Search Results (4,063)

This paper presents an analytical model for the hereditary vibrations of a coupled circular plate system interconnected by viscoelastic creep layers. The system is represented as a discrete-continuous chain of thin, isotropic plates with time-dependent material properties. Based on the theory of hereditary viscoelasticity and D’Alembert’s principle, a system of partial integro-differential equations is derived and reduced to ordinary integro-differential equations using Bernoulli’s method and Laplace transforms. Analytical expressions for natural frequencies, mode shapes, and time-dependent response functions are obtained. The results reveal the emergence of multi-frequency vibration regimes, with modal families remaining temporally uncoupled. This enables the identification of resonance conditions and dynamic absorption phenomena. The fractional parameter serves as a tunable damping factor: lower values result in prolonged oscillations, while higher values cause rapid decay. Increasing the kinetic stiffness of the coupling layers raises vibration frequencies and enhances sensitivity to hereditary effects. This interplay provides deeper insight into dynamic behavior control. The model is applicable to multilayered structures in aerospace, civil engineering, and microsystems, where long-term loading and time-dependent material behavior are critical. The proposed framework offers a powerful tool for designing systems with tailored dynamic responses and improved stability. Full article

Lignin, the most abundant renewable source of aromatic compounds, plays a pivotal role in advancing sustainable biorefineries and reducing dependence on fossil resources. Recent progress in integrated lignin valorization pathways has unlocked opportunities to convert this complex biopolymer into high-value chemicals, materials, and energy carriers, despite its structural heterogeneity and recalcitrance posing major challenges. This review highlights the significant advancements in depolymerization strategies, including catalytic, oxidative, and biological approaches, which are reinforced by innovations in catalyst design and reaction engineering that enhance selectivity and efficiency. It also discusses emerging technologies, such as hybrid chemo-enzymatic systems, solvent fractionation, and continuous-flow reactors, for their potential to improve scalability and sustainability. Furthermore, this review examines the integration of lignin valorization with upstream pretreatment and downstream recovery, emphasizing process intensification, co-product synergy, and techno-economic optimization to achieve commercial viability. Despite these developments, critical gaps remain in understanding the molecular complexity of lignin, developing universally applicable catalytic systems, and optimizing economic and environmental performance. To guide future research, it poses two key questions: how to design catalysts for selective depolymerization across diverse lignin sources, and how to configure biorefineries for maximum lignin utilization while ensuring sustainability? Addressing these challenges will be essential for lignin’s role in next-generation biorefineries and a circular bioeconomy. Full article

A biomimetic cartilage scaffold featuring a continuous hydroxyapatite (HA) concentration gradient and a spatially curved architecture was developed using a dual-channel mixing extrusion-based 3D printing approach. By dynamically regulating the feeding rates of two bioinks during printing, a continuous HA gradient decreasing from the bottom to the top of the scaffold was precisely achieved, mimicking the compositional transition from the calcified to the non-calcified cartilage region in native articular cartilage. The integration of gradient material deposition with synchronized multi-axis motion enabled accurate fabrication of curved geometries with high structural fidelity. The printed scaffolds exhibited stable swelling and degradation behavior and showed improved compressive performance compared with step-gradient counterparts. Rheological analysis confirmed that the bioinks possessed suitable shear-thinning and recovery properties, ensuring printability and shape stability during extrusion. In vitro evaluations demonstrated good cytocompatibility, supporting bone marrow mesenchymal stem cell (BMSC) adhesion and proliferation. Chondrogenic assessment based on scaffold extracts indicated that the incorporation of HA and its gradient distribution did not inhibit cartilage-related extracellular matrix synthesis, confirming the biosafety of the composite hydrogel system. Overall, this study presents a controllable and versatile fabrication strategy for constructing curved, compositionally graded cartilage scaffolds, providing a promising platform for the development of biomimetic cartilage tissue engineering constructs. Full article

Steel pipes play a vital role in energy and industrial transportation systems, where undetected defects such as cracks and wall thinning may lead to severe safety hazards. Although ultrasonic guided waves enable long-range inspection, their defect imaging performance is often limited by dispersion, multimode interference, and strong noise. In this work, a multi-frequency fusion imaging method integrating time-reversal, topological derivative, and sparse Bayesian learning is proposed for guided wave-based defect detection in steel pipes. Multi-frequency guided waves are employed to enhance defect sensitivity and suppress frequency-dependent ambiguity. Time-reversal focusing is used to concentrate scattered energy at defect locations, while the topological derivative provides a global sensitivity map as physics-guided prior information. These results are further fused within a sparse Bayesian learning framework to achieve probabilistic defect imaging and uncertainty quantification. Dispersion compensation based on the semi-analytical finite element method is introduced to ensure accurate wavefield reconstruction at different frequencies. Domain randomization is also incorporated to improve robustness against uncertainties in material properties, temperature, and measurement noise. Numerical simulation results verify that the proposed method achieves high localization accuracy and significantly outperforms conventional TR-based imaging in terms of resolution, false alarm suppression, and stability. The proposed approach provides a reliable and robust solution for guided wave inspection of steel pipelines and offers strong potential for engineering applications in nondestructive evaluation and structural health monitoring. Full article

This study investigates critical research gaps in procurement management challenges faced by Chinese contractors in international engineering–procurement–construction (EPC) projects under the Belt and Road Initiative (BRI), with a particular focus on sustainability-oriented outcomes. It examines the following: (1) prevalent procurement inefficiencies, such as communication delays and material shortages, encountered in international EPC projects; (2) the role of supply chain INTEGRATION in enhancing procurement performance; (3) the application of social network analysis (SNA) to reveal inter-organizational relationships in procurement systems; and (4) the influence of stakeholder collaboration on achieving efficient and sustainable procurement processes. The findings demonstrate that effective supply chain integration significantly improves procurement efficiency, reduces delays, and lowers costs, thereby contributing to more sustainable project delivery. Strong collaboration and transparent communication among key stakeholders—including contractors, suppliers, subcontractors, and designers—are shown to be essential for mitigating procurement risks and supporting resilient supply chain operations. SNA results highlight the critical roles of central stakeholders and their relational structures in optimizing resource allocation and enhancing risk management capabilities. Evidence from case studies further indicates that Chinese contractors increasingly adopt sustainability-oriented practices, such as just-in-time inventory management, strategic supplier relationship management, and digital procurement platforms, to reduce inefficiencies and environmental impacts. Overall, this study underscores that supply chain INTEGRATION, combined with robust stakeholder collaboration, is a key enabler of sustainable procurement and long-term competitiveness for Chinese contractors in the global EPC market. The purpose of this study is to identify critical procurement management challenges and propose evidence-based solutions for Chinese contractors. It further aims to develop a sustainability-oriented framework integrating supply chain integration and stakeholder collaboration to enhance competitiveness. Full article

Additive manufacturing has been adopted in several industries including the medical field to develop new personalised medical implants including tissue engineering scaffolds. Custom patient-specific scaffolds can be additively manufactured to speed up the wound healing process. The aim of this study was to design, fabricate, and evaluate a range of materials and scaffold architectures for 3D-printed wound dressings intended for soft tissue applications, such as skin repair. Multiple biocompatible polymers, including polylactic acid (PLA), polyvinyl alcohol (PVA), butenediol vinyl alcohol copolymer (BVOH), and polycaprolactone (PCL), were fabricated using a material extrusion additive manufacturing technique. Eight scaffolds, five with circular designs (knee meniscus angled (KMA), knee meniscus stacked (KMS), circle dense centre (CDC), circle dense edge (CDE), and circle no gradient (CNG)), and three square scaffolds (square dense centre (SDC), square dense edge (SDE), and square no gradient (SNG), with varying pore widths and gradient distributions) were designed using an open-source custom toolpath generator to enable precise control over scaffold architecture. An in vitro degradation study in phosphate-buffered saline demonstrated that PLA exhibited the greatest material stability, indicating minimal degradation under the tested conditions. In comparison, PVA showed improved performance relative to BVOH, as it was capable of absorbing a greater volume of exudate fluid and remained structurally intact for a longer duration, requiring up to 60 min to fully dissolve. Tensile testing of PLA scaffolds further revealed that designs with increased porosity towards the centre exhibited superior mechanical performance. The strongest scaffold design exhibited a Young’s modulus of 1060.67 ± 16.22 MPa and withstood a maximum tensile stress of 21.89 ± 0.81 MPa before fracture, while maintaining a porosity of approximately 52.37%. This demonstrates a favourable balance between mechanical strength and porosity that mimics key properties of engineered tissues such as the meniscus. Overall, these findings highlight the potential of 3D-printed, patient-specific scaffolds to enhance the effectiveness and customisation of tissue engineering treatments, such as meniscus repair, offering a promising approach for next-generation regenerative applications. Full article

Self-healing polymer nanocomposites are increasingly investigated as damage-tolerant materials for structural and functional applications; however, their engineering translation remains limited by the difficulty of achieving high mechanical reinforcement while retaining sufficient polymer mobility for effective repair. Previous reviews have largely summarized healing chemistries or nanofiller classes but have rarely established quantitative structure–property–healing relationships or resolved contradictory trends reported across studies. In this review, we develop an integrated framework that links polymer network architecture, nanofiller geometry/percolation behavior, and interfacial dynamics to healing kinetics, and we compile quantitative design windows for nanofiller loading, percolation thresholds, activation conditions, and durability metrics. The synthesis reveals that healing performance is maximized within intermediate filler contents near the percolation regime, whereas excessive nanofiller loading commonly suppresses healing by nanoscale confinement and interphase immobilization despite improving modulus and conductivity. Finally, we propose application-oriented design rules and benchmarking priorities, emphasizing standardized fracture/fatigue-based evaluation, multi-cycle healing retention, and scalable interphase engineering as the key pathways for translating self-healing nanocomposites from laboratory demonstrations to validated engineering systems. Full article

Cellular structures are well-established in biological materials and are often mimicked in many kinds of structural designs applicable to engineering. This results from their lightweight designs and good mechanical properties. Cellular designs in nature have extremely complex configurations. As a result, the deformation behaviour models for bioinspired hollow parts based on these geometries, that are presently available in the literature, are limited in their capacity to provide detailed descriptions of the mechanisms resulting in deformation. Extensions to the existing deformation behaviour mechanisms of cellular parts are proposed in this paper. First, a general outlook on cellular designs is given. This is followed by a review of the commonly recognised two-stage stress–strain curve for cellular parts and its comparison with the new curve suggested in this paper, which incorporates suggestions more fully accounting for the deformation mechanisms of these structures. Further, analytical models that are available in the literature, outlining the behaviour of cellular parts, are highlighted, together with new models developed here for predicting failure of lattice structures based on the Tresca and von Mises criterion. Next follows a discussion of proposed strategies that could be adopted in deformation behaviour models for optimising the design of hollow structures to improve their mechanical properties. Finally, the anticipated challenges for and future insights into the incorporation of the cellular behaviour models suggested here, in cutting-edge structural design for additive manufacturing (AM), are highlighted. Full article

The AZ31 magnesium alloy is an attractive lightweight metallic material, but its low corrosion resistance and wear resistance significantly limit its widespread application in fields such as aerospace, the automotive industry, and mechanical engineering. Moreover, most coating systems currently cannot restore their original functions and dimensions after localized damage. Based on this, this study combined cold spray (CS), micro-arc oxidation (MAO), and magnetron sputtering (MS) to develop a high-performance and repairable composite modification strategy. First, a 5056 aluminum alloy coating was prepared on AZ31 via CS, followed by the growth of a hard alumina (Al₂O₃) coating via MAO and a diamond-like carbon (DLC) coating via MS on the 5056 aluminum alloy surface. The microstructure, phase composition, hardness, tribological properties, and electrochemical corrosion behavior of the coatings were evaluated using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD), Vickers hardness testing, ball-on-disk dry sliding wear testing, and potentiodynamic polarization testing in a 3.5% sodium chloride solution. The CS 5056 aluminum alloy coating reduced the corrosion current density of AZ31 from 4.098 × 10⁻⁵ A/cm² to 2.714 × 10⁻⁶ A/cm². The MAO alumina coating increased the hardness of AZ31 from 68.60 HV_0.05 to 1614.00 HV_0.05 and decreased the wear rate from 1.703 × 10⁶ μm³/(N·m) to 2.038 × 10³ μm³/(N·m). The DLC coating further reduced the average coefficient of friction of the alumina coating from 0.48 to 0.27, decreased the wear rate to 6.979 × 10² μm³/(N·m), and lowered the corrosion current density from 3.020 × 10⁻⁶ A/cm² to 8.860 × 10⁻⁹ A/cm². This indicates that the three-phase composite coating achieves synergistic improvements in the corrosion and wear resistance of AZ31 through complementary advantages. Additionally, the thick CS aluminum alloy underlayer provides potential repairability, enabling the restoration of function and dimensions after damage without compromising the magnesium substrate. Overall, the proposed 5056Al/Al₂O₃/DLC composite coating strategy offers a reliable protective approach for AZ31 components and is expected to further expand their application fields. Full article

Soil amendments play a critical role in improving soil health and supporting sustainable crop production, especially under declining soil fertility and climate-related stress. However, their impact varies because each amendment influences the soil through different biogeochemical processes rather than a single universal mechanism. This review synthesizes current knowledge on a wide range of soil amendments, including compost, biosolids, green and animal manure, biochar, hydrochar, bagasse, humic substances, algae extracts, chitosan, and newer engineered options such as metal–organic framework (MOF) composites, highlighting their underlying principles, modes of action, and contributions to soil function, crop productivity, and soil carbon dynamics. Across the literature, three main themes emerge: improvement of soil physicochemical properties, enhancement of nutrient cycling and nutrient-use efficiency, and reinforcement of plant resilience to biotic and abiotic stresses. Organic nutrient-based amendments mainly enrich the soil and build organic matter, influencing soil carbon inputs and short- to medium-term increases in soil organic carbon stocks. Biochar, hydrochar, and related materials act mainly as soil conditioners that improve structure, water retention, and soil function. Biostimulant-type amendments, such as algae extracts and chitosan, influence plant physiological responses and stress tolerance. Humic substances exhibit multifunctional effects at the soil–root interface, contributing to improved nutrient efficiency and, in some systems, enhanced carbon retention. The review highlights that no single amendment is universally superior, with outcomes governed by soil–crop context. Its novelty lies in its mechanism-based, cross-amendment synthesis that frames both yield and carbon outcomes as context-dependent rather than universally transferable. Within this framework, humic substances and carbon-rich materials show potential for climate-smart soil management, but long-term carbon sequestration effects remain uncertain and context-dependent. Full article

Electric-field-sensitive dielectrics play a crucial role in electric field induction sensing and related capacitive conversion, with interfacial polarization and charge accumulation largely determining the signal output. This paper introduces graphene/transition metal dichalcogenide (TMD) (MoSe₂, MoS₂, and WS₂) heterojunctions as functional fillers to enhance the dielectric response and electric-field-induced voltage output of flexible polydimethylsiloxane (PDMS) composites. Density functional theory (DFT) calculations were used to evaluate the stability of the heterojunctions and interfacial electronic modulation, including binding behavior, charge redistribution, and Fermi level-referenced band structure/total density of states (TDOS) characteristics. The calculations show that the graphene/TMD interface is primarily controlled by van der Waals forces, exhibiting negative binding energy and significant interfacial charge rearrangement. Based on these theoretical results, graphene/TMD heterojunction powders were synthesized and incorporated into polydimethylsiloxane (PDMS). Structural characterization confirmed the presence of face-to-face interfacial contacts and consistent elemental co-localization within the heterojunction filler. Dielectric spectroscopy analysis revealed an overall improvement in the dielectric constant of the composite materials while maintaining a stable loss trend within the studied frequency range. More importantly, calibrated electric field induction tests (based on pure PDMS) showed a significant enhancement in the voltage response of all heterojunction composite materials, with the WS₂-G/PDMS system exhibiting the best performance, exhibiting an electric-field-induced voltage amplitude 7.607% higher than that of pure PDMS. This work establishes a microscopic-to-macroscopic correlation between interfacial electronic modulation and electric-field-sensitive dielectric properties, providing a feasible interface engineering strategy for high-performance flexible dielectric sensing materials. Full article

Magnesium–lithium alloys are the lightest structural metals and offer high specific strength, good damping capacity, and excellent thermal conductivity; however, their limited room-temperature strength restricts wider engineering applications. In this study, friction stir processing (FSP) was applied to LA103Z magnesium–lithium alloy to modify its surface microstructure and mechanical properties. The effects of tool rotational speed and travelling speed on dynamic recrystallization behavior, grain refinement, and phase evolution in the stirred zone (SZ) and thermomechanically affected zone (TMAZ) were systematically investigated. FSP induced significant grain refinement accompanied by the precipitation of a reticular α-Mg phase along β-Li grain boundaries, as well as Li₃Mg₇ and Li₂MgAl phases within the stirred zone, leading to pronounced strengthening. Under optimized processing conditions, substantial improvements in hardness and tensile properties were achieved compared with the base material. The optimal condition was obtained at 600 rpm and 100 mm/min, yielding an average hardness of 79.17 HV_0.2, a tensile strength of 243.6 MPa, and an elongation of 17.9%, corresponding to increases of 47.5% in hardness and 53.3% in tensile strength. Quantitative relationships between heat input, grain size, and mechanical properties further demonstrate that heat input governs microstructural evolution and strengthening behavior during FSP of LA103Z alloy. Full article

In the present study, post-heat treatment was applied to improve the mechanical and tribological performance of 3D-printed polymer components. Two polymers, i.e., polylactic acid (PLA) and polyether ether ketone (PEEK), were used as base materials. Re-entrant structures were incorporated into printed specimens to mitigate friction-induced vibrations (FIV). The results showed that the heat-treatment process effectively enhanced the mechanical properties of both materials by increasing their elastic modulus and yield strength. Specifically, the tensile and compressive strengths of heat-treated PLA increased from 44.14 MPa to 47.66 MPa and from 68 MPa to 82 MPa, respectively. A similar trend was observed for heat-treated PEEK, with tensile strength increasing from 75.53 MPa to 84.91 MPa and compressive strength from 106 MPa to 123 MPa. Furthermore, the increased stiffness enabled the re-entrant structures to more effectively reduce FIV during the sliding process of specimens. However, heat treatment produced contrasting effects on the wear performance of the two polymers. The specific wear rate of the heat-treated PLA sample with the re-entrant structure increased from 2.36 × 10⁻⁵ mm³/(N · m) to 4.5 × 10⁻⁴ mm³/(N · m), while it decreased for the PEEK sample from 3.18 × 10⁻⁶ mm³/(N · m) to 6.2 × 10⁻⁷ mm³/(N · m). Microscopic observations revealed that this difference was due to the variations in the brittleness of the treated materials, which influenced wear-debris formation and the development of the transfer film on the steel counterface. These findings demonstrate that post-heat treatment is an effective method for tailoring and optimizing the mechanical behavior of printed polymers while also emphasizing the necessity of systematically evaluating its influence on the tribological performance of printed engineering parts subjected to different sliding conditions. Full article

Artificial neural networks (ANNs) are widely used in engineering prediction, but excessive input dimensionality can reduce both accuracy and efficiency. This study proposes a two-stage feature-reduction framework, Feature Importance Ranking and Redundancy Elimination (FIRRE), to optimize ANN inputs by removing weakly informative and redundant variables. In Stage 1, four complementary ranking methods, namely Pearson correlation, recursive feature elimination, random forest importance, and F-test scoring, are combined into an ensemble importance score. In Stage 2, highly collinear features (ρ > 0.95) are pruned while retaining the more informative variable in each pair. FIRRE is evaluated on 32 civil engineering datasets spanning materials, structural, and environmental applications, and benchmarked against Principal Component Analysis, variance-threshold filtering, random feature selection, and K-means clustering. Across the benchmark suite, FIRRE consistently achieves competitive or improved predictive performance while reducing input dimensionality by 40% on average and decreasing computation time by 10–60%. A dynamic modulus case study further demonstrates its practical value, improving R² from 0.926 to 0.966 while reducing inputs from 25 to 7. Overall, FIRRE provides a practical, robust framework for simplifying ANN inputs and improving efficiency in civil engineering prediction tasks. Full article

Due to a number of advantages, such as the high power-to-weight ratio of the system, the possibility of easy control and the freedom of arrangement of the system components on the machine, hydrostatic drive is one of the most popular methods of machine drive. The actuators in such a system are hydraulic cylinders that convert fluid pressure energy into mechanical energy for reciprocating motion. One disadvantage of conventional actuators is their weight, so research is being conducted to make them as light as possible. Directions for this research include the use of modern engineering materials such as composites and plastics. This paper presents the possibility of using new lightweight yet strong materials for the design of a hydraulic cylinder. The base of the hydraulic cylinder were designed and subjected to FEM numerical analyses. The base was made of PET. In addition, a composite cylinder made of wound carbon fibre was subjected to numerical analyses and experimental validation. The numerical calculations were verified in experimental studies. To improve the reliability of the numerical calculations, the material parameters of the composite materials were determined experimentally instead of being taken from the manufacturer’s data sheets. The composite cylinder achieved a weight reduction of approximately 94.4% compared to a steel cylinder (95.5 g vs. 1704 g). Under an internal pressure of 20 MPa, the composite cylinder exhibited markedly higher circumferential strain (4329 μm/m) than the steel cylinder (339.6 μm/m), and axial strain was also greater (−1237 μm/m vs. −96.4 μm/m). Full article