Materials

13 pages, 2521 KiB

Open AccessArticle

Impact of Pyrolysis Temperature on the Properties of Eucalyptus Wood-Derived Biochar

by Bruno Caio Chaves Fernandes, Kassio Ferreira Mendes, Ananias Francisco Dias Júnior, Vinícius Patrício da Silva Caldeira, Taliane Maria da Silva Teófilo, Tatiane Severo Silva, Vander Mendonça, Matheus de Freitas Souza and Daniel Valadão Silva

Materials 2020, 13(24), 5841; https://doi.org/10.3390/ma13245841 - 21 Dec 2020

Cited by 70 | Viewed by 5161

Abstract

Pyrolysis conditions directly influence biochar properties and, consequently, influence the potential use of biochar. In this study, we evaluated the effects of different pyrolysis temperatures (450, 550, 650, 750, 850, and 950 °C) on the hydrogen potential, electrical conductivity, ash content, yield, volatile [...] Read more.

Pyrolysis conditions directly influence biochar properties and, consequently, influence the potential use of biochar. In this study, we evaluated the effects of different pyrolysis temperatures (450, 550, 650, 750, 850, and 950 °C) on the hydrogen potential, electrical conductivity, ash content, yield, volatile matter content, elemental analysis, Fourier-transform infrared spectroscopy results, X-ray diffraction results, scanning electron microscopy results, specific surface area, and micropore volume of eucalyptus wood-derived biochar. The degree of linear association between pyrolysis temperatures and biochar properties was examined using the Pearson correlation coefficient. The results showed a positive correlation of the pyrolysis temperature with the hydrogen potential value, electrical conductivity, and elemental carbon. There was a negative correlation of the pyrolysis temperature with the yield, volatile matter content, elemental oxygen, elemental hydrogen, surface area, aromaticity, hydrophilicity, and polarity indexes. The Fourier-transform infrared spectroscopy data indicated an increase in aromaticity and a decrease in the polarity of high-temperature biochar. The increased pyrolysis temperature caused the loss of cellulose and crystalline mineral components, as indicated by X-ray diffraction analysis and scanning electron microscopy images. These results indicated that changing the pyrolysis temperature enables the production of biochar from the same raw material with a wide range of physicochemical properties, which allows its use in various types of agricultural and environmental activities. Full article

(This article belongs to the Special Issue Carbon Materials Applied for Biomass Conversion)

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12 pages, 4392 KiB

Open AccessArticle

Alpha Spectrometry of Radon Short-Lived Progeny in Drinking Water and Assessment of the Public Effective Dose: Results from the Cilento Area, Province of Salerno, Southern Italy

by Enver Faella, Simona Mancini, Michele Guida, Albina Cuomo and Domenico Guida

Materials 2020, 13(24), 5840; https://doi.org/10.3390/ma13245840 - 21 Dec 2020

Cited by 4 | Viewed by 2185

Abstract

Radon is a naturally occurring radioactive gas present in the hydrosphere, lithosphere and atmosphere abundantly. Its ionizing radiation provides the largest human internal exposure by inhalation and ingestion to natural sources, constituting a serious health hazard. The contribution to total exposure is mainly [...] Read more.

Radon is a naturally occurring radioactive gas present in the hydrosphere, lithosphere and atmosphere abundantly. Its ionizing radiation provides the largest human internal exposure by inhalation and ingestion to natural sources, constituting a serious health hazard. The contribution to total exposure is mainly due to inhalation, as ingestion by food or drinking water is typically very small. However, because of public health concerns, the contributions from all these sources are limited by regulations and remedial action should be taken in the event that the defined threshold values are overcome. In this paper, the first campaign of measurements to control the radon activity concentration in drinking water from public water supplies in the province of Salerno, south Italy, is described. The results represent a main reference for the area, as it was never investigated before. The purpose of this survey was to contribute to data compilation concerning the presence of radon-222 in groundwater in the Campania region and to determine the associated risk for different age groups. The maximum radon activity concentrations and the related total annual public effective dose turned out to be lower than the threshold values (100 Bq/l and 0.1 mSv/y, respectively) indicated by international guidelines and the national regulation, showing that the health risks for public consumption can be considered negligible. Full article

(This article belongs to the Special Issue Detectors for Assessment of Natural Radioactivity in Drinking Water: Materials and Method)

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16 pages, 4139 KiB

Open AccessArticle

Tensile and Shear Testing of Basalt Fiber Reinforced Polymer (BFRP) and Hybrid Basalt/Carbon Fiber Reinforced Polymer (HFRP) Bars

by Kostiantyn Protchenko, Fares Zayoud, Marek Urbański and Elżbieta Szmigiera

Materials 2020, 13(24), 5839; https://doi.org/10.3390/ma13245839 - 21 Dec 2020

Cited by 24 | Viewed by 4940

Abstract

The use of sustainable materials is a challenging issue for the construction industry; thus, Fiber Reinforced Polymers (FRP) is of interest to civil and structural engineers for their lightweight and high-strength properties. The paper describes the results of tensile and shear strength testing [...] Read more.

The use of sustainable materials is a challenging issue for the construction industry; thus, Fiber Reinforced Polymers (FRP) is of interest to civil and structural engineers for their lightweight and high-strength properties. The paper describes the results of tensile and shear strength testing of Basalt FRP (BFRP) and Hybrid FRP (HFRP) bars. The combination of carbon fibers and basalt fibers leads to a more cost-efficient alternative to Carbon FRP (CFRP) and a more sustainable alternative to BFRP. The bars were subjected to both tensile and shear strength testing in order to investigate their structural behavior and find a correlation between the results. The results of the tests done on BFRP and HFRP bars showed that the mechanical properties of BFRP bars were lower than for HFRP bars. The maximum tensile strength obtained for a BFRP bar with a diameter of 10 mm was equal to approximately 1150 MPa, whereas for HFRP bars with a diameter of 8 mm, it was higher, approximately 1280 MPa. Additionally, better results were obtained for HFRP bars during shear testing; the average maximum shear stress was equal to 214 MPa, which was approximately 22% higher than the average maximum shear stress obtained for BFRP bars. However, HFRP bars exhibited the lowest shear strain of 57% that of BFRP bars. This confirms the effectiveness of using HFRP bars as a replacement for less rigid BFRP bars. It is worth mentioning that after obtaining these results, shear testing can be performed instead of tensile testing for future studies, which is less complicated and takes less time to prepare than tensile testing. Full article

(This article belongs to the Special Issue Polymer in/on Concrete)

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14 pages, 3644 KiB

Open AccessArticle

Rapid Preparation of MWCNTs/Epoxy Resin Nanocomposites by Photoinduced Frontal Polymerization

by Guofeng Hu, Wanli Fu, Yumin Ma, Jianping Zhou, Hongbo Liang, Xinmei Kang and Xiaolin Qi

Materials 2020, 13(24), 5838; https://doi.org/10.3390/ma13245838 - 21 Dec 2020

Cited by 7 | Viewed by 2913

Abstract

Due to their excellent mechanical and thermal properties and medium resistance, epoxy/carbon nanotubes and nanocomposites have been widely used in many fields. However, the conventional thermosetting process is not only time- and energy-consuming, but also causes the agglomeration of nanofillers, which leads to [...] Read more.

Due to their excellent mechanical and thermal properties and medium resistance, epoxy/carbon nanotubes and nanocomposites have been widely used in many fields. However, the conventional thermosetting process is not only time- and energy-consuming, but also causes the agglomeration of nanofillers, which leads to unsatisfactory properties of the obtained composites. In this study, multi-walled carbon nanotubes (MWCNTs)/epoxy nanocomposites were prepared using UV photoinduced frontal polymerization (PIFP) in a rapid fashion. The addition of MWCNTs modified by a surface carboxylation reaction was found to enhance the impact strength and heat resistance of the epoxy matrix effectively. The experimental results indicate that with 0.4 wt % loading of modified MWCNTs, increases of 462.23% in the impact strength and 57.3 °C in the glass transition temperature T_g were achieved. A high-performance nanocomposite was prepared in only a few minutes using the PIFP approach. Considering its fast, energy-saving, and environmentally friendly production, the PIFP approach displays considerable potential in the field of the fast preparation, repair, and deep curing of nanocomposites and coatings. Full article

(This article belongs to the Special Issue Carbon Nanotube Based Composites: Processing, Properties, Modeling and Application)

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25 pages, 10982 KiB

Open AccessEditor’s ChoiceArticle

Numerical and Experimental Results on Charpy Tests for Blends Polypropylene + Polyamide + Ethylene Propylene Diene Monomer (PP + PA + EPDM)

by Cătălin Pîrvu, Andreea Elena Musteată, George Ghiocel Ojoc and Lorena Deleanu

Materials 2020, 13(24), 5837; https://doi.org/10.3390/ma13245837 - 21 Dec 2020

Cited by 1 | Viewed by 2611

Abstract

This paper presents results from numerical and experimental investigation on Charpy tests in order to point out failure mechanisms and to evaluate new polymeric blends PP + PA6 + EPDM. Charpy tests were done for initial velocity of the impactor of 0.96 m/s [...] Read more.

This paper presents results from numerical and experimental investigation on Charpy tests in order to point out failure mechanisms and to evaluate new polymeric blends PP + PA6 + EPDM. Charpy tests were done for initial velocity of the impactor of 0.96 m/s and its mass of 3.219 kg and these data were also introduced in the finite element model. The proposed model takes into account the system of four balls, including support and the ring of fixing the three balls and it has a finer discretization of the impact area to highlight the mechanisms of failure and their development in time. The constitutive models for four materials (polypropylene with 1% Kritilen, two blends PP + PA6 + EPDM and a blend PA6 + EPDM) were derived from tensile tests. Running simulations for each constitutive model of material makes possible to differentiate the destruction mechanisms according to the material introduced in the simulation, including the initiation and the development of the crack(s), based on equivalent plastic strain at break (EPS) for each material. The validation of the model and the simulation results were done qualitatively, analyzing the shape of broken surfaces and comparing them to SEM images and quantitatively by comparing the impact duration, energy absorbed by the sample, the value of maximum force during impact. The duration of the destruction of the specimen is longer than the actual one, explainable by the fact that the material model does not take into account the influence of the material deformation speed in Charpy test, the model being designed with the help of tests done at 0.016 m/s (1000 mm/min) (maximum strain rate for the tensile tests). Experimental results are encouraging for recommending the blends 20% PP + 42% PA6 + 28% EPDM and 60% PA6 + 40% EPDM as materials for impact protection at low velocity (1 m/s). Simulation results are closer to the experimental ones for the more brittle tested materials (with less content of PA6 and EPDM) and more distanced for the more ductile materials (with higher content of PA6 and EPDM). Full article

(This article belongs to the Special Issue Synthesis, Properties and Applications of Polymer Blends)

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18 pages, 7129 KiB

Open AccessArticle

Effect of Phenolic Resin on the Rheological and Morphological Characteristics of Styrene-Butadiene Rubber-Modified Asphalt

by Peifeng Cheng, Yiming Li and Zhanming Zhang

Materials 2020, 13(24), 5836; https://doi.org/10.3390/ma13245836 - 21 Dec 2020

Cited by 17 | Viewed by 2678

Abstract

To improve the thermal-aging stability and rheological performance of styrene–butadiene rubber (SBR)-modified asphalt, phenolic resin (PF) was introduced in the process of preparing SBR-modified asphalt by melt blending. The effect of PF and SBR on the high and low-temperature rheological performance of the [...] Read more.

To improve the thermal-aging stability and rheological performance of styrene–butadiene rubber (SBR)-modified asphalt, phenolic resin (PF) was introduced in the process of preparing SBR-modified asphalt by melt blending. The effect of PF and SBR on the high and low-temperature rheological performance of the asphalt binder before and after aging was evaluated by a temperature and frequency sweep using a dynamic shear rheometer (DSR). Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and fluorescence microscopy (FM) were used to further investigate the effect of PF and SBR on the thermal stability and morphological characteristics of the asphalt binder. The results showed that the addition of PF can enhance the high-temperature deformation resistance and short-term aging resistance of SBR-modified asphalt. Moreover, PF and SBR form an embedded network structure within the asphalt binder and alleviate the deterioration of the polymer during the aging process. Compared with SBR-modified asphalt, the chemical system of composite-modified asphalt is more stable, and it can remain stable with an aging time of less than 5 h. Full article

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18 pages, 7373 KiB

Open AccessEditor’s ChoiceArticle

Analysis and Modeling of the Micro-Cutting Process of Ti-6Al-4V Titanium Alloy with Single Abrasive Grain

by Łukasz Rypina, Dariusz Lipiński, Błażej Bałasz, Wojciech Kacalak and Tomasz Szatkiewicz

Materials 2020, 13(24), 5835; https://doi.org/10.3390/ma13245835 - 21 Dec 2020

Cited by 18 | Viewed by 2696

Abstract

Modeling of material displacements in the microcutting zone is complex due to the number and interdependence of factors affecting the results of the process. An important problem in the modeling process is the selection of the constitutive model and its parameters, which will [...] Read more.

Modeling of material displacements in the microcutting zone is complex due to the number and interdependence of factors affecting the results of the process. An important problem in the modeling process is the selection of the constitutive model and its parameters, which will correctly describe the properties of the material under the conditions of triaxial compression, which is characteristic for the areas of the contact zone of the blade and the processed material in abrasive machining processes. The aim of the work was to develop computer models (with the use of the finite element method) of the microcutting process with a single abrasive grain, which were verified with the results of experimental tests. The paper presents the methodology of modeling the processes of microcutting with abrasive grains, whose geometrical models were created based on optical scanning methods. Observations of the microcutting process were carried out with the use of a high-speed camera and an optical profilometer. This enabled a detailed observation of the chip formation process, as well as the analysis of the surface topography of microcutting traces. The results presented in the paper indicate the convergence of the results of the numerical and experimental simulations with regard to the geometric parameters describing the scratches formed in the microcutting process and the compliance of the chip-forming process. Thus, the correctness of the selection of the constitutive model (Johnson Cook equation) and its parameters was demonstrated, as well as the correctness of the applied methodology for creating a geometric model that allowed for a reflection of the geometrical parameters of the abrasive grains that coincided with the real objects, thanks to which it was possible to reflect in detail the phenomena occurring in the vicinity of the abrasive grain tip. Full article

(This article belongs to the Special Issue Advanced Design for Manufacturing Processes)

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16 pages, 6100 KiB

Open AccessArticle

Polycrystal Simulation of Texture-Induced Grain Coarsening during Severe Plastic Deformation

by Chi Zhang and Laszlo S. Toth

Materials 2020, 13(24), 5834; https://doi.org/10.3390/ma13245834 - 21 Dec 2020

Cited by 3 | Viewed by 2773

Abstract

During severe plastic deformation (SPD), there is usually extended grain fragmentation, associated with the formation of a crystallographic texture. The effect of texture evolution is, however, coarsening in grain size, as neighbor grains might coalesce into one grain by approaching the same ideal [...] Read more.

During severe plastic deformation (SPD), there is usually extended grain fragmentation, associated with the formation of a crystallographic texture. The effect of texture evolution is, however, coarsening in grain size, as neighbor grains might coalesce into one grain by approaching the same ideal orientation. This work investigates the texture-induced grain coarsening effect in face-centered cubic polycrystals during simple shear, in 3D topology. The 3D polycrystal aggregate was constructed using a cellular automaton model with periodic boundary conditions. The grains constituting the polycrystal were assigned to orientations, which were updated using the Taylor polycrystal plasticity approach. At the end of plastic straining, a grain detection procedure (similar to the one in electron backscatter diffraction, but in 3D) was applied to detect if the orientation difference between neighboring grains decreased below a small critical value (5°). Three types of initial textures were considered in the simulations: shear texture, random texture, and cube-type texture. The most affected case was the further shearing of an initially already shear texture: nearly 40% of the initial volume was concerned by the coalescence effect at a shear strain of 4. The coarsening was less in the initial random texture (~30%) and the smallest in the cube-type texture (~20%). The number of neighboring grains coalescing into one grain went up to 12. It is concluded that the texture-induced coarsening effect in SPD processing cannot be ignored and should be taken into account in the grain fragmentation process. Full article

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19 pages, 9852 KiB

Open AccessEditor’s ChoiceArticle

Effect of Natural Graphite Fineness on the Performance and Electrical Conductivity of Cement Paste Mixes for Self-Sensing Structures

by Ioanna Papanikolaou, Chrysoula Litina, Amir Zomorodian and Abir Al-Tabbaa

Materials 2020, 13(24), 5833; https://doi.org/10.3390/ma13245833 - 21 Dec 2020

Cited by 25 | Viewed by 4308

Abstract

Cementitious composites are the most widely used construction materials; however, their poor durability necessitates frequent monitoring and repairs. The emergence of self-sensing composites could reduce the need for costly and time-consuming structural inspections. Natural graphite, due to its low cost and wide availability, [...] Read more.

Cementitious composites are the most widely used construction materials; however, their poor durability necessitates frequent monitoring and repairs. The emergence of self-sensing composites could reduce the need for costly and time-consuming structural inspections. Natural graphite, due to its low cost and wide availability, is a promising additive to generate an electrically conductive network which could ultimately lead to a self-sensing mechanism. Despite several studies using natural graphite as a conductive additive, the effect of its fineness on the cementitious composite’s performance has not been explored. This study experimentally investigated the effect of three graphite products of varying fineness on the early age, mechanical, and electrical conductivity performance of cement pastes. The fluidity of the graphite-cement paste reduced significantly with increasing graphite fineness, and graphite did not affect the cement hydration. The finer the graphite, the lower the effect on the mechanical performance, as confirmed by compressive strength testing and micro-indentation. Electrical conductivity testing showed that the percolation threshold depended on the graphite fineness and was found at ~20 wt % for the fine and medium graphite, while it increased to 30–40 wt % for the coarse graphite. This is the first study that has investigated holistically the effect of graphite fineness on the performance of cement pastes and will pave the way for using this material as an additive for self-sensing structures. Full article

(This article belongs to the Special Issue Research and Development of Modified Building Materials)

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33 pages, 4960 KiB

Open AccessFeature PaperReview

Thermoplastic Composites and Their Promising Applications in Joining and Repair Composites Structures: A Review

by João Pedro Reis, Marcelo de Moura and Sylwester Samborski

Materials 2020, 13(24), 5832; https://doi.org/10.3390/ma13245832 - 21 Dec 2020

Cited by 77 | Viewed by 8225

Abstract

Thermoset fiber reinforced composites, widely used in current structural applications, have complex repair procedures and generates significant amounts of scrap due to its recycling difficulties, which does not comply with the most recent environmental restrictions. These disadvantages may be overcome by using a [...] Read more.

Thermoset fiber reinforced composites, widely used in current structural applications, have complex repair procedures and generates significant amounts of scrap due to its recycling difficulties, which does not comply with the most recent environmental restrictions. These disadvantages may be overcome by using a thermoplastic matrix phase, which is very suitable to be joined and repaired by local melting, making the composite material fully recyclable. This work presents a literature review on the joining methods applicable to thermoplastic based composites and their potential applications to be used as repair procedures in structural elements. The effectiveness of selected adhesive and fusion bonding techniques for several thermoplastic composite systems is evaluated by a comparative study based on the joints’ strength and toughness results available in the literature. This work focuses on the three most promising fusion bonding techniques: Resistance welding, induction welding, and ultrasonic welding. The advantages and drawbacks for each one of these processes are discussed, as well as their suitability for several specific structural applications. In addition, several discordant aspects for each welding technique are identified and the corresponding recommendations are discussed. A compilation of analytical models for the mechanisms of heat generation and transient heat transfer modelling is also presented for each fusion bonding process in order to promote their application in numerical modelling. Full article

(This article belongs to the Special Issue Advances in Fiber-Reinforced Polymer Composites)

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20 pages, 7427 KiB

Open AccessEditor’s ChoiceArticle

Low-Cost Sensors for Determining the Variation in Interior Moisture Content in Gypsum Composite Materials

by Daniel Ferrández, Carlos Morón, Pablo Saiz, Evangelina Atanes-Sánchez and Engerst Yedra

Materials 2020, 13(24), 5831; https://doi.org/10.3390/ma13245831 - 21 Dec 2020

Cited by 1 | Viewed by 2389

Abstract

Non-destructive testing can be used to determine some of the most relevant physical properties of building materials. In this work, two low-cost measuring devices were developed capable of determining the variation in real-time of the percentage of humidity that is produced in the [...] Read more.

Non-destructive testing can be used to determine some of the most relevant physical properties of building materials. In this work, two low-cost measuring devices were developed capable of determining the variation in real-time of the percentage of humidity that is produced in the construction of gypsum and plaster during the hardening process. For this, an Arduino resistive sensor and a capacitive sensor of our design were used. The results show how it is possible to determine the variations in mixing water content during the seven days of curing established by the UNE-EN 13279-2 standard as well relate to the mechanical resistance of the test specimens with the same percentage of humidity. Additionally, the study was completed with the determination of the formation of the dihydrate compound linked to this setting process in the test specimens by conducting X-ray diffraction and thermogravimetric analysis tests at different ages of the samples. Full article

(This article belongs to the Special Issue Mechanical Characterization of Gypsum Composites)

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17 pages, 7079 KiB

Open AccessReview

Enhancing Superconductivity of the Nonmagnetic Quasiskutterudites by Atomic Disorder

by Andrzej Ślebarski and Maciej M. Maśka

Materials 2020, 13(24), 5830; https://doi.org/10.3390/ma13245830 - 21 Dec 2020

Cited by 7 | Viewed by 2361

Abstract

We investigated the effect of enhancement of superconducting transition temperature

T_{c}

by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (La

_{3} M_{4}

Sn

_{13}

, Ca

_{3}

Rh

_{4}

Sn

_{13}

, Y

_{5}

Rh

_{6}

Sn

_{18}

[...] Read more.

We investigated the effect of enhancement of superconducting transition temperature

T_{c}

by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (La

_{3} M_{4}

Sn

_{13}

, Ca

_{3}

Rh

_{4}

Sn

_{13}

, Y

_{5}

Rh

_{6}

Sn

_{18}

, Lu

_{5}

Rh

_{6}

Sn

_{18}

;

M =

Co, Ru, Rh), where the atomic disorder is generated by various defects or doping. We have shown that the disorder on the coherence length scale

ξ

in these nonmagnetic quasiskutterudite superconductors additionally generates a non-homogeneous, high-temperature superconducting phase with

T_{c}^{⋆} > T_{c}

(dilute disorder scenario), while the strong fluctuations of stoichiometry due to increasing doping can rapidly increase the superconducting transition temperature of the sample even to the value of

T_{c}^{⋆} \sim 2 T_{c}

(dense disorder leading to strong inhomogeneity). This phenomenon seems to be characteristic of high-temperature superconductors and superconducting heavy fermions, and recently have received renewed attention. We experimentally documented the stronger lattice stiffening of the inhomogeneous superconducting phase

T_{c}^{⋆}

in respect to the bulk

T_{c}

one and proposed a model that explains the

T_{c}^{⋆} > T_{c}

behavior in the series of nonmagnetic skutterudite-related compounds. Full article

(This article belongs to the Special Issue Synthesis, Microstructure and Magnetic Properties of Intermetallic Compounds)

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14 pages, 3945 KiB

Open AccessArticle

Engineering of TeO₂-ZnO-BaO-Based Glasses for Mid-Infrared Transmitting Optics

by Kadathala Linganna, Jung-Hwan In, Seon Hoon Kim, Karam Han and Ju Hyeon Choi

Materials 2020, 13(24), 5829; https://doi.org/10.3390/ma13245829 - 21 Dec 2020

Cited by 16 | Viewed by 2699

Abstract

In this paper, the glass systems, TeO₂–ZnO–BaO (TZB), TeO₂–ZnO–BaO–Nb₂O₅ (TZB–Nb) and TeO₂–ZnO–BaO–MoO₃ (TZB–Mo), were fabricated by the traditional melt-quench protocol for use as mid-infrared (mid-IR) transmitting optical material. The effect of Nb₂ [...] Read more.

In this paper, the glass systems, TeO₂–ZnO–BaO (TZB), TeO₂–ZnO–BaO–Nb₂O₅ (TZB–Nb) and TeO₂–ZnO–BaO–MoO₃ (TZB–Mo), were fabricated by the traditional melt-quench protocol for use as mid-infrared (mid-IR) transmitting optical material. The effect of Nb₂O₅ and MoO₃ on the key glass material properties was studied through various techniques. From the Raman analysis, it was found that the structural modification was clear with the addition of both Nb₂O₅ and MoO₃ in the TZB system. The transmittance of studied glasses was measured and found that the optical window covered a region from 0.4 to 6 μm. The larger linear refractive index was obtained for the Nb₂O₅-doped TZB glass system than that of other studied systems. High glass transition temperature, low thermo-mechanical coefficient and high Knoop hardness were noticed in the Nb₂O₅-doped TZB glass system due to the increase in cross-linking density and rigidity in the tellurite network. The results suggest that the Nb₂O₅-doped TZB optical glasses could be a promising material for mid-infrared transmitting optics. Full article

(This article belongs to the Section Optical and Photonic Materials)

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9 pages, 6348 KiB

Open AccessArticle

Compressive Behavior of (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ Bulk Metallic Glass at Different Strain Rates

by Yu-Ting Wang, Xu-Dong Zu, Xiang-Kui Liu, Zheng-Xiang Huang, Peng-Gang Jin and Jian Kong

Materials 2020, 13(24), 5828; https://doi.org/10.3390/ma13245828 - 21 Dec 2020

Cited by 3 | Viewed by 1996

Abstract

The mechanical properties of (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ bulk metallic glass (BMG) were characterized under various strain rates by quasi-static and dynamic compressive tests. In the quasi-static compressive tests, the yield stress of (Cu_0.47Zr_0.45 [...] Read more.

The mechanical properties of (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ bulk metallic glass (BMG) were characterized under various strain rates by quasi-static and dynamic compressive tests. In the quasi-static compressive tests, the yield stress of (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ BMG increased from 1234 MPa to 1844 MPa when the strain rate was increased from 0.001 s⁻¹ to 0.01 s⁻¹, and the yield stress decreased to 1430 MPa at the strain rate of 0.1 s⁻¹. In the dynamic compressive tests, when the strain rate increased from 1550 s⁻¹ to 2990 s⁻¹, the yield stress of (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ BMG first decreased from 1508 MPa to 1404 MPa, and then increased to 1593 MPa. The fracture behaviors of (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ BMG were studied by using scanning electron microscopy to examine the fracture surface. Fracture occurred in the pure shear mode with strain rates below 2100 s⁻¹, whereas shear fracture and normal fracture occurred simultaneously under strain rates of 2650 s⁻¹ and 2990 s⁻¹. Full article

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19 pages, 2857 KiB

Open AccessArticle

The Effect of Steel and Polypropylene Fibers on the Properties of Horizontally Formed Concrete

by Adrian Chajec and Łukasz Sadowski

Materials 2020, 13(24), 5827; https://doi.org/10.3390/ma13245827 - 21 Dec 2020

Cited by 23 | Viewed by 2850

Abstract

The article presents a comparative analysis of the impact of the addition of steel and polypropylene fibers on the properties of the concrete mixes and hardened concrete used in the concrete floor industry. The behavior of concrete intended for floors is different from [...] Read more.

The article presents a comparative analysis of the impact of the addition of steel and polypropylene fibers on the properties of the concrete mixes and hardened concrete used in the concrete floor industry. The behavior of concrete intended for floors is different from conventional structural concrete because it is formed horizontally; until now, the effect of steel and polypropylene fibers on the properties of concrete formed horizontally has not yet been fully understood. Therefore, the aim of this article is to examine this issue and compare the behavior of concrete modified with steel and polypropylene fibers in concrete that is formed horizontally. The following properties of fresh concrete mixes were analyzed: consistency, the content of air-voids, and bulk density. Consequently, the following properties of hardened concrete were analyzed: compressive strength, bending tensile strength, and brittleness. It was confirmed that steel and polypropylene fibers have a different type of effect on the properties of fresh concrete mixes and hardened concrete. Finally, a combined economic and mechanical analysis was performed. Full article

(This article belongs to the Special Issue Fracture Toughness and Modelling of Concrete Composites and Other Brittle Materials)

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16 pages, 11600 KiB

Open AccessArticle

Effects of the Processing Parameters of Friction Stir Processing on the Microstructure, Hardness and Tribological Properties of SnSbCu Bearing Alloy

by Beata Leszczyńska-Madej, Marcin Madej, Joanna Hrabia-Wiśnios and Aleksandra Węglowska

Materials 2020, 13(24), 5826; https://doi.org/10.3390/ma13245826 - 21 Dec 2020

Cited by 8 | Viewed by 2203

Abstract

In the study, the friction stir processing (FSP) method was used to modify the surface layer of a tin-based bearing alloy. The modification was aimed at extending the service life of bearings by improving their tribological properties. The results of investigations of the [...] Read more.

In the study, the friction stir processing (FSP) method was used to modify the surface layer of a tin-based bearing alloy. The modification was aimed at extending the service life of bearings by improving their tribological properties. The results of investigations of the microstructure, hardness and tribological properties of the SnSbCu bearing alloy after FSP using various rotational speeds of the tool—280, 355, 450 and 560 RPM—and the constant traverse speed of 355 mm/min are presented. Particular attention was paid to the possibility of changing the morphology of the precipitates present in the alloy, and to the impact of this parameter on improvement of the tribological properties. The research carried out in this paper covered investigations of the microstructure using light and scanning electron microscopy (SEM) along with analysis of the chemical composition in micro-areas and Brinell hardness tests. Additionally, the sizes of the SnSb and CuSn precipitates present in the microstructure before and after the modification process were determined, as were the tribological properties under technically dry friction conditions and lubrication with TU 32 oil. It was proven that using friction stir processing favors refinement of the microstructure and improves the tribological properties of the analyzed alloy. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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16 pages, 6547 KiB

Open AccessArticle

Experimental Study on Influence of Curing Time on Strength Behavior of SLA-Printed Samples Loaded with Different Strain Rates

by Danuta Miedzińska, Roman Gieleta and Arkadiusz Popławski

Materials 2020, 13(24), 5825; https://doi.org/10.3390/ma13245825 - 21 Dec 2020

Cited by 32 | Viewed by 3555

Abstract

Stereolithography (SLA) is an additive manufacturing process based on the photocuring of resins with the use of UV light. The printed samples can be used not only for the visualization of structures, but also to develop elements of real constructions. In the study, [...] Read more.

Stereolithography (SLA) is an additive manufacturing process based on the photocuring of resins with the use of UV light. The printed samples can be used not only for the visualization of structures, but also to develop elements of real constructions. In the study, SLA-printed samples made of Formlabs’ Durable Resin were tested in static, dynamic, and Hopkinson’s bar tests. The recommended UV and heat curing time for this resin is 60 min for each process. For the tests, 5-minute and 30-min curing times were also considered. The obtained stress-strain curves were compared. The resin showed a difference in response to the strain rate effect and a curing time influence was noticed. For the static tests, the post-curing time had the greatest effect with a very small standard deviation. For the dynamic tests, similar dependencies were observed but with a greater standard deviation. The tests at very high strain rates were associated with a much greater level of difficulty in execution, recording, and signal analyzing, and the influence of the exposure time on the mechanical properties was not straightforward. The tested resin showed strengthening with increases in the strain rate as well as in the curing time. Full article

(This article belongs to the Special Issue Manufacturing and Mechanics of Materials)

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12 pages, 4435 KiB

Open AccessArticle

The Surface Condition of Ni-Cr after SiC Abrasive Blasting for Applications in Ceramic Restorations

by Weronika Czepułkowska-Pawlak, Emilia Wołowiec-Korecka and Leszek Klimek

Materials 2020, 13(24), 5824; https://doi.org/10.3390/ma13245824 - 21 Dec 2020

Cited by 4 | Viewed by 2208

Abstract

Abrasive blasting is a process widely used in dentistry. One of the uses is the development of metal surfaces for connections with ceramics in fixed prosthetic restorations. The purpose of this paper was to check how the rough surface profile (width, height, and [...] Read more.

Abrasive blasting is a process widely used in dentistry. One of the uses is the development of metal surfaces for connections with ceramics in fixed prosthetic restorations. The purpose of this paper was to check how the rough surface profile (width, height, and depth on unevenness) impacts the surface’s condition, like its wettability and percentage of stuck abrasives. The Ni-Cr alloy surface was abrasive blasted by silicon carbide with the various pressure parameters (0.2, 0.4, and 0.6 MPa) and abrasive particle sizes (50, 110, and 250 µm). Cleaned surfaces were examined for roughness, wettability, and percentage of stuck abrasive particles on the surface. The surface after abrasive blasting using 110 µm of abrasive size and 0.4 MPa pressure has the best wettability results. The width of unevenness may cause it. When the unevenness has too small or too large width and depth, the fluids may not cover the entire cavities because of locking the air. The surface condition of dental alloys directly affects metal–ceramic connection strength. The knowledge about the impact of the abrasive blasting parameters on the bond strength will allow one to create durable dental restorations. Full article

(This article belongs to the Special Issue Properties of Dental Restorative Materials)

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13 pages, 9730 KiB

Open AccessArticle

Shaping and Centering Ability, Cyclic Fatigue Resistance and Fractographic Analysis of Three Thermally Treated NiTi Endodontic Instrument Systems

by Saulius Drukteinis, Vytaute Peciuliene, Ruta Bendinskaite, Vilma Brukiene, Rasmute Maneliene and Vygandas Rutkunas

Materials 2020, 13(24), 5823; https://doi.org/10.3390/ma13245823 - 21 Dec 2020

Cited by 8 | Viewed by 2675

Abstract

The better understanding of the clinically important behavioral features of new instrument systems has an important significance for the clinical endodontics. This study aimed to investigate the shaping and centering ability as well as cyclic fatigue resistance of HyFlex CM (CM), HyFlex EDM [...] Read more.

The better understanding of the clinically important behavioral features of new instrument systems has an important significance for the clinical endodontics. This study aimed to investigate the shaping and centering ability as well as cyclic fatigue resistance of HyFlex CM (CM), HyFlex EDM (EDM) and EdgeFile (EF) thermally treated nickel–titanium (NiTi) endodontic instrument systems. Sixty curved root canals of the mesial roots of mandibular molars were randomly assigned into three groups (n = 20) and shaped using CM, EDM and EF files up to the size 40 and taper 04 of the instruments. µCT scanning of the specimens before and after preparation was performed and the morphometric 2D and 3D parameters were evaluated in the apical, middle and coronal thirds of root canals. In each group, 40.04 instruments (n = 20) were subjected to the cyclic fatigue resistance test in artificial root canals at 37 °C temperature until fractures occurred, and the number of cycles to failure (NCF) was calculated. The fractographic analysis was performed using a scanning electron microscope, evaluating topographic features and surface profiles of the separated instruments. The one-way analysis of variance with post hoc Tuckey’s test was used for statistical analysis of the data; the significance level was set at 5%. All systems prepared the comparable percentage of root canal surface with the similar magnitude of canal transportation in all root thirds (p > 0.05), but demonstrated significantly different resistance to cyclic fatigue (p < 0.05). The most resistant to fracture was EF, followed by EDM and CM. The length of the fractured fragments was not significantly different between the groups, and fractographic analysis by SEM detected the typical topographic features of separated thermally treated NiTi instrument surfaces. Full article

(This article belongs to the Special Issue Dental Materials in Endodontic and Post-endodontic Therapy)

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13 pages, 9283 KiB

Open AccessArticle

Dielectric Response and Structural Analysis of (A³⁺, Nb⁵⁺) Cosubstituted CaCu₃Ti₄O₁₂ Ceramics (A: Al and Bi)

by Hicham Mahfoz Kotb, Mohamad M. Ahmad, Adil Alshoaibi and Koji Yamada

Materials 2020, 13(24), 5822; https://doi.org/10.3390/ma13245822 - 21 Dec 2020

Cited by 11 | Viewed by 2729

Abstract

CaCu₃Ti_4-x((A_0.05Nb_0.05))_xO₁₂ ceramics (A: Al and Bi; x = 0, 0.3) were synthesized by high-energy mechanical ball milling and reactive sintering at 1050 °C in air. Rietveld refinement of XRD data revealed the [...] Read more.

CaCu₃Ti_4-x((A_0.05Nb_0.05))_xO₁₂ ceramics (A: Al and Bi; x = 0, 0.3) were synthesized by high-energy mechanical ball milling and reactive sintering at 1050 °C in air. Rietveld refinement of XRD data revealed the pure and (Al³⁺, Nb⁵⁺) cosubstituted ceramics contained a minor CuO secondary phase with a mole fraction of about 3.2% and 6.9%, respectively, along with a CaCu₃Ti₄O₁₂ (CCTO)-like cubic structure. In addition, (Bi³⁺, Nb⁵⁺) cosubstituted ceramics had a pyrochlore (Ca₂(Ti, Nb)₂O₇) secondary phase of about 18%. While the (Al³⁺, Nb⁵⁺) cosubstituted CCTO showed the highest relative permittivity (ε’ = 3.9 × 10⁴), pure CCTO showed the lowest dielectric loss (tanδ = 0.023) at 1 kHz and 300 K. Impedance-spectroscopy (IS) measurements showed an electrically heterogeneous structure for the studied ceramics, where a semiconducting grain was surrounded by highly resistive grain boundary. The giant relative permittivity of the ceramics was attributed to the Maxwell–Wagner polarization effect at the blocking grain boundaries and domain boundaries. The higher tanδ of the cosubstituted samples was correlated with their lower grain boundary’s resistivity, as confirmed by IS analysis. Modulus-spectrum analysis revealed two relaxation processes for the pure and (Bi³⁺, Nb⁵⁺) cosubstituted CCTO samples. Dissimilar behavior was observed for the (Al³⁺, Nb⁵⁺) cosubstituted CCTO, where three relaxation mechanisms were observed and attributed to the grain, domain-boundary, and grain-boundary responses. Full article

(This article belongs to the Special Issue Oxide-Based Materials for Energy Storage and Conversion)

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15 pages, 5832 KiB

Open AccessArticle

Mechanical Properties of Brass under Impact and Perforation Tests for a Wide Range of Temperatures: Experimental and Numerical Approach

by Maciej Klosak, Tomasz Jankowiak, Alexis Rusinek, Amine Bendarma, Piotr W. Sielicki and Tomasz Lodygowski

Materials 2020, 13(24), 5821; https://doi.org/10.3390/ma13245821 - 21 Dec 2020

Cited by 12 | Viewed by 2831

Abstract

The originally performed perforation experiments were extended by compression and tensile dynamic tests reported in this work in order to fully characterize the material tested. Then a numerical model was presented to carry out numerical simulations. The tested material was the common brass [...] Read more.

The originally performed perforation experiments were extended by compression and tensile dynamic tests reported in this work in order to fully characterize the material tested. Then a numerical model was presented to carry out numerical simulations. The tested material was the common brass alloy. The aim of this numerical study was to observe the behavior of the sample material and to define failure modes under dynamic conditions of impact loading in comparison with the experimental findings. The specimens were rectangular plates perforated within a large range of initial impact velocities V₀ from 40 to 120 m/s and in different initial temperatures T₀. The temperature range for experiments was T₀ = 293 K to 533 K, whereas the numerical analysis covered a wider range of temperatures reaching 923 K. The thermoelasto-viscoplastic behavior of brass alloy was described using the Johnson–Cook constitutive relation. The ductile damage initiation criterion was used with plastic equivalent strain. Both experimental and numerical studies allowed to conclude that the ballistic properties of the structure and the ballistic strength of the sheet plates change with the initial temperature. The results in terms of the ballistic curve V_R (residual velocity) versus V₀ (initial velocity) showed the temperature effect on the residual kinetic energy and thus on the energy absorbed by the plate. Concerning the failure pattern, the number of petals N was varied depending on the initial impact velocity V₀ and initial temperature T₀. Preliminary results with regard to temperature increase were recorded. They were obtained using an infrared high-speed camera and were subsequently compared with numerical results. Full article

(This article belongs to the Special Issue Dynamic Behaviour of Metallic Materials)

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4 pages, 169 KiB

Open AccessEditorial

Special Issue “Advanced Composites: From Materials Characterization to Structural Application”

by Viktor Gribniak

Materials 2020, 13(24), 5820; https://doi.org/10.3390/ma13245820 - 21 Dec 2020

Cited by 12 | Viewed by 1973

Abstract

The modern industry allows synthesizing and manufacturing composite materials with a wide range of mechanical properties applicable in medicine, aviation, automotive industry, etc [...] Full article

(This article belongs to the Special Issue Advanced Composites: From Materials Characterization to Structural Application)

22 pages, 10669 KiB

Open AccessArticle

Numerical and Metallurgical Analysis of Laser Welded, Sealed Lap Joints of S355J2 and 316L Steels under Different Configurations

by Hubert Danielewski, Andrzej Skrzypczyk, Marek Hebda, Szymon Tofil, Grzegorz Witkowski, Piotr Długosz and Rastislav Nigrovič

Materials 2020, 13(24), 5819; https://doi.org/10.3390/ma13245819 - 20 Dec 2020

Cited by 8 | Viewed by 3294

Abstract

This paper presents the results of laser welding of dissimilar joints, where low-carbon and stainless steels were welded inthe lap joint configuration. Performed welding of austenitic and ferritic-pearlitic steels included a sealed joint, where only partial penetration of lower material was obtained.The authors [...] Read more.

This paper presents the results of laser welding of dissimilar joints, where low-carbon and stainless steels were welded inthe lap joint configuration. Performed welding of austenitic and ferritic-pearlitic steels included a sealed joint, where only partial penetration of lower material was obtained.The authors presented acomparative study of the joints under different configurations. The welding parameters for the assumed penetration were estimated via anumericalsimulation. Moreover, a stress–strain analysis was performed based on theestablished model. Numerical analysis showed significant differences in joint properties, therefore, further study was conducted. Investigation of the fusion mechanism in the obtained joints wascarried out using electron dispersive spectroscopy (EDS) and metallurgical analysis. The study of the lap joint under different configurations showed considerable dissimilarities in stress–strain distribution and relevant differences in the fusion zone structure. The results showed advantages of using stainless steel as the upper material of a microstructure, and uniform chemical element distribution and stress analysis is considered. Full article

(This article belongs to the Special Issue Recent Developments in Non-conventional Welding of Materials)

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14 pages, 4479 KiB

Open AccessArticle

The Friction-Induced Vibration of Water-Lubricated Rubber Bearings during the Shutdown Process

by Guangwu Zhou, Peng Li, Daxin Liao, Yuhao Zhang and Ping Zhong

Materials 2020, 13(24), 5818; https://doi.org/10.3390/ma13245818 - 20 Dec 2020

Cited by 15 | Viewed by 2953

Abstract

The vibration noise generated by water-lubricated rubber bearings (WLRBs) seriously reduces the concealment of a ship’s navigation. The purpose of this study was to obtain the relationships between friction-induced vibration and the friction coefficient, specific pressure, temperature, and stiffness of the bearing support [...] Read more.

The vibration noise generated by water-lubricated rubber bearings (WLRBs) seriously reduces the concealment of a ship’s navigation. The purpose of this study was to obtain the relationships between friction-induced vibration and the friction coefficient, specific pressure, temperature, and stiffness of the bearing support during the shutdown process of WLRBs. Using transient dynamic analysis (Abaqus/Standard), the shutdown process of the bearing system was simulated by setting a friction coefficient curve, and with the fast Fourier transform (FFT), the data in the time domain were then converted to the frequency domain. In addition, an orthogonal table was applied to select the best level for each factor. The results show that proportionally increasing the friction coefficient and specific pressure caused higher vibrations, and the effect of the specific pressure on vibration is more prominent than that of the friction coefficient. Higher temperatures led to an increase in the peak frequency of noise (squeal) and the virtual value of acceleration. Increasing the stiffness of the bearing support decreased the higher-frequency squeal but dramatically increased the lower-frequency chatter. The results of the study are of guiding significance for the improvement of research methods and the optimization of the materials and structures of WLRBs. Full article

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15 pages, 10030 KiB

Open AccessArticle

Effect of Hot Deformation on Phase Transformation Kinetics in Isothermally Annealed 3Mn-1.6Al Steel

by Adam Skowronek, Mateusz Morawiec, Aleksandra Kozłowska and Wojciech Pakieła

Materials 2020, 13(24), 5817; https://doi.org/10.3390/ma13245817 - 20 Dec 2020

Cited by 3 | Viewed by 2314

Abstract

The kinetics of ferritic transformation and the corresponding microstructural evolution in 0.17C-3.1Mn-1.6Al-0.04Nb-0.22Mo-0.22Si medium-Mn steel during isothermal annealing was investigated in dilatometric studies. The material was subjected to thermal and thermo-mechanical treatments aimed at obtaining, by the austenite → ferrite transformation, a sufficient fraction [...] Read more.

The kinetics of ferritic transformation and the corresponding microstructural evolution in 0.17C-3.1Mn-1.6Al-0.04Nb-0.22Mo-0.22Si medium-Mn steel during isothermal annealing was investigated in dilatometric studies. The material was subjected to thermal and thermo-mechanical treatments aimed at obtaining, by the austenite → ferrite transformation, a sufficient fraction of ferrite to stabilize the retained austenite by C and eventual Mn partitioning. The samples were isothermally held for 5 h in a temperature range from 600 to 750 °C to simulate simplified temperature conditions of an industrial coiling process following hot rolling. Some of the samples were plastically deformed at a temperature of 900 °C before isothermal holding in order to study the effect of hot deformation on the kinetics of phase transformations. After the dilatometric investigations the material was subjected to light and scanning electron microscopy to reveal relationships between the holding temperature, deformation and microstructure evolution. Hardness tests were performed to assess the mechanical behavior. A significant effect of manganese in slowing down diffusional transformations during the cooling of steel was found. The influence of austenite deformation on the kinetics of austenite to ferrite transformation was noted. The plastically deformed samples showed an accelerated start of ferritic transformation and the extension of its range. During dilatometric tests, low-range dynamic ferritic transformation was recorded, which was also confirmed by the microscopic tests. Full article

(This article belongs to the Special Issue Effects of Temperature and Strain Rate on Steel Strengthening)

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18 pages, 9559 KiB

Open AccessArticle

Operational Modal Analysis, Testing and Modelling of Prefabricated Steel Modules with Different LSF Composite Walls

by Maria Rashidi, Pejman Sharafi, Mohammad Alembagheri, Ali Bigdeli and Bijan Samali

Materials 2020, 13(24), 5816; https://doi.org/10.3390/ma13245816 - 20 Dec 2020

Cited by 14 | Viewed by 3324

Abstract

The modal properties of modular structures, such as their natural frequencies, damping ratios and mode shapes, are different than those of conventional structures, mainly due to different structural systems being used for assembling prefabricated modular units onsite. To study the dynamic characteristics of [...] Read more.

The modal properties of modular structures, such as their natural frequencies, damping ratios and mode shapes, are different than those of conventional structures, mainly due to different structural systems being used for assembling prefabricated modular units onsite. To study the dynamic characteristics of modular systems and define a dynamic model, both the modal properties of the individual units and their connections need to be considered. This study is focused on the former aspect. A full-scale prefabricated volumetric steel module was experimentally tested using operational modal analysis technique under pure ambient vibrations and randomly generated artificial hammer impacts. It was tested in different situations: [a] bare (frame only) condition, and [b] infilled condition with different configurations of gypsum and cement-boards light-steel framed composite walls. The coupled module-wall system was instrumented with sensitive accelerometers, and its pure and free vibration responses were synchronously recorded through a data acquisition system. The main dynamic characteristics of the module were extracted using output-only algorithms, and the effects of the presence of infill wall panels and their material are discussed. Then, the module’s numerical micromodel for bare and infilled states is generated and calibrated against experimental results. Finally, an equivalent linear strut macro-model is proposed based on the calibrated data. The contribution of this study is assessing the effects of different infill wall materials on the dynamic characteristics of modular steel units, and proposing simple models for macro-analysis of infilled module assemblies. Full article

(This article belongs to the Special Issue Emerging Trends in Structural Health Monitoring)

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28 pages, 471 KiB

Open AccessReview

EMG Characterization and Processing in Production Engineering

by Manuel del Olmo and Rosario Domingo

Materials 2020, 13(24), 5815; https://doi.org/10.3390/ma13245815 - 20 Dec 2020

Cited by 20 | Viewed by 5241

Abstract

Electromyography (EMG) signals are biomedical signals that measure electrical currents generated during muscle contraction. These signals are strongly influenced by physiological and anatomical characteristics of the muscles and represent the neuromuscular activities of the human body. The evolution of EMG analysis and acquisition [...] Read more.

Electromyography (EMG) signals are biomedical signals that measure electrical currents generated during muscle contraction. These signals are strongly influenced by physiological and anatomical characteristics of the muscles and represent the neuromuscular activities of the human body. The evolution of EMG analysis and acquisition techniques makes this technology more reliable for production engineering applications, overcoming some of its inherent issues. Taking as an example, the fatigue monitoring of workers as well as enriched human–machine interaction (HMI) systems used in collaborative tasks are now possible with this technology. The main objective of this research is to evaluate the current implementation of EMG technology within production engineering, its weaknesses, opportunities, and synergies with other technologies, with the aim of developing more natural and efficient HMI systems that could improve the safety and productivity within production environments. Full article

(This article belongs to the Special Issue Special Issue of Manufacturing Engineering Society-2020 (SIMES-2020))

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14 pages, 2273 KiB

Open AccessArticle

The Influence of HEMC on Cement and Cement-Lime Composites Setting Processes

by Edyta Spychał and Przemysław Czapik

Materials 2020, 13(24), 5814; https://doi.org/10.3390/ma13245814 - 20 Dec 2020

Cited by 8 | Viewed by 2686

Abstract

In this article, the effect of hydroxyethyl methyl cellulose (HEMC), which is a polymeric viscosity modifying admixture on the mineral based composites setting processes, was studied. Previous studies available in the literature included the evaluation of the influence of this admixture on the [...] Read more.

In this article, the effect of hydroxyethyl methyl cellulose (HEMC), which is a polymeric viscosity modifying admixture on the mineral based composites setting processes, was studied. Previous studies available in the literature included the evaluation of the influence of this admixture on the hydration processes of cement or lime pastes. In this paper, the analysis of this issue was extended to include cement-lime composites. The composition of the pastes and mortars differed in the type of binder (the tests were carried out on cement-based and cement-lime-based materials, in which the cement was replaced in 50% with hydrated lime), as well as the amount and viscosity of the admixture. The study of mortars setting processes and hardening processes using the ultrasonic method was supplemented in the work with calorimetric measurements and phases analysis by the X-ray diffraction method. Finally, it was found that the HEMC reduces the rate of a hydration reaction in cement and cement-lime pastes. The amount of admixture used has a greater influence on the changes taking place during the setting process than the admixture viscosity or the type of binder. Full article

(This article belongs to the Special Issue Research and Development of Modified Building Materials)

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19 pages, 4318 KiB

Open AccessArticle

Evaluation of the In Vitro Cytotoxic Activity of Caffeic Acid Derivatives and Liposomal Formulation against Pancreatic Cancer Cell Lines

by Magdalena Zaremba-Czogalla, Anna Jaromin, Katarzyna Sidoryk, Agnieszka Zagórska, Marcin Cybulski and Jerzy Gubernator

Materials 2020, 13(24), 5813; https://doi.org/10.3390/ma13245813 - 19 Dec 2020

Cited by 20 | Viewed by 3500

Abstract

Pancreatic cancer belongs to the most aggressive group of cancers, with very poor prognosis. Therefore, there is an important need to find more potent drugs that could deliver an improved therapeutic approach. In the current study we searched for selective and effective caffeic [...] Read more.

Pancreatic cancer belongs to the most aggressive group of cancers, with very poor prognosis. Therefore, there is an important need to find more potent drugs that could deliver an improved therapeutic approach. In the current study we searched for selective and effective caffeic acid derivatives. For this purpose, we analyzed twelve compounds and evaluated their in vitro cytotoxic activity against two human pancreatic cancer cell lines, along with a control, normal fibroblast cell line, by the classic MTT assay. Six out of twelve tested caffeic acid derivatives showed a desirable effect. To improve the therapeutic efficacy of such active compounds, we developed a formulation where caffeic acid derivative (7) was encapsulated into liposomes composed of soybean phosphatidylcholine and DSPE-PEG₂₀₀₀. Subsequently, we analyzed the properties of this formulation in terms of basic physical parameters (such as size, zeta potential, stability at 4 °C and morphology), hemolytic and cytotoxic activity and cellular uptake. Overall, the liposomal formulation was found to be stable, non-hemolytic and had activity against pancreatic cancer cells (IC₅₀ 19.44 µM and 24.3 µM, towards AsPC1 and BxPC3 cells, respectively) with less toxicity against normal fibroblasts. This could represent a promising alternative to currently available treatment options. Full article

(This article belongs to the Special Issue Advanced Biomedical Hydrogels and Bioactive Materials in Medicinal Chemistry)

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20 pages, 4050 KiB

Open AccessArticle

Ecological Cutting Fluids

by Marian Włodzimierz Sułek, Anna Bąk-Sowińska and Jacek Przepiórka

Materials 2020, 13(24), 5812; https://doi.org/10.3390/ma13245812 - 19 Dec 2020

Cited by 4 | Viewed by 2588

Abstract

This study deals with metalworking fluids (MWFs). According to DIN 51385, depending on their base, the fluids are divided into oil and water fluids. The oil bases include, among others, mineral, synthetic, vegetable and paraffin oils. This division does not comprise surfactant solutions [...] Read more.

This study deals with metalworking fluids (MWFs). According to DIN 51385, depending on their base, the fluids are divided into oil and water fluids. The oil bases include, among others, mineral, synthetic, vegetable and paraffin oils. This division does not comprise surfactant solutions which can be successfully used in metalworking. Due to the fact that this type of fluid was not qualified, a new type of lubricant based on the aqueous solutions of surfactants has been proposed. Two new notions have been introduced: surfactant working fluids (SWFs) for working fluids and surfactant lubricants (SLs) for all kinds of lubricants as a broader term. The effect of the physicochemical properties of aqueous solutions of sodium lauroyl sarcosinate (SLS), also known as sodium N-dodecanoyl-N-methyl glycinate, on tribological properties determined using a four-ball machine (Tester T-02) (Łukasiewicz Research Network—The Institute for Sustainable Technologies, Radom, Poland) was analyzed. On the basis of aqueous SLS solutions a composition of working fluids was developed and their functional properties were verified by means of tribological and stand tests as well as during operation. The test results obtained clearly indicate that functional properties of 2% solutions of sodium lauroyl sarcosinate with a foam inhibitor (0.05%) and a biocide (0.1%) are comparable to those of a quality commercial hydraulic fluid. Full article

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