bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving Enamel Acid Resistance by an Intraoral Fluoride-Release Device Incorporating Cationic Hydroxy Cellulose Gel Using 3D Printer Molding
Authors: Satou Ryouichi , Odaka Kento , Sako Ryo , Ando Masatoshi , Sugihara Naoki
Published: November 2024

An intraoral fluoride-releasing device (IFRD) is a cost-effective tool for introducing fluoride into the oral cavity. It allows prolonged uptake of low concentrations of fluoride into teeth. We developed a new IFRD using 3D additive manufacturing and a new low-release fluoride gel. Gels for IFRDs were synthesized from hydroxyethyl cellulose (SE600) and cationic hydroxyethyl cellulose (L200). We compared the effects of the new cationic fluoride slow-release gel and non-cationic gel on enamel acid resistance in vitro. Cationization significantly increased fluoride ion concentration, as evident from its concentrations of 0.68 ± 0.08 ppm for SE600 and 4.24 ± 0.83 ppm for L200 after 60 min of immersion in distilled water. In addition, the acid resistance of bovine tooth enamel post-application was analyzed by measuring tooth loss, mineral loss (ΔZ), and lesion depth (Ld) using polarized light microscopy, electron microscopy, and micro-radiography. Compared to the SE600 group, the cationic L200 group had significantly reduced ΔZ and Ld, enhancing enamel acid resistance. This device could be implemented in areas where adequate oral care is challenging, including preventive dentistry, ward management, nursing homes, and dental clinic visits.
Influence of the Applied Protective Coating on the Technological Parameters of the Moulding or Core Sand Surface
Authors: Łucarz Mariusz , Drożyński Dariusz , Kaczmarska Karolina , Pribulová Alena , Futáš Peter
Published: November 2024

An important issue in obtaining a good casting surface without defects in contact with the liquid metal is the use of protective coatings on the surface of the moulding sand forming the mould cavity. Protective coatings are based on highly refractory materials that are finely ground and protect the moulding sand from thermal stresses from the molten metal. An important aspect of obtaining the appropriate properties of the protective coatings used is the method of application. This article presents the results of a quality study of the protective coatings obtained, which were applied by dip and painting with a brush. Four different coatings were applied to mould sand samples prepared on grain matrices with different average grain sizes. During the tests, the viscosity of the protective coatings, their gas-forming capacity, sieve analyses of the grain matrix used, the permeability of the moulding sand with the protective coating and the abrasiveness and adhesion of the protective coatings were determined. The quality of the coating obtained was found to depend on its type, the size of the grain matrix used in the moulding sand and the method of application. The experiments carried out indicate that a comparative study of the available protective coatings can indicate the best solution, taking into account the grain matrix used and the method of application adopted.
Suppressing Interface Defects in Perovskite Solar Cells via Introducing a Plant-Derived Ergothioneine Self-Assembled Monolayer
Authors: Yeh Cheng-Hsien , Hsu Hung-Chieh , Tsao Jung-Che , Wu Hsuan-Ta , Lin Teh-Pei , Wu Chien-Te , Wu Shih-Hsiung , Shih Chuan-Feng
Published: November 2024

Perovskite solar cells are among the most promising renewable energy devices, and enhancing their stability is crucial for commercialization. This research presents the use of L-Ergothioneine (L-EGT) as a passivation material in perovskite solar cells, strategically placed between the electron transport layer and the perovskite absorber layer to mitigate defect states at the heterojunction interface. Surface analysis reveals that introducing L-EGT passivation material significantly improves the quality of the perovskite film. X-ray diffraction analysis indicates that L-EGT slows down perovskite film degradation and successfully suppresses secondary phase formation. X-ray photoelectron spectroscopic analysis shows that oxygen vacancies in the lattice decrease from 29.21% to 15.81%, while Ti4+ content increases from 70.75% to 79.15%, suggesting that L-EGT effectively passivates trap states at the interface between perovskite and TiO2 electron transport layer. The reduction of defects at the interface inhibits charge accumulation and lowers the device’s internal series resistance, leading to improved overall performance. The study finds that the introduction of L-EGT significantly improves the fill factor and efficiency, with the power conversion efficiency (PCE) rising from 16.88% to 17.84%. After 720 h of aging, the PCE retains approximately 91%. The results demonstrate the significant impact of the amino acid L-EGT passivation material in suppressing interfacial defects and greatly improving the long-term stability of perovskite devices.
Leather Waste Hydrolysation, Carbonization, and Microbial Treatment for Nitrogen Recovery by Ryegrass Cultivation
Authors: Kuligowski Ksawery , Skrzypczak Dawid , Mikula Katarzyna , Chojnacka Katarzyna , Bandrów Paulina , Tylingo Robert , Mania Szymon , Woźniak Adrian , Cenian Adam
Published: November 2024

Leather waste contains up to 10% nitrogen (N); thus, combustion or gasification only for the energy recovery would not be rational, if safety standards are met. On the other hand, the chromium (Cr) content exceeding 5% in half of the waste stream (w/w) is too significant to be applied in agriculture. In this work, four acid hydrolysates from leather waste shavings, both wet-white free of Cr and wet-blue with Cr, were used: two with a mixture of acids and supplemented with Cu, Mn, and Zn, and the other two as semi-products from collagen extraction using hydrochloric acid. Additionally wet-green leather waste shavings, e.g., impregnated with olive extract, were used followed by the two treatments: amendment with a biochar from “wet white” leather waste shavings and amendment with this biochar incubated with the commercial phosphorus stimulating microbial consortia BactoFos. They were applied as organic nitrogen-based fertilizers in a glasshouse experiment, consisting of 4–5 subsequent harvests every 30 days, under spring–autumn conditions in northern Poland. Biochar-amended wet-greens provided the highest nitrogen use efficiencies, exceeding 100% after 4 months of growth (for 20 kg N/ha) and varying from 17% to 37% in particular months. This is backed up by another parameter (relative agronomic effectiveness) that for these materials exceeded 150% for a single month and in total was around 33%. Biochar amendments significantly increased agronomic parameters for wet-greens, and their microbial treatment enhanced them even further. Recycling this type of waste can replace inorganic fertilizers, reducing greenhouse gas emissions and carbon footprint.
An Oriented Recrystallization Nucleation Mechanism of a Cold-Rolled Pure Ti with Electric-Pulse Treatment
Authors: Shi Qi , Wang Lei , Song Xiu , Liu Yang
Published: November 2024

The effect of electric-pulse treatment (EPT) on the nucleation behavior of a cold-rolled pure Ti was investigated. The specimens are subjected to EPT and then annealed at 650 °C within 10 min. Both the electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) techniques were used for detailing the microstructural evolution of the specimens at the initial stage of recrystallization processing during annealing. The results show that oriented nucleation occurs in the EPTed specimen. The recrystallized grains form in a similar orientation with the deformed matrix grains, and the oriented nucleation originates from the deformed grains with <0001> poles tilted about 20° away from the normal direction (ND20 grains) in the EPTed specimen. Pyramidal  dislocations could be extensively activated in ND20 grains, while the activated dislocations were mainly on prismatic planes in the other oriented grains. Because the formation of sub-grains cannot be without the pyramidal  dislocation, oriented recrystallized grains easily form in the EPTed specimen. It is suggested that the increasing of pyramidal dislocation climbing activity is considered the key mechanism of the formation of sub-grains as well as oriented nucleation, resulting from high contents of vacancy induced by EPT.
Pull-Out Progressive Damage and Failure Analysis of Laminated Composite Bolted Joints
Authors: Zeng Zhaowei , Fan Qixiang , Liao Feng , Liu Gang , Yan Jianwei
Published: November 2024

Laminated composite bolted joints are increasingly used in the aerospace field, and their damage and failure behavior has been studied in depth. In view of the complexity and stability requirements of laminated composite bolted structures, accurate prediction of damage evolution and failure behavior is significant to ensure the safety and reliability of the structures. In this paper, a novel asymptotic damage model is developed to predict the damage process and failure behavior of laminated composite bolted joints. In this model, the modified Puck criterion and the maximum shear stress criterion are used for fiber yarns. The parabolic yield criterion is adopted for the matrix, and the fiber fracture, inter-fiber fracture and matrix fracture are considered at the microscopic level. The pull-out strength and progressive failure behavior of countersunk and convex bolted joints structures are predicted by using the proposed model, and the corresponding experimental studies are carried out. The results show that the prediction results are in good agreement with the experimental data, which verifies the reliability of the model. Additionally, the effects of different structural parameters (thickness and aperture) on the progressive damage and failure behavior during pull-out is analyzed by the proposed model, and correction factors of pull-out strength are obtained, which provides a powerful tool for the design, analysis and progression of laminated composite bolted joint structures.
Microstructure Evolution and Mechanical Properties of 16-Layer 2195 Al-Li Alloy Components Manufactured by Additive Friction Stir Deposition
Authors: Liu Qinglin , Lai Ruilin , Wang Hui , Li Yidi , Li Yunping , Zhan Lihua
Published: November 2024

The fabrication of multi-layer alloys by additive friction stir deposition (AFSD) results in a complicated microstructure and mechanical property evolution due to the repeated thermal inputs impacting the existing deposited layers. This work systematically studied the microstructure and mechanical properties of several areas (last layers, intermediate layers, and first layers) of a 16-layer 2195 alloy component fabricated by AFSD to ascertain the effect of repeated thermal cycling. The periodic heat input resulted in the minimal quantities of T1-phase only appearing in the last layers of the sample, while the θ′-phase developed a complex precipitate with the δ′ and β′ phases. The mechanical properties of the 2195 sample exhibit a gradient development related to the microstructure, with a decrease in strength and hardness from top to bottom. The samples located in the last layers show the highest microhardness of 117.0 Hv, yield strength of 296.6 MPa, ultimate tensile strength of 440.6 MPa, and elongation of 27.1%, respectively.
The Effect of Y Addition on Oxidation Resistance of Bulk W-Cr Alloys
Authors: Reuban Anicha , Chen Jie , Povstugar Ivan , Litnovsky Andrey , Coenen Jan Willem , Linsmeier Christian , Gonzalez-Julian Jesus
Published: November 2024

The self-passivating tungsten-based alloy W-11.4Cr-0.6Y (in wt.%) is a potential plasma-facing material for the first wall of future fusion reactors, which has been shown to suppress oxidation of tungsten and withstand temperatures of up to 1000 °C. In this study, the effect of Y addition on the microstructure and oxidation behavior of W-11.4Cr alloy at 1000 °C is analyzed by comparing it with W-11.4Cr-0.6Y, both prepared using identical synthesis routes. While the binary W-Cr alloy already exhibits improved oxidation resistance over pure W due to the formation of an outer Cr2WO6 layer, it still shows a tendency for spallation and, hence, is not protective. A continuous passivating chromia layer is only obtained with the addition of Y, and we demonstrate that it results in a 50-fold decrease in the oxide growth rate and eliminates the preferred growth of the oxide at edges seen in the binary alloy. Although a porous, complex oxide scale containing mixed oxide layers and WO3 is formed in both cases, the addition of Y results in lower porosity, which makes the oxide scale more adherent.
Dynamic Recrystallization Simulation of PH13-8Mo Stainless Steel by Cellular Automata Method Based on Laasraoui–Jonas Dislocation Density Model
Authors: Hu Linli , Zhou Shaoshuai , Yuan Xunyu , Xu Xiwen , Yang Ruizhi , Shu Xiaoyong
Published: November 2024

The Gleeble-1500 hot simulation experimental equipment was used to investigate the effects of hot simulation compression on PH13-8Mo stainless steel with strain rates ranging from 0.1 to 10 s−1 and deformation temperatures ranging from 900 to 1150 °C. The stress–strain charts for each deformation condition clearly show the characteristics of dynamic recrystallization behavior. The rheological stress rises as the deformation temperature falls and the strain rate rises. A coupled Laasraoui–Jonas (L–J) model was developed based on the discovery that the dislocation density is crucial to the nucleation and micro-structure evolution of dynamic recrystallization during thermal deformation. The findings demonstrate that the model accurately captures the combined action of dynamic reversion and recrystallization inside the material during hot compression of PH13-8Mo stainless steel and that as deformation rises, the dislocation density first increases and subsequently drops. For calculations and numerical simulations of the evolution of the micro-structure under hot compression, the created model was integrated into the DEFORM-3D finite element simulation program. The projected micro-structure evolution of the PH13-8Mo stainless steel under various deformation circumstances is compared to the measured grain distribution, grain size, and the degree of dynamic recrystallization in the metallographic pictures. The fact that the simulated result plots resemble the metallographic charts so closely demonstrates that the L–J dislocation density model can reliably forecast how dynamic recrystallization of PH13-8Mo stainless steel would behave under hot compression.
Graphene/Metal Composites Decorated with Ni Nanoclusters: Mechanical Properties
Authors: Kolesnikov Vyacheslav , Mironov Roman , Baimova Julia
Published: November 2024

With the developments in nanotechnology, the elaborate regulation of microstructure shows attractive potential in the design of new composite materials. Herein, composite materials composed of graphene network filled with metal nanoparticles are analyzed to optimize the fabrication process and mechanical properties. In the present work, molecular dynamic simulations are used to analyze the possibility of obtaining a composite structure with Ni-decorated graphene. The weak bonding at the graphene–copper and graphene–aluminum interfaces is manipulated by functionalizing graphene with nickel nanoclusters. It is found that Ni decoration considerably increases interfacial bonding and, at the same time, prevents the formation of a strong graphene network. It is found that Ni decoration for the Al/graphene composite increases the its ductility by 0.6, while increasing it for the Cu/graphene composite by about 0.5. Ultimate tensile strength of the composite with Al and Cu is close and equal to 22 GPa, respectively. The strength of the composite with Ni-decorated graphene is much lower and equal to 13 GPa for Cu/graphene/Ni and 17 GPa for Al/graphene/Ni. While Young’s modulus for the Cu/graphene composite is 18 GPA, for Al/graphene, Al/graphene/Ni, and Cu/graphene/Ni, it is 12 GPa. The obtained results demonstrate the future prospects of the graphene modification for better composite enhancement.
Evaluation of the Protective Effect of a Nanoscale Deep Penetration Sealer in Improving Chloride Erosion Resistance of Concrete
Authors: Liu Yan , Peng Xiaoli , Hui Jia , Zhang Peng , Zhang Zhiqian
Published: November 2024

In this study, the protective effect of a Nanoscale Deep Penetration Sealer (NDPS) in improving the chloride erosion resistance of concrete was evaluated and the influence of water–cement ratio (w/c) and the NDPS spray volume on the protective effect was explored, in order to gain a deeper insight into the effect of NDPS on the durability of concrete in chloride environments. The thickness of the protective layer formed by NDPS within the concrete was determined and the effectiveness of this protective layer was verified. Based on the determination of the ability of NDPS to form a protective layer in concrete, the diffusion laws of chloride in concrete at different w/c and NDPS spray volumes were investigated, and a prediction model was established. The results show that NDPS forms a 2–3 cm protective layer in concrete to resist chloride penetration, which is nearly as thick as the concrete cover. The protective layer weakens the capillary absorption of concrete and prevents the penetration of aggressive substances into the concrete. NDPS significantly improves the chloride erosion resistance of concrete. The chloride diffusion coefficient of concrete with a w/c ratio of 0.6 was reduced by approximately 35% after being sprayed with 1000 mL/m2 of NDPS, and the protective effect strengthens with increasing spray volume at a fixed w/c and weakens with decreasing w/c at a fixed NDPS spray volume. The proposed predictive model is the basis for predicting the diffusion of chloride in concrete with NDPS protection in practical engineering applications and provides a guide for the application of NDPS in practical engineering.
The Effect of Specimen Width on the Deformation Behavior and Formability of cp-Ti Grade 4 Sheets During Uniaxial and Cyclic Bending Under Tension Loading
Authors: Mensah Desmond , Pitkin Nicholas , Miles Michael P. , Fullwood David T. , Knezevic Marko , Kinsey Brad
Published: November 2024

This study examines the specimen size-dependent deformation behavior of commercially pure titanium grade 4 (cp-Ti grade 4) sheets under tension, with strain paths between uniaxial tension (UT) and plane-strain tension and compares the results with cyclic bending under tension (CBT) data. Specimens of varying widths (11.7, 20, 60, 100, and 140 mm) were tested in both rolling (RD) and transverse (TD) directions. The research employed digital image correlation for full-field strain measurements, finite element simulations, and fracture surface thickness data. Contrary to traditional forming concepts, i.e., the forming limit diagram (FLD) has the lowest major strain at the plane-strain condition, and the fracture forming limit has decreased major strain with increasing (less negative) minor strain, wider specimens exhibited higher major strains at strain localization and fracture under UT. In contrast, CBT findings showed decreased formability with increasing width, i.e., closer to plane-strain deformation, as expected. Strain distribution analyses revealed a transition from nearly uniform deformation in narrow specimens to multiaxial strain states in wider specimens. Thickness measurements along the fracture surface revealed a steeper profile in UT compared to CBT, indicating more localized deformation and necking in UT. In comparison with AA6016-T4, the cp-Ti grade 4 showed greater thickness, suggesting lower susceptibility to localized thinning. Strong anisotropy was observed between the RD and TD, with TD specimens showing higher formability and steeper thickness gradients in UT. Strain fields, along with thickness reduction and adiabatic heating, are used to rationalize the observed width-sensitive deformation behavior of cp-Ti sheets. Notably, CBT improved overall formability compared to UT due to its ability to distribute strain more evenly and delay critical necking. The contrasting trends between simple UT and CBT emphasize the relationship between loading conditions, specimen geometry, and material behavior in determining formability. These findings highlight the ability of the CBT test to create known and desired deformation effects, i.e., lower major strain at failure with increasing specimen width, and more uniform deformation, i.e., consistent thinning across the specimen width, for cp-Ti. Given the observed effects of width in UT, the selection of the testing method is critical for cp-Ti to ensure that results reflect expected material behavior.
Effect of 0.20% Beryllium (Be)-Added CuAl10Ni5Fe4 Alloy on Tribological Behavior and Microstructural Properties After Post-Casting Heat Treatment and Forging Process
Authors: Babay Khaled A. A. , Esen Ismail , Sagiroglu Selami , Ahlatci Hayrettin , Keskin Esma
Published: November 2024

This study explored how post-casting heat treatment and forging affected the tribological and microstructural characteristics of 0.20% beryllium (Be)-added CuAl10Ni5Fe4 alloys. The heat-treated CuAl10Ni5Fe4 microstructure exhibits a copper-rich α (alpha)-solid-solution phase, a martensitic β (beta)-phase, and diverse intermetallic κ (kappa)-phases, such as leaf-shaped κI, thin κIII, and black globs. Adding 0.20% beryllium to CuAl10Ni5Fe4 alloys enhanced the dendritic arm thickness, needle-like shape, and κ-phase quantities. Significant κIV- and κII-phase precipitation was observed in the tempered β-phase. Beryllium improves the aluminum matrix’s microstructure. Forging greatly reduced the microstructural thickness of CuAl10Ni5Fe4 and CuAl10Ni5Fe4-0.20% Be alloys. The forging process also developed new κIV-phases. Wear resistance and hardness improved with beryllium. The CuAl10Ni5Fe4-0.20% Be alloy had the highest hardness values (235.29 and 255.08 HB) after solution treatment (ST) and tempering (T) after casting and forging (F). The CuAl10Ni5Fe4-0.20% alloy with Be added had the best wear after solution treatment, tempering, and forging. The CuAl10Ni5Fe4-0.20% Be alloy demonstrated a 0.00272 g weight loss, a 1.36 × 10−8 g/N*m wear rate, and a 0.059 friction coefficient at 10,000 m after forging (F).
Airborne-Particle Abrasion vs. Hydrofluoric Acid Etching of Dental Ceramics: Impact on the Tensile Bond Strength
Authors: Lankes Valerie , Coldea Andrea , Meinen John , Schwendicke Falk , Stawarczyk Bogna
Published: November 2024

This study evaluated whether airborne-particle abrasion could be an alternative to hydrofluoric acid etching as a pretreatment for the adhesive bonding of silicate ceramic restorations. Feldspar (FEL; n = 100), lithium silicate (LiSi; n = 100), and zirconia (ZrO2; (n = 80) substrates were CAD/CAM-fabricated and airborne-particle-abraded with Al2O3 (25 µm or 50 µm of mean particle size) at pressures of 0.05 or 0.1 MPa. The controls included FEL (60 s) and LiSi (20 s) etched with hydrofluoric acid. The surface free energy (SFE) and roughness (Ra) were measured. For the tensile bond strength (TBS), surfaces were conditioned using a primer (Monobond Plus) and luted to a resin composite (Variolink Esthetic). TBS was assessed initially (24 h, 37 °C water storage) and after thermocycling (5/55 °C, 10,000×). Statistical analysis (SPSS, V29) was performed using a one-way ANOVA, post hoc Scheffé, and a two-group t-test (p = 0.05). Abrasion with 50 µm and 0.1 MPa induced the highest Ra values across the materials (62.5 ± 3.88 µm). ZrO2 exhibited a higher TBS (35.4–49.5 MPa) than FEL and LiSi. For aged LiSi, the specimens treated at 0.1 MPa showed a higher TBS (18.7 ± 9.0 MPa) than those treated at 0.05 MPa, regardless of the particle size. The etched and aged FEL showed a higher SFE but a lower TBS compared to abrasion. Al2O3 particle abrasion (25 or 50 µm at 0.1 MPa) may replace etching for silicate-based ceramics, while 50 µm is recommended for ZrO2 at either pressure.
Thermal Conversion of Coal Bottom Ash and Its Recovery Potential for High-Value Products Generation: Kinetic and Thermodynamic Analysis with Adiabatic TD24 Predictions
Authors: Janković Bojan , Janković Marija , Mraković Ana , Krneta Nikolić Jelena , Rajačić Milica , Vukanac Ivana , Sarap Nataša , Manić Nebojša
Published: November 2024

Thermal decomposition (pyrolysis) of coal bottom ash (collected after lignite combustion in coal-fired power plant TEKO-B, Republic of Serbia) was investigated, using the simultaneous TG-DTG techniques in an inert atmosphere, at various heating rates. By using the XRD technique, it was found that the sample (CBA-TB) contains a large amount of anorthite, muscovite, and silica, as well as periclase and hematite, but in a smaller amount. Using a model-free kinetic approach, the complex nature of the process was successfully resolved. Thermodynamic analysis showed that the sample is characterized by dissociation reactions, which are endothermic with positive activation entropy changes, where spontaneity is achieved at high reaction temperatures. The model-based method showed the existence of a complex reaction scheme that includes two consecutive reaction steps and one single-step reaction, described by a variety of reaction models as nucleation/growth phase boundary-controlled, the second/n-th order chemical, and autocatalytic mechanisms. It was established that an anorthite I1 phase breakdown reaction into the incongruent melting product (CaO·Al2O3·2SiO2) represents the rate-controlling step. Autocatalytic behavior is reflected through chromium-incorporated SiO2 catalyst reaction, which leads to the formation of chromium(II) oxo-species. These catalytic centers are important in ethylene polymerization for converting light olefin gases into hydrocarbons. Adiabatic TD24 prediction simulations of the process were also carried out. Based on safety analysis through validated kinetic parameters, it was concluded that the tested sample exhibits high thermal stability. Applied thermal treatment was successful in promoting positive changes in the physicochemical characteristics of starting material, enabling beneficial end-use of final products and reduction of potential environmental risks.
Mechanical–Chemical Activation of Cement-Ash Binders to Improve the Properties of Heat-Resistant Mortars
Authors: Dvorkin Leonid , Zhitkovsky Vadim , Tracz Tomasz , Sitarz Mateusz , Mróz Katarzyna
Published: November 2024

The article demonstrates the effectiveness of the mechanochemical activation of a cement-ash binder by increasing the specific surface area of the ash and introducing a sodium fluorosilicate additive (Na2SiF6). It has been experimentally proved that the introduction of a Na2SiF6 additive makes it possible to increase the degree of cement hydration, as well as the intensity of free CaO binding when heating the cement-ash binder in the range of 500 °C to 800 °C. Mechanochemical activation prevents a decrease in the strength of the preheated cement-ash binder. During cyclic heating and cooling of slag mortars based on the activated cement-ash binder, an improvement in the set of basic properties was observed: compressive strength, flexural strength, water absorption, dynamic modulus of elasticity, and conditional elongation. Experimental design was carried out to obtain experimental–statistical models of mortar properties based on composition, heating temperature, and number of heating–cooling cycles. These models made it possible to develop quantitative relationships for predicting mortar properties at elevated temperatures and to rank the factors in order of importance. The optimal values for the dosage of fly ash, sodium silicofluoride additive, and the binder’s specific surface area were established. It was demonstrated that the activator has a positive effect on the thermal deformation of mortars.
Influence of Loading Mode on the Biaxial Stress–Strain Curve at Hydraulic Bulge Test
Authors: Sobotka Jiří , Solfronk Pavel , Švec Martin , Koreček David
Published: November 2024

Stress–strain curves are generally a very important material characteristic. For example, in numerical simulations, especially in sheet metal forming, stress–strain curves represent one of the most important data inputs. However, there is quite a wide range of parameters that influence their outline under the chosen technological conditions and, therefore, must always be taken into account. Among them, the influence of stress state and loading history is also relevant. In addition to that, to properly define the advanced yield conditions used in numerical simulations, it is also necessary to perform material tests under multi-axial stress states. For the above reasons, the present paper deals with the influence of the loading mode on the resulting outline of stress–strain curves under the equi-biaxial stress state at hydraulic bulge test (HBT). In light of the different loading modes, the classical continuous increase in pressure in accordance with ISO 16808 was compared with the so-called ramp test, where holding times for a duration of 90 s were applied. Two materials were selected for experiments, namely, a dual-phase steel (DP steel) with UTS of 500 MPa and an interstitial-free steel (IF steel) with a yield strength of 150 MPa. The results revealed totally different deformation behaviour of the tested materials depending on the used loading mode. Moreover, an evaluation of the microstructure was performed as well to clarify the measured results. The contactless optical system GOM Correlate Pro was used to evaluate the results of the HBT.
Effects of Preformed Composition and Pore Size on Microstructure and Properties of SiCf/SiC Composites via Reactive Melt Infiltration
Authors: Nie Haifeng , Si Pingzhan , Ren Quanxing , Yin Ziqiang , Cao Tihao , Huang Zhengren , Huang Qing , Li Yinsheng
Published: November 2024

This study investigated the influence of preformed composition and pore size on the microstructure and properties of SiCf/SiC composites fabricated via reactive melt infiltration (RMI). The process began with the impregnation of SiC fiber cloth with phenolic resin, followed by lamination and pyrolysis. Subsequent steps included further impregnations with phenolic resin, SiC slurry, and carbon black slurry, each followed by additional pyrolysis. This process resulted in three types of preforms, designated as PP, PS, and PC. These preforms exhibited a multimodal distribution of pore size, with peak pore diameters around 5 μm for PP, ranging from 200 nm to 4 μm for PS, and approximately 150 nm for PC. The preforms were then subjected to molten silicon infiltration at 1600 °C under vacuum for 1 h to create SiCf/SiC composites. The PP preform contained only pyrolytic carbon, leading to a composite with high closed porosity and unreacted carbon, resulting in poor mechanical properties. The PS preform, which was impregnated with SiC particles, displayed an optimized pore size distribution but retained significant amounts of residual silicon and carbon in the final composite. In contrast, the PC preform featured both an ideal pore size distribution and an adequate amount of carbon, achieving high density and low porosity with reduced residual phases in the final composite. This optimization led to a flexural strength of 152.4 ± 15.4 MPa, an elastic modulus of about 181.1 ± 0.1 GPa, and a thermal conductivity of 27.7 W/mK in the SiCf/SiC composites product. These findings underscore the importance of preform optimization in enhancing the performance of SiCf/SiC composites, potentially paving the way for more reliable nuclear fuel cladding solutions.
Low-Velocity Impact Analysis in Composite Plates Incorporating Experimental Interlaminar Fracture Toughness
Authors: Lee Gyeong-Han , Yang Ji-Yoon , Kim Sang-Woo , Lee Soo-Yong
Published: November 2024

Reliable performance of composite adhesive joints under low-velocity impact is essential for ensuring the structural durability of composite materials in demanding applications. To address this, the study examines the effects of temperature, surface treatment techniques, and bonding processes on interlaminar fracture toughness, aiming to identify optimal conditions that enhance impact resistance. A Taguchi experimental design and analysis of variance (ANOVA) were used to analyze these factors, and experimentally derived toughness values were applied to low-velocity impact simulations to assess delamination behavior. Sanding and co-bonding were identified as the most effective methods for improving fracture toughness. Under the identified optimal conditions, the low-velocity impact analysis showed a delamination area of 319.0 mm2. These findings highlight the importance of parameter optimization in enhancing the structural reliability of composite adhesive joints and provide valuable insights for improving the performance and durability of composite materials, particularly in aerospace and automotive applications.
Thermal and Structural Analysis of a High-Entropy Cr16Mn16Fe16Co16Ni16P20 Alloy—Influence of Cooling Rates on Phase Transformations
Authors: Ziewiec Krzysztof , Błachowski Artur , Prusik Krystian , Jasiński Marcin , Ziewiec Aneta , Wojciechowska Mirosława
Published: November 2024

This study investigates the influence of cooling rates on the microstructure and phase transformations of the high-entropy alloy Cr16Mn16Fe16Co16Ni16P20. The alloy was synthesized via arc melting and subjected to three cooling conditions: slow cooling (52 K/s), accelerated cooling after a short electric arc pulse (3018 K/s), and rapid quenching (10⁵–10⁶ K/s) using the melt-spinning method. The microstructures were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Mössbauer spectroscopy. The thermal properties and phase transformations were analyzed using differential scanning calorimetry (DSC) and thermography. Slow cooling produced a complex crystalline microstructure, while accelerated cooling resulted in fewer phases. Rapid cooling yielded an amorphous structure, demonstrating that phosphorus and high mixing entropy enhance glass-forming ability. Phase transformations exhibited significant undercooling under accelerated cooling, with FCC phase crystallization shifting from 1706 K (slow cooling) to 1341 K, and eutectic crystallization from 1206 K to 960 K. These findings provide a foundation for optimizing cooling processes in high-entropy alloys for advanced structural and functional applications.
Nanoparticle-Composed Photosensitive Thin Films Based on ZnO
Authors: Dilova Tina , Dikovska Anna , Baeva Aleksandra , Atanasova Genoveva , Avdeev Georgi , Genova Tsanislava , Nedyalkov Nikolay
Published: November 2024

In this work, atmospheric pulsed laser deposition was used to prepare photosensitive elements. This technology is a practical and relatively inexpensive way of obtaining highly porous nanostructures composed of nanoparticles or nanoaggregates characterized by a large surface-to-volume ratio. Samples were produced via laser nanosecond or picosecond laser ablation of pure ZnO or mixed ZnO-TiO2 targets on quartz substrates with pre-deposited gold electrodes. The structure, morphology, optical, and electrical properties of the nanostructures obtained were studied regarding the sample composition and laser ablation regime applied. The ablation of a mixed ZnO-TiO2 target led to the fabrication of composite samples consisting of ZnO and Zn2TiO4 nanoparticles. The electrical properties of pure and composite samples were studied under exposure to UV light irradiation. It was found that the photosensitive properties of the samples depended on the ablation regime applied. The dark current measured for the nanosecond-deposited samples was a few nA, which was an order of magnitude larger compared to the picosecond-deposited samples. The value of the photogenerated current of the nanosecond-deposited samples was 103-times higher than that of the picosecond-deposited samples. This is due to the lower absorption of the picosecond-deposited samples, as well as to the presence of defect-related radiative recombination in the picosecond-deposited samples, which limits the photocurrent rise. The estimated rise and decay times were longer for the composite samples independently of the deposition regime applied.
Effect of Cement Substitution with Mineral Fillers on NOx Air-Purification Efficiency and Photocatalytic Reaction Selectivity of Nano-TiO2-Modified Cementitious Composites
Authors: Chilmon Karol , Kalinowski Maciej , Jackiewicz-Rek Wioletta
Published: November 2024

This research investigated the properties of photocatalytic cementitious composites, including their air-purification efficiency. A method of characterizing the removal of airborne pollutants (nitrogen oxides), simulating the actual NOx concentration and irradiation conditions in Warsaw, Poland, in the autumn/winter season was established. The study analyzed the impact of changes in the composition of cement mortars—partial substitution of the binder with mineral fillers—on the properties of the external photoactive surface of the composite. The designed experimental plan included both quantitative and qualitative variables (type and amount of fillers used). It was found that the photocatalytic performance of the composite was correlated with its pore total content and pore size distribution—the higher the content of mineral fillers, the lower the porosity and the less effective its photocatalytic properties. The selectivity of the photocatalytic NOx reactions also deteriorated as the content of the mineral fillers increased. The study confirmed the validity of increasing the binder content in cementitious composites to enhance their photocatalytic performance.
Porosity Effects on the Composite Girder by Rheological Dynamics and FEM
Authors: Mrđa Bošnjak Nataša , Milašinović Dragan D. , Goleš Danica , Gučević Jelena , Čeh Arpad
Published: November 2024

A theoretical model for porous viscoelastoplastic (VEP) materials in the dry state is investigated in this research study. The model is based on the principles of conservation of mass and energy using the rheological dynamic theory (RDT). The model provides expressions for the creep coefficient, Poisson’s ratio, modulus of elasticity, damage variable, and strength as a function of porosity and/or void volume fraction (VVF). The reliability of the proposed model was analyzed by comparing numerical results with experimental ones on hardened concrete. A numerical model was created and analyzed in the commercial software Abaqus and validated by comparison with experimental data obtained by geodetic measurements on a composite wood–lightweight concrete girder. The deflections and stresses of the beam resulting from the influence of concrete creep and porosity were analyzed at the initial moment of time and after 6 years. The results showed that the RDT provided a reliable model for estimating parameters after exposure to long-term loads.
A Case Study on Assessing the Capability and Applicability of an Articulated Arm Coordinate Measuring Machine and a Touch-Trigger Probe for On-Machine Measurement
Authors: Samelova Vendula , Marek Tomas , Jelinek Adam , Jankovych Robert , Maradova Karla , Holub Michal
Published: November 2024

In modern manufacturing, there is an increasing demand for reliable in-process measurement methods directly on large CNC machine tools, eliminating the need to transport workpieces to metrological laboratories. This study assesses the capability and applicability of an articulated arm coordinate measuring machine and a machine tool touch-trigger probe when measuring to a specified tolerance of 0.05 mm in a production environment. Experiments were conducted using the KOBA calibration standard and included measurements with and without applying the articulated arm coordinate measuring machine leapfrog method. The results were evaluated according to ISO 22514-7:2021 and ISO 14253-1:2017, which establish criteria for measurement system capability. The findings revealed that neither measurement system met the capability requirements of ISO 22514-7:2021, particularly due to unsatisfactory QMS and CMS values. However, under ISO 14253-1:2017, both systems were deemed conditionally suitable for verifying conformity to the specifications, with the articulated arm coordinate measuring machine showing lower applicability when using the leapfrog method. This research supports the idea that unreasonable demands for compliance with current standards may lead to questioning of the systems that previously met older standards. The study contributes to the ongoing discussion on integrating advanced metrological tools into the manufacturing process and underscores the need for careful evaluation to ensure the capability and reliability of measurement systems in industrial practice.
Detection of Damage on Inner and Outer Races of Ball Bearings Using a Low-Cost Monitoring System and Deep Convolution Neural Networks
Authors: You Handeul , Kim Dongyeon , Kim Juchan , Park Keunu , Maeng Sangjin
Published: November 2024

Bearings are vital components in machinery, and their malfunction can result in equipment damage and reduced productivity. As a result, considerable research attention has been directed toward the early detection of bearing faults. With recent rapid advancements in machine learning algorithms, there is increasing interest in proactively diagnosing bearing faults by analyzing signals obtained from bearings. Although numerous studies have introduced machine learning methods for bearing fault diagnosis, the high costs associated with sensors and data acquisition devices limit their practical application in industrial environments. Additionally, research aimed at identifying the root causes of faults through diagnostic algorithms has progressed relatively slowly. This study proposes a cost-effective monitoring system to improve economic feasibility. Its primary benefits include significant cost savings compared to traditional high-priced equipment, along with versatility and ease of installation, enabling straightforward attachment and removal. The system collects data by measuring the vibrations of both normal and faulty bearings under various operating conditions on a test bed. Using these data, a deep neural network is trained to enable real-time feature extraction and classification of bearing conditions. Furthermore, an explainable AI technique is applied to extract key feature values identified by the fault classification algorithm, providing a method to support the analysis of fault causes.
Review of Automated Operations in Drilling and Mining
Authors: Kokkinis Athanasios , Frantzis Theodore , Skordis Konstantinos , Nikolakopoulos George , Koustoumpardis Panagiotis
Published: November 2024

Current advances and trends in the fields of mechanical, material, and software engineering have allowed mining technology to undergo a significant transformation. Aiming to maximize the efficiency and safety of the mining process, several enabling technologies, such as the recent advances in artificial intelligence, IoT, sensor fusion, computational modeling, and advanced robotics, are being progressively adopted in mining machine manufacturing while replacing conventional parts and approaches that used to be the norm in the rock ore extraction industry. This article aims to provide an overview of research trends and state-of-the-art technologies in face exploration and drilling operations in order to define the vision toward the realization of fully autonomous mining exploration machines of the future, capable of operating without any external infrastructure. As the trend of mining at large depths is increasing and as the re-opening of abandoned mines is gaining more interest, near-to-face mining exploration approaches for identifying new ore bodies need to undergo significant revision. This article aims to contribute to future developments in the use of fully autonomous and cooperative smaller mining exploration machines.
Short-Term Predictions of the Trajectory of Mpox in East Asian Countries, 2022–2023: A Comparative Study of Forecasting Approaches
Authors: Shishkin Aleksandr , Bleichrodt Amanda , Luo Ruiyan , Skums Pavel , Chowell Gerardo , Kirpich Alexander
Published: November 2024

The 2022–2023 mpox outbreak exhibited an uneven global distribution. While countries such as the UK, Brazil, and the USA were most heavily affected in 2022, many Asian countries, specifically China, Japan, South Korea, and Thailand, experienced the outbreak later, in 2023, with significantly fewer reported cases relative to their populations. This variation in timing and scale distinguishes the outbreaks in these Asian countries from those in the first wave. This study evaluates the predictability of mpox outbreaks with smaller case counts in Asian countries using popular epidemic forecasting methods, including the ARIMA, Prophet, GLM, GAM, n-Sub-epidemic, and Sub-epidemic Wave frameworks. Despite the fact that the ARIMA and GAM models performed well for certain countries and prediction windows, their results were generally inconsistent and highly dependent on the country, i.e., the dataset, as well as the prediction interval length. In contrast, n-Sub-epidemic Ensembles demonstrated more reliable and robust performance across different datasets and predictions, indicating the effectiveness of this model on small datasets and its utility in the early stages of future pandemics.
C-Finite Sequences and Riordan Arrays
Authors: Merlini Donatella
Published: November 2024

Many prominent combinatorial sequences, such as the Fibonacci, Lucas, Pell, Jacobsthal and Tribonacci sequences, are defined by homogeneous linear recurrence relations with constant coefficients. These sequences are often referred to as C-finite sequences, and a variety of representations have been employed throughout the literature, largely influenced by the author’s background and the specific application under consideration. Beyond the representation through recurrence relations, other approaches include those based on generating functions, explicit formulas, matrix exponentiation, the method of undetermined coefficients and several others. Among these, the generating function approach is particularly prevalent in enumerative combinatorics due to its versatility and widespread use. The primary objective of this work is to introduce an alternative representation grounded in the theory of Riordan arrays. This representation provides a general formula expressed in terms of the vectors of constants and initial conditions associated with any recurrence relation of a given order, offering a new perspective on the structure of such sequences.
DBN-MACTraj: Dynamic Bayesian Networks for Predicting Combinations of Long-Term Trajectories with Likelihood for Multiple Agents
Authors: Cui Haonan , Qi Haolun , Zhou Jianyu
Published: November 2024

Accurately predicting the long-term trajectories of agents in complex traffic environments is crucial for the safety and effectiveness of autonomous driving systems. This paper introduces DBN-MACTraj, a probabilistic model that takes historical trajectories and surrounding lane information as inputs to generate a distribution of predicted trajectory combinations for all agents. DBN-MACTraj consists of two main components: a single-agent probabilistic model and a multi-agent risk-averse sampling algorithm. The single-agent model utilizes a dynamic Bayesian network, which incorporates the driver’s maneuvering decisions along with information about surrounding lanes. The multi-agent sampling algorithm simultaneously generates predictions for all agents, using a risk potential field model to filter out samples that may lead to traffic accidents. Ultimately, this results in a probability distribution of the combinations of long-term trajectories. Experimental evaluations on the nuScenes dataset demonstrate that DBN-MACTraj delivers competitive performance in trajectory prediction compared to other state-of-the-art approaches.