China Mechanical Engineering

Directional Tool Radius Compensation Solution of STS Turning Based on Segment Approximation

LI Jiawei;DU Wenhao;HAN Changqing

2020, 31(17): 2017-2023. DOI: 10.3969/j.issn.1004-132X.2020.17.001

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In STS turning of complex surfaces, compensated values of all linear servo axes were created by normal cutter compensation algorithm. This algorithm was not optimal when surfaces had sudden changing normal vector，while applying compensated value in linear servo axis with less load was optimal choice. A directional cutter compensation numerical algorithm was introduced based on segment approximation, which might solve the directional compensated value，and the normal error was convergence by further optimization of radius subdivision strategy. Verification of algorithm examples and comparison with related algorithm show that the proposed algorithm may be applied in cutter radius compensation of point cloud surfaces or piecewise surfaces.

Friction and Wear Properties of FeS/Cu Composite Materials Fabricated by Mechanical Alloying

LI Rongrong;YIN Yanguo;ZHANG Kaiyuan;ZENG Qingqin;CHEN Qi

2020, 31(17): 2024-2030. DOI: 10.3969/j.issn.1004-132X.2020.17.002

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FeS/Cu composite materials were prepared by mechanical alloying and powder metallurgy with FeS and CuSn8Ni1 powders as raw materials. The tribological properties and lubrication film and transfer film characteristics of FeS/Cu composite materials prepared under different loads were systematically discussed. The results show that the mechanical alloying may improve the interfacial properties of FeS and copper alloy matrix, and thus reduce wear resistance. When the loads are relatively small, the surface contacts of friction pair are unstable, the composite transfer films are incomplete, and the friction coefficients fluctuate greatly. When the loads are larger, the composite transfer films ares easy to be damaged, and the wear resistance of the materials becomes worse. When the load is 150 N, the load is appropriate. The material surfaces are softened, making the composite transfer films more complete and the friction coefficient smaller.

An Efficient Mechanical Structure Reliability Analysis Method Based on Evidence Theory

LIU Xin1;GONG Min1;ZHOU Zhenhua1;LI Baotong2;DONG Jianye1

2020, 31(17): 2031-2037. DOI: 10.3969/j.issn.1004-132X.2020.17.003

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An efficient mechanical structure reliability analysis method was proposed based on combination of evidence theory and approximation model technology. Firstly, a corresponding mathematical model of reliability analysis was established based on evidence theory. Then, an approximate model of limit state functions was constructed by radial basis function. Local-densifying samples were used to improve the fitting accuracy of the approximationg model. Finally, the approximation reliability analysis problems were solved by the first-order approximation reliability analysis method, and the belief measures and plausibility measures of mechanical structure reliability were obtained. Computational results demonstrate that the method may ensure the accuracy of the calculation results, and improve the computational efficiency.

Lamb Waves Inspection Based on Cross-shaped Array and 2D-MUSIC Algorithm

LIU Zenghua1,2;ZHANG Tingting1,2;SU Ruixiang1,2;CHEN Honglei1,2;HE Cunfu1,2;WU Bin1,2

2020, 31(17): 2038-2044. DOI: 10.3969/j.issn.1004-132X.2020.17.004

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A cross-shaped array which was composed of piezoelectric sensors was used for the excitation and reception of Lamb wave signals. A two-dimensional multiple signal classification (2D-MUSIC) method was proposed to locate and detect defects in aluminum plates. Firstly, the appropriate excitation frequency was selected for the generation of a single mode signal to avoid the influences of multi-mode and reduce the dispersion of Lamb waves. Then, received signals were segmented by 2D-MUSIC algorithm. Finally, reflected signals and 2D steering vectors were combined to locate the defects in the aluminum plate. The results show that the proposed 2D-MUSIC algorithm is more accurate than traditional multiple signal classification algorithm for defecting locations in aluminum plates.

Intrinsic Dissipation in Low Cycle Fatigue for Stainless Steel Weldments

HAO Zhiyan;HUANG Zhiyong;WANG Qingyuan

2020, 31(17): 2045-2050. DOI: 10.3969/j.issn.1004-132X.2020.17.005

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DIC and infrared thermography(IRT) were used to measure the deformation and surface temperature fields during low cycle fatigue of 310S with welded joints. DIC was used to observe the nonuniformity of local deformations of the welded joints. IRT provided the temperature field distribution of sample surfaces. The test results show that in high stress areas, fatigue failure occurs mostly in the welded joints; in the low stress areas, fatigue failure occurs mostly in base metal areas. The intrinsic dissipation distribution of specimen surfaces may be acquired by solving the local thermal diffusion equation, which may be used to predict the crack initiation positions.

Stiffness Modeling and Analysis of Semi-symmetrical Three-translation Delta-CU Parallel Mechanism

WANG Yixi1;WU Guanglei2;SHEN Huiping1;LI Jiayu1;MENG Qingmei1;LI Ju1;DENG Jiaming1

2020, 31(17): 2050-2058. DOI: 10.3969/j.issn.1004-132X.2020.17.006

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Stiffness and performance of Delta-CU were studied herein. Compliance model of limb was established by using virtual spring method, and the static equations of the limb were given. Kinematic differential mapping was obtained by the screw theory, and the Cartesian stiffness matrix of the mechanisms was obtained by making use of the static equations. Finite element analyses showed that the matrix is applicable in the stiffncss analysis. Finally，based on the defined virtual work stiffness index，the Delta-CU mechanism under given parameters was analyzed and compared with the Delta mechanisms，which shows that the Delta-CU mechanism has the same translational stiffness with the conventional Delta mechanisms.

Principle and Experimental Analysis of a Novel Piezoelectric Inchworm Actuator Based on Rotating Magnet Clamping

LI Jianping1,2;GAO Yunye2;WEN Jianming1,2;MA Jijie1;WANG Renming2

2020, 31(17): 2059-2063,2070. DOI: 10.3969/j.issn.1004-132X.2020.17.007

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To simplify signal control systems and reduce friction of piezoelectric inchworm actuators, a novel piezoelectric inchworm actuator was proposed based on rotating magnet clamping. The actuator utilized DC motor to drive permanent magnet rotation to achieve alternating clamping, and the opposite type laser photoelectric sensors were applied to generate excitation signals to drive piezoelectric stack for linear motions. Relevant parameters of the actuator structure were optimized, and a prototype of the actuator was made and tested. The results show the performance of the proposed piezoelectric inchworm actuator with rotating magnet clamping is stable; the min resolution is as 0.119 μm, the max speed is as 481.43 μm/s, and the max load is as 950 g.

Experimental Study and Design of Piezoelectric Actuators with Suspension Spherical Rotor

WANG Junshan;CHEN Chao;SHI Mingyou;CAO Jing

2020, 31(17): 2064-2070. DOI: 10.3969/j.issn.1004-132X.2020.17.008

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Aiming at the specific requirements of stable levitation and high rotary speed of mechanical rotor gyroscopes, a hybrid stator using both longitudinal Langevin vibrator and piezoelectric disc was designed. In this way, the large vibration amplitude traveling waves of output surfaces of the stator were excited, and the ultrasonic near-field non-contact supports and high-speed drives of the spherical rotor were realized. Structural dynamics design of the piezoelectric disks was conducted, and the expected vibrations of the composite stators were excited at the same working frequency. Modal experiments were conducted on the prototype to validate the good frequency consistency of the composite stators. Measured levitation height and rotary speed results show that the rotor is completely levitated, and the rotary speed is related to the driving frequency. The spherical rotor achieves the maximum rotary speed 3 880 r/min with the voltage of 200 V nearing the resonance frequency.

Prediction Model of Milling Cutter Wear Status Based on Deep Learning

DAI Wen1;ZHANG Chaoyong1;MENG Leilei1;XUE Yanshe1;XIAO Pengfei1;YIN Yong2

2020, 31(17): 2071-2078. DOI: 10.3969/j.issn.1004-132X.2020.17.009

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In order to improve the prediction accuracy and generalization performance of tool wear monitoring, the milling tool wear state prediction was studied based on deep learning. Two prediction models were proposed based on stacked sparse auto-encoder network and convolutional neural network. The stack sparse auto-encoder network used dimensionality reduction processing of feature vectors and incorporated them into the classifier to achieve classification prediction, avoiding the dependence on prior knowledges in feature selection. Convolutional neural networks completed the conversion of milling vibration data into wavelet scale maps as model inputs, and greatly simplified the traditional modeling processes. Finally, the two proposed models were compared with traditional neural network models to verify the efficiency and accuracy of the proposed models.

A Trajectory Planning Method for Automatic Placement of Carbon n Fiber Screw Propellers

LIU Zhiqiang1;GU Xianan1;GUO Hao1;XI Hao1;WANG Mingqiang1;LI Junli2

2020, 31(17): 2079-2084,2094. DOI: 10.3969/j.issn.1004-132X.2020.17.010

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Because the propeller surfaces are high-order free form surfaces, trajectory planning of carbon fiber placement and formation was carried out with four-wire carbon fiber screw propeller surface placement device as platform. According to the requirements of surface trajectory planning of marine fixed pitch paddle blades, a trajectory optimization placement algorithm, aiming at low-precision defects of traditional curved mesh trajectory and placement method, was proposed based on Laplacian mesh optimization and equal-arc length surface stratification, and the algorithm simulation and physical verification were completed. Results show that the trajectory planning method may meet the placement requirements of carbon fiber screw propellers.

Tool Optimization for Splicing Die Milling Processes Based on Finite Element Simulation

YUE Caixu;LIU Xin;LIU Zhibo;XIE Na;WANG Yanwu

2020, 31(17): 2085-2094. DOI: 10.3969/j.issn.1004-132X.2020.17.011

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ABAQUS software was secondary developed to realize splicing die rapid modeling of milling process simulation before treatment. The milling force, stress and cutting tool temperature were simulated, and compared with the milling experiments. Results verify the accuracy of the simulation model. The processes of milling splicing die for ball end milling cutter with different rakes, clearances, helical angles and cutting edge radii were simulated. The structure of milling cutter was optimized by genetic algorithm. The tool wear and workpiece surface quality were compared with the structure parameters after optimization and in tradition, so as to verify the effectiveness of the optimization. Research shows that the secondary development of rapid modeling is successful and the simulation results are accurate. The results provide fundamental basis for reducing manufacturing costs, improving milling tool life and workpiece surface quality.

Optimization of Assembly Line Material Distribution Planning under Fuzzy Time Window Constraints

LIU Xuemei1;WANG Xiao1;LIU Yuelei2

2020, 31(17): 2095-2103. DOI: 10.3969/j.issn.1004-132X.2020.17.012

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In order to solve the problems that the materials of the assembly line could not be timely and accurately distributed, a dynamic joint distribution strategy was proposed. A mathematical model of material distribution was established based on fuzzy time window constraints with the goal of minimizing the distribution cost per product and maximizing customer satisfaction. The NSGA-Ⅱ algorithm was adopted to solve the optimal station group division, car departure time and distribution path, and optimize the distribution car capacity and delivery time window. The simulation model of a production line was built by Plant Simulation software to verify the feasibility of the distribution scheme. Compared with the general distribution strategy, the results show that optimizing the time window may further reduce the distribution cost per product under the premise of ensuring the satisfaction of the distribution station.

Construction Method of Workshop Manufacturing Service Collaboration Chains for Mass Personalization Manufacturing

PANG Shibao1;GUO Shunsheng1;WANG Lei1;LI Xixing2

2020, 31(17): 2104-2111. DOI: 10.3969/j.issn.1004-132X.2020.17.013

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Under mass personalization production environments, manufacturing resources within the workshop needed to be reorganized frequently to build new service collaboration chains to complete different manufacturing tasks. In order to improve efficiency and stability of the service collaborative chains, a manufacturing resource aggregation model was established to describe the aggregation relationships of workshop manufacturing resources. Manufacturing resources were encapsulated into workshop manufacturing services based on improved K-means ++ algorithm. Frequent sub-network mining algorithm was used to mine frequently occurring service collaboration chains, and service collaboration chain evaluation was proposed to evaluate and filter the obtained service collaboration chains. Finally, feasibility and effectiveness of the proposed method were verified by case analysis.

Feedback Collaborative Optimization for Multi-line Manufacturing Systems

KONG Weichang;QIAO Fei;WU Qidi

2020, 31(17): 2112-2117,2127. DOI: 10.3969/j.issn.1004-132X.2020.17.014

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A general description of multi-line manufacturing systems with alternative coupled machines was given and designed to study performance optimization problems of the multi-line manufacturing systems on the basis of classic MiniFAB model. A feedback structure optimization method was proposed to solve the problems of insufficient training data when optimizing a multi-line manufacturing system. Structure optimization method was further collaborated with selection of heuristic rules to improve accuracy of performance optimization. As a result, the collaborative optimization method for multi-line manufacturing systems was proposed. Feasibility and effectiveness of the proposed methods were verified through cases.

Analytical Model of Thermo-mechanics Coupling and Experimental Verification for Friction Pull Plug Welding

CHEN Yongliang1;YANG Zichao1;LIN Hengli1;CUI Lei2;SONG Jianling3;WANG Dongpo2

2020, 31(17): 2118-2127. DOI: 10.3969/j.issn.1004-132X.2020.17.015

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In order to quickly obtain welding parameters of FPPW and predict welding processes, mechanics models and thermo-mechanics coupling analytical models of FPPW processes containing indicators such as torque, axial force, power, and energy were established. Inputs of this model were geometric parameters, material properties, welding speed, and feed speed of plug rod, and outputs were torque, axial force, power, and energy of welding processes. Welding tests were carried out on self-designed FPPW equipment. Feasibility of the analytical models was verified by comparing the inputs and outputs of welding data with the theoretical model.

Plasticizing Mechanism and Formability of AA7075 Sheet Heat Treatment

SUN Yufei1;ZHAO Changcai1;YANG Shengfu2;YANG Zhuoyun1

2020, 31(17): 2128-2136. DOI: 10.3969/j.issn.1004-132X.2020.17.016

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Combined with production processes, effects of solution treatment required for forming, natural aging required for process connection, and artificial aging required for performance recovery on the mechanics properties and forming properties of the sheets were studied. The influences of heat treatment on the microstructure and macroscopic mechanics properties of the sheets were investigated by optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. The results show that the percentage of total elongation at maximum force increases by 85% and yield strength decreases by 60% after the AA7075 sheets are heat-treated with solution treatment(480 ℃, 0.5 h) and natural aging. The sheets may restore mechanical properties completely after artificial aging(120 ℃, 12 h). The forming properties of the sheets are greatly improved and the rebound rate of the sheets is reduced significantly after solution treatment. The influence of subsequent aging treatment on the bending angle changes are weak.

Weld Formation of High Strength Steels by Low-power Pulsed Laser Induced Mental Active Gas Hybrid Welding in Overhead Positions

LIU Liming;CHEN Liang;SONG Gang

2020, 31(17): 2137-2141. DOI: 10.3969/j.issn.1004-132X.2020.17.017

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A low-power pulsed laser induced metal active gas(MAG) arc hybrid welding tests in overhead positions were carried out for 5mm thick E36 high strength steel plates. The results show that heat input of laser induced MAG arc hybrid welding is 29% lower than that of single arc welding. By reducing weld pool sizes, hybrid welding may effectively inhibit the formation of concave defects, and then increase the processsing parameter ranges. Tensile tests and bending tests show that the welding joints without internal concave defects have good static tensile strength and bending load. Static tensile strength of the welding joints with internal concave is equivalent to the base metal, but the maximum bending load is significantly reduced.

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