber Laser

YAO Chenjiao, LI Liang, HE Ning, ZHAO Guolong, WU Xian

2017, 28(03): 334-339.

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In order to improve the machinability of cemented carbides, a study of the temperature field distribution of cemented carbides induced oxidation by pulsed fiber laser was carried out. A transient, three-dimensional thermal model with moving heat sources was established in ABAQUS. The temperature field was simulated and the influences of laser parameters on temperature field distribution were studied. The simulation results show that the maximum temperature and the maximum depth and width increase with increase of the single pulse energy and decrease with increase of scanning velocity and spot diameter. The simulation results may provide theoretic evidences for choosing proper laser parameters.

Numerical Simulation and Experiments of Fluid-solid Coupling-based Ultrasonic Echo Detection of Pipeline Fouling

SUN Lingfang, XU Manfei, PIAO Heng, LI Xia

2017, 28(03): 340-348.

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Analyses and discussion were provided on finite element modeling of heat exchange pipeline fouling and on the treatment of the coupling boundary. With pressure acoustics and solid mechanics as the theoretical basis, sound wave vibration control equations under plane wave source radiation were developed based on Comsol Multiphysics in PDE mode. Heat exchange pipes were nondestructively examined for their fouling thicknesses using ultrasonic echo technique, and the echo vibration mode and response time history were found for various vibration frequencies. The paper offers theoretical reference to the choice of mode and frequency in examining multi-layer pipes. With respect to the echo characteristics corresponding to the fouling thickness of sets of pipes made of various materials, a comparison was made with the results of the test points, which attested to the accuracy of this model. With heat exchange fouling dynamic simulation testing equipment, a quantitative testing study was performed on fouling. The results suggest: it is feasible to perform ultrasonic echo detection of heat exchange pipeline fouling by a method that combines testing and finite element technique, the numerical simulation is in agreement with the test results, and ultrasonic detection produces an error around ±4% in examining pipeline fouling deposit. These results have practical significances to the operations and pipe cleaning of in-service heat gathering and transportation systems.

Adaptive Wavelet Envelope Detection Based on AR Model and Spectral Entropy

HE Xiang, GAO Hongli, GUO Liang, WU Yuanhao

2017, 28(03): 348-352.

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For the envelope problems of traditional fault diagnosis, a method of adaptive complex analytic wavelet envelope detection was proposed based on AR model and spectral entropy herein. The method eliminated the stationary components for linear prediction from the mechanical vibration signals by AR model, and extracted the non-stationary components of resonance damping. The generated signals were enveloped by complex analytic wavelet in different frequency bands, the best envelope was selected based on the correlation between the spectral entropy and the band-pass filter in the frequency domain. This method owns higher adaptivity, better robustness and envelope effectiveness than that of the traditional one. Thus it has favorable prospect in engineering applications.

Tube Design Method with Small Bend Radius in Elbow Forming Using Reverse Push Straight and Forward Forming Simulation

CHEN Qinggen, XU Xuefeng, MA Yuanyuan, LI Lingling, ZHAO Shuang, XU Long

2017, 28(03): 353-358.

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According to the numerical simulation technology of reverse push straight the approximate and optimized sizes of tubes with small bend radius elbow（1D） were obtained in push-bending forming. The forward push straight method was used to verify the push-bending forming simulations based on the optimized sizes of the tube and finally the accurate sizes were obtained. The forming specification was aluminum alloy tube of LF2M of 32mm×1mm which was adopted to push with small bending radius.First,with the final forming elbow product sizes and in reverse push straight simulation the optimized sizes were obtained，then adopted to verify the forward simulation. Finally,the pushing-bending experiments were based on the final accurate sizes of the tubes and the results show that: by means of the combination of reverse push straight and forward bending simulation, the method of bending the tube blank with small bending radius is of high reliability. And the sizes of tube and forming elbow of LF2M aluminium alloy tube of 32mm×1mm were obtained in process of 1D hard push-bending relative bending radius elbow.

Establishment and Applications of Thermal Forming Limit Margin Field Graph for Automobile Components

CUI Junjia, HU Ming, LI Guangyao,

2017, 28(03): 358-365.

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In hot stamping processes, the sheet maintained in a high temperature state and the temperature varied at different positions, for which traditional method was difficult to evaluate the sheet formability. Temperature dependent 3D forming limit graph was a new method to evaluate formability of hot stamping components, however, the prediction of forming margin remained a blank. To solve the problems discussed above, a way to calculate the forming margin was proposed herein based on the temperature dependent 3D forming limit graph. Then, combining numerical simulations and theoretical analyses, a safe margin field graph for evaluating high strength steel sheet in hot stamping was established. Using the safe margin field graph, different hot stamping processes of an automobile B pillar were analyzed by numerical simulation and were compared to experiments. Results show that the proposed forming margin field graph may effectively predict the fracture positions and cracked degrees of HSS components in hot stamping at different process parameters and blank shapes.

Control Method of Vehicle Semi Active Suspensions Based on Variable Universe Fuzzy Control

WANG Dayong, WANG Hui

2017, 28(03): 366-372.

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A fuzzy control method was proposed based on variable universe fuzzy PID for vehicle semi-active suspension systems herein. The goals were to improve the ride comfort of vehicles under random road excitations. The fuzzy PID controller was combined with variable universe method to solve the problems that the fuzzy rules were blind and the online regulation time was too long. The simulations and experimental results show that, variable universe fuzzy PID control semi-active suspension systems in the body vertical vibration velocity and acceleration are reduced by 46.56% and 29.21% respectively in comparison with conventional PID controls, compared to the passive suspension systems they are reduced by 58.05% and 49.74% respectively. The vehicle semi-active suspension fuzzy control method has better effects on vehicle ride comfort.

Design and Control of a Automobile Novel Magneto-rheological Shock Absorber with Asymmetric Mechanics Properties

YU Jianqiang, DONG Xiaomin, ZHANG Zonglun

2017, 28(03): 372-377.

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In order to reduce the costs of sensors and to improve the reliability of the magnetorheological (MR) semi-active suspension system, a novel structure for MR shock absorber with asymmetric damping force and the corresponding control strategy were put forward herein. On the basis of the design structures, the output damping of the MR shock absorber was analytically derived. A shock absorber was fabricated and tested under different sinusoidal excitations. A quarter car's model was developed to analyze the control performance of suspension which applied the novel magneto-rheological shock absorber. The results show that the MR shock absorber may continuously generate asymmetrical damping forces which verify the validity of the design method. In addition, the semi-active suspension under hierarchical control strategy has better performance than that of passive suspension. In spite of the skyhook control strategy had better performance than that of hierarchical control strategy under some road surfaces, the damping systems via the hierarchical control strategy need less number of sensors, which is beneficial to reduce costs, improve reliability, and practical applications.

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