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A review of selective laser melting of aluminum alloys: Processing,microstructure, property and developing trends

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Journal of Materials Science & Technology 2019年第2期35卷 270-284页

作者： Jinliang Zhang Bo Song Qingsong Wei Dave Bourell Yusheng Shi state key laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Dave Bourell laboratory for Freeform Fabrication Mechanical Engineering Department The University of Texas at Austin

Selective laser melting(SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most pervasive structural materials, is well known for high specific strength and good corrosion resistance. But the poor laser formability of aluminum alloy restricts its application. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing aluminum alloys. Some efforts have been made to solve the above problems. This paper discusses the current research status both related to the scientific understanding and technology applications. The paper begins with a brief introduction of basic concepts of aluminum alloys and technology characterization of laser selective melting. In addition, solidification theory of SLM process and formation mechanism of metallurgical defects are discussed. Then, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively. Lastly, a future outlook is given at the end of this review paper.

关键词： Selective laser melting Aluminum alloy Metallurgical defects mechanical properties Heat treatment Developing trend

Time of flight improved thermally grown oxide thickness measurement with terahertz spectroscopy

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Frontiers of mechanical Engineering 2022年第4期17卷 205-215页

作者： Zhenghao ZHANG Yi HUANG Shuncong ZHONG Tingling LIN Yujie ZHONG Qiuming ZENG Walter NSENGIYUMVA Yingjie YU Zhike PENG Fujian Provincial key laboratory of Terahertz Functional Devices and Intelligent Sensing School of Mechanical Engineering and AutomationFuzhou UniversityFuzhou 350108China Institute of Precision Instrument and Intelligent Measurement&Control Fuzhou UniversityFuzhou 350108China School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200072China School of mechanical Engineering Ningxia UniversityYinchuan 750000China

As a nondestructive testing technique,terahertz time-domain spectroscopy technology is commonly used to measure the thickness of ceramic coat in thermal barrier coatings(TBCs).However,the invisibility of ceramic/thermally grown oxide(TGO)reflective wave leads to the measurement failure of natural growth TGO whose thickness is below 10μm in *** detect and monitor TGO in the emergence stage,a time of flight(TOF)improved TGO thickness measurement method is proposed.A simulative investigation on propagation characteristics of terahertz shows the linear relationship between TGO thickness and phase shift of feature *** accurate TOF increment could be acquired from wavelet soft threshold and cross-correlation function with negative effect reduction of environmental noise and system ***,the TGO thickness could be obtained efficiently from the TOF increment of the monitor area with different heating *** averaged error of 1.61μm in experimental results demonstrates the highly accurate and robust measurement of the proposed method,making it attractive for condition monitoring and life prediction of TBCs.

关键词： thermal barrier coatings thermally grown oxide terahertz spectroscopy time of flight

Maxwell-Schrodinger Equation for X-Ray Laser Propagation and Interferometry Measurement of Plasma Electron Density

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Chinese Physics Letters 2001年第11期18卷 1490-1492页

作者：刘承宜郭弘付喜泉胡巍喻松 laboratory of Light transmission Optics South China Normal UniversityGuangzhou 510631

By starting with the Maxwell theory of x-ray laser propagation in collisionless plasmas, we study the phase difference of the probe and reference beams of x-ray laser interferometry in measuring the plasma electron density. The basic idea is to reduce the Maxwell equation to a Schrodinger-like equation. By using the quantum mechanical technique and introducing a novel picture, we obtain a modified relation between the phase and the electron density, where the phase corresponds to the interference of probe and reference light and the contribution of gradient of the electron density has been taken into account.

关键词： Maxwell Electron phase

Synthesis of Refractory Cordierite from Calcined Bauxite, Talcum and Quartz

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Journal of Wuhan University of Technology(Materials Science) 2013年第2期28卷 329-333页

作者：吴建锋 FANG Binzheng XU Xiaohong XU Xiaoyang ZHENG Shuqing YI Guoxia state key laboratory of Silicate Materials for Architectures

A cordierite was synthesized from calcined bauxite, talcum, and quartz. The properties and microstructure of the cordierite sintered samples were characterized by Archimedes＇ method, thermal dilatometry, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and so on. The experimental results showed that calcined bauxite could broaden the range of synthesizing temperature from 1300 ℃ to 1420 ℃ and get pure cordierite. The bulk density and linear thermal expansion coefficient of the sample synthesized at 1420 ℃ for 2 h were 1.97 g·cm^-3 and 2.1×10^-6 ℃^-1, respectively. The XRD analysis showed that the major crystalline phase was a-cordierite with almost no glassy matters, the SEM images illustrated a small vent hole and the size were 5 -100 μm, the well-grown hexagonal and granular cordierite grains had the sizes distributed among 0.1-8 ;xm, and providing high mechanical strength and lower linear thermal expansion coefficient.

关键词： cordierite calcined bauxite synthesizing temperature properties and microstructure

Optimal Motion Planning for Differentially Flat Underactuated mechanical Systems

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Chinese Journal of mechanical Engineering 2009年第3期22卷 347-354页

作者： HE Guangping GENG Zhiyong state key laboratory for Turbulence and Complex System Peking University Beijing 100871 China Department of mechanical and Electrical Engineering North China University of Technology Beijing 100041 China

Underactuated mechanical system has less independent inputs than the degrees of freedom（DOF） of the mechanism. The energy efficiency of this class of mechanical systems is an essential problem in practice. On the basis of the sufficient and necessary condition that concludes a single input nonlinear system is differentially flat, it is shown that the flat output of the single input underactuated mechanical system can be obtained by finding a smooth output function such that the relative degree of the system equals to the dimension of the state space. If the flat output of the underactuated system can be solved explicitly, and by constructing a smooth curve with satisfying given boundary conditions in fiat output space, an energy efficiency optimization method is proposed for the motion planning of the differentially flat underactuated mechanical systems. The inertia wheel pendulum is used to verify the proposed optimization method, and some numerical simulations show that the presented optimal motion planning method can efficaciously reduce the energy cost for given control tasks.

关键词： differential flatness underactuated system motion planning optimization

A Computational Investigation of the Group Effect of Pits on the Ultimate Strength of Steel Plates

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China Ocean Engineering 2018年第6期32卷 665-674页

作者： FU Qiang FANG Hui WU Ren-xia YU Xue-hui LI Hua-jun Institute of Coastal and Offshore Engineering School of Engineering Ocean University of China state key laboratory for Strength and Vibration of mechanical Structures School of Aerospace Engineering Xi'an Jiaotong University

In this work, we focus on assessing the group effect of localized corrosion on the ultimate strength of the marine structural plates and study the load-deformation behaviors of plates of various slenderness and uniaxial ***, we investigate different corroded patterns from a single circular pit to 25 circular pits distributed over the plate and carry out hundreds of nonlinear finite element simulations by combining the number, depth, distribution of pits with imperfections and slenderness of plate. The distribution of multiple pits causes scattering of stress concentration on the plate, then the plastic section of plate changes with wider distribution of damage simultaneously. The ultimate strength arises when un-loading zone comprised of the yielding strips and holes extends across the plate. It can be concluded that the corroded condition defined as group effect of pits manipulates the deformation state and the loading capacity of plate at the ultimate strength mode that coincides with the proportion of effective loading area and section in the process of post-buckling. To validate the effect of pits group, we perform the numerical experiments of the post-buckling of steel plates containing pits in a row with different orientation.

关键词： group effect localized corrosion post-buckling ultimate strength

Science Letters: Equivalent thickness of materials of fused silica and stainless steel in the flow of microtubes

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2005年第9期6卷 1004-1006页

作者：包福兵林建忠石兴 Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China Department of mechanical Engineering National University of Singapore 119260 Singapore

The deviation of flow characteristics from the predictions of the conventional theory for microtubes was attrib- uted to the change of fluid viscosity resulted from the interactions between the molecules on solid wall and in fluid. The degree of this departure is dependent on the microtubes materials. A concept of equivalent thickness with which conventional theory can be used to predict the flow in microtubes without modifying the fluid viscosity was put forward. The values of equivalent thickness for fused silica and stainless steel materials were determined as 1.8 μm and 1.5 μm, respectively, by repeated numeri- cal simulation.

关键词：粘性流体交互作用微管材料不锈钢厚度

Graphene-based dual-function acoustic transducers for machine learning-assisted human-robot interfaces

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InfoMat 2023年第2期5卷 66-79页

作者： Hao Sun Xin Gao Liang-Yan Guo Lu-Qi Tao Zi Hao Guo Yangshi Shao Tianrui Cui Yi Yang Xiong Pu Tian-Ling Ren Institute of Microelectronics and Beijing National Research Center for Information Science and Technology(BNRist) Tsinghua UniversityBeijingPeople's Republic of China CAS Center for Excellence in Nanoscience Beijing Key Laboratory of Micro-nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijingPeople's Republic of China state key laboratory of Power transmission Equipment and System Security and New Technology School of Electrical EngineeringChongqing UniversityChongqingPeople's Republic of China School of Computer Science&Technology Beijing Institute of TechnologyBeijingPeople's Republic of China School of Automation and Electrical Engineering University of Science and Technology BeijingBeijingPeople's Republic of China

Human–robot interface(HRI)electronics are critical for realizing robotic ***,we report graphene-based dual-function acoustic transducers for machine learning-assisted human–robot interfaces(GHRI).The GHRI functions both an artificial ear through the triboelectric acoustic sensing mechanism and an artificial mouth through the thermoacoustic sound emission *** success of the integrated device is also attributed to the multifunctional laser-induced graphene,as either triboelectric materials,electrodes,or thermoacoustic *** systematically optimizing the structure parameters,the GHRI achieves high sensitivity(4500 mV Pa^(–1))and operating durability(1000000 cycles and 60 days),capable of recognizing speech identities,emotions,content,and other information in the human *** the assistance of machine learning,30 speech categories are trained by a convolutional neural network,and the accuracy reaches 99.66%and 96.63%in training datasets and test ***,GHRI is used for artificial intelligence communication based on recognized speech *** work shows broad prospects for the development of robotic intelligence.

关键词： human-robot interface laser-induced graphene machine learning thermoacoustic triboelectric nanogenerator

Horizontal Velocity of Variable Gauge Rolling:Theory and Finite Elements Simulation

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Journal of Iron and Steel Research(International) 2013年第10期20卷 10-16页

作者： ZHANG Guang-ji LIU Xiang-hua HU Xian-lei ZHI Ying state key laboratory of Rolling and Automation Northeastern University

Within the production chain of longitudinal profiled （LP） plates and tailor rolled blanks （TRB）, variable gauge roiling （VGR） represents the vital important forming stage, in which shape and properties are tailored to sat- isfy customers＇ requirements. It is of vital importance to reveal the relationship between work-piece horizontal veloci- ty and roll vertical velocity during VGR, which is not only a key point to understand the deformation law, but also an important content for setting VGR process parameters. It is proved that the simplified assumption of equal dis- charge per second condition （EDSC） breaks down during VGR. Due to this reason the differential equation of the work-piece horizontal velocity （VGR-V） is performed by keeping the material volume constant. To attain a compre- hensive understanding of this underlying process in detail, numerical approaches based on finite elements method have been performed by utilizing the Abaqus Explicit. Rolling experiment is carried out which indicates that the nu- merical result coincides with the expel＇imental result well. A fine spatial discretization of work-piece is essential for special emphasis has to be put on detecting different horizontal velocity of work-piece cross section, often leading to a hundred thousand degrees of freedom even for plane strain calculations. The data obtained by using Abaqus Explicit coincide with the results determined by theory. A theoretical basis on deformation parameters and mechanical param- eters during VGR process is provided.

关键词： variable gauge rolling horizontal velocity non-linear finite element analysis