Table of Content

    10 April 2021, Volume 32 Issue 07
    Development History and Future Trends of Numerical Control Machine Tools
    LIU Qiang,
    2021, 32(07):  757-770.  DOI: 10.3969/j.issn.1004-132X.2021.07.001
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     From the viewpoints of industrialization and technology development, the paper summarized the revolutionary history of machine tools and the development processes of NCMT, with the analysis of the kernel technologies of NCMT. The development process of NCMT in China was divided into 3 periods, initial development, consistent technical research and industrialization, and highspeed development, transformation and upgrading as well. The milestone events and achievements were introduced. The industrial scale of NCMT all over the world and the advanced NCMT technologies in several developed countries were presented, followed by the comparative analysis of respects relative with NCMT at home and abroad. Finally, the future development trends were summarized prospectively.
    Plunge Milling of Titanium Alloys Based on Machine Learning and Multi-objective Optimization
    WENG Jian, ZHUANG Kejia, PU Donglin, DING Han,
    2021, 32(07):  771-777.  DOI: 10.3969/j.issn.1004-132X.2021.07.002
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    Based on the experimental work and optimization research of plunge milling of titanium alloys, a hybrid method integrated with machine learning and multi-objective optimization algorithm was proposed herein to optimize the processing parameters considering material removal rate and cutting force as objectives. Spindle speed, radial cutting width, cutting step and feed per tooth were used as test variables. Taguchi method was used to reduce the number of test variable groups. The performance of the model given by machine learning was compared with traditional first-order and second-order regression models. Results show that machine learning has a better performance in prediction accuracies and the distributions of solutions. Four algorithms(MOEA/D, NSGA-Ⅱ, SPEA2, and NSPSO) were used and compared in solving the problem, and NSGA-Ⅱ shows a better comprehensive performance. Finally, the optimal results were compared with the initial reference. Results show that the optimal results may improve the material removal rate and reduce the cutting forces, which may help to achieve the goal of efficient and stable machining.
    Rolling Bearing Fault Diagnosis Method Based on Adaptive Autogram
    ZHENG Jinde, WANG Xinglong, PAN Haiyang, TONG Jinyu, LIU Qingyun
    2021, 32(07):  778-785,792.  DOI: 10.3969/j.issn.1004-132X.2021.07.003
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    In Autogram method, the signal spectrum was divided by the maximum overlap discrete wavelet packet transform, and the signals in the frequency band corresponding to the maximum kurtosis value were selected for diagnostic analysis. However, the method followed the binary tree structure when the frequency band was divided, and the division area of this structure was fixed. A fault diagnosis method of rolling bearings was proposed based on adaptive Autogram to solve this problem. The improved empirical wavelet transform was used as the basis of adaptive Autogram. In this process, the original signal Fourier spectrum was enveloped and smoothed and then segmented, thus achieving the purpose of frequency band was adaptively divided by Autogram. The simulation signals and experimental data were analyzed through the proposed method, and the analysis results were compared with the existing fast kurtogram and Autogram. The results show that the optimal demodulation frequency band may be accurately detected by the proposed method, and the fault characteristics are more obvious.
    Study on Infrared Image Enhancement of Wind Turbine Blades Based on Adaptive Differential Multiscale Morphology(ADMM)
    KANG Shuang, CHEN Changzheng, ZHAO Siyu, LUO Yuanqing, KONG Xiangxi
    2021, 32(07):  786-792.  DOI: 10.3969/j.issn.1004-132X.2021.07.004
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    In order to improve the ability of infrared detection of internal defects of wind turbine blades and overcome the problems of low definition of infrared thermal images, uneven background illumination, and weak ability of detail recognition, an image enhancement algorithm was proposed based on ADMM. Different scale structural elements were selected as the operation objects in the expansion and corrosion operations, and the maximum contrast improvement coefficient ratio was used as the objective function of multi-scale and difference scale selection. The light and dark details of multi-scale images were extracted by using the advantages of open, close, and top-hat operations. Then, the differences between the white cap and the black cap were calculated to get the detail enhancement information, and the enhanced infrared images were obtained by fusing with the original images. Finally, the grayscale distribution of the image was adjusted to achieve the best visual effectiveness. Simulation results show that the algorithm has strong robustness and may effectively enhance the infrared image details under uneven illumination, improve the detection ability of infrared detection in wind turbine blades.  
    Study on Steady-state Heat Transfer of Soft Manipulators with Variable Stiffness Based on Low-melting-point Alloy Phase Transition
    WANG Fengxu, XING Zhiguang, YANG Pengpeng, LIN Jun, ZHAO Jianwen,
    2021, 32(07):  793-798.  DOI: 10.3969/j.issn.1004-132X.2021.07.005
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    The steady-state heat transfer model for the soft manipulators with variable stiffness based on LMPA phase transition was established to calculate the temperature changing, heat transfer power of each parts and the convective heat transfer of water in the spiral coil during steady-state heat transfer. Then, the steady-state heat transfer process was simulated by COMSOL Multiphysics. The differences between simulation and analysis model are within 4.5%. The theoretical analysis and simulation may be used to guide the design of variable stiffness modules. 
    Identification of Fault Degree of Oil Filter Blockage in Electro-hydraulic Actuator Based on an Improved PCA-SOM
    CHEN Huanguo, LIU Peijun, YU Hang, XIAO Xue
    2021, 32(07):  799-805.  DOI: 10.3969/j.issn.1004-132X.2021.07.006
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    In view of the oil filter plugging faults of EHA, to using adjustable ball head oil plug was proposed to preset different degrees of plugging conditions for data collection, and based on the traditional SOM, PCA was introduced to revise each dimensional coefficient of the neuron competition domain values by using the contribution rates of each principal component, as well as proposed an improved PCA-SOM neural network to identify the blockage states of the system. The results show that compared with the traditional SOM neural network and PCA-SOM neural network, the improved PCA-SOM neural network has higher applicability in EHAs oil filter blockage fault diagnosis, which is embodied in that the clustering effectiveness is improved while the accuracy and training speed of the model are also promoted.
    Inversion Analysis of Surface Micro-geomorphology in Splicing Areas of Cover Molds
    WU Shi, ZHAO Hongwei, LI Xin
    2021, 32(07):  806-804.  DOI: 10.3969/j.issn.1004-132X.2021.07.007
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    In order to improve processing quality of splicing areas for body cover panel die, the geometric characteristics of surface appearance and spatial characteristics of residual height before and after splicing seams were analyzed separately under different processing parameters. And then, energy entropy of different frequency bands for contour signals of the processing surfaces was extracted based on wavelet packets characteristics. Finally, processing parameters of the surface topography were retrieved according to the energy entropy characteristics, material removal rate, and tool life prediction function. Research results show that the processing parameters obtained based on inversion analysis method may achieve controllable micro-geometry of the splicing areas.
    Welding Joint Performance of Inclined Stationary Shoulder Friction Stir Welding for Aluminum Alloy Sections
    FANG Yuanfang, , ZHANG Hua
    2021, 32(07):  815-820.  DOI: 10.3969/j.issn.1004-132X.2021.07.008
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    6005A commercial aluminum alloy was welded by a FSW device with stationary shoulder. After welding, stretching and bending characteristics of joints were tested, and the cross sectional structures of welds and tensile fracture cross-sections were observed. The results show that surfaces of stationary shoulder FSW are smooth without arc grain; grooves of weld surfaces are disappeared by inclined stationary shoulder FSW. When weld speed is as 1 m/min and rotational speed is as 2100 r/min, the tensile strength of joints is as 73% that of parent metal, and yield strength of joints is as 55% that of parent metal. At the rotational speed of 1700 r/min and 1800r/min, cracks appear in back bending specimen, and the cracks disappear with the increase of rotational speed. S curves appear in cross sections of welds, and the fracture mechanism of the specimen is ductile fracture. With the increase of rotating speed, the degree of tissue refinement and degree of distribution both increase.
    Review on Repair Technologies for Key Part Remanufacturing of Shield Machines
    LI Fangyi, QI Xiaoxia, LI Yanle, WANG Liming, DU Jiyu, XU Jingwei, MENG Xiaoning
    2021, 32(07):  820-831.  DOI: 10.3969/j.issn.1004-132X.2021.07.009
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    The development situation of shield machine remanufacturing in China was expounded, and the development shortages and challenges were pointed out. The damage forms and the repair methods of key parts of shield machines, such as main bearing, cutter and cutter head, hydraulic system, reducer, screw conveyer were summarized. The potential and advantages of additive repairing technologies such as laser cladding, thermal spraying, cold spraying and cold welding in shield machine remanufacturing were analyzed. The future development trends of shield machine remanufacturing were finally provided.
    Multi-objective Optimization and Decision-making Method of High Speed Dry Gear Hobbing Processing Parameters
    NI Hengxin, YAN Chunping, CHEN Jianlin, HOU Yuehui, CHEN Liang
    2021, 32(07):  832-838.  DOI: 10.3969/j.issn.1004-132X.2021.07.010
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    To reduce energy consumption and improve gear hobbing quality, a multi-objective optimization and decision-making method of high-speed dry gear hobbing processing parameters was proposed based on improved multi-objective grey wolf optimization(MOGWO) algorithm and TOPSIS. The gear hobbing processing parameters were analyzed, and cutting parameters and hob parameters were taken as optimization variables. A multi-objective optimization model for minimum energy consumption and optimal gear hobbing quality was established. The improved MOGWO algorithm was used to optimize the model iteratively, and TOPSIS was subsequently utilized to make multi-attribute decision on the optimized processing parameters. Effectiveness of the proposed method was verified by experimental results.
    Dynamic Resource Allocation of Manufacturing Network for Emergency Equipment
    PEI Zhi, DAI Xu, YUAN Yilun, YI Wenchao, CHEN Yong
    2021, 32(07):  839-848.  DOI: 10.3969/j.issn.1004-132X.2021.07.011
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    Emergency equipment manufacturing was of high variability and volatility. In order to stabilize the abandonment probability of waiting customers in the manufacturing network, a multi-echelon manufacturing service network was proposed, together with a dynamic resource allocation strategy for each node based on queueing theory. Based on various target levels of the manufacturing service network, a closed-formed approximation algorithm and a numerical method were proposed to dynamically configure the manufacturing resources in the separate nodes. In the numerical examples, the methods were validated in terms of the target performance and coordinated strategy. The methods may be applied to the design of manufacturing networks for emergency equipment, and also support the configuration for more complex manufacturing service network structures. 
    Collaboration of Cloud Manufacturing Service Based on Service Choreography
    LU Jianfeng, HAN Tiaojuan, YU Yaoping
    2021, 32(07):  849-859.  DOI: 10.3969/j.issn.1004-132X.2021.07.012
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    The value creation of manufacturing products was evolved to cross-organizational collaboration, and the service-based orchestration such as business process execution language was difficult to meet multi-agent, diverse and dynamic flow management of service composition. A service choreography method was proposed to predefine and implement the collaborative flow of cloud manufacturing service based on WS-CDL protocol. By designing the interface specification for interacting information and extending WS-CDL protocol, the standardized description of the service collaboration was achieved to promote communication of cross-organizational services. A case study was given to illustrate that the service collaboration may improve the efficiency of service execution and the resource utilization rate of service providers.
    Quantitative Evaluation Method of Defects Based on Transient Characteristics of PMFL
    XU Peng, FANG Zhou, WANG Ping, GENG Ming, XU Yong
    2021, 32(07):  860-866,881.  DOI: 10.3969/j.issn.1004-132X.2021.07.013
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    Rail head transverse cracks were a kind of rail damages that possessed the greatest threat to railway traffic. Therefore, simultaneously quantifying the surface and subsurface defects of the rails were of great significance. A new defect evaluation method was presented based on the transient features of PMFL detection signals, which allowed simultaneous evaluation of the depth and burial depth of surface or subsurface defects. The detection signals fluctuated on the rising edges when the excitation was large and two novel features were extracted from this phenomenon. The functional relationships among the features and the defect parameters were established, thus the measured defects could be quantitatively evaluated. Finally, three other defects were used to verify this method, and the evaluation and actual data errors of the defects depth and burial depth are all within 0.2 mm.
    Improvements for Landing Impact Characteristics and Concentrated Stress Structures of Full Ocean Depth Landing Vehicles
    GUO Wei, SUN Hongming, XU Gaofei, LI Guangwei, ZHOU Yue, WANG Minjian,
    2021, 32(07):  867-874.  DOI: 10.3969/j.issn.1004-132X.2021.07.014
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    In order to analyze the impacting characteristics and improve landing safety of the full ocean depth landing vehicles, the landing processes were divided into 6 imitated landing states based on the rules of diving-floating and landing motion, the landing impact model of the full ocean depth landing vehicles was numerically simulated using an explicit dynamics method, and therefore the improvement design of vehicle’s tension wheel brackets was carried out. The maximum stresses of six imitated landing states before and after the improvement of the vehicle’s tension wheel bracket were analyzed, and the response characteristics of impacting rocky and muddy ground were compared and analyzed respectively. Results demonstrate that the improved tension wheel brackets have obvious cushioning effect, the maximum stresses of the landing vehicles when impacting the rocky ground and muddy ground are reduced to 13% and 30%, respectively. The concentrated stress of vehicles may be reduced by spring damping structure, while the stiffness coefficient has little effects on the impacting stress. According to the numerical simulation results of the landing states, the improved vehicle structure has higher safety, and a theoretical basis is provided for developing the full ocean depth landing vehicles which may adapt to complex seabeds.
    Simulation Analysis of Tram-mounted Energy-storing Scheme for Short Group Tramcars Based on Lithium Titanate Battery
    PU Sipei
    2021, 32(07):  875-881.  DOI: 10.3969/j.issn.1004-132X.2021.07.015
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    In terms of the short group on board energy storage low floor tramcars which were suitable for the small and medium-sized cities, since only charging stations were required for the entire line, no contact system was required in the main line sections, and barely any impacts on the urban landscapes and height limit, thus they were received a rapid development in recent years. However, due to the restrictions from both of the relatively short length of the tramcars and a limited roof installation space, the capacity of their on board energy storage devices were very limited, which resulted in high costs with a large number of charging stations along the lines. In order to increase the capacity of the on board energy storage devices for tramcars, the lithium titanate batteries were adopted to replace the supercapacitors commonly used in tramcars for this research, and the simulations analysis were carried out on Baoshan Tramcar T1 line under the real line conditions. The simulation results show that with the use of lithium titanate batteries instead of supercapacitors, under the same volume, the capacity of the on board energy storage devices may be increased by nearly one time, and the number of inter-section charging may be reduced by nearly half, which reduces the costs of project implementation and later maintenance costs of charging stations.