bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Band Gap Characteristics of Two-Dimensional Periodic Double-Wall Grillages
Authors: Wang Chuanlong , Yao Xiongliang , Wu Guoxun , Tang Li
Published: December 2021

In this article, the wave finite element method (WFEM) is used to calculate the band gap characteristics of two-dimensional (2D) periodic double-wall grillages (DwGs), which are verified by the grillage model vibration measurement experiment and finite element calculation. To obtain the band gap characteristics of periodic DwGs, the finite element calculation model is established according to the lattice and energy band theory and the characteristic equation of the periodic unit cell under the given wave vector condition is solved based on Bloch theorem. Then, the frequency transfer functions of finite-length manufactured and finite element models are obtained to verify the band gap characteristics of periodic DwGs. Finally, the effects of material parameters and structural forms on band gap characteristics and transfer functions are analyzed, which can provide a reference for engineering structure vibration and noise reduction design.
Anisotropy of Mechanical Properties and Residual Stress in Additively Manufactured 316L Specimens
Authors: Fedorenko Alexey , Fedulov Boris , Kuzminova Yulia , Evlashin Stanislav , Staroverov Oleg , Tretyakov Mikhail , Lomakin Evgeny , Akhatov Iskander
Published: December 2021

In the presented study, LPBF 316L stainless steel tensile specimens were manufactured in three different orientations for the analysis of anisotropy. The first set of specimens was built vertically on the build platform, and two other sets were oriented horizontally perpendicular to each other. Tensile test results show that mean Young’s modulus of vertically built specimens is significantly less then horizontal ones (158.7 GPa versus 198 GPa), as well as yield strength and elongation. A role of residual stress in a deviation of tensile loading diagrams is investigated as a possible explanation. Simulation of the build process on the basis of ABAQUS FEA software was used to predict residual stress in 316L cylindrical specimens. Virtual tensile test results show that residual stress affects the initial stage of the loading curve with a tendency to reduce apparent Young’s modulus, measured according to standard mechanical test methods.
Investigation on the Thermodynamic Stability of Nanocrystalline W-Based Alloys: A Combined Theoretical and Experimental Approach
Authors: Torre Francesco , Mingazzini Claudio , Mirabile Gattia Daniele , Huminiuc Teodor , Rinaldi Antonio , Polcar Tomas , Delogu Francesco , Locci Antonio Mario
Published: December 2021

The stability of nanostructured metal alloys is currently being extensively investigated, and several mathematical models have been developed to describe the thermodynamics of these systems. However, model capability in terms of thermal stability predictions strongly relies on grain boundary-related parameters that are difficult to measure or estimate accurately. To overcome this limitation, a novel theoretical approach is proposed and adopted in this work to identify W-based nanocrystalline alloys which are potentially able to show thermodynamic stability. A comparison between model outcomes and experimental findings is reported for two selected alloys, namely W-Ag and W-Al. Experimental results clearly highlight that W-Ag mixtures retain a segregated structure on relatively coarse length scales even after prolonged mechanical treatments. Moreover, annealing at moderate temperatures readily induces demixing of the constituent elements. In contrast, homogeneous nanostructured W-Al solid solutions are obtained by ball milling of elemental powders. These alloys show enhanced thermal stability with respect to pure W even at high homologous temperatures. Experimental evidences agree with model predictions for both the investigated systems.
Local Behavior of Lap-Spliced Deformed Rebars in Reinforced Concrete Beams
Authors: Gillani Agha Syed Muhammad , Lee Seung-Geon , Lee Soo-Hyung , Lee Hyerin , Hong Kee-Jeung
Published: December 2021

Twelve full-scale reinforced concrete beams with two tension lap splices were constructed and tested under a four-point loading test. Half of these beams had shorter lap splices than that recommended by American Concrete Institute Building Code ACI 318-19; they failed by bond loss between steel and concrete at the lap splice region before rebar yielding. The other half of the beams were designed with a lap splice length slightly exceeding that recommended by ACI 318-19; they failed by rebar yielding and exhibited a ductile behavior. Several strain gauges were attached to the longitudinal bars in the lap splice region to study the local behavior of deformed bars during loading. The strain in a rebar was maximum at the loaded end of the lap splice and progressively decreased toward the unloaded end because the rebar at this end could not sustain any load. Stress flow discontinuity occurred at the loaded end and caused stress concentration. The effect of this concentration was investigated based on test results. The comparison of bond strengths calculated by existing equations and those of tested specimens indicated that the results agreed well.
Study of Thermal, Mechanical and Barrier Properties of Biodegradable PLA/PBAT Films with Highly Oriented MMT
Authors: Ludwiczak Joanna , Frąckowiak Stanisław , Leluk Karol
Published: December 2021

In order to improve the properties of biodegradable polylactide (PLA), mixtures with polybutylene adipate-co-terephthalate (PBAT) were prepared. PLA is a bio-based and renewable biodegradable material, made from starch. PBAT is a biodegradable polyester for compostable film. In order to improve the composite properties, two types of additives were implemented via melt mixing, a chain extender (CE) and montmorillonite (MMT). CE was used as an interfacial modifier to enhance the adhesion between components. Montmorillonite is a widely studied clay added to polymer nanocomposites. Due to the lamellar structure, it improves the barrier properties of materials. PLA/PBAT films were oriented in the extrusion process and the amounts of filler introduced into the PLA/PBAT nanocomposites were 1.0, 3.0, and 5.0%. The improvement in the PLA barrier properties by the addition of PBAT and 5% of MMT was confirmed as the oxygen permeability decreased almost by a factor of 3. The addition of the biodegradable polymer, chain extender, montmorillonite, and the implemented orientation process resulted in a decrease in composite viscosity and an increase in the PLA crystallinity percentage (up to 25%), and the wettability tests confirmed the synergic behavior of the selected polymer blend.
Enzymatically Crosslinked In Situ Synthesized Silk/Gelatin/Calcium Phosphate Hydrogels for Drug Delivery
Authors: Grava Andra , Egle Karina , Dubnika Arita
Published: December 2021

Our research focuses on combining the valuable properties of silk fibroin (SF) and calcium phosphate (CaP). SF is a natural protein with an easily modifiable structure; CaP is a mineral found in the human body. Most of the new age biocomposites lack interaction between organic/inorganic phase, thus SF/CaP composite could not only mimic the natural bone, but could also be used to make drug delivery systems as well, which can ensure both healing and regeneration. CaP was synthesized in situ in SF at different pH values, and then crosslinked with gelatin (G), horseradish peroxide (HRP), and hydrogen peroxide (H2O2). In addition, dexamethasone phosphate (DEX) was incorporated in the hydrogel and drug delivery kinetics was studied. Hydrogel made at pH 10.0 was found to have the highest gel fraction 110.24%, swelling degree 956.32%, and sustained drug delivery for 72 h. The highest cell viability was observed for the hydrogel, which contained brushite (pH 6)—512.43%.
Effect of a Compound Energy Field with Temperature and Ultrasonic Vibration on the Material Properties and Bending Process of TC2 Titanium Alloy
Authors: Gao Tiejun , Wang Kaifeng , Ling Zhiyuan , Wang Zhongjin
Published: December 2021

Due to the low formability and forming quality of titanium alloy, the forming process of a compound energy field (CEF) with temperature and ultrasonic vibration was proposed. Tensile tests were carried out to investigate the effect of the CEF on the true stress–strain curve, yield strength, elastic modulus, and other mechanical properties of the TC2 titanium alloy. Bending tests assisted by CEF were also performed to investigate the effect of different parameters of the CEF on bending force, spring-back, bending fillet radius, and microstructure of TC2 titanium. The results demonstrate that compared to the process under a single-temperature field, the CEF can reduce yield strength, elastic modulus, bending force, bending fillet, and the spring-back angle, which shows that the CEF can further increase the high-temperature softening effect of TC2 titanium. Furthermore, this effect becomes more remarkable when ultrasonic vibration energy increases. As a result, the formability of titanium alloy can be improved.
Buckling Analysis of Functionally Graded Sandwich Plates under Both Mechanical and Thermal Loads
Authors: Li Dongdong , Zhu He , Gong Xiaojing
Published: December 2021

This paper presents an analytical solution for the thermomechanical buckling of functionally graded material (FGM) sandwich plates. The solution is obtained using a four-variable equivalent-single-layer (ESL) plate theory. Two types of sandwich plates are included: one with FGM facesheets and homogeneous core, and vice versa for the other. The governing equations are derived based on the principle of minimum total potential energy. For simply supported boundary conditions, these equations are solved via the Navier method. The results on critical buckling load and temperature increment of simply supported FGM sandwich plates are compared with the available solutions in the literature. Several results are presented considering various material and geometrical parameters as well as their effect on the thermomechanical buckling response of FGM sandwich plates. The relationship between the mechanical load and the temperature increment for uniform/linear temperature rise of FGM sandwich plates under combined mechanical and thermal loads is studied.
On the Calibration of a Numerical Model for Concrete-to-Concrete Interface
Authors: Dudziak Sławomir , Jackiewicz-Rek Wioletta , Kozyra Zofia
Published: December 2021

The study was devoted to the numerical modelling of concrete-to-concrete interfaces. Such an interface can be found in many modern composite structures, so proper characterisation of its behaviour is of great importance. A strategy for calibration of a model based on cohesive finite elements and the elastic-damage traction–separation constitutive law available by default in the Abaqus code was proposed. Moreover, the default interface material model was enhanced with the user-field-variables subroutine to include a real strength envelope for such interfaces. Afterwards, the modelling approach was validated with numerical simulation of the most popular tests for determining the strength characteristics of concrete-to-concrete interfaces: three-point bending beam with a notch, splitting bi-material cubic specimens, and slant-shear tests. The results of own pilot studies were used as well as those reported by other researchers. The performed simulations proved the accuracy of the proposed modelling strategy (the mean ratio of ultimate forces obtained with numerical models and from experiments was equal to 1.01). Furthermore, the presented examples allowed us to better understand the basic test methods for concrete interfaces and the observed mechanisms of failure during them.
Friction and Wear Performance Evaluation of Bio-Lubricants and DLC Coatings on Cam/Tappet Interface of Internal Combustion Engines
Authors: Zahid Rehan , Bhutta Muhammad Usman , Mufti Riaz Ahmad , Abdullah Muhammad Usman , Masjuki Haji Hassan , Varman Mahendra , Kalam Muhammad Abul , Ali Mian Ashfaq , Aslam Jawad , Akhtar Khalid
Published: December 2021

The environmental concerns associated with artificially formulated engine oils have forced a shift towards bio-based lubricants. The deposition of hard coatings on engine components and migrating to environmentally friendly green lubricants can help in this regard. Chemically modified forms of vegetable oils, with better low-temperature characteristics and enhanced thermo-oxidative stability, are suitable substitutes to conventional lubricant base oils. The research presented in this manuscript was undertaken to experimentally investigate the wear and friction performance of a possible future generation of an environmentally friendly bio-based lubricant as a potential replacement for conventional engine lubricants. In order to quantify the tribological benefits which can be gained by the deposition of DLC coatings, (an (a-C:H) hydrogenated DLC coating and an (a-C:H:W) tungsten-doped DLC coating) were applied on the cam/tappet interface of a direct acting valve train assembly of an internal combustion engine. The tribological correlation between DLC-coated engine components, lubricant base oils and lubricant additives have been thoroughly investigated in this study using actual engine operating conditions. Two additive-free base oils (polyalphaolefines (PAO) and chemically-modified palm oil (TMP)) and two multi-additive-containing lubricants were used in this investigation. Real-time drive torque was measured to determine the friction force, detailed post-test analysis was performed, which involved the use of a specialized jig to measure camlobe wear. An optical profilometer was used to measure the wear on the tappet, high-resolution scanning electron microscopy was employed to study the wear mechanism and energy-dispersive X-ray spectroscopy was performed on the tested samples to qualitatively access the degradation of the coating. When using additive-free TMP, a low friction coefficient was observed for the cam/tappet interface. The presence of additives further improved the friction characteristics of TMP, resulting in reduced average friction torque values. A tremendous enhancement in wear performance was recorded with a-C:H-coated parts and the coating was able to withstand the test conditions with little or no delamination.
A New Stripline-Based Atmospheric Pressure Microwave Plasma Sheet Source Designed for Surface Modification of Materials
Authors: Nowakowska Helena , Czylkowski Dariusz , Hrycak Bartosz , Jasiński Mariusz
Published: December 2021

A new type of microwave plasma source is presented in which plasma at atmospheric pressure is generated inside a quartz rectangular flat box placed in a stripline supplied by a 2.45 GHz coaxial line. The plasma has a sheet shape and is designed for surface modification. Electric field and power flux distributions, tuning characteristics, and power characteristics (ratios of radiated, absorbed, and entering power) are numerically studied for three configurations: open, semi-closed, and closed. The calculations show that near-zero radiation reduction is possible only for the closed configuration, while the ratio of radiated power to entering power is always greater than 30% for the other configurations. The moving plunger is not sufficient for the ratio of reflected to incident power to fall below 20% for both the closed and open configurations. This is possible for the semi-closed configuration, but then the radiated power is the highest. The experiment shows that for the same entering power, the plasma volume is largest for the closed configuration and smallest for the open configuration, which we attribute to the difference in radiated power. The plasma generated using the closed stripline configuration has a larger volume than plasma generated using the rectangular waveguide.
High-Temperature Effect on the Tensile Mechanical Properties of Unidirectional Carbon Fiber-Reinforced Polymer Plates
Authors: Zhang Yongqiang , Li Yue , Zhang Jialei , Pan Jinwu , Zhang Li , Tan Fuli , Wei Hongjian , Zhang Wei
Published: December 2021

Carbon fiber-reinforced polymer (CFRP) has the advantages of a high strength-weight ratio and excellent fatigue resistance and has been widely used in aerospace, automotive, civil infrastructure, and other fields. The properties of CFRP materials under high temperatures are a key design issue. This paper presents the quasi-static tensile mechanical properties of unidirectional CFRP plates at temperatures ranging from 20 to 600 °C experimentally. The laser displacement transducer was adopted to capture the in situ displacement of the tested specimen. The results showed that the tensile strength of the CFRP specimen was affected by the high-temperature effect significantly, which dropped 68% and 16% for the 200 and 600 °C, respectively, compared with that of the room temperature. The degradation measured by the laser transducer system was more intensive compared with previous studies. The elastic modulus decreased to about 29% of the room temperature value at 200 °C. With the evaporation of the resin, the failure modes of the CFRP experienced brittle fracture to pullout of the fiber tow. The study provides accurate tensile performance of the CFRP plate under high-temperature exposure, which is helpful for the engineering application.
Hardness–Deformation Energy Relationship in Metals and Alloys: A Comparative Evaluation Based on Nanoindentation Testing and Thermodynamic Consideration
Authors: Yamamoto Masayuki , Tanaka Masaki , Furukimi Osamu
Published: December 2021

Nanoindentation testing using a Berkovich indenter was conducted to explore the relationships among indentation hardness (H), elastic work energy (We), plastic work energy (Wp), and total energy (Wt = We + Wp) for deformation among a wide range of pure metal and alloy samples with different hardness, including iron, steel, austenitic stainless steel (H ≈ 2600–9000 MPa), high purity copper, single-crystal tungsten, and 55Ni–45Ti (mass%) alloy. Similar to previous studies, We/Wt and Wp/Wt showed positive and negative linear relationships with elastic strain resistance (H/Er), respectively, where Er is the reduced Young’s modulus obtained by using the nanoindentation. It is typically considered that Wp has no relationship with We; however, we found that Wp/We correlated well with H/Er for all the studied materials. With increasing H/Er, the curve converged toward Wp/We = 1, because the Gibbs free energy should not become negative when indents remain after the indentation. Moreover, H/Er must be less than or equal to 0.08. Thermodynamic analyses emphasized the physical meaning of hardness obtained by nanoindentation; that is, when Er is identical, harder materials show smaller values of Wp/We than those of softer ones during nanoindentation under the same applied load. This fundamental knowledge will be useful for identifying and developing metallic materials with an adequate balance of elastic and plastic energies depending on the application (such as construction or medical equipment).
Reasons for Reduced Moisture Resistance of Sulfur-Extended Asphalt Concrete
Authors: Le Huu Tuan , Korolev Evgenij V. , Grishina Anna N. , Gladkikh Vitaly A.
Published: December 2021

The paper presents the results of a study of the mechanism for reducing the moisture resistance of sulfur-extended asphalt concrete. It is shown that a decrease in moisture resistance occurs due to the occurrence of chemical and physical processes. At the same time, it was found that during the manufacture of sulfur-bitumen composites, toxic gases H2S and SO2 are formed, which are capable of interacting with a mineral filler, as well as the interaction of sulfur with a mineral powder with the formation of sulfur-containing water-soluble salts, the extraction of which leads to a decrease in the moisture resistance of sulfur-bitumen materials. The change in the rate of leaching of these substances from the composite is due to the physical process caused by the crystallization of sulfur and the formation of a capillary structure, which significantly increases the rate of leaching of calcium and magnesium salts, which are products of dissolution or hydrolytic decomposition of water-soluble products of the interaction of sulfur, H2S and SO2 gases with calcium and magnesium carbonates. The intensity of chemical and physical processes intensifies with an increase in the amount of sulfur in sulfur-bitumen materials.
Influence of Impurities on the Front Velocity of Sputter Deposited Al/CuO Thermite Multilayers
Authors: Dulmaa Altangerel , Depla Diederik
Published: December 2021

CuO and Al thin films were successively deposited using direct current (reactive) magnetron sputter deposition. A multilayer of five bilayers was deposited on glass, which can be ignited by heating a Ti resistive thin film. The velocity of the reaction front which propagates along the multilayer was optically determined using a high-speed camera. During the deposition of the aluminum layers, air was intentionally leaked into the vacuum chamber to introduce impurities in the film. Depositions at different impurity/metal flux ratios were performed. The front velocity reaches a value of approximately 20 m/s at low flux ratios but drops to approximately 7 m/s at flux ratios between 0.6 and 1. The drop is rather abrupt as the front velocity stays constant above flux ratios larger than 1. This behavior is explained based on the hindrance of the oxygen transport from the oxidizer (CuO) to the fuel (Al).
Synthesis of Mg-Al Hydrotalcite Clay with High Adsorption Capacity
Authors: Li Zhaoyi , Zhang Jie , Qu Chengtun , Tang Ying , Slaný Michal
Published: December 2021

A novel Mg-Al metal oxide has been successfully synthesized by the calcination of hierarchical porous Mg-Al hydrotalcite clay obtained by using filter paper as a template under hydrothermal conditions. Various characterizations of the obtained nanoscale oxide particles verified the uniform dispersion of Mg-Al metal oxides on the filter paper fiber, which had a size of 2–20 nm and a highest specific surface area (SSA) of 178.84 m2/g. Structural characterization revealed that the as-prepared Mg-Al metal oxides preserved the tubular morphology of the filter paper fibers. Further experiments showed that the as-synthesized Mg-Al metal oxides, present at concentrations of 0.3 g/L, could efficiently remove sulfonated lignite from oilfield wastewater (initial concentration of 200 mg/L) in a neutral environment (pH = 7) at a temperature of 298 K. An investigation of the reaction kinetics found that the adsorption process of sulfonated lignite (SL) on biomorphic Mg-Al metal oxides fits a Langmuir adsorption model and pseudo-second-order rate equation. Thermodynamic calculations propose that the adsorption of sulfonated lignite was spontaneous, endothermic, and a thermodynamically feasible process.
The Mechanism of Fracture and Damage Evolution of Granite in Thermal Environment
Authors: Wang Suran , Chen Youliang , Xiong Min , Du Xi , Liu Guanlin , Fernández-Steeger Tomás Manuel
Published: December 2021

In the study of rock mechanics, the variation of rock mechanical characteristics in high-temperature environments is always a major issue. The discrete element method and Voronoi modeling method were used to study the mechanical characteristics and crack evolution of granite specimens subjected to the high temperature and uniaxial compression test in order to study the internal crack evolution process of granite under the influence of high temperatures. Meanwhile, dependable findings were acquired when compared to experimental outcomes. A modified failure criterion was devised, and a Fish function was built to examine the evolution behavior of tensile and shear cracks during uniaxial compression, in order to better understand the evolution process of micro-cracks in granite specimens. Shear contacts occurred first, and the number of shear cracks reached its maximum value earliest, according to the findings. The number of tensile contacts then rapidly grew, whereas the number of shear cracks steadily declined. Furthermore, it was found that when temperature rises, the number of early tensile cracks grows. This study develops a fracture prediction system for rock engineering in high-temperature conditions.
Synergistic Effect of Screen-Printed Single-Walled Carbon Nanotubes and Phosphorylated Cellulose Nanofibrils on Thermophysiological Comfort, Thermal/UV Resistance, Mechanical and Electroconductive Properties of Flame-Retardant Fabric
Authors: Kolar Tjaša , Kokol Vanja
Published: December 2021

Single-walled carbon nanotubes (SWCNTs) and phosphorylated nanocellulose fibrils (PCNFs) were used as functional screen-print coatings on flame-retardant (FR) fabric, to improve its thermal resistance and thermophysiological comfort (wetting, water vapour and heat transmission) properties, while inducing it with electrical conductivity and UV protection. The effect of PCNF printing, followed by applying a hydrophobic polyacrylate (AP), on the same (back/B, turned outwards) or other (front/F, turned towards skin) side of the fabric, with and without the addition of 0.1–0.4 wt% SWCNTs, was studied by determining the amount of applied coating and its distribution (microscopic imaging), and measuring the fabric’s colour, air permeability, thickness, mechanical, flame and abrasion resistance properties. Due to the synergistic effect of PCNF and SWCNTs, both-sided printed fabric (front-side printed with PCNF and back-side with SWCNTs within AP) resulted in an increased heat transfer (25%) and an improved thermal resistance (shift of degradation temperature by up to 18 °C towards a higher value) and UV protection (UPF of 109) without changing the colour of the fabric. Such treatment also affected the moisture management properties with an increased water-vapour transfer (17%), reduced water uptake (39%) and asymmetric wettability due to the hydrophilic front (Contact Angle 46°) and hydrophobic back (129°) side. The increased tensile (16%) and tear (39%) strengths were also assessed in the warp direction, without worsening the abrasion resistance of the front-side. A pressure-sensing electrical conductivity (up to 4.9∙10−4 S/cm with an increase to 12.0∙10−4 S/cm at 2 bars) of the SWCNT-printed side ranks the fabric among the antistatic, electrostatic discharge (ESD) or electromagnetic interference (EMI) shielding protectives.
Study on Mechanical and Frost Resistance Properties of Slag and Macadam Stabilized with Cement and Fly Ash
Authors: Li Hongbo , Yan Pengfei , Tian Juncang , Sun Hao , Yin Jianguang
Published: December 2021

China is a large country in terms of coal production and consumption. The fly ash and slag produced by thermal power plants pose a great threat to the environment. To reduce the adverse effects of fly ash and slag on the environment, a mixture of slag and macadam stabilized with cement and fly ash was prepared as pavement base material. Compaction tests, unconfined compressive strength tests, splitting strength tests, frost resistance tests, and ultrasonic tests were performed on the mixture. The results show that with an increase in slag replacement rate, the unconfined compressive strength and splitting strength decreased. However, the adverse influence of the slag replacement rate on unconfined compressive strength and splitting strength of specimens gradually weakened with increasing curing time. The frost resistance of the mixture first increased and then decreased with an increase in the slag replacement rate. When cement content was 5% and the slag replacement rate was 50%, the frost resistance of the mixture was the best. Regression analysis of the ultrasonic test showed that the ultrasonic test can effectively characterize the strength of the mixture and the internal damage degree under freeze–thaw cycles. In conclusion, the slag replacement rate of the mixture is recommended to be ~50%, which has preferable mechanical and frost resistance performance.
Analysis of the Risk of Wear on Cemented and Uncemented Polyethylene Liners According to Different Variables in Hip Arthroplasty
Authors: De la Torre Basilio , Barrios Loreto , De la Torre-Mosquera Juan , Bujan Julia , Ortega Miguel A. , González-Bravo Carlos
Published: December 2021

Wear debris in total hip arthroplasty is one of the main causes of loosening and failure, and the optimal acetabular fixation for primary total hip arthroplasty is still controversial because there is no significant difference between cemented and uncemented types for long-term clinical and functional outcome. To assess and predict, from a theoretical viewpoint, the risk of wear with two types of polyethylene liners, cemented and uncemented, a simulation using the finite element (FE) method was carried out. The risk of wear was analyzed according to different variables: the polyethylene acetabular component’s position with respect to the center of rotation of the hip; the thickness of the polyethylene insert; the material of the femoral head; and the relationship of the cervical–diaphyseal morphology of the proximal end of the femur to the restoration of the femoral offset. In all 72 simulations studied, a difference was observed in favour of a cemented solution with respect to the risk of wear. With regard to the other variables, the acetabular fixation, the thickness of the polyethylene, and the acetabular component positioning were statistically significant. The highest values for the risk of wear corresponded to a smaller thickness (5.3 mm), and super-lateral positioning at 25 mm reached the highest value of the von Mises stress. According to our results, for the reconstruction of the acetabular side, a cemented insert with a thickness of at least 5 mm should be used at the center of rotation.
Light-Actuated Liquid Crystal Elastomer Prepared by Projection Display
Authors: Chen Juan , Akomolafe Oluwafemi Isaac , Jiang Jinghua , Peng Chenhui
Published: December 2021

Soft materials with programmability have been widely used in drug delivery, tissue engineering, artificial muscles, biosensors, and related biomedical engineering applications. Liquid crystal elastomers (LCEs) can easily morph into three-dimensional (3D) shapes by external stimuli such as light, heat, and humidity. In order to program two-dimensional (2D) LCE sheets into desired 3D morphologies, it is critical to precisely control the molecular orientations in LCE. In this work, we propose a simple photopatterning method based on a maskless projection display system to create spatially varying molecular orientations in LCE films. By designing different synchronized rotations of the polarizer and projected images, diverse configurations ranging from individual to 2D lattice of topological defects are fabricated. The proposed technique significantly simplified the photopatterning procedure without using fabricated masks or waveplates. Shape transformations such as a cone and a truncated square pyramid, and functionality mimicking the responsive Mimosa Pudica are demonstrated in the fabricated LCE films. The programmable LCE morphing behaviors demonstrated in this work will open opportunities in soft robotics and smart functional devices.
Indentation Size Effect in CoCrFeMnNi HEA Prepared by Various Techniques
Authors: Čech Jaroslav , Haušild Petr , Karlík Miroslav , Čapek Jiří , Průša Filip
Published: December 2021

High entropy alloys (HEAs) are materials of great application potential and which have been extensively studied during the last two decades. As the number of possible element combinations is enormous, model materials representing certain groups of HEAs are used for the description of microstructure, properties, and deformation mechanisms. In this study, the microstructure and mechanical properties of the so-called Cantor alloy composed of Co, Cr, Fe, Mn, and Ni in equiatomic ratios prepared by various techniques (casting, melt-spinning, spark plasma sintering) were examined. The research focused on the indentation measurements, namely, the indentation size effect describing the evolution of the hardness with penetration depth. It was found that the standard Nix–Gao model can be used for this type of alloy at higher penetration depths and its parameters correlate well with microstructural observations. The Nix–Gao model deviates from the measured data at the submicrometer range and the applied modification affords additional information on the deformation mechanism.
Modification of the Cavity of Plastic Injection Molds: A Brief Review of Materials and Influence on the Cooling Rates
Authors: Carrupt Maria C. , Piedade Ana P.
Published: December 2021

In the 21st century, a great percentage of the plastic industry production is associated with both injection molding and extrusion processes. Manufactured plastic components/parts are used in several industry sectors, where the automotive and aeronautic stand out. In the injection process cycle, the cooling step represents 60% to 80% of the total injection process time, and it is used to estimate the production capabilities and costs. Therefore, efforts have been focused on obtaining more efficient cooling systems, seeking the best relationship between the shape, the quantity, and the distribution of the cooling channels into the injection molds. Concomitantly, the surface coating of the mold cavity also assumes great importance as it can provide increased hardness and a more straightforward demolding process. These aspects contribute to the decrease of rejected parts due to surface defects. However, the effect of the coated cavity on the heat transfer and, consequently, on the time of the injection cycle is not often addressed. This paper reviews the effects of the materials and surface coatings of molds cavity on the filling and cooling of the injection molding cycle. It shows how the design of cooling channels affects the cooling rates and warpage for molded parts. It also addresses how the surface coating influence the mold filling patterns and mold cooling. This review shows, more specifically, the influence of the coating process on the cooling step of the injection cycle and, consequently, in the productivity of the process.
Development of Gelatin/Misoprostol Compounds for Use in Pregnancy Failures
Authors: Pedrosa Thiago Cajú , Trócolli Rossanna , de Sousa Wladymyr Jefferson Bacalhau , de Cerqueira Glauber Rodrigues Cerqueira , da Silva Henrique Nunes , Barbosa Rossemberg Cardoso , de Souza Matheus Ferreira , Galdino Taynah Pereira , Tissiani Jackeline Nascimento Apolori , Fook Marcus Vinícius Lia
Published: December 2021

Early abortion is one of the most common complications during pregnancy. However, the frequent handling of the genital region, more precisely the vagina, which causes discomfort to patients in this abortion process due to the frequency of drug insertion, as four pills are inserted every six hours, has led to the search for alternatives to alleviate the suffering caused by this practice in patients who are already in a shaken emotional state. Hence, this work aimed to develop composites of gelatin and misoprostol, using a conventional single-dose drug delivery system. These composites were prepared by freeze/lyophilization technique, by dissolving the gelatin in distilled water, with a concentration of 2.5% (w/v), and misoprostol was incorporated into the gelatin solution at the therapeutic concentration (800 mcg). They were subsequently molded, frozen and lyophilized. The samples of the composites were then crosslinked with sodium tripolyphosphate (TPP) 1% (v/v) with respect to the gelatin mass for 5 min. The characterization techniques used were: Optical Microscopy (OM), Fourier Transformed Infrared Spectroscopy (FTIR), Thermogravimetry (TG), Swelling, Biodegradation and Cytotoxicity. In OM it was observed that the addition of the drug improved the cylindrical appearance of the compounds, in comparison with the sample that was composed of only gelatin. There was a reduction in the degree of swelling with the addition of the drug and crosslinking. The cytotoxicity test indicated the biocompatibility of the material. Based on the results obtained in these tests, the composites have therapeutic potential for uterine emptying in pregnancy failures, especially in the first trimester.
Study on Behavior of Steel Hoop Connections for Raw Bamboo Members
Authors: Hu Chao , Cheng Rui , Cheng Qilin , Liu Jichun
Published: December 2021

Bamboo structures have various types of connections, such as bolting and lashing. One crucial issue in bamboo structures is that the connection with bolts and nails has a lower load-carrying capacity associated with the bamboo failure resulting from the bolt or nail invading them. This paper focuses on the connection for raw bamboo members with steel hoops (BHC), of which the two semi-circular steel hoops are fastened to the raw bamboo with high-strength bolts. The sliding friction is controlled by the interfacial pressure, which can be increased by tightening the bolts. A push-out experiment on thirty-six specimens was conducted considering the following two parameters: the different surface conditions of raw bamboo (with or without the epidermis) and the different interfacial pressure. The test results mainly showed the two failure modes of specimens under certain conditions: continuous longitudinal slip after the vertical load reached the peak; and the steel hoop stuck in the bamboo skin after a period of slip. It is found that the sliding friction was controlled by the interfacial pressure, and the difference in the anti-sliding capacity between the epidermal bamboo specimen and the non-epidermal bamboo specimen was magnified with the increase of interfacial pressure. The contact stress on the surface of bamboo is approximately uniformly distributed based on the finite element analyses. The interfacial pressure can be predicted by the torque value of the digital electronic torque wrench and the equations established by mechanical analysis, respectively. Moreover, the design formulae of bearing capacity for BHC under three guaranteed rates (50%, 95%, and 99.9%) were developed based on probability theory, while the fourth design formula was derived by regression analysis. The reliability indices of the four design formulae were up to 0.07, 1.44, 3.09, and 0.97, respectively, and the resistance partial coefficients were suggested accordingly.
3D Printed In Vitro Dentin Model to Investigate Occlusive Agents against Tooth Sensitivity
Authors: Naseri Shiva , Cooke Megan E. , Rosenzweig Derek H. , Tabrizian Maryam
Published: December 2021

Tooth sensitivity is a painful and very common problem. Often stimulated by consuming hot, cold, sweet, or acidic foods, it is associated with exposed dentin microtubules that are open to dental pulp. One common treatment for tooth hypersensitivity is the application of occlusive particles to block dentin microtubules. The primary methodology currently used to test the penetration and occlusion of particles into dentin pores relies upon dentin discs cut from extracted bovine/human teeth. However, this method is limited due to low accessibility to the raw material. Thus, there is a need for an in vitro dentin model to characterize the effectiveness of occlusive agents. Three-dimensional printing technologies have emerged that make the printing of dentin-like structures possible. This study sought to develop and print a biomaterial ink that mimicked the natural composition and structure of dentin tubules. A formulation of type I collagen (Col), nanocrystalline hydroxyapatite (HAp), and alginate (Alg) was found to be suitable for the 3D printing of scaffolds. The performance of the 3D printed dentin model was compared to the natural dentin disk by image analysis via scanning electron microscopy (SEM), both pre- and post-treatment with occlusive microparticles, to evaluate the degree of dentinal tubule occlusion. The cytocompatibility of printed scaffolds was also confirmed in vitro. This is a promising biomaterial system for the 3D printing of dentin mimics.
A Simple Method of Reducing Coolant Leakage for Direct Metal Printed Injection Mold with Conformal Cooling Channels Using General Process Parameters and Heat Treatment
Authors: Kuo Chil-Chyuan , Qiu Shao-Xuan
Published: December 2021

Direct metal printing is a promising technique for manufacturing injection molds with complex conformal cooling channels from maraging steel powder, which is widely applied in automotive or aerospace industries. However, two major disadvantages of direct metal printing are the narrow process window and length of time consumed. The fabrication of high-density injection molds is frequently applied to prevent coolant leakage during the cooling stage. In this study, we propose a simple method of reducing coolant leakage for a direct-metal-printed injection mold with conformal cooling channels by combining injection mold fabrication with general process parameters, as well as solution and aging treatment (SAT). This study comprehensively investigates the microstructural evolution of the injection mold after SAT using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. We found that the surface hardness of the injection mold was enhanced from HV 189 to HV 546 as the Ni-Mo precipitates increased from 12.8 to 18.5%. The size of the pores was reduced significantly due to iron oxide precipitates because the relative density of the injection mold increased from 99.18 to 99.72%. The total production time of the wax injection mold without coolant leakage during the cooling stage was only 62% that of the production time of the wax injection mold fabricated with high-density process parameters. A significant savings of up to 46% of the production cost of the injection mold was obtained.
Recycled Polyester Geosynthetic Influence on Improvement of Road and Railway Subgrade Bearing Capacity— Laboratory Investigations
Authors: Malicki Konrad , Górszczyk Jarosław , Dimitrovová Zuzana
Published: December 2021

After years of using geosynthetics in civil engineering and infrastructure construction, it has recently become necessary to consider the possibility of recycling and reusing these materials. This paper presents the results of laboratory tests of the effect of recycled geogrid on the bearing capacity of soils using a CBR test. A polyester geosynthetic was selected for testing due to its high resistance to biodegradation and wide application. In a series of laboratory tests, two types of road and railway subgrade were used, mixed with geosynthetic cuttings in two different weight concentrations. The aim of the research was to demonstrate whether old demolition geosynthetics could be used to strengthen road and rail subgrade as recycled material. The influence of the geosynthetic cutting shape was also considered. The obtained results confirm the possibility of using recycled geogrid to improve the bearing capacity of the pavement subgrade, at least under these laboratory conditions. In the case of sand, the use of 2.0% additive causes that the poorly compacted soil obtains sufficient bearing capacity for the layer of road improved subgrade. As expected, the level of this improvement depends on the type of soil and the shape of geogrid cuttings.
Eu-Doped Zeolitic Imidazolate Framework-8 Modified Mixed-Crystal TiO2 for Efficient Removal of Basic Fuchsin from Effluent
Authors: Zhang Wanqi , Liu Hui , Liu Zhechen , An Yuhong , Zhong Yuan , Hu Zichu , Li Shujing , Chen Zhangjing , Wang Sunguo , Sheng Xianliang , Zhang Xiaotao , Wang Ximing
Published: December 2021

Zeolitic imidazolate framework-8 (ZIF-8) was doped with a rare-earth metal, Eu, using a solvent synthesis method evenly on the surface of a mixed-crystal TiO2(Mc-TiO2) structure in order to produce a core–shell structure composite ZIF-8(Eu)@Mc-TiO2 adsorption photocatalyst with good adsorption and photocatalytic properties. The characterisation of ZIF-8(Eu)@Mc-TiO2 was performed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET) and ultraviolet–visible light differential reflectance spectroscopy (UV-DRs). The results indicated that Eu-doped ZIF-8 was formed evenly on the Mc-TiO2 surface, a core–shell structure formed and the light-response range was enhanced greatly. The ZIF-8(Eu)@Mc-TiO2 for basic fuchsin was investigated to validate its photocatalytic performance. The effect of the Eu doping amount, basic fuchsin concentration and photocatalyst dosage on the photocatalytic efficiency were investigated. The results revealed that, when 5%-Eu-doped ZIF-8(Eu)@Mc-TiO2 (20 mg) was combined with 30 mg/L basic fuchsin (100 mL) under UV irradiation for 1 h, the photocatalytic efficiency could reach 99%. Further, it exhibited a good recycling performance. Thus, it shows certain advantages in its degradation rate and repeatability compared with previously reported materials. All of these factors suggested that, in an aqueous medium, ZIF-8(Eu)@Mc-TiO2 is an eco-friendly, sustainable and efficient material for the photocatalytic degradation of basic fuchsin.
Poloxamer 407-Based Thermosensitive Emulgel as a Novel Formulation Providing a Controlled Release of Oil-Soluble Pharmaceuticals—Ibuprofen Case Study
Authors: Grela Kamil P. , Marciniak Dominik M. , Karolewicz Bożena
Published: December 2021

This article covers the design and evaluation of a novel drug vehicle: a thermosensitive, injectable, high-oil-content (50% w/w) emulgel providing a controlled release of lipophilic pharmaceuticals. Different vegetable (castor, canola, olive, peanut, grapeseed, linseed), mineral (paraffin) and semisynthetic (isopropyl myristate, oleic acid) oils were screened for ibuprofen (IBU) solubility and for their capacity for high-shear emulsification in a 17% (w/w) aqueous solution of poloxamer 407. Chosen emulgels were subject to a rheological evaluation, a syringeability test (TA.XT texture analyser; 2 mL syringe; 18 G, 20 G and 22 G needles) and a drug release study (48 h; cellulose membrane; 0.05 mol/L phosphate buffer at pH 7.4). Castor oil turned out to be an optimal component for IBU incorporation. Blank and drug-loaded castor oil emulgels were susceptible to administration via a syringe and needle, with the absolute injection force not exceeding 3 kg (29.4 N). The drug release test revealed dose-dependent, quasi-linear kinetics, with up to 44 h of controlled, steady, linear release. The results indicate the significant potential of high-oil-content, oil-in-water thermosensitive emulgel formulations as vehicles for the controlled release of lipophilic APIs.
Polymeric Micelles: A Promising Pathway for Dermal Drug Delivery
Authors: Parra Ana , Jarak Ivana , Santos Ana , Veiga Francisco , Figueiras Ana
Published: December 2021

Nanotechnology is an area in great development and with application in the most varied fields of science, including cosmetic and pharmaceutical industries. Because conventional formulations for topical application are not always able to effectively penetrate the physical barrier that human skin exerts against factors and compounds of the external environment, polymeric micelles appear as alternative carriers for drugs and active ingredients delivery, also allowing ingredients with lower solubility and higher lipophilicity to be delivered. In fact, the augmented bioavailability of drugs, greater efficacy even at a lower dose, and selective drug delivery in specific organelles are very interesting advantages of the polymeric micelles usage in cutaneous application. As a consequence, they show a reduction in many of the local and systemic adverse effects, which might lead to an increase in patient compliance to the therapeutics, constituting a promising alternative to conventional topical formulations.