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34th Congress of the International Council of the Aeronautical Sciences, ICAS 2024

作者： Li, Qin Yang, Xiaofeng Dong, Wei Du, Yanxia School of Mechanical Engineering Shanghai Jiao Tong University China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center China

Heterogeneous catalytic reactions between dissociated atoms after the shockwave and thermal protective materials can lead to a significant part of aerodynamic heating on the surface of high-speed aircraft. A kinetic Monte Carlo (KMC) based catalytic model simulating four-step heterogeneous catalysis was constructed and was coupled into computational fluid dynamics (CFD) method as catalytic viscous wall boundary by interpolation. The KMC-embedded CFD simulation method aimed at involving microscale reaction kinetics in CFD simulation, further obtaining heat transfer rate with physical basis on chemical reacting gas-solid interface. Local aerothermal environment calculated from a self-developed CFD solver provided thermochemical parameters for the KMC method. The output of KMC, namely the recombination coefficient of atoms, was used as a catalytic viscous wall boundary condition in the CFD solver. The accuracy of KMC method in predicting recombination coefficient, the effectiveness of the self-developed CFD solver in simulating chemical reacting gas flow, and the ability of the KMC-embedded CFD method in calculating heat transfer rate was verified. The results showed that simulation of high-enthalpy flow with the current method could drive a deterministic heat transfer rate on the surface of high-speed aircraft, thus improving the reliability of aerodynamic heating prediction on thermal protection material. © 2024, International Council of the Aeronautical Sciences. All rights reserved.

关键词： Flow of gases

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A Two-Way FSI Model for Pathologic Respiratory Processes with Precisely Structured and Flexible Upper Airway

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Acta Mechanica Solida Sinica 2024年第6期37卷 910-918页

作者： Yuan Qin Honghao Zhang Zhiwei Qiu Lei Liu Hui Yang Jiutao Hang Dong Wei Guangkui Xu Department of Engineering Mechanics SVLSchool of Aerospace EngineeringXi’an Jiaotong UniversityXi’an710049China School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an710000China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development CenterMianyang621000SichuanChina School of Life Sciences Northwestern Polytechnical UniversityXi’an710000China

The human body displays various symptoms of altitude sickness due to hypoxia in environments with low pressure and oxygen *** existing studies are primarily focused on the adverse effects of hypoxia and oxygen supplementation strategies at high altitudes,there is a notable gap in understanding the fundamental mechanisms driving altitude *** this context,we propose a sophisticated two-way fluid–structure interaction model that simulates respiratory processes with precisely structured and deformable upper *** model reveals that,under identical pressure differentials at the airway’s inlet and outlet,the inspiratory air volume remains largely consistent and is minimally affected by specific pressure ***,an increase in the pressure differential enhances gas inhalation ***,airway morphology emerges as a pivotal factor influencing oxygen *** airway shapes create areas of high flow velocity,where low wall pressure hampers effective airway opening,thus diminishing gas *** results may shed light on the effects of low-pressure conditions and upper airway structure on respiratory dynamics at high altitudes and inform the development of effective oxygen supply strategies.

关键词： mechanical model Mechanics of soft tissues Respiratory process Flexible

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Flow Characteristics and Aerodynamic Heating of Tube Trains in Choked/Unchoked Flow:A Numerical Study

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Journal of Thermal Science 2023年第4期32卷 1421-1434页

作者： SUI Yang YU Qiujun NIU Jiqiang CAO Xiaoling YANG Xiaofeng YUAN Yanping Graduate School of Tangshan Southwest Jiaotong UniversityTangshan063000China School of Mechanical Engineering Southwest Jiaotong UniversityChengdu610031China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development CenterMianyang621000China

Hyperloop has become one of the key reserve technologies for future high-speed rail *** gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating *** research on the flow field characteristics and aerodynamic heating effect of hyperloop is in its infancy,and that on the flow field structure is *** this study,the nozzle theory was used to make a preliminary judgment on the choked flow phenomenon in the *** on the flow results obtained under different working conditions,the identification basis of the choked flow phenomenon in the hyperloop was ***,the effect of the choked/unchoked flow on the flow structure,temperature,and pressure distribution of the annular space in the tube was *** on traditional high-speed railway aerodynamics,according to relevant theories and calculation in aerospace field,and combined with the model test data,the reliability verification analysis on the characteristics of the flow field are carried *** structure of the flow filed in the tube can be divided into choked and *** judgment is dependent on whether the throat reaches the speed of *** the choked flow,a normal shock wave is formed in front of the tube *** temperature rise of the local flow field exceeds 50 K;the temperature rise of the stagnation region exceeds 88 K,and the pressure is approximately 1.7 times that of the initial pressure in the *** the flow is unchoked,differences arise in the distribution of the flow field corresponding to different incoming Mach *** the incoming flow is supersonic,the flow field maintains a supersonic speed,and a bow-shaped shock wave is formed at the front of the tube *** to the shock wave or expansion wave,the local flow field exhibits significant fluctuations in temperature and ***,when the incoming flow is subsonic,the flow field in the tube maintains a subsonic speed,and no shock wave structure is

关键词： hyperloop choked/unchoked flow aerodynamic phenomenon numerical simulation

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Prediction model of volume average diameter and analysis of atomization characteristics in electrostatic atomization minimum quantity lubrication

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Friction 2023年第11期11卷 2107-2131页

作者： Dongzhou JIA Changhe LI Jiahao LIU Yanbin ZHANG Min YANG Teng GAO Zafar SAID Shubham SHARMA School of Mechanical&Automotive Engineering Qingdao University of TechnologyQingdao 266520China College of Mechanical Engineering and Automation Liaoning University of TechnologyJinzhou 121001China State Key Laboratory of Ultra-precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHong Kong 999077China College of Engineering University of SharjahSharjah 27272United Arab Emirates Mechanical Engineering Department University Center for Research and DevelopmentChandigarh UniversityMohaliPunjab 144603India

Minimum quantity lubrication(MQL)is a relatively efficient and clean alternative to flooding workpiece *** atomization has the merits of small droplet diameter,high uniformity of droplet size,and strong coating,hence its superiority to pneumatic ***,as the current research hotspot,the influence of jet parameters and electrical parameters on the average diameter of droplets is not ***,by observing the shape of the liquid film at the nozzle outlet,the influence law of air pressure and voltage on liquid film thickness(h)and transverse and longitudinal fluctuations are ***,the mathematical model of charged droplet volume average diameter(VAD)is constructed based on three dimensions of the liquid film,namely its thickness,transverse wavelength(λ_(h)),and longitudinal wavelength(λ_(z)).The model results under different working conditions are obtained by numerical *** of the model results with the experimental VAD of the droplet confirm the error of the mathematical model to be less than 10%.The droplet diameter distribution span value Rosin–Rammler distribution span(R.S)and percentage concentrations of PM10(particle size of less than 10μm)/PM2.5(particle size of less than 2.5μm)under different working conditions are further *** results show that electrostatic atomization not only reduces the diameter distribution span of atomized droplets but also significantly inhibits the formation of PM10 and PM2.5 fine-suspension *** the air pressure is 0.3 MPa,and the voltage is 40 kV,the percentage concentrations of PM10 and PM2.5 can be reduced by 80.72%and 92.05%,respectively,compared with that under the pure pneumatic atomization condition at 0.3 MPa.

关键词： minimum quantity lubrication(MQL) electrostatic atomization volume average diameter(VAD) atomization characteristics

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Modeling of Inconel Powder Flow and Thermal Distribution During the Direct Energy Deposition Process 8th

Modeling of Inconel Powder Flow and Thermal Distribution Dur...

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8th International and 29th All India Manufacturing Technology, Design and research Conference, AIMTDR 2021

作者： Kumar, Dharmendra Rahate, Ojas Praveen Imam, Murshid John Rozario Jegaraj, J. Chinthapenta, Viswanath Mechanical Engineering IIT Patna Patna801103 India Defence Research and Development Laboratory Hyderabad500058 India Mechanical and Aerospace Engineering IIT Hyderabad Hyderabad502284 India

ISBN: (纸本)9789811976117

This study explored the discrete element method to model the Inconel powder flow through the laser head nozzles. The laser head was modeled with four nozzles. Bi-particulate powder flow simulations were carried out using discrete element modeling through LIGGGHTS open-source software. Then, the temperature distribution on the powder particles on the base plate was captured using finite element simulations using COMSOL. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Sintering

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Surface Integrity of Inconel 738LC Parts Manufactured by Selective Laser Melting Followed by High-speed Milling

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Chinese Journal of mechanical engineering 2023年第1期36卷 65-79页

作者： Guanhui Ren Sai Guo Bi Zhang Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen518055China Shenzhen Key Laboratory for Additive Manufacturing of High-performance Materials Shenzhen518055China Research and Development Department Shenzhen Xinjinquan Precision Techonology Co.Ltd.Shenzhen518055China School of Mechanical Engineering Shandong UniversityJinan250061China

This study is concerned with the surface integrity of Inconel 738LC parts manufactured by selective laser melting(SLM)followed by high-speed milling(HSM).In the investigation process of surface integrity,the study employs ultradepth three-dimensional microscopy,laser scanning confocal microscopy,scanning electron microscopy,electron backscatter diffractometry,and energy dispersive spectroscopy to characterize the evolution of material microstructure,work hardening,residual stress coupling,and anisotropic effect of the building direction on surface integrity of the *** results show that SLM/HSM hybrid manufacturing can be an effective method to obtain better surface quality with a thinner machining metamorphic ***-speed machining is adopted to reduce cutting force and suppress machining heat,which is an effective way to produce better surface mechanical properties during the SLM/HSM hybrid manufacturing *** general,high-speed milling of the SLM-built Inconel 738LC samples offers better surface integrity,compared to simplex additive manufacturing or casting.

关键词： Surface integrity Inconel 738LC Selective laser melting High-speed milling

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Computational study on subsonic impact resistance of lattice structures in 3D printed thin Ti6Al4V parts

Computational study on subsonic impact resistance of lattice...

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13th International Symposium on Plasticity and Impact Mechanics, IMPLAST 2022

作者： Harithsa, Shreyas Nandakumar Kumar, S. Anand Nagesha, B.K. Nataraj, J.R. Department of Mechanical Engineering RV College of Engineering Bangalore India Additive Manufacturing Research Laboratory Department of Mechanical Engineering Indian Institute of Technology Jammu Nagrota India Gas Turbine Research Establishment Defence Research and Development Organization Karnataka India

Additive manufacturing (AM) is a set of digital manufacturing processes which is gaining momentum in the industries for its flexibility, versatility and ability to manufacture complex geometries with limited human interaction. It has enabled relatively fast materialization of a conceptualized design for testing, inspecting and examining the components. AM is highly suitable for fabricating functional gas turbine components owing to its low volume production requirements, lightweight components and geometrical complexity requirements. Laser powder bed fusion (LPBF), is the most common form of metal AM method used. The shape complexity attribute of LPBF can be taken advantage of to fabricate lattice-induced gas turbine inlet components prone to hail or bird impact. In this study, a computational approach was implemented to assess the behaviour of thin Ti6Al4V parts induced with a single-layer lattice subjected to projectile impact. Homogenization of lattice structures was carried out in nTopology to shortlist them for impact studies based on Young’s modulus distribution. The impact analysis was performed on eight lattice structures, two of which were derived from topology optimization, along with a solid plate and hollow plate acting as benchmarks for comparison. The high-velocity impact (250 m/s) was simulated using the ‘‘Explicit Dynamics" module in Ansys. It was observed that the lattice geometry directly below the impact site influenced the deformation, stress and energy values. It was concluded that lattices such as isotruss, kelvin cell and FCC, which have more struts interfacing with the impact region, tend to show deformation comparable to solid plates (4.89E-04 m). The equivalent stress values were within the material’s elastic limit, indicating elastic deformation. The reduction in kinetic energy of the projectile for lattice-induced plates was also comparable with the values for solid plates (68 %). A correlation coefficient of -0.807 was obtained between p

关键词： Aluminum alloys

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Material Removal Rate and Tool Life Improvement Studies on Machining of Fused Silica Ceramic Radome Using Diamond Tip Brazed (DTB) Tool 8th

Material Removal Rate and Tool Life Improvement Studies on M...

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8th International and 29th All India Manufacturing Technology , Design and research Conference, AIMTDR 2021

作者： Kumar, J. Vimal Theenathayalan, K. Jegaraj, J. John Rozario Sankar, M. Ravi Research Centre Imarat DRDO Hyderabad India Defence Research and Development Laboratory DRDO Hyderabad India Department of Mechanical Engineering IIT Tirupati India

ISBN: (纸本)9789811938658

Ceramic radomes are made of fused silica and are widely used for critical aerospace applications. In this paper, an attempt has been made to improve the tool life while machining fused silica ceramic radome. Various methodologies such as dry machining, wet machining, green ceramic machining (GCM) and machining using poly crystalline diamond (PCD) inserts/diamond tip brazed (DTB) tool have been evolved for machining of ceramic radomes. From the literature, it is found that wet machining with the application of demineralized water in limited quantity proved to be beneficial in terms of improved tools life and better machinability. Wear of PCD tools was found to be much slower in the case of wet machining. It is also found that green ceramic machining can be adopted for machining of ceramic radome with higher raw material stock. In this work, an attempt has been made to study the use of the DTB tool for the machining of fused silica ceramic radome. The study revealed that the DTB tool is beneficial in terms of cost-effectiveness, tool life, material removal rate (MRR) and machining time over PCD inserts. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Cost effectiveness

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Multifunctional HDPE/Cu biocidal nanocomposites for MEX additive manufactured parts: Perspectives for the defense industry

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Defence Technology（防务技术） 2024年第8期38卷 16-32页

作者： Nectarios Vidakis Nikolaos Michailidis Markos Petousis Nektarios K.Nasikas Vassilios Saltas Vassilis Papadakis Nikolaos Mountakis Apostolos Argyros Mariza Spiridaki Ioannis Valsamos Department of Mechanical Engineering Hellenic Mediterranean UniversityHeraklion 71410Greece Physical Metallurgy Laboratory Mechanical Engineering DepartmentSchool of EngineeringAristotle University of ThessalonikiThessaloniki 54124Greece Centre for Research&Development of Advanced Materials(CERDAM) Center for Interdisciplinary Research and InnovationBalkan CentreThessaloniki 57001Greece Division of Mathematics and Engineering Sciences Department of Military SciencesHellenic Army AcademyVari GR16673AtticaGreece Department of Electronic Engineering Hellenic Mediterranean UniversityChania 73133Greece Department of Industrial Design and Production Engineering University of West AtticaAthens 12244Greece Institute of Electronic Structure and Laser Foundation for Research and Technology-HellasHeraklion 70013Greece

In this study, we investigated the performance improvement caused by the addition of copper(Cu)nanoparticles to high-density polyethylene(HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion(MEX)3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis(TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy(SEM), as well as atomic force microscopy(AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive Xray spectroscopy(EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties(for example, it exhibited a 36.7%improvement in the flexural strength, compared to the pure matrix). At the same

关键词： High-density polyethylene(HDPE) Copper(Cu) Material extrusion(MEX) mechanical performance Electrical properties Antibacterial Defense and security

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Enhanced engineering and biocidal polypropylene filaments enabling melt reduction of AgNO_(3) through PVP agent:A scalable process for the defense industry with MEX additive manufacturing

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Defence Technology(防务技术) 2025年第2期44卷 52-66页

作者： Markos Petousis Nikolaos Michailidis Vassilis Papadakis Apostolos Argyros Mariza Spiridaki Nikolaos Mountakis John Valsamos Nektarios K.Nasikas Amalia Moutsopoulou Nectarios Vidakis Department of Mechanical Engineering Hellenic Mediterranean UniversityHeraklion 71410Greece Physical Metallurgy Laboratory Mechanical Engineering DepartmentSchool of EngineeringAristotle University of ThessalonikiThessaloniki 54124Greece Centre for Research&Development of Advanced Materials(CERDAM) Centre for Interdisciplinary Research and InnovationBalkan CentreBuilding B’10th Km Thessaloniki-Thermi RoadThessaloniki 57001Greece Institute of Electronic Structure and Laser of the Foundation for Research and Technology-Hellas(IESL-FORTH)e Hellas N.Plastira 100mHeraklion 70013Greece Department of Industrial Design and Production Engineering University of West AtticaAthens 12243Greece Division of Mathematics and Engineering Sciences Department of Military SciencesHellenic Army AcademyGR 16673VariAtticaGreece

This study focused on the production of polypropylene(PP)/silver(Ag)composites via additive *** study aimed to enhance the quality of medical-grade PP in material extrusion(MEX)three-dimensional printing(3DP)by improving its mechanical properties while simultaneously adding antibacterial *** latter can find extremely important and versatile properties that are applicable in defense and security ***/Ag nanocomposites were prepared using a novel method based on a reaction occurring while mixing appropriate quantities of the starting polymers and additives,namely polyvinylpyrrolidone(PVP)as the matrix material and silver nitrate(AgNO_(3))as the *** process produced three-dimensional(3D)printed filaments,which were then used to create specimens for a series of standardized *** was found that the mechanical properties of the nanocomposites were enhanced in relation to pristine PP,especially for the PP matrix with various loadings of AgNO_(3)and PVP,such as 5.0 wt%and 2.5 wt%,*** voids,inclusions,and actual-to-nominal dimensions also showed improved *** 3DP specimens exhibited a more effective biocidal performance against Staphylococcus aureus than Escherichia coli,which developed an inhibition zone only in the case of PP with filler loading percentages of AgNO_(3)and PVP at 10.0 wt%and 5.0 wt%,respectively Compounds possessing such properties can be beneficial for various applications requiring increased mechanical properties and biocidal capabilities,such as in the Defence or medical industries.

关键词： Polypropylene(PP) Polyvinyl pyrrolidone(PVP) Silver nitride(AgNO_(3)) In-situ reactive melt mixing process Material extrusion(MEX)3D printing Biocidal performance

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