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arXiv 2025年

作者： Taylor, Z. Reddy, T. Fitzpatrick, M. Kim, K. Li, W. Leung, C.L.A. Lee, P.D. Bertsch, K.M. Dresselhaus-Marais, L. Department of Materials Science and Engineering Stanford University United States SLAC National Accelerator Laboratory United States European Synchrotron Radiation Facility France Department of Mechanical Engineering University College London United Kingdom Research Complex at Harwell Rutherford Appleton Laboratory United Kingdom Lawrence Livermore National Laboratory United States

In the laser welding and additive manufacturing (AM) communities, the balling defect is primarily attributed to the action of fluid instabilities with a few authors suggesting other mechanisms. Without commenting on the validity of the fluid instability driven mechanism of balling in AM, this work intends to present the most realistic analytical discussion of the balling defect driven purely by fluid instabilities. Synchrotron-based X-ray radiography of thin samples indicate that fluid instability growth rates and solidification can be comparable in magnitude and thus compete. Neglecting the action of fluid flows and heat transport, this work presents an analytical formalism which accounts for fluid instabilities and solidification competition, giving a continuous transition from balling to non-balling which is lacking in current literature. We adapt a Rivulet instability model from the fluid physics community to account for the stabilizing effects of the substrate which the Plateau-Rayleigh instability model does not account for, and estimate the instability growth rate. Our model predicts instability growth at higher wavelengths and shallower melt pool depths relative to width, as well as strong sensitivity to the solidification front curvature. Deviations between model predictions and our experimental results demonstrate the importance of fluid flows and heat transport in the balling process. Our experiments further demonstrate at least one mechanism by which the melt pool length and balling wavelength are not equivalent, as commonly claimed. © 2025, CC BY.

关键词： Stream flow

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Facile fabrication of 3D-printed cellulosic fiber/polylactic acid composites as low-cost and sustainable acoustic panels

Sustainable Chemistry for the Environment

引用

Sustainable Chemistry for the Environment 2024年 8卷

作者： Wijekoon, Nelum K. Appuhamillage, Gayan A. Dassanayake, Rohan S. Liyanage, Renuka N. Mapage, Dulanjaya Wijenayake, Achintha Lokuge, Eshani L. Rajapaksha, Suranga M. Abeygunawardane, Gayan A. Senarath, N.D.D. Danuka Department of Materials and Mechanical Technology Faculty of Technology University of Sri Jayewardenepura Homagama 10206 Sri Lanka Department of Biosystems Technology Faculty of Technology University of Sri Jayewardenepura Homagama 10206 Sri Lanka Department of Materials Science and Engineering Faculty of Engineering University of Moratuwa Katubedda 10400 Sri Lanka Department of Physics Faculty of Science University of Peradeniya Peradeniya 20400 Sri Lanka

This work presents a green, cost-effective and eco-friendly strategy to reduce noise pollution by developing biopolymer-based 3D-printed acoustic panels. We successfully fabricated two series of composites by varying the weight percentage (wt%) of cellulose fibers of water hyacinth (WH) and pineapple leaf (PAL), with polylactic acid (PLA) as the matrix via the heat-press method. All samples were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Physico-mechanical properties, including hardness, tensile, and impact strength, were improved with increasing fiber loading. Filaments of 1 wt% water hyacinth fibers (WHFs) in PLA (1 WHF/PLA) and 1 wt% pineapple leaf fibers (PALFs) in PLA (1 PALF/PLA) were prepared and tested for 3D printability. The sound absorption coefficients (α) of the 3D-printed panels were investigated from 500 to 5000 Hz sound frequency range. The 3D-printed 1 WHF/PLA and 1 PALF/PLA acoustic panels achieve a maximum α (α-max) of 0.55 and 0.83 at 5000 and 4000 Hz, respectively, featuring the first work to report α-max > 0.5 at low fiber loadings in the high-frequency sound range. The tensile strength of the 3D-printed versions is significantly higher than non-3D-printed counterparts and commercial acoustic absorbers. Our data suggest the prepared 3D-printed panels are excellent candidates for acoustic applications at high-frequency noises. This study exhibits a facile, environmentally benign and sustainable approach to construct highly efficient and mechanically robust biopolymer-based 3D-printed sound-proof panels, which have promising potential as green engineering materials. Interestingly, this research also proposes a mitigation technology for the freshwater invader, Eichhornia crassipes (water hyacinths). © 2024 The Authors

关键词： 3D printing Acoustic panels Cellulosic fiber Polylactic acid (PLA) Sound absorbers

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Chiral, Topological, and Knotted Colloids in Liquid Crystals

arXiv

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arXiv 2024年

作者： Yuan, Ye Smalyukh, Ivan I. Hiroshima University Hiroshima Higashi-Hiroshima739-8526 Japan Department of Physics Department of Electrical Computer and Energy Engineering Materials Science and Engineering Program Soft Materials Research Center University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

The geometric shape, symmetry, and topology of colloidal particles often allow for controlling colloidal phase behavior and physical properties of these soft matter systems. In liquid crystalline dispersions, colloidal particles with low symmetry and nontrivial topology of surface confinement are of particular interest, including surfaces shaped as handlebodies, spirals, knots, multi-component links, and so on. These types of colloidal surfaces induce topologically nontrivial three-dimensional director field configurations and topological defects. Director switching by electric fields, laser tweezing of defects, and local photo-thermal melting of the liquid crystal host medium promote transformations among many stable and metastable particle-induced director configurations that can be revealed by means of direct label-free three-dimensional nonlinear optical imaging. The interplay between topologies of colloidal surfaces, director fields, and defects is found to show a number of unexpected features, such as knotting and linking of line defects, often uniquely arising from the nonpolar nature of the nematic director field. This review article highlights fascinating examples of new physical behavior arising from the interplay of nematic molecular order and both chiral symmetry and topology of colloidal inclusions within the nematic host. Furthermore, the article concludes with a brief discussion of how these findings may lay the groundwork for new types of topology-dictated self-assembly in soft condensed matter leading to novel mesostructured composite materials, as well as for experimental insights into the pure-math aspects of low-dimensional topology. © 2024, CC BY.

关键词： Crystal symmetry

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Interfacial Delamination Mechanism of Thermal Barrier Coatings with Real Microstructure Considering Gradient Thermal and Growth Stresses Based on the Fracture Phase Field

SSRN

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SSRN 2023年

作者： Xiao, Yiqi Liu, Zhiyuan Zhu, W. Peng, Xiaomin Hunan Provincial Key Laboratory of Vehicle Power and Transmission System Department of Mechanical Engineering Hunan Institute of Engineering Xiangtan411104 China Hunan Province Engineering Laboratory of Wind Power Operation Maintenance and Testing Technology Hunan Institute of Engineering Xiangtan411104 China School of Materials Science and Engineering Central South University of Forestry and Technology Hunan Changsha410004 China Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education School of Materials Science and Engineering Xiangtan University Hunan Xiangtan411105 China

The interface of atmospheric plasma spray (APS) thermal barrier coatings (TBCs) is highly irregular and rough, while their microstructure is porous and extremely uneven. This complexity leads to intricate patterns during the growth of thermally grown oxide (TGO), the distribution and evolution of the generated stress, as well as the initiation and expansion of cracks. Along these lines, in this work, a phase-field theory considering both the thermal gradient stress and TGO growth was established to thoroughly investigate the interface oxidation cracking in TBCs. More specifically, a two-dimensional geometric model of APS TBCs was established, incorporating real interface morphology and microstructure. Numerical simulations and experiments were also conducted to study the temperature and stress distribution, as well as the underlying mechanism of interface cracking during the service of TBCs. The results indicated that at high temperatures, the bottom temperature of the TC layer with a porosity of 3.1% and a thickness of 200 μm was approximately 5 °C lower than that of the TC layer without porosity. The maximum tensile stress occurred in the peak region near the interface, serving as the primary driving force for crack initiation and propagation near the interface, with opposite shear stress directions being developed at the interface between the peaks or valleys. The stress distribution near the interface in the model considering the real microstructure was similar to the simplified model without porosity, but the stress fluctuation range was greater. the inter-lamella cracks (Type A) in the TC near the peaks initiated earliest, followed by the creation of inter-lamella cracks at other locations, accompanied by the appearance of lamella-fracture cracks (Type B), inter-lamella to interfacial cracks (Type C), inter-lamella to TGO cracks (Type D), and internal TGO cracks (Type E). The coalescence of all these types of cracks will ultimately lead to coating failure. © 2

关键词： Cracks

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Implemented in-situ heat treatment process for controlling the residual thermal stresses during the fabrication of Ti-6Al-4V titanium alloy through additive manufacturing

引用

materials Letters 2024年 356卷

作者： Yadav, B.N. Lin, De-Wei Lin, Min-Chieh Tseng, Yu-Jen Yen, Hung-Wei Van Tran, Xuan Lin, Pai-Chen Advanced Institute of Manufacturing with High-tech Innovations Department of Mechanical Engineering National Chung-Cheng University Chia-Yi62102 Taiwan Department of Materials Science and Engineering National Taiwan University Taipei106 Taiwan Institute of Development of Strategy Thu Dau Mot University Phu Hoa Ward Thu Dau Mot City0650 Viet Nam

The aim of this study is to eliminate the conventional heat treatment process and save on associated equipment, time, energy, and professional labor costs. In this work, an in-situ heat treatment scanning strategy has been implemented to control the thermal residual stress produced during the fabrication of Ti-6Al-4V titanium alloy through the selective laser melting (SLM) manufacturing process. The laser scanning was performed twice: first, it was used for melting and bonding the powder to build the samples, and second, it was used to remove the residual stress. Additionally, the laser power variation impact was also analyzed from 100 W to 300 W. It has been found that the strength and ductility both improved by 20–25 %. The microstrain and dislocation density were also analyzed and found that the significant reduction in microstrain and dislocation denticity after in-situ heat treatment. © 2023 Elsevier B.V.

关键词： Aluminum alloys

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Second law of thermodynamics: A case study searching for quantum non-thermodynamic phenomena

arXiv

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arXiv 2023年

作者： Qiao, Yu Program of Materials Science and Engineering University of California – San Diego La Jolla CA92093 United States Department of Structural Engineering University of California – San Diego La Jolla CA92093-0085 United States

Recent research on the fundamentals of statistical mechanics has led to an interesting discovery: With locally nonchaotic barriers, as Boltzmann’s H-theorem is inapplicable, there exist nontrivial non-thermodynamic systems that can produce useful work by absorbing heat from a single thermal reservoir without any other effect, thereby breaking the boundaries of the second law of thermodynamics. The previous analyses used classical mechanical models. In the current investigation, the study is extended to quantum mechanics. First, we reiterate that the Fermi-Dirac distribution and the Bose-Einstein distribution are compatible with the generalized Maxwell’s relations, which demonstrates the overall robustness of the framework of quantum statistical mechanics. Next, we analyze a set of simple-step scattering problems. When the system is in contact with a thermal reservoir, a bound state inherently follows the second law of thermodynamics, while a scattering state may not. The root cause is associated with the nonlocal nature of the wave function. It implies that the non-thermodynamic phenomena favor unquantized energy, exhibiting a tendency to occur in classical mechanical or "semiclassical" setups. © 2023, CC BY.

关键词： Wave functions

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A Highly Ductile Composite of 3D-Printed Poly(Lactic Acid)With InSe Particles and Flakes as a

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SmartMat 2025年第1期6卷 155-163页

作者： Huihui Li:!Zhongiang YuI Bowen Liu-|Yang Gao-+|Ming Liu-I Jianqi Zhang-|Rodney SRuoffiD Bin Wang iD ICAS Key Laboratory of Nanosystem and Hierarchical Fabrication National Center for Nanoscience and Technology(NCNST)BeijingChina I 2Tianjin Key Laboratory of Molecular Optoelectronic SciencesDepartment of ChemistrySchool of SciencesTianjin UniversityTianjinChina I 3College of Mechanical EngineeringYangzhou UniversityYangzhouChina I*University of Chinese Academy of SciencesBeijingChina I'Center for Multidimensional Carbon Materials(CMCM)Institute for Basic Science(IBS)UlsanRepublic of Korea I°Department of ChemistryUlsan National Institute of Science and Technology(UNIST)UlsanRepublic of Korea I Department of Materials Science and EngineeringUlsan National Institute of Science and Technology(UNIST)UlsanRepublic of Korea I 8School of Energy and Chemical EngineeringUlsan National Institute of Science and Technology(UNIST)UlsanRepublicofKorea

The biodegradable polymer poly(lactic acid)(PLA)is ***-based composites reinforced by indium selenide(InSe)particles or flakes are prepared;each is found to have outstanding *** nanosheets are prepared by sonication of solid InSe in N-methyl pyrrolidone,followed by washing/dispersion in ethanol,and subsequent *** InSe nanosheets,or in separate studies InSe particles,are mixed with PLA to make composite *** PLA composite materials are 3D-printed into“dogbone"samples that are *** optimum dogbone specimen is 1.5 times stronger and 5.5 times tougher than neat PLA specimens prepared in the same *** the best of our knowledge,this concurrent improvement in tensile strength and toughness has not been achieved before in PLA with any fller *** element analysis,together with experimental analysis of(i)fracture surfaces,(ii)the PLA crystal structure,and(ii)the internal structure by micro-CT scanning,suggests that the exceptional mechanical performance is due to the intrinsic properties of InSe and,particularly,the emergence of crack shielding and crack deflection at the interfaces of PLA and InSe *** findings indicate that PLA-InSe composites may offer opportunities to broaden the applications of PLA composites,including as load-bearing materials.

关键词： 3D printing I InSe I PLA composites I strength I toughness

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A data-driven framework to predict the morphology of interfacial Cu6Sn5 IMC in SAC/Cu system during laser soldering

引用

Journal of materials science & Technology 2020年第15期47卷 115-127页

作者： Anil Kunwar Lili An Jiahui Liu Shengyan Shang Peter Raback Haitao Ma Xueguan Song Department of Materials Engineering KU LeuvenKasteelpark Arenberg 44B-3001 LeuvenBelgium School of Mechanical Engineering Dalian University of TechnologyDalian 116024China School of Materials Science and Engineering Dalian University of TechnologyDalian 116024China CSC-IT Center for Science Keilaranta 14P.O.Box 405FIN-02101 EspooFinland

A data-driven approach combining together the experimental laser soldering,finite element analysis and machine learning,has been utilized to predict the morphology of interracial intermetallic compound(IMC) in Sn-xAg-yCu/Cu(SAC/Cu) *** types of SAC solders with varying weight proportion of Ag and Cu,have been processed with fiber laser at different magnitudes of power(30-50 W) and scan speed(10-240 mm/min),and the resultant IMC morphologies characterized through scanning electron microscope are categorized as prismatic and scalloped *** the different alloy composition and laser parameters,finite element method(FEM) is employed to compute the transient distribution of temperature at the interface of solder and *** FEM-generated datasets are supplied to a neural network that predicts the IMC morphology through the quantified values of temperature dependent Jackson parameter(αJ).The numerical value of αJ predicted from neural network is validated with experimental IMC *** critical scan speed for the morphology transition between prismatic and scalloped IMC is estimated for each solder composition at a given ***-0.7 Cu having the largest critical scan speed at 30 W and Sn-3.5 Ag alloy having the largest critical scan speed at input power values of 40 W and 50 W,thus possessing the greatest likelihood of forming prismatic interfacial IMC during laser soldering,can be inferred as most suitable SAC solders in applications exposed to shear loads.

关键词： Intermetallic compound Neural network Finite element method(FEM) Laser parameters Lead-free solders Morphology

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Constitutive Model of Elastic Response for Fe-Tib2 Composites

SSRN

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SSRN 2022年

作者： Ye, Yicong Ni, Ziqi Huang, Caiming Bai, Shuxin Chen, Qiang Department of Materials Science and Engineering College of Aerospace Science and Engineering National University of Defense Technology Changsha410073 China School of Mechanical and Electrical Engineering Guilin University of Electronic Technology Guilin541004 China

The elastic response of steel-based metal matrix composites to the macroscopic stress was established for revealing the elastic properties at multiscale. The effective elastic constants (EECs) of the Fe-TiB 2 composites were predicted by the constitutive model in this study, including the effective elastic modulus [[EQUATION]] , effective bulk modulus [[EQUATION]] , effective shear modulus [[EQUATION]] , and effective Poisson's ratio [[EQUATION]] . And then, the diffraction elastic constants (DECs) related to the crystal planes ( hkl ), [[EQUATION]] and [[EQUATION]] of the constituents of the composites, were also evaluated based on the multiscale correlation constitutive equations. Compared with experimental values, there was excellent agreement for the EECs of the Fe-TiB 2 composites and reasonable error in DECs of the steel-based matrixes and TiB 2 reinforcement. Furthermore, the multiscale coupling between the EECs and DECs related to elastic response and residual stress was also concerned in this micromechanical model. The internal stress in the TiB 2 reinforcements is higher than the steel-based matrixes at the same applied stress of the composites, which means the desired load transfer has occurred. © 2022, The Authors. All rights reserved.

关键词： Reinforcement

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Flaw Type Dependent Tensile Properties of 316l Stainless Steel Additively Manufactured by Laser Powder Bed Fusion

SSRN

引用

SSRN 2022年

作者： Vallejo, Nathalia Diaz Kljestan, Nemanja Ayers, Nicolas Knezevic, Marko Sohn, Yongho Advanced Materials Processing and Analysis Center Department of Materials Science and Engineering University of Central Florida OrlandoFL United States Department of Mechanical Engineering University of New Hampshire Durham NH United States

In this laser powder bed fusion (LPBF) study for 316L stainless steel (316L SS), the laser scan speed was varied to produce samples with keyhole (KH) and lack of fusion (LoF) flaws, each with three levels of density (i.e., > 97%, ~ 98%, and ~ 99%). KH and LoF flaws were characterized by circularity, size, and aspect ratio from extensive image analysis of optical micrographs. The samples were tested in uniaxial tension to correlate the flaw characteristics with yield strength (YS), ultimate tensile strength (UTS), and elongation at failure (EL%). Results showed that the circularity decreased, while the size and aspect ratio increased for both KH and LoF flaws when the laser scan speed (at constant power) deviates from the LPBF parameters that yields nearly fully dense 316L SS. Additional to the influence of the density, the YS and UTS of the samples showed more sensitivity to the LoF than KH, while the EL% was comparable between the two types of flaws when the porosity is below 2%. The difference in mechanical properties for the 316L samples containing KH and LoF flaws with similar density was minimal because of the intrinsically high ductility of the alloy. © 2022, The Authors. All rights reserved.

关键词： Austenitic stainless steel

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