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Search Results (157)

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Keywords = microstrain

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15 pages, 7741 KiB  
Article
Experimental Study on Low-Shrinkage Concrete Mix Proportion for Post-Casting Belt of Full-Section Casting in Immersed Tube
by Bang-Yan Liang, Wen-Huo Sun, Chun-Lin Deng, Qian Hu and Yong-Hui Huang
Materials 2025, 18(14), 3315; https://doi.org/10.3390/ma18143315 - 14 Jul 2025
Viewed by 222
Abstract
Full-section interval casting technology was adopted for the integral immersed tube of the Chebei Immersed Tunnel. Field tests (Chebei Immersed Tunnel) were conducted to establish the time-dependent development of the concrete shrinkage strain of the full-section casting segments. And laboratory experiments were then [...] Read more.
Full-section interval casting technology was adopted for the integral immersed tube of the Chebei Immersed Tunnel. Field tests (Chebei Immersed Tunnel) were conducted to establish the time-dependent development of the concrete shrinkage strain of the full-section casting segments. And laboratory experiments were then carried out to investigate the influence of factors such as the reinforcement ratio and stress, expansive agent content and composition, fly ash content, and curing temperature and humidity on the expansive effect of calcium–magnesium composite expansive agents. Field tests revealed that casting segments exhibit initial expansion followed by shrinkage, reaching a final strain of 348 με (microstrain). Laboratory investigations demonstrated that reinforcement (20–30 MPa stress) in post-casting belts effectively restrains segments without compromising the performance of calcium–magnesium composite expansive agents. The optimal 5:3:2 ratio of CaO, MgO 90s, and MgO 200s agents controlled shrinkage strain within 80 με by combining CaO’s rapid early expansion with MgO’s sustained effect. Field validation confirmed the mix’s effectiveness in preventing cracking, with key findings: (1) fly ash content and curing conditions significantly influence expansive behavior, and (2) shrinkage development can be precisely regulated through agent composition adjustments. Full article
(This article belongs to the Section Construction and Building Materials)
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20 pages, 13368 KiB  
Article
Influence of Soaking Duration in Deep Cryogenic and Heat Treatment on the Microstructure and Properties of Copper
by Dhandapani Chirenjeevi Narashimhan and Sanjivi Arul
J. Manuf. Mater. Process. 2025, 9(7), 233; https://doi.org/10.3390/jmmp9070233 - 7 Jul 2025
Viewed by 318
Abstract
The extensive use of copper in thermal and electrical systems calls for constant performance enhancement by means of innovative material treatments. The effects on the microstructural, mechanical, and electrical characteristics of copper in deep cryogenic treatment (DCT) and deep cryogenic treatment followed by [...] Read more.
The extensive use of copper in thermal and electrical systems calls for constant performance enhancement by means of innovative material treatments. The effects on the microstructural, mechanical, and electrical characteristics of copper in deep cryogenic treatment (DCT) and deep cryogenic treatment followed by heat treatment (DCT + HT) are investigated in this work. Copper samples were treated for various soaking durations ranging from 6 to 24 h. Mechanical properties such as tensile strength, hardness, and wear rate were analyzed. In the DCT-treated samples, tensile strength increased, reaching a peak of 343 MPa at 18 h, alongside increased hardness (128 HV) and a refined grain size of 9.58 µm, primarily due to elevated dislocation density and microstrain. At 18 h of soaking, DCT + HT resulted in improved structural stability, high hardness (149 HV), a fine grain size (7.42 µm), and the lowest wear rate (7.73 × 10−10 mm3/Nm), consistent with Hall–Petch strengthening. Electrical measurements revealed improved electron mobility (52.08 cm2/V·s) for samples soaked for 24 h in DCT + HT, attributed to increased crystallite size (39.9 nm), reduced lattice strain, and higher (111) texture intensity. SEM–EBSD analysis showed a substantial increase in low-angle grain boundaries (LAGBs) in DCT + HT-treated samples, correlating with enhanced electrical conductivity. Overall, an 18 h soaking duration was found to be optimal for both treatments. However, the strengthening mechanism in DCT + HT is influenced by grain boundary stabilization and thermal recovery and is different to DCT, which is strain-induced enhancement. Full article
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28 pages, 12296 KiB  
Article
Phase Stability and Structural Reorganization of Silica in Cherts Under Thermal and Mechanochemical Stress
by María de Uribe-Zorita, Pedro Álvarez-Lloret, Beatriz Ramajo, Javier F. Reynes and Celia Marcos
Materials 2025, 18(13), 3077; https://doi.org/10.3390/ma18133077 - 28 Jun 2025
Viewed by 511
Abstract
This work investigated the structural response and phase transformation dynamics of silica-bearing cherts subjected to high-temperature processing (up to 1400 °C) and prolonged mechanochemical activation. Through a combination of X-ray diffraction (XRD) with Rietveld refinement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and [...] Read more.
This work investigated the structural response and phase transformation dynamics of silica-bearing cherts subjected to high-temperature processing (up to 1400 °C) and prolonged mechanochemical activation. Through a combination of X-ray diffraction (XRD) with Rietveld refinement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and transmission electron microscopy (HRTEM), we trace the crystallographic pathways of quartz, moganite, tridymite, and cristobalite under controlled thermal and mechanical stress regimes. The experimental results demonstrated that phase behavior is highly dependent on intrinsic properties such as initial phase composition, impurity presence, and crystallinity. Heating at 1400 °C induced irreversible conversion of quartz, moganite, and tridymite into cristobalite. Samples enriched in cristobalite and tridymite exhibited notable increases in crystallinity, whereas quartz-dominant samples showed either stability or a decline in structural order. Rietveld analyses underscored the critical influence of microstrain and crystallite size on thermal resilience and phase persistence. Thermal profiles revealed by DSC and TGA expose overlapping processes including polymorphic transitions, minor phase dehydration, and redox-driven changes, likely associated with trace components. Mechanochemical processing resulted in partial amorphization and the emergence of phases such as opal and feldspar minerals (microcline, albite, anorthite), interpreted as the product of lattice collapse and subsequent reprecipitation. Heat treatment of chert leads to a progressive rearrangement and recrystallization of its silica phases: quartz collapses around 1000 °C before recovering, tridymite emerges as an intermediate phase, and cristobalite shows the greatest crystallite size growth and least deformation at 1400 °C. These phase changes serve as markers of high-temperature exposure, guiding the identification of heat-altered lithic artefacts, reconstructing geological and diagenetic histories, and allowing engineers to adjust the thermal expansion of ceramic materials. Mechanochemical results provide new insights into the physicochemical evolution of metastable silica systems and offer valuable implications for the design and thermal conditioning of silica-based functional materials used in high-temperature ceramics, glasses, and refractory applications. From a geoarchaeological standpoint, the mechanochemically treated material could simulate natural weathering of prehistoric chert tools, providing insights into diagenetic pathways and lithic degradation processes. Full article
(This article belongs to the Section Construction and Building Materials)
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13 pages, 5319 KiB  
Article
Self-Healing and Tough Polyacrylic Acid-Based Hydrogels for Micro-Strain Sensors
by Chuanjie Liu, Zhihong Liu and Bing Lu
Gels 2025, 11(7), 475; https://doi.org/10.3390/gels11070475 - 20 Jun 2025
Viewed by 438
Abstract
Self-healing hydrogels hold promise for smart sensors in bioengineering and intelligent systems, yet balancing self-healing ability with mechanical strength remains challenging. In this study, a self-healing hydrogel exhibiting superior stretchability was developed by embedding a combination of hydrogen bonding and dynamic metal coordination [...] Read more.
Self-healing hydrogels hold promise for smart sensors in bioengineering and intelligent systems, yet balancing self-healing ability with mechanical strength remains challenging. In this study, a self-healing hydrogel exhibiting superior stretchability was developed by embedding a combination of hydrogen bonding and dynamic metal coordination interactions, introduced by modified fenugreek galactomannan, ferric ions, and lignin silver nanoparticles, into a covalent polyacrylic acid (PAA) matrix. Synergistic covalent and multiple non-covalent interactions enabled the hydrogel with high self-healing ability and enhanced mechanical property. In particular, due to the introduction of multiple energy dissipation mechanisms, particularly migrative dynamic metal coordination interactions, the hydrogel exhibited ultra-high stretchability of up to 2000%. Furthermore, with the incorporation of lignin silver nanoparticles and ferric ions, the hydrogel demonstrated excellent strain sensitivity (gauge factor ≈ 3.94), with stable and repeatable resistance signals. Assembled into a flexible strain sensor, it effectively detected subtle human motions and organ vibrations, and even replaced conductive rubber in gaming controllers for real-time inputs. This study provides a versatile strategy for designing multifunctional hydrogels for advanced sensing applications. Full article
(This article belongs to the Special Issue Synthesis, Properties, and Applications of Novel Polymer-Based Gels)
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17 pages, 2559 KiB  
Article
Thermal Strain and Microstrain in a Polymorphic Schiff Base: Routes to Thermosalience
by Teodoro Klaser, Marko Jaklin, Jasminka Popović, Ivan Grgičević and Željko Skoko
Molecules 2025, 30(12), 2567; https://doi.org/10.3390/molecules30122567 - 12 Jun 2025
Viewed by 352
Abstract
We present a comprehensive structural and thermomechanical investigation of N-salicylideneaniline, a Schiff base derivative that exhibits remarkable thermosalient phase transition behavior. By combining variable-temperature X-ray powder diffraction (VT-XRPD), differential scanning calorimetry (DSC), hot-stage microscopy, and Hirshfeld surface analysis, we reveal two distinct [...] Read more.
We present a comprehensive structural and thermomechanical investigation of N-salicylideneaniline, a Schiff base derivative that exhibits remarkable thermosalient phase transition behavior. By combining variable-temperature X-ray powder diffraction (VT-XRPD), differential scanning calorimetry (DSC), hot-stage microscopy, and Hirshfeld surface analysis, we reveal two distinct thermosalient mechanisms operating in different polymorphic forms. Form I displays pronounced anisotropic thermal expansion with negative strain along a principal axis, culminating in a sudden and explosive phase transition into Form IV. In contrast, Form III transforms more gradually through a microstrain accumulation mechanism. Fingerprint plots and contact evolution from Hirshfeld surface analysis further support this dual-mechanism model. These insights highlight the importance of integrating macro- and microscale structural descriptors to fully capture the mechanical behavior of responsive molecular solids. The findings not only enhance the fundamental understanding of thermosalience but also inform the rational design of functional materials for actuating and sensing applications. Full article
(This article belongs to the Section Materials Chemistry)
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24 pages, 7561 KiB  
Article
Mechanism of Strain-Resistance Response of CNT/Polymer Composite Materials for Pavement Strain Self-Sensing Based on the Molecular Dynamics Simulation Method
by Xue Xin, Xingchi Zhao, Jing Gao, Zhanyong Yao and Yunzhen Li
Polymers 2025, 17(11), 1427; https://doi.org/10.3390/polym17111427 - 22 May 2025
Viewed by 446
Abstract
Embedded and real-time monitoring of pavement mechanical state changes based on the strain detected by self-sensing sensors of polymer/conductive composites is a new way for pavement health monitoring. Strain monitoring, using polymer-based composite mechanosensitive materials, requires the formation of effective conductive networks and [...] Read more.
Embedded and real-time monitoring of pavement mechanical state changes based on the strain detected by self-sensing sensors of polymer/conductive composites is a new way for pavement health monitoring. Strain monitoring, using polymer-based composite mechanosensitive materials, requires the formation of effective conductive networks and conductive channels within the composite material so that the mechanosensitive material is electrically conductive at the macroscopic level. However, the deformation of the pavement structure is much smaller in magnitude, which is about hundreds or even tens of microstrains (10−6). Therefore, it is especially important to study the strain self-sensing mechanism of conductive composites at the με level. Micro- and nanostructured polymer composites have a complex structure with multiple layers, scales, and interactions, and thus present many difficulties when studying their microscopic conductive mechanisms. In this paper, the all-atom system of the micro-nanostructured composite mechanosensitive materials model was proposed with the help of molecular dynamics simulations. This achieved a breakthrough and realized the systematic study of the microscopic level of the relevant parameters of the composite’s conductivity from the molecular point of view to construct a relationship between the microscopic parameters, conductive network, and conductivity. The kinetic models of the micro-nanostructure and resin interface based on the molecular dynamics simulation technology were constructed to explore the dispersion state of the conductive filler, the interfacial interactions between the conductive filler and epoxy resin matrix, and the structural changes in the conductive network within the system under the tension state. Full article
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34 pages, 7018 KiB  
Article
Strontium-Doped Tin Oxide Nanofibers for Enhanced Visible Light Photocatalysis
by Pranta Barua, Tan Thai, Kannoorpatti Krishnan and Naveen Kumar Elumalai
Energies 2025, 18(10), 2495; https://doi.org/10.3390/en18102495 - 12 May 2025
Viewed by 746
Abstract
This study investigates the photocatalytic degradation of methylene blue (MB) using strontium-doped SnO2 nanofibers synthesized via electrospinning. The 1% Sr-doped SnO2 nanofibers exhibited remarkable photocatalytic activity, achieving 84.74% MB degradation under visible light irradiation, substantially outperforming both undoped SnO2 nanofibers [...] Read more.
This study investigates the photocatalytic degradation of methylene blue (MB) using strontium-doped SnO2 nanofibers synthesized via electrospinning. The 1% Sr-doped SnO2 nanofibers exhibited remarkable photocatalytic activity, achieving 84.74% MB degradation under visible light irradiation, substantially outperforming both undoped SnO2 nanofibers (61%) and the same catalyst under UV light (69%) under identical experimental conditions. Comprehensive electrochemical investigations revealed that Sr doping fundamentally transformed interfacial charge transfer kinetics, with 1% Sr-doped nanofibers exhibiting a remarkable three-fold decrease in charge transfer resistance (404 Ω compared to 1350 Ω for undoped samples), a dramatic enhancement in charge carrier density (5.17 × 1022 versus 9.24 × 1019 for undoped samples), and an approximately eight-fold increase in diffusion coefficient (8.78 × 10−10 versus 1.13 × 10−10 cm2s−1). These electrochemical improvements were corroborated by comprehensive structural characterization, which demonstrated that strategic Sr incorporation induced beneficial oxygen vacancies, reduced crystallite size, increased microstrain, and enhanced dislocation density, collectively contributing to superior surface reactivity and accelerated photocatalytic mechanisms. This work establishes a quantitative correlation between electrochemical characteristics and photocatalytic activity in Sr-doped SnO2 nanofibers, revealing the fundamental mechanisms that transform the SnO2 nanostructure from UV-dependent to efficient visible light-driven catalysts for organic pollutant degradation. Full article
(This article belongs to the Section D1: Advanced Energy Materials)
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18 pages, 3776 KiB  
Article
A Viscoelastic-Plastic Creep Model for Initial Damaged Coal Sample Affected by Loading Rate
by Peng Huang, Yimei Wei, Meng Li, Erkan Topal, Xinyong Teng and Wei Wang
Appl. Sci. 2025, 15(10), 5265; https://doi.org/10.3390/app15105265 - 8 May 2025
Viewed by 395
Abstract
Underground engineering rock masses are significantly affected by stress redistribution induced by mining or adjacent engineering disturbances, leading to initial damage accumulation in coal-rock masses. Under sustained geostress, these masses exhibit pronounced time-dependent creep behavior, posing serious threats to long-term engineering stability. Dynamic [...] Read more.
Underground engineering rock masses are significantly affected by stress redistribution induced by mining or adjacent engineering disturbances, leading to initial damage accumulation in coal-rock masses. Under sustained geostress, these masses exhibit pronounced time-dependent creep behavior, posing serious threats to long-term engineering stability. Dynamic loading effects triggered by adjacent mining activities (manifested as medium strain-rate loading) further exacerbate damage evolution and significantly influence creep characteristics. In this study, coal samples with identical initial damage were prepared, and graded loading creep tests were conducted at rates of 0.005 mm·s−1 (50 microstrains·s−1), 0.01 mm·s−1 (100 microstrains·s−1), 0.05 mm·s−1 (500 microstrains·s−1), and 0.1 mm·s−1 (1000 microstrains·s−1) to systematically analyze the coupled effects of loading rate on creep behavior. Experimental results demonstrate that increased loading rates markedly shorten creep duration, with damage rates during the acceleration phase showing nonlinear surges (e.g., abrupt instability at 0.1 mm·s−1 (1000 microstrains·s−1)). Based on experimental data, an integer-order viscoelastic-plastic creep model incorporating stress-dependent viscosity coefficients and damage correlation functions was developed, fully characterizing four behaviors stages: instantaneous deformation, deceleration, steady-state, and accelerated creep. Optimized via the Levenberg–Marquardt algorithm, the model achieved correlation coefficients exceeding 0.96, validating its accuracy. This model clarifies the impact mechanisms of loading rates on the long-term mechanical behavior of initially damaged coal samples, providing theoretical support for stability assessment and hazard prevention in underground engineering. Full article
(This article belongs to the Special Issue Technologies and Methods for Exploitation of Geological Resources)
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12 pages, 8928 KiB  
Article
MXene-Enhanced Laser-Induced Graphene Flexible Sensor with Rapid Response for Monitoring Pilots’ Body Motion
by Xia Lei, Hongyun Fan, Yilin Zhao, Mian Zhong, Zhanghui Wu, Lin Li, Shouqing Li, Xiaoqing Xing, Jianhua Liu, Yibo Sun, Yong Jiang and Guogang Ren
Micromachines 2025, 16(5), 513; https://doi.org/10.3390/mi16050513 - 27 Apr 2025
Viewed by 684
Abstract
Flexible wearable strain sensors demonstrate promising application prospects in health monitoring, human-machine interaction, motion tracking, and the detection of human physiological signals. Although laser-induced graphene (LIG) materials have been extensively utilized in these scenarios, traditional types of LIG sensors are constrained by intrinsic [...] Read more.
Flexible wearable strain sensors demonstrate promising application prospects in health monitoring, human-machine interaction, motion tracking, and the detection of human physiological signals. Although laser-induced graphene (LIG) materials have been extensively utilized in these scenarios, traditional types of LIG sensors are constrained by intrinsic limitations, including discontinuous conductive networks and electromechanical responsive hysteresis. These limitations hinder their applications in micro-strain detection scenarios. Consequently, enhancing the performance of LIG-based sensors has become a crucial priority. To address this challenge, we developed a novel MXene/LIG composite featuring optimized conductive networks and interfacial coupling effects through the systematic enhancement of LIG. The flexible strain sensor fabricated using this composite exhibits exceptional performance, including an ultra-low sheet resistance of 14.1 Ω, a high sensitivity of 20.7, a micro-strain detection limit of 0.05%, and a rapid response time of approximately 65 ms. These improvements significantly enhance electromechanical responsiveness and strain detection sensitivity. Furthermore, the sensor exhibits remarkable stability under varying tensile strains, particularly showing outstanding repeatability across 2500 cyclic tests. Notably, when applied to the pilot health monitoring scenarios, the MXene/LIG-based sensor demonstrates robust capability in detecting body movement signals such as micro-expressions and joint movements. This establishes a novel and highly effective technological solution for the real-time monitoring of pilots’ motion states during operational scenarios. Full article
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16 pages, 7371 KiB  
Article
Anisotropic Wear Resistance of Heat-Treated Selective Laser-Melted 316L Stainless Steel
by Menghui Sun, Qianqian Zhang, Jinxiu Wu, Hao Wang, Xu Wang, Hao Zhang, Yinong An, Yujie Liu and Long Ma
Lubricants 2025, 13(4), 189; https://doi.org/10.3390/lubricants13040189 - 19 Apr 2025
Viewed by 534
Abstract
Anisotropic microstructures and wear resistance are caused by large thermal gradients during selective laser melting (SLM). Investigating the wear resistance in different planes of SLM specimens is crucial. Hence, the effect of heat treatment on the anisotropy of the microstructure, density, microhardness, and [...] Read more.
Anisotropic microstructures and wear resistance are caused by large thermal gradients during selective laser melting (SLM). Investigating the wear resistance in different planes of SLM specimens is crucial. Hence, the effect of heat treatment on the anisotropy of the microstructure, density, microhardness, and wear resistance of SLM 316L stainless steel was studied. Specimens subjected to solution + aging treatment exhibited γ austenite and α ferrite phases with lower microstrain, as determined via X-ray diffraction (XRD) analysis. Microstructure observations demonstrated that SLM 316L appears as intersecting melt pools on the XOY plane and fish scale-like melt pools on the XOZ plane. After heat treatment, the melt boundaries disappeared, carbides (M23C6) precipitated at grain boundaries and within the grains, and the microstructures coarsened and became more uniform. The microhardness and wear resistance of the XOY plane were shown to be superior to those of the XOZ plane, and the microhardness decreased following heat treatment. Compared with SLM 316L, the microhardness of the XOY and XOZ planes of the specimen subjected to solution + aging treatment decreased by 5.96% and 4.98%. The friction and wear test results revealed that the specimen after solution + aging treatment had the lowest friction coefficient and the smallest wear rate. The wear rates of specimens from the XOY and XOZ planes after solution + aging treatment were 21.1% and 27.1% lower than that of SLM 316L, exhibiting the best wear resistance. Full article
(This article belongs to the Special Issue Friction and Wear of Alloys)
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17 pages, 2318 KiB  
Article
Finite Element Modeling and Laboratory Performance Evaluation of Lignin, Basalt and Polyester Fiber-Reinforced Asphalt Mixtures
by Mohammad Fahad and Richard Nagy
Appl. Sci. 2025, 15(7), 3953; https://doi.org/10.3390/app15073953 - 3 Apr 2025
Cited by 1 | Viewed by 394
Abstract
The performance of styrene-butadiene-styrene (SBS) modified asphalt mixtures can be further improved by adding a variety of fibers available. Addition of fibers provides a cost-effective solution against increasing the dosage of SBS modified asphalt mixtures. Therefore, in this research three different types of [...] Read more.
The performance of styrene-butadiene-styrene (SBS) modified asphalt mixtures can be further improved by adding a variety of fibers available. Addition of fibers provides a cost-effective solution against increasing the dosage of SBS modified asphalt mixtures. Therefore, in this research three different types of fibers—basalt fiber, polyester fiber and lignin fiber—were added to SBS-7% bitumen binder and their performance was compared with SBS-7% mixture without any fibers. The performance was compared using laboratory tests, including indirect tensile strength tests and dynamic shear rheometer. Indirect tensile strength of all the mixtures was evaluated at various loading rates from 10 MPa/s to 70 MPa/s. Furthermore, stiffness moduli of mixtures were evaluated at frequency rages of 5 Hz, 3.5 Hz, 1.9 Hz and 1.2 Hz. Finite element simulations were conducted using the Burger’s logit model, and microstrain analysis was performed to evaluate rutting and fatigue damage. The results show increased performance in terms of gained tensile strength and complex shear modulus for fiber-modified mixtures. Among the fiber-modified mixtures, basalt fiber outperforms other mixtures. PF and LF exhibit almost similar performances. Basalt fiber mixture outperforms the SBS-7% mixture by 25% and 28% in terms of rutting and fatigue damage, respectively. Full article
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32 pages, 29310 KiB  
Article
Microstructure Evolution, Tensile/Nanoindentation Response, and Work-Hardening Behaviour of Prestrained and Subsequently Annealed LPBF 316L Stainless Steel
by Bohdan Efremenko, Yuliia Chabak, Ivan Petryshynets, Vasily Efremenko, Kaiming Wu, Sundas Arshad and František Kromka
Materials 2025, 18(5), 1102; https://doi.org/10.3390/ma18051102 - 28 Feb 2025
Cited by 1 | Viewed by 1064
Abstract
Additive manufacturing is increasingly used to produce metallic biomaterials, and post-processing is gaining increasing attention for improving the properties of as-built components. This study investigates the effect of work hardening followed by recrystallisation annealing on the tensile and nanoindentation behaviour of laser powder [...] Read more.
Additive manufacturing is increasingly used to produce metallic biomaterials, and post-processing is gaining increasing attention for improving the properties of as-built components. This study investigates the effect of work hardening followed by recrystallisation annealing on the tensile and nanoindentation behaviour of laser powder bed-fused (LPBF) 316L stainless steel, with the aim of optimising its mechanical properties. As-built and thermally stabilised (at 900 °C) specimens were prestrained in a uniaxially tensile manner at room temperature (0.12 plastic strain, ~75% of maximum work hardening) and subsequently annealed (at 900 °C or 1050 °C for 1 h). The microstructure and mechanical properties were then characterised by optical microscopy, SEM, EBSD, XRD, nanoindentation, and tensile testing. It was found that prestraining increased yield tensile strength (YTS) 1.2–1.7 times (to 690–699 MPa) and ultimate tensile strength (UTS) ~1.2 times (to 762–770 MPa), but decreased ductility 1.5 times. Annealing led to recovery and partial static recrystallisation, decreasing YTS (to 403–427 MPa), restoring ductility, and increasing the strain hardening rate; UTS and indentation hardness were less affected. Notably, the post-LPBF thermal stabilisation hindered recrystallisation and increased its onset temperature. Mechanical property changes under prestraining and annealing are discussed with respect to microstructure and crystalline features (microstrain, crystal size, dislocation density). All specimens exhibited ductile fractures with fine/ultra-fine dimples consistent with the as-built cellular structure. The combined treatment enhanced tensile strength whilst preserving sufficient ductility, achieving a strength–ductility product of 40.3 GPa·%. This offers a promising approach for tailoring LPBF 316L for engineering applications. Full article
(This article belongs to the Special Issue Research and Development of New Metal-Based Biomaterials)
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31 pages, 9707 KiB  
Article
Strain Decay Monitoring and Analytical Prediction of RC Columns Using Brillouin Optical Technology and Time-Dependent Deterioration Factor
by Ittipon Pasityothin, Phromphat Thansirichaisree, Apichat Buatik, Thanongsak Imjai, Radhika Sridhar, Reyes Garcia and Takafumi Noguchi
Sensors 2025, 25(3), 741; https://doi.org/10.3390/s25030741 - 26 Jan 2025
Viewed by 859
Abstract
This study presents a novel approach to the design and assessment of slender reinforced concrete (RC) columns by integrating Brillouin Optical Time Domain Analysis (BOTDA) for real-time, distributed strain monitoring and introducing a “time-dependent deterioration factor” strain decay (ηdecay). Experimental tests [...] Read more.
This study presents a novel approach to the design and assessment of slender reinforced concrete (RC) columns by integrating Brillouin Optical Time Domain Analysis (BOTDA) for real-time, distributed strain monitoring and introducing a “time-dependent deterioration factor” strain decay (ηdecay). Experimental tests on 200 mm × 200 mm RC columns with lengths of 1800 mm and slenderness ratios of 29.4, reinforced with four 12 mm bars, captured strain variations up to 400 microstrain under an axial load of 1200 kN, demonstrate BOTDA’s sensitivity and precision. Unlike conventional strain gauges, BOTDA provided a continuous strain profile along the column height, accurately capturing strain decay with a resolution exceeding 95%, enabling the detection of localized strain reductions often missed by traditional methods. The integration of ηdecay into ACI 318 and Eurocode 2 models conservatively improved predictions, particularly for specimens tested with long-term testing (720 days), with experimental-to-predicted (E/P) ratios of 1.42 and 1.29, respectively, compared to higher discrepancies in the original codes. The ηdecay factor accounts for strain reduction along the column height caused by time-dependent effects such as creep, shrinkage, and material degradation, significantly improving the accuracy of axial load capacity predictions. Finite element analysis (FEA) validated these improvements, showing good agreement with experimental data up to the yield load. Post-yield, the modified equations effectively addressed underestimations caused by microcracking, highlighting the necessity of ηdecay for reliable long-term performance predictions. This research combines advanced BOTDA technology with an innovative ηdecay framework, addressing long-term structural deterioration and refining design codes. It establishes a robust foundation for integrating time-dependent effects into predictive models, enhancing the resilience, safety, and sustainability of RC structures under real-world conditions. Full article
(This article belongs to the Section Physical Sensors)
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17 pages, 7192 KiB  
Article
Effect of Dy3+ Ions on Structural, Thermal and Spectroscopic Properties of L-Threonine Crystals: A Visible Light-Emitting Material
by João G. de Oliveira Neto, Otávio C. da Silva Neto, Jéssica A. O. Rodrigues, Jailton R. Viana, Alysson Steimacher, Franciana Pedrochi, Francisco F. de Sousa and Adenilson O. dos Santos
Quantum Beam Sci. 2025, 9(1), 3; https://doi.org/10.3390/qubs9010003 - 13 Jan 2025
Cited by 1 | Viewed by 1324
Abstract
In this study, L-threonine crystals (L-thr) containing Dy3+ ions (L-thrDy5 and L-thrDy10) with varying mass concentrations (5% and 10%) were successfully synthesized using a solvent slow evaporation method. The structural properties were characterized by Powder X-ray diffraction and Rietveld refinement. The data [...] Read more.
In this study, L-threonine crystals (L-thr) containing Dy3+ ions (L-thrDy5 and L-thrDy10) with varying mass concentrations (5% and 10%) were successfully synthesized using a solvent slow evaporation method. The structural properties were characterized by Powder X-ray diffraction and Rietveld refinement. The data revealed that all three samples crystallized in orthorhombic symmetry (P212121-space group) and presented four molecules per unit cell (Z = 4). However, the addition of Dy3+ ions induced a dilation effect in the lattice parameters and cell volume of the organic structure. Additionally, the average crystallite size, lattice microstrain, percentage of void centers, and Hirshfeld surface were calculated for the crystals. Thermogravimetric and differential thermal analysis experiments showed that L-thr containing Dy3+ ions are thermally stable up to 214 °C. Fourier transform infrared and Raman spectroscopy results indicated that the Dy3+ ions interact indirectly with the L-thr molecule via hydrogen bonds, slightly affecting the crystalline structure of the amino acid. Optical analysis in the ultraviolet–visible region displayed eight absorption bands associated with the electronic transitions characteristic of Dy3+ ions in samples containing lanthanides. Furthermore, L-thrDy5 and L-thrDy10 crystals, when optically excited at 385 nm, exhibited three photoluminescence bands centered around approximately 554, 575, and 652 nm, corresponding to the 4F7/26H11/2, 4F9/26H13/2, and 4F9/26H11/2 de-excitations. Therefore, this study demonstrated that L-thr crystals containing Dy3+ ions are promising candidates for the development of optical materials due to their favorable physical and chemical properties. Additionally, it is noteworthy that the synthesis of these systems is cost-effective, and the synthesis method used is efficient. Full article
(This article belongs to the Section Engineering and Structural Materials)
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20 pages, 4070 KiB  
Article
An Investigation of the Influence of Paste’s Rheological Characteristics on the Tensile Creep of HVFAC at Early Ages
by Tongyuan Ni, Kang Chen, Fangshi Gao, Xingrui Li, Yang Yang, Deyu Kong and Shuifeng Yao
Materials 2025, 18(2), 305; https://doi.org/10.3390/ma18020305 - 11 Jan 2025
Viewed by 784
Abstract
The rheological properties of concrete paste significantly influence its tensile creep behavior. In this study, the tensile creep behavior of high-volume fly ash concrete (HVFAC) employing the same cementitious pastes was experimentally investigated, and the rheological properties of the paste containing a high [...] Read more.
The rheological properties of concrete paste significantly influence its tensile creep behavior. In this study, the tensile creep behavior of high-volume fly ash concrete (HVFAC) employing the same cementitious pastes was experimentally investigated, and the rheological properties of the paste containing a high volume of fly ash using the nanoindentation (NI) technique was investigated in order to explore the influence of the paste’s rheological properties (such as micro-mechanical properties and microscopic creep) on the early-age tensile creep of HVFAC. The results demonstrated that the micro-strain of paste containing a high volume of fly ash (HVFA) showed a larger value than that without fly ash. As the test age extends, a decreasing trend in microscopic creep was observed which could be attributed to the growth of the content of HD C–S–H (high density C–S–H) gel. Moreover, within the same age period, the experimental data revealed that the incorporation of fly ash resulted in the reduction of the values of the creep modulus C and characteristic time τ. The effects of fly ash dosages and loading age on the creep properties of concrete was consistent with the micro-creep properties of the cementitious paste. The tensile specific creep values derived from the ZC (“ZC” are initials for the word ‘‘self-developed” in Chinese) model based on nanoindentation data closely match those obtained from experiments. Full article
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