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Microstructure and Mechanical Properties in Friction Stir Welded Thick Al–Zn–Mg–Cu Alloy Plate

Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1329-1342页

作者： Fei Qiang Wen Wang Ke Qiao Pai Peng Ting Zhang Xiao-Hu Guan Jun Cai Qiang Meng Hua-Xia Zhao Kuai-She Wang School of Metallurgical Engineering National and Local Joint Engineering Research Center for Functional Materials ProcessingXi'an University of Architecture and TechnologyXi'an 710055China Northwest institute for Non-Ferrous Metal Research Xian 710016China avic manufacturing technology institute Bejing 100024China Beijing FSW technology Co.Ltd Bejing 101107China

In this work, 20-mm-thick aluminum-alloy plates were joined via friction stir welding. The temperature gradient was reduced by reducing the surface welding heat input to achieve uniformity of the mechanical properties across the thick plate joints. The welding temperature was measured using thermocouples. The microstructures were observed via electron backscatter diff raction and transmission electron microscopy. The tensile properties of the samples sliced along the thickness direction of the joint were evaluated. The results show that the highest welding peak temperature is 430℃ on the advancing side on the top surface of the joint. The grain size gradually decreased along the thickness direction, and grain refi nement was due to the combination of continuous, discontinuous, and geometric dynamic recrystallization. The tensile properties of the sliced samples were found to be uniform, and the ultimate tensile strength reached 62% of that of the base metal. The main strengthening mechanism of the Al–Zn–Mg–Cu alloy joints consists of precipitation strengthening. In addition, the η ` → η phase transition and grain coarsening in the heat-affected zone were found to be responsible for the fracture of the joints.

关键词： Friction stir welding Aluminum alloy thick plate Dynamic recrystallization Mechanical properties Precipitated phase

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Laser peening of aluminum alloy 7050 with fastener holes

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Chinese Optics Letters 2008年第2期6卷 116-119页

作者：邹世坤曹子文赵勇钱鸣 Beijing Aeronautical manufacturing technology Research institute Chengdu Aircraft Design & Research institute institute of Laser Engineering Beijing University of technology

The fatigue properties of laser peened aluminum alloy 7050 specimens with fastener holes were investigated. The surface profile and residual stress induced in the shock affected zone were characterized. Then, the fatigue specimens with notch were treated by laser peening （LP）, and the fatigue lifes of LP-treated specimens were measured and compared with base materials without LP. The results indicated that LP improved the fatigue lifes of all tested specimens. The average fatigue lifes of specimens treated by LP before hole-drilling were 173% longer than those of untreated samples and had better effects than those specimens treated by LP after hole-drilling.

关键词： Aluminum alloys Drilling Fatigue of materials Residual stresses Shot peening

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Influences of boron contents on microstructures and mechanical properties of as-casted nearαtitanium alloy

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Journal of Materials Science & technology 2021年第18期77卷 1-18页

作者： Xiaozhao Ma Zhilei Xiang Chao Tan Zhitian Wang Yingying Liu Ziyong Chen Qun Shu College of Materials Science and Engineering.Beijing University of technology Beijing 100124China Aviation Industry of China(avic)Manufacture technology institute Beijing 100024China

Ti-6.5 Al-2.5 Sn-9 Zr-0.5 Mo-0.25 Si-1 Nb-1 W-0.1 Er-x B(x=0,0.1,0.2,0.4,0.6 and 0.8 wt%)with different boron contents are fabricated for *** of boron element and its amounts on phase constitutions,microstructures,textures and compression mechanical properties are carefully *** the increasing boron additions,contents of TiB phase increase,and the maximum intensities of textures *** are significantly and continuously refined after adding boron element and with the increasing boron additions,and turning point of refinement rates for different microstructural parameters is found at 0.2 wt%boron *** increase monotonously,while elongations increase firstly and decrease *** maximum value of elongation is acquired at boron content of 0.2 wt%.On the premise of ensuring plasticity,0.2 wt%boron content is the most appropriate amount for microstructural refinement and mechanical properties enhancement for current nearαtitanium ***,aspect ratios of TiB whiskers increase with the increasing boron *** of near equiaxedαgrains orαgrains with irregular morphologies are discovered around TiB *** and twistedαgrain boundaries are also obviously detected in boron containing ***,premature fracture of alloys containing TiB whiskers is largely influenced by the fracture of these brittle reinforcements.

关键词： Boron element Mechanical properties Microstructures Fracture behaviors Nearαtitanium alloy Textures

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Effect of connection processes on mechanical properties of 7B04 aluminum alloy structures

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China Welding 2021年第2期30卷 50-57页

作者： Wang Yue Chai Peng Guo Xiaojuan Qi Bojin School of Mechanical Engineering and Automation Beihang UniversityBeijing 100083China Beijing FSW technology Co.Ltd. AVIC Manufacturing Technology InstituteBeijing 100024China

The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and *** show that the static compression load of the typical structure connected by riveting and refill FSSW fluctuated in the range of 117-124 kN,and the shear load was in the range of 89-95 *** spacing had a small influence on the static load of the structures joined by refill ***,the fatigue life of riveted structures was lower than that joined by refill *** the welded structure,the heterogeneous microstructures of the welded joint led to the uneven microhardness,and the hook at the lap interface bent upwards at the same *** factors made the welded structures during the fatigue test failure along the path of sleeve moving.

关键词： refill friction stir spot welding 7B04 aluminum alloy microstructure fatigue life fracture path

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A Context Sensitive Multilevel Thresholding Using Swarm Based Algorithms

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IEEE/CAA Journal of Automatica Sinica 2019年第6期6卷 1471-1486页

作者： Shreya Pare Anil Kumar Varun Bajaj Girish Kumar Singh PDPM Indian institute of Information technology Design and manufacturing Jabalpur 482005MPIndia institute of technology Roorkee Uttarakhand 247667India

In this paper, a comprehensive energy function is used to formulate the three most popular objective functions:Kapur's, Otsu and Tsalli's functions for performing effective multilevel color image thresholding. These new energy based objective criterions are further combined with the proficient search capability of swarm based algorithms to improve the efficiency and robustness. The proposed multilevel thresholding approach accurately determines the optimal threshold values by using generated energy curve, and acutely distinguishes different objects within the multi-channel complex images. The performance evaluation indices and experiments on different test images illustrate that Kapur's entropy aided with differential evolution and bacterial foraging optimization algorithm generates the most accurate and visually pleasing segmented images.

关键词： Color image segmentation Kapur's entropy multilevel thresholding Otsu method swarm based optimization algorithms Tsalli's entropy

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Motion-Planning Algorithm for a Hyper-Redundant Manipulator in Narrow Spaces

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Computers, Materials & Continua 2022年第9期72卷 4817-4832页

作者： Lei Zhang Shouzhi Huang Zhaocai Du Guangyao Ouyang Heping Chen Faculty of Mechanical Engineering&Automation Zhejiang Sci-Tech UniversityHangzhou310018China Key Laboratory of Transplanting Equipment and technology of Zhejiang Province Hangzhou310018China Aeronautical Key Laboratory for Digital manufacturing technology AVIC Manufacturing Technology InstituteBeijing100024China Ingram School of Engineering Texas State UniversitySan MarcosTexasUSA

In this study,a hyper-redundant manipulator was designed for detection and searching in narrow spaces for aerospace and earthquake rescue applications.A forward kinematics equation for the hyper-redundant manipulator was derived using the homogeneous coordinate transformation *** on the modal function backbone curve method and the known path,an improved modal method for the backbone curves was ***,the configuration of the backbone curve for the hyper-redundant manipulator was divided into two parts:a mode function curve segment of the mode function and a known path *** changing the discrete points along the known path,the backbone curve for the manipulator when it reached a specified path point was dynamically obtained,and then the joint positions of the manipulator were fitted to the main curve by *** with engineering examples,simulation experiments were performed using the new algorithm to extract mathematical models for external narrow space *** experimental results showed that when using the new algorithm,the hyper-redundant manipulator could complete the tasks of passing through curved pipes and moving into narrow *** effectiveness of the algorithm was also proven by these experiments.

关键词： Hyper-redundant manipulator backbone curve narrow workspace motion-planning

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Mechanism of size effects in microcylindrical compression of pure copper considering grain orientation distribution

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Rare Metals 2013年第1期32卷 18-24页

作者： Chuan-Jie Wang Chun-Ju Wang Bin Guo De-Bin Shan Yan-Yan Chang School of Materials Science and Engineering Harbin Institute of Technology Key Laboratory of Micro-Systems and Micro-Structures manufacturing Harbin Institute of Technology

In microscale deformation, the magnitudes of specimen and grain sizes are usually identical, and size- dependent phenomena of deformation behavior occur, namely, size effects. In this study, size effects in micro- cylindrical compression were investigated experimentally. It was found that, with the increase of grain size and decrease of specimen size, flow stress decreases and inhomogeneous material flow increases. These size effects tend to be more distinct with miniaturization. Thereafter, a modified model considering orientation distribution of surface grains and continuity between surface grains and inner grains is developed to model size effects in micro- forming. Through finite element simulation, the effects of specimen size, grain size, and orientation of surface grains on the flow stress and inhomogeneous deformation were analyzed. There is a good agreement between experimental and simulation results.

关键词： Microforming Cylindrical compression Sizeeffects Grain orientation Inhomogeneous deformation

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Bipartite Graphs with the Maximum Sum of Squares of Degrees

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Acta Mathematicae Applicatae Sinica 2014年第3期30卷 801-806页

作者： Sheng-gui ZHANG Chun-cao ZHOU Department of Applied Mathematics Northwestern Polytechnical University The State Key Laboratory for manufacturing Systems Engineering Xi'an Jiaotong University avic Chengdu Aircraft Design and Research Institute

In this paper we determine all the bipartite graphs with the maximum sum of squares of degrees among the ones with a given number of vertices and edges.

关键词： bipartite graphs sum of squares of degrees extremal graphs

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Steam as coolant and lubricant in turning of metal matrix composites

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第9期9卷 1245-1250页

作者： Raviraj SHETTY Raghuvir PAI Vasanth KAMATH Shrikanth S.RAO Department of Mechanical and manufacturing Engineering Manipal Institute of TechnologyKarnatakaIndia Department of Mechanical Engineering National Institute of TechnologyKarnatakaIndia

Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.

关键词： Metal matrix composites (MMCs) Turning Cutting force Thrust force Friction coefficient Surface roughness Built-up edge (BUE)

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Simulation and Verification of Machining Deformation for Composite Materials

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Journal of Wuhan University of technology(Materials Science) 2014年第5期29卷 917-922页

作者：刘凯叶金蕊 TANG Zhanwen LIU Weiping ZHANG Boming School of Materials Science and Engineering Beihang University Aeronautical manufacturing technology institute Shanghai Aircraft Manufacturing CO

Prepreg properties including cure kinetics, cure shrinkage, and coefficient of thermal expansion were analyzed. A simulation method based on ＂element birth and death＂ method of Finite element analysis （FEA） was presented to simulate the cutting process and predict the machining deformation for composite laminates and stiffened panels. The comparisons between the simulation results and experimental data showed good agreement. It is found that residual stresses are the main source of machining deformation for composites and machining deformation is expected to happen only if there are stress gradients along the machining direction. There is no machining deformation for composite laminates due to its uniform stresses distribution in plane, while machining deformation can be observed obviously for T-shape stiffened composite panels. Attention should be paid to machining deformation to avoid the mismatch during assembly.

关键词： composite machining deformation residual stress finite element analysis (FEA)

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