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Numerical analysis of the influence of the contact boundary condition and specimen geometry on concrete compressive strength

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Procedia Structural Integrity 2023年 47卷 261-267页

作者： Caroline Bremm Luísa Inda Leandro Ferreira Friedrich Sabrina Vantadori Ignacio Iturrioz Luis Kosteski Engineering Post Graduation Program Federal University of Pampa Av. Tiaraju 810 Alegrete 97546-550 Brazil Civil Engineering Graduate Program Federal University of Pampa Av. Tiaraju 810 Alegrete 97546-550 Brazil Program of Mechanical Pos-Graduation Federal University of Rio Grande do Sul Sarmento Leite 425 Porto Alegre 90040-060 Brazil Department of Engineering & Architecture University of Parma Parco Area delle Scienze 181/A 43124 Parma Italy

In the present paper, the influence of the contact boundary condition and specimen geometry on the concrete compressive strength is numerically investigated by using a version of the Lattice Discrete Element Method (LDEM), implemented on Abaqus/Explicit. More precisely, two types of contact boundary conditions are considered and, for each of them, three different slenderness levels (height/width ratio - h/b) are analyzed (that is, h/b = 0.5, 1.0, and 2.0) by considering a square cross-section. Moreover, for h/b = 2.0, a circular cross-section is also examined. Two models are developed: one by using the LDEM and the other by using a hybrid model, combining Finite Elements and LDEs. The results show that both the boundary conditions and the sample geometry influence the axial compressive strength.

关键词： Abaqus concrete compressive strength Lattice Discrete Element Method (LDEM)

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A Critical Review on Cryopreservation of Cells Technics: Thermal Aspects 6th

A Critical Review on Cryopreservation of Cells Technics: The...

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6th Multiphase Flow Journey, JEM 2021

作者： Steffenon, Guilherme D. Copetti, Jacqueline B. de Oliveira, Jeferson D. Macagnan, Mario H. Cardoso, Elaine M. the University of Vale do Rio dos Sinos Mechanical Engineering Graduate Program LETEF Laboratory of Thermal and Fluid Dynamic Studies Unisinos Avenue 950 RS São Leopoldo93022-750 Brazil FSG—University Center Center of Innovation and Technology Department of Mechanical Engineering Os Dezoito do Forte 2366 RS Caxias do Sul95020-472 Brazil UNESP—São Paulo State University Post-Graduation Program in Mechanical Engineering Brasil Avenue 56 SP Ilha Solteira15385-000 Brazil

ISBN: (纸本)9783030934552

The studies carried out in the area of cell preservation have been of significant importance in recent years. This process, known as cryopreservation, has been used for decades and aims to preserve various cellular materials at cryogenic temperatures. Different methods allow cryopreservation, where the best known are the slow freezing and vitrification processes. Regardless of the process, it is necessary to use cryoprotective agents (CPAs) in conjunction with the cells to avoid possible cell damage during cryopreservation. Regarding the methods, they differ in their cooling rates and the concentration of CPAs used. According to some studies, the method that has been most studied is that of vitrification, which seeks to increase the cooling rate, reaching values above 20,000 ∘ C/min. Evaporation by a thin film of liquid nitrogen is one of the methods of vitrification, which uses a microstructure with a finned or porous surface for evaporation, and in these conditions cooling rates of up to 150,000 ∘ C/min were found, which shows a significant advance and alternative for cell cryopreservation. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Cryopreservation Slow freezing Thin film evaporation Vitrification

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Bo-derived waste neem to enriching reinforced hybrid composite for environmental remediation

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Chemosphere 2024年 350卷 141055页

作者： Anbuchezhiyan, Gnanasambandam Mubarak, Nabisab Mujawar Hussain Siddiqui, Muhammad Tahir Malafaia, Guilherme Abnisa, Faisal Department of Mechanical Engineering Saveetha School of Engineering Saveetha Institute of Medical and Technical Sciences Tamil Nadu Chennai602105 India Petroleum and Chemical Engineering Faculty of Engineering Universiti Teknologi Brunei Bandar Seri BegawanBE1410 Brunei Department of Chemistry School of Chemical Engineering and Physical Sciences Lovely Professional University Punjab Jalandhar India Department of Chemical and Materials Engineering Faculty of Engineering King Abdulaziz University Rabigh21911 Saudi Arabia School of Engineering RMIT University MelbourneVIC3001 Australia Post-Graduation Program in Ecology Conservation and Biodiversity Federal University of Uberlândia MG Uberlândia Brazil Laboratory of Toxicology Applied to the Environment Goiano Federal Institute – Urutaí Campus. Rodovia Geraldo Silva Nascimento 2 5 Km Zona Rural GO Urutaí Brazil Post-Graduation Program in Conservation of Cerrado Natural Resources Goiano Federal Institute Post-Graduation Program in Biotechnology and Biodiversity Federal University of Goiás GO Goiânia Brazil

The utilization of natural fibres often entails a lesser environmental impact when compared to synthetic fibres. Biodegradable natural fibres minimize waste and pollution, and promote sustainability, but their weaker bonds limit their resilience. These issues can be addressed by customizing the composite's mechanical properties with natural and synthetic fibres. In this study, hybrid composites were created using the hand layup method with a novel dissimilar layer arrangement of neem (N), sisal (S), and glass (G) fibre and analyze its mechanical and thermal properties. Experimental observation shows that the GN composite had a higher maximum ultimate tensile strength of 26 N/mm2 than the GS, GNS, and GSN composites. The GN composite had a percentage elongation of 6.33%, similar to the percentage elongation of the GS composite (6.833%), and it also had a higher ultimate shear strength of 50 MPa. The composite GS absorbed 6.6 J energy, higher than the composites GN, GNS, and GNS, which absorbed 6.1 J, 4.5 J, and 4.5 J, respectively. The fractured surface's SEM images were obtained and analyzed for failure. The results demonstrated that the hybridization was effective, and better properties can be obtained by combining neem, sisal, and glass fiber, and it can be used for other requirements, including strength, weight, cost, and ecological impact. © 2024 Elsevier Ltd

关键词： Glass

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Biopolymers Applied to Packaging:A Brief Literature Review on Their Impact on Sustainability

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Non-Metallic Material Science 2022年第2期4卷 4-14页

作者： Diogo Cardoso Rego Harrison Lourenço Corrêa Post-graduation Program in Manufacturing Engineering(PPGEM) Federal University of ParanáCity of CuritibaParanáStateBrazil Laboratory of Polymer Materials Department of Mechanical EngineeringFederal University of ParanáCity of CuritibaParanáStateBrazil

The replacement of fossil raw materials by renewable alternatives is imper***,biodegradable,and compostable polymers are options to be developed and *** in this concept,the present study evaluates whether biopolymers are sustainable alternatives to replace traditional polymers used in packaging,such as *** that end,a systematic literature review(SLR)was carried out on biopolymers applied to packaging,with an analysis of its *** sustainability criteria were adopted:a)Criteria for Developing Sustainable Packaging;b)Goals of Sustainable Development;and c)Circular Economy *** Methodology Section presents the state of the art of potential polymers for packaging and their characteristics related to the evaluation criteria adopted based on the *** data collection,it was observed that advanced obtaining techniques enable polymers economically and that,environmentally speaking,there is a positive consensus about some types of those ***,technological maturity and productive scale capacity are necessary to reduce costs in a competitive scenario with conventional polymers.

关键词： Packaging Biopolymers Sustainability Circular economy

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Investigation of Vorticity Fields During Two-Phase Flow in Flow Boiling 6th

Investigation of Vorticity Fields During Two-Phase Flow in F...

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6th Multiphase Flow Journey, JEM 2021

作者： de Oliveira, Jeferson D. Copetti, Jacqueline B. Cardoso, Elaine M. FSG-University Center Center of Innovation and Technology Department of Mechanical Engineering Os Dezoito do Forte 2366 RS Caxias do Sul95020-472 Brazil The University of Vale do Rio dos Sinos Mechanical Engineering Graduate Program LETEF Laboratory of Thermal and Fluid Dynamic Studies Unisinos Avenue 950 RS São Leopoldo93022-750 Brazil UNESP—São Paulo State University Post-Graduation Program in Mechanical Engineering Av. Brasil 56 SP Ilha Solteira15385-000 Brazil

ISBN: (纸本)9783030934552

Flow patterns are found in many processes involving multiphase flows in the industry. This experimental investigation focuses on the behavior of the vorticity fields found in the liquid-vapor interface during flow boiling of R-600a with heat flux varying from 5 to 20 kW/m 2 and fixed mass flux of 890 kg/(m 2 s) at a saturation temperature of 17 ∘ C. Tests were performed in a horizontal tube with 1.0 mm ID. Four different flow patterns were identified based on images, and the vorticity fields were investigated using an optical flow method. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Flow boiling Flow patterns Optical flow Vorticity

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A Methodology for Obtaining and Validating Parameters for Surface Repairs Using the Pulsed Gmaw Process

SSRN

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SSRN 2023年

作者： Muñoz Chávez, Jairo José de Souza Lira, Margareth Nascimento Bestard, Guillermo Alvarez da Cruz Payão Filho, João Alfaro, Sadek Crisostomo Absi Post-Graduation Program in Mechatronics Engineering Department of Mechanical Engineering University of Brasilia CEP 70.910-900 Brazil Federal University of Rio de Janeiro Department of Metallurgical and Materials Engineering National Laboratory of Welding Technology Rio de Janeiro RJ Ilha do FundãoCEP 21941-972 Brazil

This study aims to develop a methodology for obtaining and validating surface parameters using the pulsed GMAW process, capable of producing a weld with appropriate geometric properties as a response. For this purpose, profiling was used as a capture tool together with stability analysis algorithms and metallic transfer criteria. The Fast Fourier Transform was used to analyze the intensity of electric current and voltage oscillogram for the delimitation of the most efficient pulse, detachment characteristics, and drop frequency in each analyzed parameter. In parallel, mathematical modelling of the overlapping of welding beads and volume filling simulation was carried out to obtain a repair methodology of satisfactory quality. Such strategies defined a working window with a voltage between 22 V and 28 V and an intensity of electric current between 190 A and 220 A. For the analyzed material, the best response values were at the base intensity of electric current of 80 A, base time of 1.47 ms, drop separator intensity of electric current of 110 A, drop separator time of 0.5 ms, the peak intensity of electric current of 375 A and peak time of 2.2 ms, corresponding to a working frequency of 240 Hz. With this work methodology, using signal analysis and profiling filming, it is possible to adapt the choice of process parameters to any material with energy and cost savings. These techniques are highly efficient and low-cost. In addition, the GMAW-P transfer mode allows quality work with the intensity of electric current values lower than conventional GMAW. © 2023, The Authors. All rights reserved.

关键词： Drops

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Synthesis of PMMA Nanoparticles Loaded with Geopropolis Extract from the Brazilian Stingless Bee Melipona quadrifasciata Lepeletier, 1836 by Miniemulsion Polymerization

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Macromolecular Symposia 2022年第1期406卷 2200046-2200046页

作者： da Silva, Thiago S. Nogueira, André L. Lafratta, Fernando H. Department of Chemical and Food Engineering Federal University of Santa Catarina – UFSC Florianópolis88040-900 Brazil Department of Chemical Engineering and Post-Graduation Program in Process Engineering University of the Region of Joinville – UNIVILLE Santa Catarina Joinville89219-710 Brazil Department of Mechanical Engineering Santa Catarina State University – UDESC Santa Catarina Joinville89219-710 Brazil

The present work aims to encapsulate the concentrated geopropolis extract from the Brazilian stingless bee Melipona quadrifasciata quadrifasciata Lepeletier, 1836 in poly(methyl methacrylate) (PMMA) nanoparticles produced by miniemulsion polymerization. The concentrated geopropolis extract is obtained by hydroalcoholic maceration and characterized by ultraviolet–visible spectrophotometry (UV–Vis) to quantify flavonoids and polyphenols in terms of quercetin (Q) and galic acid (GA), respectively. The PMMA-Propolis nanoparticles is characterized by size exclusion chromatography (SEC), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV–Vis and nuclear magnetic resonance (NMR1H). UV–Vis results of the geopropolis extract revealed an average flavonoid content of 22.51 mg Q g–1 and an average polyphenol content of 10.15 mg GA g–1. TEM images showed that the produced PMMA nanoparticles are spherical, and their average diameter reduced from 72.62 to 44.60 nm by increasing the propolis concentration from 0% to 40%. Additionally, the kinetic data reveal a reduction of the polymerization reaction rate as well as the average molecular weight when raising the propolis extract concentration in the reaction media. These results suggest that propolis extract may be used as a biocompatible and biodegradable co-stabilizer and chain transfer agent in miniemulsion polymerization reactions of vinyl monomers. © 2022 Wiley-VCH GmbH.

关键词： Thermogravimetric analysis

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Influence of Phase Transformation Coefficient on Thermomechanical Modeling of Laser Powder Bed Fusion for Maraging 300 Steel

SSRN

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SSRN 2024年

作者： dos Santos Silva, Bruno Caetano de Figueiredo Soares, Lucas Coelho, Rodrigo Santiago Sitek, Wojciech Król, Mariusz Batalha, Gilmar Ferreira University Center SENAI CIMATEC SENAI Innovation Institute for Forming and Joining of Materials Av. Orlando Gomes 1845 Piata BA Salvador41650-010 Brazil Department of Mechatronics and Mechanical Systems Engineering Polytechnic School of Engineering University of Sao Paulo Av. Prof. Mello Moraes 2231 Butantã SP Sao Paulo05508-030 Brazil University Center SENAI CIMATEC Post-Graduation Program MPDS/GETEC/MCTI Av. Orlando Gomes 1845 Piata Salvador-BA41650-010 Brazil Department of Engineering Materials and Biomaterials Faculty of Mechanical Engineering Silesian University of Technology 18A Konarskiego St. Gliwice44-100 Poland

Manufacturing maraging steel components using laser-based powder bed fusion (LPBF) presents an attractive proposition for industries due to the material's combination of mechanical properties such as hardness, wear resistance, and toughness, and the capability to produce parts with complex geometries and high precision. Despite these advantages, the LPBF process induces defects such as distortion and residual stress associated with the complex thermal cycles, compromising final part quality. Numerical simulations have been developed to predict these defects. However, LPBF simulations remain challenging due to the complexity of the process and the substantial computational resources required. For maraging steel, for example, the occurrence of phase transformation promotes compressive stress that interferes in results and makes simulations inaccurate. This research aims to simulate a geometry with a circular inner channel and investigate distortion, volume fraction of martensite and equivalent stress results. Modeling was performed by varying phase transformation rate parameters to assess the impact of transformations on simulation outcomes. Results showed minimal impact of these parameters on distortions and equivalent stress. Equivalent stress results were compared with literature findings, while distortion results were validated against experimental data to validate the accuracy of the model. © 2024, The Authors. All rights reserved.

关键词： Phase transitions

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Pack aluminizing austenitic stainless steel thermal spray coatings

Pack aluminizing austenitic stainless steel thermal spray co...

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Materials Science and Technology 2019, MS and T 2019

作者： Varela, Edson D.B. D'Oliveira, Ana Sofia C.M. Post-graduation Program on Mechanical Engineering Universidade Federal do Paraná Curitiba Brazil Mechanical Engineering Department Universidade Federal do Paraná Curitiba Brazil

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Corporate Venture Capital and Sustainability

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Journal of Open Innovation: Technology, Market, and Complexity 2022年第3期8卷

作者： Döll, Luciano Mathias Ulloa, Micaela Ines Castillo Zammar, Alexandre Prado, Guilherme Francisco do Piekarski, Cassiano Moro Post-Graduation Program of Production Engineering Federal University Technology (UTFPR) Ponta Grossa 84016-210 Brazil Department of Informatics Universidade Estadual de Ponta Grossa (UEPG) Ponta Grossa 84030-900 Brazil Coordination of Technology in Mechanical Manufacturing Instituto Federal de Santa Catarina (IFPR) Florianópolis 88020-300 Brazil

Corporate Venture Capital (CVC) has been receiving increasingly more attention all over the world as a special way for accessing new ideas and innovative opportunities through minor-share investing in established companies. The purpose of CVC investments may either be purely financial or to pursue strategic goals. Organisations often seek to take actions that impact positively on sustainability by assembling related knowledge and technologies. These resources may come from invested startups through the use of a CVC programme. This research aims to measure and analyse the Corporate Venture Capital programmes of companies listed in the ISE B3 Corporate Sustainability Index. To this end, a three-step methodology was conducted. First, a systematic review of the literature took place, followed by a review of companies based on secondary sources such as their websites. Finally, a survey was developed and was opted to survey companies through their Investor Relationship (IR) public channels. Results show that 27 of the companies listed in the ISE B3 Index have CVC programmes that contemplate organizational initiatives besides investment. In this sense, one can claim that at least 70% of the ISE B3 Index companies are somehow involved in CVC operations. The results contribute to the literature on corporate venture capital and sustainability by showing that companies spend from 10% to 15% of their capital in sustainable businesses in order to remain competitive. © 2022 by the authors.

关键词： corporate venture capital open innovation startups sustainability

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