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Achieving High‑Quality Aluminum to Copper Dissimilar Metals Joint via Friction Stir Double‑Riveting Welding

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Acta Metallurgica Sinica(English Letters) 2023年第4期36卷 552-572页

作者： Shude Ji Xiao Cui Lin Ma Hua Liu Yingying Zuo Zhiqing Zhang college of aerospace engineering Shenyang Aerospace UniversityShenyang 110136China

In order to achieve a high-quality joining of aluminum(Al)and copper(Cu)dissimilar metals,a new friction stir doubleriveting welding(FSDRW)with a Cu rod as the rivet was proposed,and the rotating tool with a large concave angle shoulder was specially designed.The results showed that under the thermal–mechanical effect of rotating tool,the Cu rod was deformed to be a double riveting heads structure with a Cu anchor at the upper surface of Al plate and an Al anchor above the lap interface of joint,and these two anchors greatly enhanced the mechanical interlocking of Al/Cu joint.The effective bonding interfaces were formed among the double riveting heads structure,the upper Al plate and the lower Cu plate,which contained the Cu/Cu interface and the Al/Cu interface.The Cu/Cu interface without the kissing bond and the Al/Cu interface with the rationally thin AlCu and Al_(2)Cu intermetallic compounds(IMCs)layers were beneficial to heightening the joint tensile shear strength.The maximum tensile shear load of the FSDRW joint achieved 5.52 kN,and the joint under different plunging depths of rotating tool presented a mixed mode of ductile fracture and brittle fracture.This novel FSDRW technique owns the advantages of strong mechanical interlocking and superb metallurgical bonding,and provides a new approach to acquiring a high-quality Al/Cu dissimilar metals joint.

关键词： Al/Cu dissimilar metals joint Friction stir double-riveting welding Bonding interface Mechanical interlocking Tensile shear load

Aeroelastic Properties and Nonlinear Vibration Control of a Simply-Supported Lattice Sandwich Beam Embedded with Nitinol-Steel Wire Ropes

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Acta Mechanica Solida Sinica 2022年第5期35卷 755-764页

作者： Yewei Zhang Xichao Chen Donghui Li Jian Zang college of aerospace engineering Shenyang Aerospace UniversityShenyang110136China

As a novel vibration absorber,Nitinol-steel wire rope(NiTi-ST)has rarely been studied on vibration suppression for lattice sandwich beams in supersonic airflow.In this paper,NiTi-ST with nonlinear stiffness and hysteretic damping is embedded in a lattice sandwich beam to control the beam's vibration.The nonlinear restoring and hysteretic damping force of NiTi-ST are treated as polynomials.The dynamic equation is established based on Hamilton's principle.The amplitude responses of the beam with different NiTi-ST configurations are calculated.The vibration-suppression effects and energy dissipation of lattice sandwich beam with different NiTi-ST configurations under different air velocities are also compared.The frequency-domain and time-domain methods are used to analyze the structural aeroelastic properties.Simulation results show that the use of NiTi-ST can significantly suppress excessive vibration of a lattice sandwich beam in supersonic airflow.

关键词： Lattice sandwich beam Nonlinear vibration control Nitinol-steel wire rope Supersonic airflow

Impact localization of composite laminates based on weight function compensation localization algorithm of thin film sensors

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International Journal of Smart and Nano Materials 2023年第2期14卷 139-154页

作者： Ying Wang Hongmei Li Shaowei Lu Xingmin Liu Wei Li Xiaoqiang Wang Lu Zhang Qingxuan Wang college of aerospace engineering Shenyang Aerospace University(SAU)ShenyangChina college of Material Science and engineering Shenyang Aerospace University(SAU)ShenyangChina

Composite structures are sensitive to impact damage in practical engineering.Electric resistance change method(ERCM)is an ideal technique for damage monitoring of composite structures.Due to the anisotropy of fiber-resin matrix composites,impact location monitoring is difficult,and research on impact location of fiber composite laminates(FRPs)is limited.A preparation method of MXene/CNT/CuNps thin film sensor is proposed.According to the modeling simulation and theoretical calculation,the resistance change characteristics of the thin film sensor are obtained,the relationship between the impact distance and the resistance change is established,and the sensor array is designed.A three-point localization algorithm and a weight function compensation localization algorithm are proposed,which can improve the imaging accuracy of the impact position.The impact point location was observed and analyzed using ultrasonic C-scan technology.The results show that the weight function compensation positioning algorithm can accurately locate the impact of the composite structure,and the error in the X direction is 7.1%,the error in the Y direction is 0.03%,which verifies the effectiveness of the method.

关键词： Electric resistance change method Mxene/CNT/CuNps film sensor damage localization Weighting function

Effect prediction of stiffened-ring cylindrical shells subjected to drop mass impact

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Defence Technology（防务技术） 2022年第2期18卷 305-323页

作者： Sheng-zhuo Lu Jing-xin Ma Lan Liu Chun-long Xu Shi-bo Wu Wei-dong Chen college of aerospace and Civil engineering Harbin Engineering UniversityHarbin150001PR China

This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.

关键词： Drop mass impact Stiffened ring Cylindrical shell Impact load Dynamic response Parametric studies

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复杂风速廓线下风力机柔性叶片的气弹模型

Acta Mechanica Sinica 2023年第9期39卷 25-38页

作者：何攀夏健 college of aerospace engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

为了建立复杂风速廓线下风力机柔性叶片的气弹模型.将控制系统耦合到叶素动量理论中建立了气动模型;再以几何精确梁理论为基础,建立了可以求解任意材料和任意截面形状的结构模型;并将两者结合,建立了风力机气弹模型,编写了完整的C++代码... 详细信息

为了建立复杂风速廓线下风力机柔性叶片的气弹模型.将控制系统耦合到叶素动量理论中建立了气动模型;再以几何精确梁理论为基础,建立了可以求解任意材料和任意截面形状的结构模型;并将两者结合,建立了风力机气弹模型,编写了完整的C++代码;最后将该模型应用到实际工程,计算了低空急流入流条件下风轮的气动特性和叶片的动态响应.结果表明:本文的模型和代码是准确的,并且当控制系统耦合到气动力计算方法中时,在额定风速之前,部分功率误差传递到了转速,在额定风速以后,全部的功率误差传递到了桨距角;结构模型可以准确的计算风力机叶片的静态,动态变形以及特征频率;当低空急流高度不同时,控制系统弱化了强剪切风对风轮平均气动力的影响,但是气动力变化的幅值仍然受低空急流高度影响很大,因此风场微观选址时,塔筒高度的选择需要考虑低空急流高度的影响;当叶片上的气动力相似时,叶片动态响应的规律相似,主要被叶片的特征频率影响。本文工作对风力机叶片气弹研究具有参考意义.

关键词：风力机叶片额定风速风轮气弹模型叶素动量理论特征频率结构模型微观选址

节流式燃氧分离固体发动机准一维内弹道数值研究

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Acta Mechanica Sinica 2024年第1期40卷 85-101页

作者：王立民王富祺王志邦王英男王革关奔周星 college of aerospace Science and engineering National University of Defense TechnologyChangsha 410073China Inner Mongolia Dynamic and Mechanical Institute Hohhot 010011China college of aerospace and Civil engineering Harbin Engineering UniversityHarbin 150001China college of engineering Peking UniversityBeijing 100871China

本文建立了用于计算节流式燃氧分离固体发动机内弹道的准一维数值模型。节流式燃氧分离固体发动机通过改变富燃燃烧室和富氧燃烧室之间的节流阀开口半径来实现其推力的调节。数值模型采用简化的反应机理来描述化学非平衡过程,且考虑了... 详细信息

本文建立了用于计算节流式燃氧分离固体发动机内弹道的准一维数值模型。节流式燃氧分离固体发动机通过改变富燃燃烧室和富氧燃烧室之间的节流阀开口半径来实现其推力的调节。数值模型采用简化的反应机理来描述化学非平衡过程,且考虑了燃烧室中的质量添加、壁面摩擦和推进剂燃面退移过程。利用该数值模型展示了节流式燃氧分离固体发动机的内部流动参数分布和工作性能.发动机稳定工作状态结果显示,当节流阀开度半径由10.5mm调节至1.4mm时,发动机推力由121.82N增加至250.60N,推力提升了206%,验证了节流式燃氧分离固体发动机概念的可行性.流动参数也表明节流阀的调节作用仅在阀门开度较小时才得以充分体现.发动机动态工作过程结果显示,在调节阀停止作动时,节流式燃氧分离固体发动机性能会产生负调现象,因而需要对发动机采取额外的保护措施.对节流式燃氧分离固体发动机调节能力的理论预测发现,发动机的推力调节能力受限于富燃燃烧室压力和初始质量流量比,需要在多个参数之间进行权衡以实现合理的推力调节比.最后对推进剂的布置方式进行了初步探讨结果表明,燃氧推进剂布置下发动机的推力调节能力优于氧燃推进剂布置。

关键词：固体发动机化学非平衡燃烧室压力阀门开度质量流量比流动参数节流阀开度准一维

Semi-supervised remote sensing image scene classification with prototype-based consistency

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Chinese Journal of Aeronautics 2024年第2期37卷 459-470页

作者： Yang LI Zhang LI Zi WANG Kun WANG Qifeng YU college of aerospace Science and engineering National University of Defense TechnologyChangsha 410073China

Deep learning significantly improves the accuracy of remote sensing image scene classification,benefiting from the large-scale datasets.However,annotating the remote sensing images is time-consuming and even tough for experts.Deep neural networks trained using a few labeled samples usually generalize less to new unseen images.In this paper,we propose a semi-supervised approach for remote sensing image scene classification based on the prototype-based consistency,by exploring massive unlabeled images.To this end,we,first,propose a feature enhancement module to extract discriminative features.This is achieved by focusing the model on the foreground areas.Then,the prototype-based classifier is introduced to the framework,which is used to acquire consistent feature representations.We conduct a series of experiments on NWPU-RESISC45 and Aerial Image Dataset(AID).Our method improves the State-Of-The-Art(SOTA)method on NWPU-RESISC45 from 92.03%to 93.08%and on AID from 94.25%to 95.24%in terms of accuracy.

关键词： Semi-supervised learning Remote sensing Scene classification Prototype network Deep learning

Aerodynamic characteristics of co-flow jet wing with simple high-lift devices

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Chinese Journal of Aeronautics 2022年第10期35卷 67-83页

作者： Zhenhao ZHU Tianhang XIAO Haolin ZHI Shuanghou DENG Yujin LU college of aerospace engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Numerical investigations are conducted to explore the aerodynamic characteristics of three-dimensional Co-Flow Jet(CFJ) wing with simple high-lift devices during low-speed takeoff and landing. Effects of three crucial parameters of CFJ wing, i.e., angle of attack, jet momentum and swept angle, are comprehensively examined. Additionally, the aerodynamic characteristics of two CFJ configurations, i.e., using open and discrete slots for injection, are compared. The results show that applying CFJ technique to a wing with simple high-lift device is able to generate more lift,reduce drag and enlarge stall margin with lower energy expenditure due to the super-circulation effect. Increasing the jet intensity can reduce the drag significantly, which is mainly contributed by the reaction jet force. The Oswald efficiency factor is, in some circumstances, larger than one,which indicates the potential of CFJ in reducing induced drag. Compared with clean wing configuration, using CFJ technique allows the aerodynamic force variation less sensitive to the swept angle, and such phenomenon is better observed for small swept angle region. Eventually, it is interesting to know that the discrete slotted CFJ configuration demonstrates a promising enhancement in aerodynamic performance in terms of high lift, low drag and efficiency.

关键词： Active flow control Co-flow jet Continuous injection Discrete injection slot Simple high-lift device

Some basic aspects of polymer nanocomposites: A critical review

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Nano Materials Science 2019年第1期1卷 2-30页

作者： Shaoyun Fu Zheng Sun Pei Huang Yuanqing Li Ning Hu college of aerospace engineering Chongqing University

Polymer nanocomposites have been investigated for about three decades. To get deep insights into the modifying effects of various nanofillers on mechanical and physical properties of polymer nanocomposites, the three basic aspects of processing, characterization and properties are critically reviewed in this paper. Nanofillers can be classified into three major types of two-dimensional (2D) layered, one-dimensional (1D) fibrous and zerodimensional (0D) spherical ones and this review thus discusses in detail the processing, characterization and properties of the three types of polymer nanocomposites. It starts with an introduction of various nanoscale fillers such as two-dimensional (2D) nano-clay, graphene and MXene, one dimensional (1D) carbon nanofibers and nanotubes, zero dimensional (0D) silica nanoparticles and ZnO quantum dots as well as nanofiller-polymer interfaces. The processing of these polymer nanocomposites using different methods and the characterization of nanofillers and polymer nanocomposites using various techniques are described. Finally, the mechanical and physical properties of these polymer nanocomposites are discussed by considering the effects of nanofiller type, dispersion and contents;also, interface properties show significant effects on the mechanical properties of polymer nanocomposites and are discussed in some details.

关键词： Polymer nanocomposite Nanofiller Processing Characterization Mechanical and physical properties