Table of Content

25 October 2023, Volume 34 Issue 20

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On Sound Absorption Characteristics of Lightweight Structures Constructed by UMPPs

LIU Jie, JIAN Linjie, DOU Zecheng, WEN Guilin, WANG Ruikun, LI Fangyi

2023, 34(20):  2395-2402.  DOI: 10.3969/j.issn.1004-132X.2023.20.001

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 To address the problems that the effective sound absorption bandwidth of conventional micro-perforated panels was too narrow in the middle and low frequencies, a UMPP constructed lightweight structure was proposed. A theoretical model of sound absorption based on the micro-perforated plate theory and a high-fidelity finite element model were established, and an acoustic impedance tube-based sound absorption test system was built. The sound absorption characteristics of single-layer, double-layer, and triple-layer UMPP sound absorbing structure were investigated. Results show that the single-layer UMPP sound absorbing structure has a better sound absorption bandwidth, but there are obvious sound absorption valleys. The sound absorption mechanism was revealed from the perspective of normalized acoustic resistance and normalized acoustic reactance. To further improve the sound absorption performance of the proposed UMPP structures, a structural optimization design strategy was proposed to realize effective sound absorption in the sub-wavelength scale(1/8 wavelength) with a wide frequency range of 369~7000 Hz.

Study on Groove Structures of Inconel 718 Alloy Fabricated by WJGL

ZHAO Chuang, ZHAO Yugang, ZHAO Dandan, MENG Shuo, YU Hanlin, LI Zhihao, CAO Chen, ZHANG Haiyun, MENG Jianbing

2023, 34(20):  2403-2410.  DOI: 10.3969/j.issn.1004-132X.2023.20.002

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In order to explore the laws of manufacturing groove structures on Inconel 718 alloy by WJGL, multiple sets of single factor experiments were designed and carried out on the self-developed WJGL equipment. The effects of water jet velocity and laser energy density on the depth, width and burr size of groove structures were analyzed. The experimental results show that the influence of laser energy density on the size of groove structure is higher than that of water jet velocity. Under the condition of constant nozzle aperture, laser energy density and water jet velocity have little effects on the width of groove structures. A nozzle with an aperture of 0.5 mm is used, when the laser power density is as 40 J/cm2 and the water jet velocity is as 60 m/s, the maximum depth of the groove is as 523 μm. When the laser energy density is as 10 J/cm2, the narrowest width of the groove is as 403 μm. When the laser energy density is as 40 J/cm2, the minimum burr size is as 54 μm.According to the theoretical analysis, the mechanism of WJGL technology to remove Inconel 718 alloy material is to ablate the molten material by laser, and then the molten material is washed away by water jet.

Experiments and Analyses of Effects of Axial Low-frequency Vibration on Feed Forces of Cortical Bone Drilling

BAI Xiaofan, LIU Zhiqiang, LIU Yanshi

2023, 34(20):  2411-2427.  DOI: 10.3969/j.issn.1004-132X.2023.20.003

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 For studying the effects of axial LFVAD method on the feed forces in the cortical bone drilling processes, the comparative experiments of feed forces for whole drill bit and chisel edge were performed. The kinematics analyses and the transient machining processes of the cutting unit in LFVAD method were also studied. The experimental results show that, compared with conventional drilling(CD) method, the feed forces of whole drill bit and chisel edge in LFVAD method decrease about 60% and 60%~80% respectively with the same drilling parameters. According to the analyses of kinematics and the comparisons of typical morphology of bone chips, a periodic separation motion between the drill bit and workpiece may be achieved in LFVAD method with the specific drilling and vibration parameters. This motion may significantly change the transient machining processes. This motion may be one of the main reasons for the feed force reduction.

Rail Crack Detection Method Based on Differential Flexible Eddy Current Probe

XU Peng, LIU Bailin, CHEN Yaxiong

2023, 34(20):  2419-2427.  DOI: 10.3969/j.issn.1004-132X.2023.20.004

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 A rail surface crack detection method was proposed based on flexible printed circuit board(FPCB) probe. Through the combination of simulation analyses and high-speed turntable experiments, the detection abilities of probes with different excitation frequencies, different depth defects and cluster dense defects were tested. The test results indicate the optimal excitation frequency suitable for FPCB probe and the applicable detection depth range of defects, and obtain the corresponding relationship between the ability of FPCB square coils which is used to detect dense defects with different spacing and coil size, that is, when the minimum distance between dense defects is known to be X, the side length of the square FPCB coil may be designed to be 2X to basically identify all defects, and the best single-coil detection signals may be obtained if the design is within X, while the best differential detection signals may be obtained within X/2. The conclusions are only applicable to the square coil studied herein.

Study on Hydrodynamic Stability of a Dot Matrix Offshore Wind Turbine Foundation Structure

ZHU Jiangfeng, CAO Yuguang, ZHAO Qiankun, LI Lei

2023, 34(20):  2428-2433，2474.  DOI: 10.3969/j.issn.1004-132X.2023.20.005

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A dot matrix offshore wind turbine integrated foundation design scheme was established based on the concept of wind turbine integration. The overall structural parameters and mechanics model were analyzed， and the feasibility and advantages of the overall scheme of the new dot matrix foundation（DMF） were established. Combined with the traditional OC4 semi-submersible wind turbine system， the hydrodynamic simulation was carried out under wind wave current loads. Results show that the stability of DMF in pitch motion is 70% higher than that of the traditional OC4 system. The small-scale prototype processing of DMF and the simulation experiments of wind and wave trough were completed based on similarity theory. Experimental results are in good agreement with the simulation data. 

Experimental Research of Floating Grinding Processes for 2.5D Cf/SiC Brake Materials

WANG Ming, DONG Hai, WANG Baihe, WANG Zheng, WANG Jiawei

2023, 34(20):  2434-2441.  DOI: 10.3969/j.issn.1004-132X.2023.20.006

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To investigate the floating grinding performance of 2.5D Cf/SiC brake materials, the influences of grinding wheel speed, table setting pressure and grinding depth on grinding force, surface roughness and surface profile were investigated in a single-factor test, and the typical machining defects on grinding surfaces and material removal mechanism were analyzed. The results show that the grinding wheel speed, table setting pressure and grinding depth produce significant influences on the normal grinding forces, but little effect on tangential grinding forces. The table setting pressure produces the greatest influences on the surface roughness. 2.5D Cf/SiC is mainly removed by brittle fracture, and there are differences in the forms of processing defects in different fiber directions, and the main processing defects are interfacial debonding, microcracking, matrix fragmentation, fiber peeling and fragmentation. The experiments were analyzed by a single factor method to obtain good surface quality, with a surface roughness Sa of 0.6 μm.

Research on Distributed and Multi-flexible Assembly Job-shop Scheduling Problems

WEI Guangyan, YE Chunming

2023, 34(20):  2442-2455.  DOI: 10.3969/j.issn.1004-132X.2023.20.007

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Aiming at distributed flexible assembly job-shop environments, the machine selection flexibility, worker scheduling flexibility, and process sequence flexibility in scheduling were comprehensively considered, and a model of DMFAJSP was constructed taking minimizing the makespan and minimizing the total energy consumption as optimization objectives. To solve the DMFAJSP model, MDMA was proposed using estimation of distribution algorithm as the global search component and the neighborhood search operators as the local search component. Finally, comparative experiments were conducted between the proposed algorithm and other algorithms, and the results show that the MDMA has significant advantages in solving DMFAJSP model.

Adaptive Kalman Filtering and PSO-GA-BP Algorithm for Robot Error Compensation

LI Guangbao, GAO Dong, LU Yong, PING Hao, ZHOU Yuanyuan

2023, 34(20):  2456-2465.  DOI: 10.3969/j.issn.1004-132X.2023.20.008

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 The cutting holes of a certain type of launcher were machined by a seven-axis robot device clamping laser. In the machining processes due to the low trajectory accuracy and absolute positioning accuracy, it was easy to cause damage and error cutting to the launcher of the model products. The ideal model of the seven-axis robot was established using the D-H algorithm, and the ideal model was verified by the numerical algorithm of forward and inverse kinematics. Based on Sage-Husa adaptive Kalman filter, the theoretical pose parameters of the ideal model and the measured pose parameters of the laser tracker were used to solve the real pose coordinate information of the seven-axis robots, and the joint errors of the ideal pose parameters and the real pose coordinate information were obtained. Then, the error prediction model of the seven-axis robots was established by combining the PSO-GA-BP joint algorithm. The theoretical pose parameters of the seven-axis robots were used as input samples. The joint angle differences between the real pose and the theoretical pose were taken as the output sample. The joint angle values of the seven-axis robots were compensated according to the model output values by KUKA Robot Workvisual 5.0 software. Through simulation experiments and machining processes, the trajectory errors and absolute positioning errors of the seven-axis robots after the joint error compensation are decreased by 72%, meeting the production requirements. 

Smooth Tool Orientation Generation Method of Five-axis Ball-end Milling via RTOs Interpolation

LU Yaoan, QIU Hongjian, WANG Chengyong,

2023, 34(20):  2466-2474.  DOI: 10.3969/j.issn.1004-132X.2023.20.009

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A method of determining the RTOs was proposed herein based on a greedy strategy, and a method of generating smooth tool orientations was proposed for five-axis ball-end milling via RTOs interpolation. The feasible domains of the tool orientation at the cutter contact points of each RTO were calculated. Then the RTOs along the tool path were selected from the tool orientation feasible domains based on the greedy strategy, and the RTOs were interpolated to check whether the tool orientations along the whole tool path occured collision. Afterward, the feasible RTOs set was obtained. The optimal RTOs were selected from the feasible RTOs set according to the tool path smooth evaluation indicators, and then the whole tool path was acquired. The test results show that the tool path of the complex surface generated by the proposed approach may make the machine tool rotary axes move smoothly.

Hybrid Algorithm of Machining Feature Segmentation and Recognition for Aero-engine Casings

ZHANG Yuhang, SUN Yuwen, XU Jinting

2023, 34(20):  2475-2481.  DOI: 10.3969/j.issn.1004-132X.2023.20.010

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There were many intersection features and surface features in aero-engine casing parts. In order to solve the problems that the existing methods couldnt recognize them effectively, a hybrid feature segmentation algorithm was proposed based on heuristics and rules. Firstly, based on the attribute adjacency graph of parts, the transition feature recognition was used to simplify the topological hierarchy of features. Secondly,based on the determination of the initial surfaces of feature segmentation, a heuristic search condition was set to perform convex edge diffusion and concave edge diffusion on the feature surfaces, and the machining features were divided into convex and concave features. Thirdly, the seed surface was determined according to the topological structures and geometric information of the feature surfaces, which were used as the driving surfaces for feature combination, and the feature parameters that could represent different features were extracted to realize the rule-based feature recognition. The effectiveness of the proposed method was verified by experiments on typical aero-engine casing parts.

Structural Optimization Method of Additive Manufacturing Model Based on Point Cloud Data

XUE Kai, GUO Runlan, HUANG Huiyang, HUANG Hua

2023, 34(20):  2482-2488.  DOI: 10.3969/j.issn.1004-132X.2023.20.011

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Due to the characteristics of layer by layer accumulation in additive manufacturing, it was necessary to consider the correct forming of overhanging structures in the forming processes to avoid the formation of redundant support structures in the structural optimization processes. An optimization method for 3D model structure was proposed herein. Firstly, the point cloud data method was used to process the 3D model to obtain the contour features. Then the model was divided according to different features. Finally, the corresponding internal ellipsoid structures were established according to different external features, and the self-supporting structures were rebuilt in the interior in order to ensure that the optimized structure molding process would not generate extra support because of the special structure. The experimental results show that the method proposed herein may reduce the molding time and material cost by 16.4% and 12% on average respectively on the premise of guaranteeing the performance of the solid model with four different characteristic models as examples.

Contour Offset Algorithm Based on Topological Relationship of Line Segments

HU Pingshan, DING Haoliang, FENG Yangyang, YAN Bo

2023, 34(20):  2489-2495.  DOI: 10.3969/j.issn.1004-132X.2023.20.012

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Most of the existing offset algorithms were limited to simple graphics, which might not meet the complex structure requirements of real additive manufacturing parts. Therefore, a contour offset framework was proposed based on line segment topology. The types and formation mechanism of offset anomalies were studied, and the multi-loop processing algorithms such as line segment coincidence, (self) intersection, ring formation, ring reversal and ring failure were proposed to realize the processing of complex anomalies. The formation mechanism and influences of local sharp corners on the boundary were investigated, and the patching smoothing algorithm was proposed to optimize the angle of adjacent edges, almost eliminating the problems of singular sharp corners and void defects, and ensuring the stability of the algorithm. Using C++ language to write the algorithm program, compared with the results of the offset algorithm of the CGAL geometric graph library, the calculation speed of the contour offset method is faster, and the planned path is more in line with the machining geometric characteristics of the machining equipment. Compared with other scanning methods such as parallel line scanning and partition scanning, the total length of the present contour offset path is relatively lower and the overall scanning efficiency is higher.

Design and Laser Etching of Embedded Microchannels on AlN Substrate

MA Yupu, WEI Tao, WANG Li, ZHAO Junyi, ZHANG Xinlei, CHEN Ni, LI Liang, HE Ning

2023, 34(20):  2496-2503.  DOI: 10.3969/j.issn.1004-132X.2023.20.013

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AlN HTCC substrates had the advantages of high thermal conductivity and good thermal stability. Embedding micro flow channels in AlN substrates might significantly improve heat dissipation and reduce package thickness, but it was diffeeicult to precision machine small size, hard brittle AlN micro flow channels. Based on the heat dissipation requirements of an array power device, a research was conducted on the design of AlN embedded microchannels. In order to solve the problems of machining micro channels on AlN ceramic substrates, laser etching of AlN ceramic substrates was conducted, the effects of line etching thresholds and laser parameters on the size and morphology of line etching grooves on AlN ceramic substrates were explored, and a composite processing method of laser and chemical milling was proposed. The experimental results show that the power threshold of laser etching in line etching is positively correlated with the scanning speed. With the increase of laser power, the width of the line etching groove will be larger than the diameter of the light spot, resulting in excessive machining. The dimensional errors of the micro channel structure obtained by laser and chemical milling combined processing are less than 50 μm. The surface roughness values may reach 5.6 μm.

Sensitivity Analysis and Optimization of High Speed Train Cooling Centrifugal Fan Performance

QU Xiaozhang, ZHANG Jiabei, ZHAI Fangzhi

2023, 34(20):  2504-2512.  DOI: 10.3969/j.issn.1004-132X.2023.20.014

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In order to improve the performance of the centrifugal fans in the cooling systems of high-speed trains, the parametric model of the centrifugal impeller structure and the computational fluid dynamics(CFD) simulation model were adopted. Combined with the performance tests, the CFD simulation model of the centrifugal fan performance was established. The reasonable values of blade number and impeller width were identified by single factor sensitivity analysis respectively. The Latin hypercube sampling(LHS) model was used to sample the impeller structure and performance parameters of the centrifugal fans. The RBFNN model was used to study the structure and performance parameters, and the performance analysis model of centrifugal fans was reconstructed. The multi-factor sensitivity of the structure parameters of centrifugal impellers was studied. Through the global sensitivity analysis, the key parameters affecting the performance were identified. Finally, an optimization scheme was proposed to improve the performance of the centrifugal fans by reasonably matching the structural parameters of the centrifugal impellers. The efficiency of the working point is increased from 67.2% to 73.7%, which may significantly improve the efficiency of the centrifugal fans and reduce the flow loss.

Manufacturing Readiness Level Assessment Method of Complex Product Assembly Based on BP-AdaBoost Algorithm

XU Meijiao, XUE Shanliang, ZHANG Hui, ZHOU Guoqing, LU Honggen

2023, 34(20):  2513-2519.  DOI: 10.3969/j.issn.1004-132X.2023.20.015

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In the existing manufacturing readiness level assessment of complex product assembly, the index weight and index score were evaluated by experts from experience. This resulted in some deficiencies such as subjectivity, heavy work, long time, and non-impartment of knowledge in the assessment cases. To improve the efficiency and objectivity of manufacturing readiness level assessment of complex product assembly, utilizing the dataset of manufacturing readiness level assessment cases, the manufacturing readiness level assessment was discussed herein based on BP artificial neural network and AdaBoost algorithm. A manufacturing readiness assessment index system of complex product assembly was established. The quantification of index and readiness level assessment were proposed based on fuzzy evaluation and membership function. Then the manufacturing readiness level assessment of complex product assembly was modeled based on BP neural network. The AdaBoost algorithm was applied to optimize readiness level assessment model based on BP neural network. To optimize the assessment model, it is trained on the dataset of manufacturing readiness level assessment cases and the results of BP-AdaBoost algorithm was analyzed. The optimal assessment model was obtained. Experimental results show that the assessment is good in reliability and accuracy based on BP-AdaBoost algorithm.