China Mechanical Engineering

Research on Forming Manufacturing Technology and Equipment of Composite Preforms

SHAN Zhongde, LIU Yang, FAN Congze, WANG Jun

2021, 32(23): 2774-2784，2931. DOI: 10.3969/j.issn.1004-132X.2021.23.001

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The revolutionary history of composite preforms forming technique was summarized from the standpoints of manufacturing technology and equipment development.The technical characteristics of the composite preform forming manufacturing technology were analyzed.The status of typical technology and equipment of composite preform forming manufacturing at home and abroad as well as existing challenges and gaps were listed.Finally，the future development directions and trends of composite preform forming technique were discussed prospectively.The development of digital precision forming manufacturing technology and equipment for high-performance composite components may promote the technical progresses of composites in China better，and achieve more extensive promotions and applications.

Research Status and Development Prospect of Machining Technology for Turbine Disc Slots

DING Wenfeng, LI Benkai, FU Yucan, XU Jiuhua

2021, 32(23): 2785-2798. DOI: 10.3969/j.issn.1004-132X.2021.23.002

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For turbine disk slots of high-end power equipment such as aero engines and gas turbines， the machining technologies were analyzed from two aspects of mechanical machining （e.g.， broaching， milling， grinding） and nontraditional machining （e.g.， wire electric discharge machining and wire electrochemical machining）， respectively. The development current situations were systematically explained from the viewpoints of design and application of tools， evaluation and control of machining quality. The important achievements of the research work in this field at home and abroad were also introduced. Finally， the development trends were generalized prospectively.

Capillary Liquid Transport on Biomimetic Topological Surfaces for Film Boiling Heat Transfer

YANG Xiaolong, TANG Yu, ZHU Di

2021, 32(23): 2799-2807. DOI: 10.3969/j.issn.1004-132X.2021.23.003

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In order to improve the capillary limit of surface structures for enhancing capillary-fed film boiling heat transfer， the microgroove arrays overlaid with microparticle structures were fabricated on titanium substrates by taking advantages of melting and solidification， and phase explosion of nanosecond pulsed lasers. A modified capillary liquid transport characteristic coefficient was developed to characterize the capillary liquid transport capability of the fabricated microgrooves based on flow resistance in open microgrooves model. The results show that the microparticle structures obtained during laser ablation improve the superhydrophilicity as well as the capillary liquid transport capability. The capillary coefficient increases with the decrease of the microgroove width. Moreover， the capillary limit may be further increased by fabricating minor microgrooves at the bottom of the major microgrooves with unique layered capillary transport configuration in imitation of sarracenia trichome.

Experimental Study of WECM Trimming for Titanium-Aluminum Intermetallic Compounds

HAN Zhao, FANG Xiaolong, ZHU Di

2021, 32(23): 2808-2816. DOI: 10.3969/j.issn.1004-132X.2021.23.004

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A method of machining titanium-aluminum intermetallic compounds TiAl 45XD was proposed by combining WEDM and WECM. During the WECM， the recast layers were removed by first “pass”， and the possible intergranular corrosions were eliminated by second “pass”. The electrochemical characteristics of the cast TiAl 45XD mechanical polished surfaces and the WEDM surfaces were studied respectively. It is found that both of the surfaces have passivation in water-based solutions（WBS）， and there are almost no obvious passivation in glycol-based solutions（GBS）. Compared with the WBS， both of the surfaces are more susceptible to corrosion in the GBS， and the WEDM surfaces are more corroded than that of the polished surfaces. Then the effects of feed speed and cutting depth on surface integrity were analyzed， the testing results show that when the feed speed of first “pass” is as 25 μm/s and the cutting depth is as 20 μm， the feed speed of second “pass” is as 60 μm/s and the cutting depth is as 0， the recast layers are removed， the intergranular corrosions are eliminated， the surface roughness value is reduced to 1.6 μm， and the average feed speed is as 17.65 μm/s， which proves that the use of WEDM for rough forming， WECM with GBS for trimming is a feasible method for machining straight-grained titanium-aluminum intermetallic compound components with high surface integrity.

Research on Machinability of Laser Modified AlN Substrates

CHEN Ni, WEI Jiawei, ZHANG Xinlei, LI Liang, HE Ning

2021, 32(23): 2817-2882. DOI: 10.3969/j.issn.1004-132X.2021.23.005

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The machinability of AlN ceramic substrates widely used in the packaging of microelectronic components were studied by laser modification method under different gas environments， laser powers and scanning intervals. The surface hardnesses and element contents of AlN specimen were measured by tests. The testing results show that under N2， Ar， and O2 gas environments， the surface components of the specimen are mainly AlN， Al and Al2O3， and the hardness of the cladding layers measured by microhardness tester is the lowest under the Ar environment， which is most conducive to the subsequent cutting. Under the Ar environment， with the increase of laser power and the decrease of scanning interval， the hardnesses of AlN surface modification decrease， and the minimum value may reach 174.83HV， making it easier to perform cutting.

Fibre Distribution and Bending Performance of Composite Grid Stiffeners Manufactured by Automated Fibre Placement

ZHAO Cong, XIAO Jun, ZHOU Laishui, AN Luling

2021, 32(23): 2823-2831. DOI: 10.3969/j.issn.1004-132X.2021.23.006

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In order to improve the load carrying efficiency of composite stiffeners，“cut and restart”method was proposed based on the automated fibre placement process，to optimise the fibre distribution around intersection of grid stiffeners.Influences of content and distribution of discontinuous plies，induced by “cut and restart” method，on the fibre distribution and bending performance of grid stiffeners was comprehensively studied via micro-observation，finite element simulation and experimental validation.Results show that structural efficiency of grid stiffeners maybe improved significantly with appropriate ratio of discontinuous plies in the intersection of grid stiffeners.Moreover，pseudo-ductile bending behavior also maybe achieved in grid stiffeners within discontinuous plies.Corresponding finite element models were developed and good correlation with the experimental response was established.The errors between numerical and experimental results are less than 8%.Furthermore, the failure mechanism of grid stiffeners with discontinuous plies was studied based on the finite element model established herein.Taking the mechanics performance and weight reduction into account，the optimal ratio of discontinuous plies in grid stiffeners manufactured by automated fibre placement are 25% and all discontinuous plies should locate in the top region of intersection of grid stiffeners.

Performance Analysis of Pulse Current Assisted Press Riveting for Ti45Nb Rivets

QI Zhenchao, XIAO Yexin, WANG Xingxing, CHEN Wenliang

2021, 32(23): 2832-2839，2849. DOI: 10.3969/j.issn.1004-132X.2021.23.007

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In order to improve the connection performance of Ti45Nb rivets when fastening aircraft carbon fiber reinforced polymer（CFRP） structures， broaden the applicable fastening range of ordinary rivets， reduce riveting costs and increase connection strength， the pulse currents were introduced to assist press riveting. The current pre-treatment assisted riveting test and the synchronous current treatment assisted riveting test were designed， and then the fastening quality and characteristics of two new riveting processes were compared with those of conventional riveting processes. The typical hardnesses in the cross sections of rivets were tested under different processes. The microscopic metallography and structure composition of the different areas of the rivets were compared and observed. The reasons for difference in the microstructure and element composition caused by the currents were analyzed. Finally， the tensile strength and failure behavior of different joints were evaluated， and the results proved the effectiveness and feasibility of the current assisted riveting processes.

Deadlock-free Task Scheduling with Task Traveling Time for a Multi-load AGV System

WU Xing, ZHAI Jingjing, LOU Peihuang, HU Ya, XIAO Haining

2021, 32(23): 2840-2849. DOI: 10.3969/j.issn.1004-132X.2021.23.008

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In order to solve the problems of task scheduling and buffer deadlock for a multi-load AGV system，a deadlock-free task scheduling scheme with task traveling time was proposed.Firstly，the task scheduling model was established with the objective of minimizing the delay rate and the imbalance degree of traffic loads.Secondly，the practical constraints in task scheduling were analyzed，and a prediction model was developed under the constraint of task traveling time.Thirdly，a multi-objective deadlock-free task scheduling method was proposed based on the AI-GWO algorithm for the task scheduling model.Deadlock prevention rules were used to prohibit tasks that would cause the buffer deadlock of workstations, and the AI-GWO algorithm was combined to perform the multi-objective optimization for the operation sequence of tasks.Finally，the tasks were assigned to different AGVs according to the balance degree of AGV loads.The simulation results show that the task-traveling time prediction model achieves high accuracy，and the task scheduling model and the deadlock-free scheduling method have the satisfactory optimization performance and computation efficiency.Therefore，the task punctuality rate of the material handling systems and the traffic-load balance degree of the path network are improved significantly.

Feature-preserving Denoising Method for Aero-engine Profile Point Cloud

YAN Jieqiong, ZHOU Laishui, HU Shaoqian, WEN Siyang

2021, 32(23): 2850-2860，2889. DOI: 10.3969/j.issn.1004-132X.2021.23.009

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The 3D laser scanning devices might provide the raw data of aero-engine profiles，but the noise would directly affect the reconstruction accuracy of the 3D geometric model of aero-engine profiles.In order to ensure that the noise was removed without blurring or destroying the complex geometry features of the aero-engine profiles，a feature-preserving point cloud denoising method was proposed based on deep learning.The noisy point cloud of aero-engine profiles was divided into feature data and non-feature data.The feature denoising network and the non-feature denoising network were designed to predict the position correction vectors of the feature noisy points and the non-feature noisy points respectively.The noisy points moved along above vectors and were projected back onto the original clean surfaces of the model.The data sets were constructed separately for feature denoising learning and non-feature denoising learning.The verification results show that when the proposed method is applied to the point cloud of aero-engine profiles with various noise scales，the denoising effectiveness is improved respectively compared with the existing learn-based methods.The proposed method has better geometric feature protection ability and may provide high quality point cloud for subsequent reconstruction.

A Circular Target Stability Detection Method Based on Deep Learning Image Super-resolution

CUI Haihua, XU Zhenlong, YANG Yapeng, MENG Yayun, WANG Baojun

2021, 32(23): 2861-2867. DOI: 10.3969/j.issn.1004-132X.2021.23.010

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In order to improve the recognition rate and location accuracy of circular targets under the conditions of long-distance and large deflection angle， a circular target stability detection method was proposed based on deep learning image super-resolution. The multi-angle and multi-distance image sets were constructed through a hybrid data set of real images and synthetic images， the pixel loss and perceptual loss were used to improve the loss function of image super-resolution model， so the super-resolution reconstruction of images might be realized and the image details of target contours might be enriched. By using the pretrained super-resolution model， the images were reconstructed. Finally， traditional detection algorithm was used to recognize and locate the circular targets. The experimental results show that the circular target recognition rate is increased by 40%， and the target location accuracy is increased by 8.47%.

Muscle Torque Estimation and Neural Network Compensation Coordination Control of Soft Elbow Exoskeletons

WU Qingcong, CHEN Bai, ZHANG Zuguo, LIANG Conghui, LI Xiong, WU Hongtao

2021, 32(23): 2868-2875. DOI: 10.3969/j.issn.1004-132X.2021.23.011

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In order to assist the patients with hemiplegia to carry out multi-mode elbow rehabilitation training， a soft elbow rehabilitation exoskeleton robot was developed. In addition， a coordination control strategy was proposed based on human muscle torque estimation and adaptive neural network compensation. The surface electromyogram signals were used to identify the motion intention of human and adjust the trajectory of rehabilitation training. The closed-loop control stability of the control algorithm was proved by Lyapunov method. A real-time control experimental platform was established to conduct the trajectory tracking experiments and free active training experiments based on human motion intention. The experimental results show that the proposed control strategy may guarantee the trajectory tracking accuracy in passive training processes. Moreover， the movement trajectory in active training processes may be adjusted based on the motion intention of patients and realize active rehabilitation training with different intensities.

Design，Fabrication and Mechanics Property Analysis of Bionic Multilayer Flexible Lightweight Structures

ZHENG Yu, GUO Ce, MA Yaopeng, GUAN Jigang

2021, 32(23): 2876-2882. DOI: 10.3969/j.issn.1004-132X.2021.23.012

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Inspired by the bony scales and fish skin in the Chinese sturgeon， a new bionic multi-layer flexible protective light wight-structure was designed. Nylon， polydimethylsiloxane （PDMS） and Kevlar fibers were used to prepare the composite structures by high temperature curing technology， which effectively solved the problems of weak connection between scale and substrate. The impact tests were used to analyze the mechanics properties of the bionic composite structures and the influences of the angle γ， the embedding angle θ and the overlapping rate Kd on the energy-absorption performance of the composites were studied. The results show that the bionic bony scale with ridge-like shape and the flexible substrate with fiber layers may significantly improve the impact resistance of the bionic composites.

Kinematics Analysis and Teleoperation Technology of Multi-joint Continuum Robots

JI Aihong, LIU Rongxing, CHEN Hui, SUN Ke

2021, 32(23): 2883-2889. DOI: 10.3969/j.issn.1004-132X.2021.23.013

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A multi-joint wire driven continuum robot was designed. The continuum robots had four bending degrees of freedom and one feeding degree of freedom. The kinematics model of the continuum robot was established， and the workspace was analyzed by MATLAB. Three master-slave mapping algorithms were designed for Geomagic Touch to realize the master-slave heterogeneous teleoperation control of continuous robots. The correctness of the master-slave control algorithm was verified by experiments， and the good bending ability of the continuum robots was shown. The experimental results show that the continuum robots have certain control accuracy and good following ability.

Grey Design Decision Method Based on Visual Perception Data

LU Weihua, SUN Tianqi

2021, 32(23): 2890-2897. DOI: 10.3969/j.issn.1004-132X.2021.23.014

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Aiming at the problems that tacit knowledge was difficult to be revealed in the design decision processes， which led to the uncertain decision results， a grey design decision method blending visual perception data was proposed. Based on the mapping among visual perception， attention and preference， a cognitive model of visual perception was created. Integrating the decision makers subjective choice of explicit dimension and the eye tracking data of implicit dimension， a preference design decision-making evaluation mechanism was constructed, cosine distance was used to assign the weight of decision makers， and the gray decision comprehensive ranking was used to obtain the order of proposals. A case study was carried out on the rice cooker， the results show that the method may obtain objective and accurate decision-making conclusion. This protocol may be effectively applied to group decision-making under the conditions of limited information， and provide method reference for design innovation.

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