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Additive manufacturing of copper-stainless steel hybrid components using laser-aided directed energy deposition

Journal of Materials Science & Technology 2021年第21期80卷 100-116页

作者： Xinchang Zhang Tan Pan Yitao Chen Lan Li Yimlu Zhang Frank Liou department of mechanical&aerospace Engineering Missouri University of Science and TechnologyRollaMO65409USA

Combining dissimilar materials in a single component is an effective solution to integrate diverse material properties into a single ***-stainless steel hybrid components are attracting more and more attention since the high thermal conductivity of copper can greatly enhance the thermal performance of stainless steel,which benefits its applications in many ***,direct joining of copper and stainless steel such as SS316 L is challenging since they preserve significant dissimilarities in physical,chemical,and thermo-mechanical *** paper aims to fabricate well-bonded copper-SS316 L hybrid parts using a laser-aided directed energy deposition(DED) process.A nickel-based alloy Deloro22(D22) is introduced between copper and SS316 L to address the detrimental issues in copper-SS316 L direct *** this technique,defect-free interfaces are achieved at both the D22-SS316 L and copper-D22 transition *** testing of Cu-D22-SS316 L and D22-SS316 L hybrid parts shows the fracture occurs at pure copper and SS316 L region,respectively,indicating an excellent bonding at the *** in the building direction,a transition of grain structure is observed.A significant diffusion zone is obtained at both the D22-SS316 L and the Cu-D22 *** large diffusion distance results in a smooth variation in microhardness over the dissimilar *** microhardness increases from SS316 L to D22 with the highest value of 240 HV and then decreases from D22 to Cu with the lowest value of 63 ± 4 *** of thermophysical properties of the Cu-D22-SS316 L system indicates there is a ~300 % increase in thermal diffusivity and a ~200 % increase in thermal conductivity when compared to pure SS316 *** significant increase in thermal diffusivity and conductivity validates the enhanced thermal performance of SS316 L when it is joined with pure copper.

关键词： Additive manufacturing Directed energy deposition Multi-material components Dissimilar materials Copper Stainless steel

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Bridge pier failure probabilities under combined hazard effects of scour, truck and earthquake. Part Ⅰ: occurrence probabilities

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Earthquake Engineering and Engineering Vibration 2013年第2期12卷 229-240页

作者： Zach Liang George C. Lee department of mechanical and aerospace Engineering Unidersity at Buffalo Depart of Civil Structural and Environmental EngineeringUniversity at Buffalo

In many regions of the world, a bridge will experience multiple extreme hazards during its expected service life. The current American Association of State Highway and Transportation Officials （AASHTO） load and resistance factor design （LRFD） specifications are formulated based on failure probabilities, which are fully calibrated for dead load and nonextreme live loads. Design against earthquake loads is established separately. Design against scour effect is also formulated separately by using the concept of capacity reduction （or increased scour depth）. Furthermore, scour effect cannot be linked directly to an LRFD limit state equation, because the latter is formulated using force-based analysis. This paper （in two parts） presents a probability-based procedure to estimate the combined hazard effects on bridges due to truck, earthquake and scour, by treating the effect of scour as an equivalent load effect so that it can be included in reliability-based bridge failure calculations. In Part I of this series, the general principle of treating the scour depth as an equivalent load effect is presented. The individual and combined partial failure probabilities due to truck, earthquake and scour effects are described. To explain the method of including non-force-based natural hazards effects, two types of common scour failures are considered. In Part 11, the corresponding bridge failure probability, the occurrence of scour as well as simultaneously having both truck load and equivalent scour load are quantitatively discussed.

关键词： multi-hazards load and resistance factor design bridge scour

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Numerical Study of Aeroacoustic Sound on Performance of Bladeless Fan

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Chinese Journal of mechanical Engineering 2017年第2期30卷 483-494页

作者： Mohammad Jafari Atta Sojoudi Parinaz Hafezisefat aerospace Engineering department Iowa State UniversityAmesUSA mechanical Engineering department University of TehranTehranIran mechanical Engineering department Iowa State UniversityAmesUSA

Aeroacoustic performance of fans is essential due to their widespread application. Therefore, the original aim of this paper is to evaluate the generated noise owing to different geometric parameters. In current study, effect of five geometric parameters was investigated on well performance of a Bladeless fan. Airflow through this fan was analyzed simulating a Bladeless fan within a 2 m×2 m×4 m room. Analysis of the flow field inside the fan and evaluating its performance were obtained by solving conservations of mass and momentum equations for aerodynamic investigations and FW-H noise equations for aeroacoustic analysis. In order to design Bladeless fan Eppler 473 airfoil profile was used as the cross section of this fan. Five distinct parameters, namely height of cross section of the fan, outlet angle of the flow relative to the fan axis, thickness of airflow outlet slit, hydraulic diameter and aspect ratio for circular and quadratic cross sections were considered. Validating acoustic code results, we compared numerical solution of FW-H noise equations for NACA0012 with experimental results. FW-H model was selected to predict the noise generated by the Bladeless fan as the numerical results indicated a good agreement with experimental ones for NACA0012. To validate 3-D numerical results, the experimental results of a round jet showed good agreement with those simulation data. In order to indicate the effect of each mentioned parameter on the fan performance, SPL and OASPL diagrams were illustrated.

关键词： Bladeless fan · Computational fluid dynamic (CFD) · Aeroacoustic performance · Ffowcs Williams and Hawkings (FW-H) formulation

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Realising high aspect ratio 10 nm feature size in laser materials processing in air at 800 nm wavelength in the far-field by creating a high purity longitudinal light field at focus

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Light(Science & Applications) 2022年第12期11卷 3028-3043页

作者： Zhaoqing Li Olivier Allegre Lin Li department of mechanical Aerospace and Civil EngineeringThe University of ManchesterManchester M139PLUK

In semiconductor and data storage device manufacturing,it is desirable to produce feature sizes less than 30 nm with a high depth-to-width aspect ratio on the target material rapidly at a low ***,optical diffraction limits the smallest focused laser beam diameter to around half of the laser wavelength(λ/2).The existing approach to achieving nanoscale fabrication is mainly based on costly extreme ultraviolet(EUV)technology operating within the diffraction *** this paper,a new method is shown to achieve materials processing resolution down to 10 nm(λ/80)at an infrared laser wavelength of around 800 nm in the far-field,in air,well beyond the optical diffraction limit.A highquality longitudinal field with a purity of 94.7% is generated to realise this *** experiments and theoretical modelling have been carried out to verify and understand the *** ablation craters induced on polished silicon,copper,and sapphire are compared for different types of light *** of 10-30 nm in diameter are produced on sapphire with a depth-to-width aspect ratio of over 16 and a zero taper with a single pulse at 100-120 nJ pulse *** high aspect ratio sub-50 nm holes produced with single pulse laser irradiation are rarely seen in laser processing,indicating a new material removal mechanism with the longitudinal *** working distance(lens to target)is around 170μm,thus the material processing is in the far *** nano-holes can also be produced by adjusting the lens to the target distance.

关键词： sapphire field purity

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Towards establishing practical multi-hazard bridge design limit states

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Earthquake Engineering and Engineering Vibration 2013年第3期12卷 333-340页

作者： Zach Liang George C.Lee department of mechanical and aerospace Engineering Unidersity at Buffalo Depart of Civil Structural and Environmental Engineering University at Buffalo

In the U.S., the current Load and Resistance Factor Design （LRFD） Specifications for highway bridges is a reliability-based formulation that considers failure probabilities of bridge components due to the actions of typical dead load and frequent vehicular loads. Various extreme load effects, such as earthquake and vessel collision, are on the same reliability-based platform. Since these extreme loads are time variables, combining them with not considered frequent. non- extreme loads is a significant challenge. The number of design limit state equations based on these failure probabilities can be unrealistically large and unnecessary from the view point of practical applications. Based on the opinion of AASHTO State Bridge Engineers, many load combinations are insignificant in their states. This paper describes the formulation of a criterion to include only the necessary load combinations to establish the design limit states. This criterion is established by examining the total failure probabilities for all possible time-invariant and time varying load combinations and breaking them down into partial terms. Then, important load combinations can be readily determined quantitatively,

关键词： multi-hazards load and resistance factor design re.liability based bridge design specifications design limit state equations

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The Importance of Flapping Kinematic Parameters in the Facilitation of the Different Flight Modes of Dragonflies

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Journal of Bionic Engineering 2021年第2期18卷 419-427页

作者： Xiaohui Liu Csaba Hefler Wei Shyy Huihe Qiu department of mechanical and aerospace Engineering The Hong Kong University of Science and TechnologyHong Kong SARChina

To better understand dragonflies’remarkable flapping wing aerodynamic performance,we measured the kinematic parameters of the wings in two different flight modes(Normal Flight Mode(NFM)and Escape Flight Mode(EFM)).When the specimens switched from normal to escape mode the flapping frequency was invariant,but the stroke plane of the wings was more horizontally *** flapping of both wings was adjusted to be more ventral with a change of the pitching angle that resulted in a larger angle of attack during downstroke and smaller during upstroke to affect the flow directions and the added mass ***,the phasing between the fore and hind pair of wings varies between two flight modes,which affects the wing-wing interaction as well as body *** is found that the momentum stream in the wake of EFM is qualitatively different from that in *** change of the stroke plane angle and the varied pitching angle of the wings diverts the momentum downwards,while the smaller flapping amplitude and less phase difference between the wings compresses the momentum *** seems that in order to achieve greater flight maneuverability a flight vehicle needs to actively control positional angle as well as the pitching angle of the flapping wings.

关键词： wing kinematics flight mode dragonfly flight aerodynamics

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Joining of Individual Silver Nanowires via Electrical Current

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Nano-Micro Letters 2014年第4期6卷 293-300页

作者： Arash Vafaei Anming Hu Irene A.Goldthorpe department of Electrical and Computer Engineering University of Waterloo department of mechanical and Mechatronics Engineering University of Waterloo department of mechanical Aerospace and Biomedical Engineering University of Tennessee Knoxville

A procedure for joining polyol-synthesized silver nanowires in air using current-induced Joule heat welding is reported. Using a common probe station and photolithographically patterned gold electrodes, the welding process is completed using a common semiconductor analyzer. A unique two-step procedure eliminates the dielectric barrier at the point of contact without damaging the nanowires away from the junction. This procedure is designed for metal–metal contacts where a strong dielectric intermediate layer might exist, which can occur with metals prone to oxidation or corrosion in air, or as a result of the electrode deposition process. Ohmic connections are also established in cases where there is an initial gap between two nanowires.

关键词： Nanowires Nanowelding Joule heating

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Cavitation dynamics in a vitrimer

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Acta Mechanica Sinica 2021年第5期37卷 767-772,I0001页

作者： Zhaoqiang Song Shengqiang Cai department of mechanical and aerospace Engineering University of CaliforniaSan DiegoLa JollaCA 92093USA

Vitrimer is a polymer network with dynamic covalent bonds,which can be dynamically broken and *** to the dynamic covalent bonds,vitrimer behaves like an elastomer at high deformation rate or low temperature but a viscous fluid at low deformation rate or high *** this article,we study the cavitation dynamics in a vitrimer,which is known to be an important damaging mechanism in *** the formulation,a nonlinear three-dimensional rate-dependent constitutive model for the vitrimer is adopted,in which both of the strain stiffening and the kinetics of dynamic exchanging reactions are *** theory predicts strong dependence of the cavitation dynamics on the loading *** computational results may help to reveal some critical insights into the rate-dependent fracture in vitrimer.

关键词： Vitrimer Cavitation dynamics Strain stiffening Viscoelasticity

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Simulation of vessel tissue remodeling with residual stress:an application to in-stent restenosis

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International Journal of Smart and Nano Materials 2019年第1期10卷 11-27,I0002页

作者： Jie Cheng Lucy T.Zhang department of mechanical aerospace and Nuclear Engineering Rensselaer Polytechnic InstituteTroyNYUSA

We present a numerical procedure to model the artery wall remodeling stimulated by stenting considering varying degree of residual *** framework sets up biological remodeling with the existence of residual *** studies suggest that the residual stress originates from the growth and remodeling of the premature ***,it is known that tissue remodeling can happen under mechanical ***,none of the existing research studies the impact of residual stress on the mechanical-driven growth of *** fill this gap,we build a numerical framework that couples the residual stress with a growth model,and examine its impact on tissue *** proposed approach is applied to in-stent restenosis,where the tissue remodeling process is modeled with finite element method,and the residual stress is generated geometrically using open angle *** result shows that residual stress reverses the radial distribution of stress concentration,which is ameliorated by tissue *** thickening of vessel wall tends to increase with residual stress,which links to more severe in-stent *** results demonstrate the important interplay between residual stress and tissue *** findings suggest that residual stress should be considered in the future simulation of tissue remodeling.

关键词： Residual stress remodeling growth model in-stent restenosis

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On the trajectory of nonturbulent liquid jets in subsonic crossflows at different density ratios

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Theoretical & Applied Mechanics Letters 2018年第4期8卷 277-283,300页

作者： Mehdi Jadidi Ali Dolatabadi department of mechanical Industrial and Aerospace Engineering Concordia University

Numerical simulations using volume of fluid(VOF)method are performed to study the impact of liquid-to-gas density ratio on the trajectory of nonturbulent liquid jets in gaseous *** this paper,large eddy simulation(LES)turbulence model is coupled with the VOF method to describe the turbulence effects *** addition,dynamic adaptive mesh refinement method with two refinement levels is applied to refine the size of the cells located at gas-liquid *** ratio is changed from 10 to 5000 while other nondimensional numbers are kept *** density ratios are considered in this paper since they are common in many practical applications such as solution precursor/suspension plasma *** simulations show that the penetration height,especially in the farfield,increases as the density ratio increases.A general correlation for the jet trajectory,which can be used for a wide range of density ratios,is developed based on our simulation results.

关键词： Primary breakup Liquid jet Density ratio Gaseous crossflow Spray trajectory

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