Hasil untuk "Materials of engineering and construction. Mechanics of materials"

Mehdi Pouragha, Gertraud Medicus, Selvarajah Premnath et al.

Anisotropy in granular materials arises from both the internal fabric and the directionality of the stress state, yet separating these effects experimentally remains challenging. This study develops a first-order linearisation of the incremental stress-strain response that isolates mechanical anisotropy from structural anisotropy using two independent orientation measures. The formulation enables both contributions to be quantified directly from macroscopic laboratory data. The method is applied to hollow-cylinder tests with systematically varied loading directions. Results show that both anisotropy components intensify as the stress state becomes more deviatoric; mechanical anisotropy is consistently stronger; and its relative dominance decreases with increasing deviatoric stress. Comparison with an isotropic hypoplastic model confirms that mechanically induced directional effects are captured even without fabric anisotropy. The framework offers a practical and physically transparent means for quantifying and comparing anisotropy mechanisms in granular materials.

Fuzhou Niu, Quhao Xue, Qing Cao et al.

Soft robots, inspired by the flexibility and versatility of biological organisms, have potential in a variety of applications. Recent advancements in magneto-soft robots have demonstrated their abilities to achieve precise remote control through magnetic fields, enabling multi-modal locomotion and complex manipulation tasks. Nonetheless, two main hurdles must be overcome to advance the field: developing a multi-component substrate with embedded magnetic particles to ensure the requisite flexibility and responsiveness, and devising a cost-effective, straightforward method to program three-dimensional distributed magnetic domains without complex processing and expensive machinery. Here, we introduce a cost-effective and simple heat-assisted in-situ integrated molding fabrication method for creating magnetically driven soft robots with three-dimensional programmable magnetic domains. By synthesizing a composite material with neodymium-iron-boron (NdFeB) particles embedded in a polydimethylsiloxane (PDMS) and Ecoflex matrix (PDMS:Ecoflex = 1:2 mass ratio, 50% magnetic particle concentration), we achieved an optimized balance of flexibility, strength, and magnetic responsiveness. The proposed heat-assisted in-situ magnetic domains programming technique, performed at an experimentally optimized temperature of 120 °C, resulted in a 2 times magnetization strength (9.5 mT) compared to that at 20 °C (4.8 mT), reaching a saturation level comparable to a commercial magnetizer. We demonstrated the versatility of our approach through the fabrication of six kinds of robots, including two kinds of two-dimensional patterned soft robots (2D-PSR), a circular six-pole domain distribution magnetic robot (2D-CSPDMR), a quadrupedal walking magnetic soft robot (QWMSR), an object manipulation robot (OMR), and a hollow thin-walled spherical magneto-soft robot (HTWSMSR). The proposed method provides a practical solution to create highly responsive and adaptable magneto-soft robots.

LIU Xiaochen, YUE Junsong, WU Zhansheng et al.

The disadvantages of high purification cost and difficult reuse of free enzymes restrict their application in the green biochemical industry, and immobilized enzymes with good performance are the necessary conditions for their industrialization. To reduce the cost of separation and purification of UDP-glycosyltransferase (UGT)in the catalytic synthesis of ginsenoside Rh2 and to overcome the problem of the inability to reused free enzyme, a magnetic Fe3O4/MPN-Ni2+ material was synthesized to purify while immobilizing recombinant UGT. The resulting immobilized enzyme could be quickly separated from the reaction for reuse. It is proved that the immobilized material has a specific adsorption effect on UGT, and the immobilized enzyme (Fe3O4/MPN-Ni2+@UGT) has a high enzyme load (100.91 mg/g) and stability. The immobilized enzyme still maintains 65.07% activity after 6 cycles. After 21 days of storage, its activity is still 54.01%. Under the optimal conditions, the immobilized enzyme can catalyze the synthesis of Rh2 at 40.73 μg/mL and the conversion rate of protopanaxadiol (PPD) is 70.88%. This lowcost, efficient and stable material has great potential and value for industrial application in enzyme purification and synthesis of ginsenosides.

Wenqiang Liu, Ruijie Zhang, Xiaoyan Wu et al.

In this paper, an improved cellular automaton (CA) model with low grid anisotropy has been implemented using the zigzag capture rule and growth anisotropy reduction with diffusion method. The improved CA model can describe the evolution of the spherical growth, dendritic growth, and undercooling field, thus achieving a more accurate estimation of grain size than previous models. The model was used to simulate nucleation behavior and grain size of Al-8Si-0.2 Mg (wt.%) alloy inoculated with Al-Nb-B refiner, quantitatively revealing the factors that suppressed nucleation. Results show that when the inoculant particles were uniformly distributed, latent heat was the main factor restricting nucleation. Latent heat inhibited nucleation by reducing the available undercooling and terminating nucleation at the recalescence. When considering the agglomeration of particles, the effects of latent heat and solute suppressed nucleation (SSN) on nucleation inhibition accounted for 37.57 % and 58.58 %, respectively. Agglomeration caused the particle spacing to be smaller than that of a uniform distribution, and the SSN effect significantly increased as the separation distance decreased, resulting in a large portion of particles losing nucleation potency. In addition, it was found that the refinement by high cooling rate was attributed to not only providing more undercooling but also reducing SSN zone thickness.

Hsin-Ying Lee, Mu-Ju Wu, Shao-Yu Chu et al.

In this study, using a sensing membrane composed of p-type reduced graphene oxide (rGO)-decorated hydrothermally synthesized n-type gallium oxide (Ga2O3) nanorods, nitrogen dioxide (NO2) gas sensors were successfully fabricated. The characteristics of the rGO-decorated Ga2O3 nanorods were analyzed by X-ray photoelectron spectroscopy (XPS). The experimental results indicated that the rGO decoration on the surface of the Ga2O3 nanorods increased the amount of gas adsorption sites and oxygen vacancies, thereby enhancing electrical conductivity. Consequently, compared to NO2 gas sensors utilizing only Ga2O3 nanorods, the NO2 gas sensors using rGO-decorated Ga2O3 nanorod sensing membrane exhibited lower resistance, reduced activation energy, and higher response. Optimal response, reaching 51.14, was achieved by decorating with 15 mg of rGO. Additionally, the response and recovery times of the NO2 gas sensors were shortened with an increase in the amount of rGO decoration on the Ga2O3 nanorods. This improvement could be attributed to the trend of lower activation energy associated with an increased amount of rGO decoration. This study demonstrates the efficacy of rGO decoration in improving the performance of Ga2O3 nanorod-based NO2 gas sensors.

Wenjuan Zhou, Can Yang, Niutao Hu

Hayato Ishida, Amal Elsokary, Maria Aslam et al.

Realisation of significant advances in capabilities of sensors, computing, timing, and communication enabled by quantum technologies is dependent on engineering highly complex systems that integrate quantum devices into existing classical infrastructure. A systems engineering approach is considered to address the growing need for quantum-secure telecommunications that overcome the threat to encryption caused by maturing quantum computation. This work explores a range of existing and future quantum communication networks, specifically quantum key distribution network proposals, to model and demonstrate the evolution of quantum key distribution network architectures. Leveraging Orthogonal Variability Modelling and Systems Modelling Language as candidate modelling languages, the study creates traceable artefacts to promote modular architectures that are reusable for future studies. We propose a variability-driven framework for managing fast-evolving network architectures with respect to increasing stakeholder expectations. The result contributes to the systematic development of viable quantum key distribution networks and supports the investigation of similar integration challenges relevant to the broader context of quantum systems engineering.

Jiaqi Zhou, Samuel Poncé, Jean-Christophe Charlier

Spin Hall effect (SHE) in two-dimensional (2D) materials is promising to effectively manipulate spin angular momentum and identify topological properties. In this work, we implemented an automated Wannierization with spin-orbit coupling on 426 non-magnetic monolayers including 210 metal and 216 insulators. Intrinsic spin Hall conductivity (SHC) has been calculated to find candidates exhibiting novel properties. We discover that Y$_2$C$_2$I$_2$ has an unconventional SHE with canted spin due to low crystal symmetry, Ta$_4$Se$_2$ is a metallic monolayer with exceptionally high SHC, and the semi-metal Y$_2$Br$_2$ possesses efficient charge-to-spin conversion induced by anti-crossing in bands. Moreover, quantum spin Hall insulators are investigated for quantized SHC. The present work provides a high-quality Wannier Hamiltonian database of 2D materials, and paves the way for the integration of 2D materials into high-performance and low-power-consumption spintronic devices.

Keith Y Patarroyo, Abhishek Sharma, Ian Seet et al.

Quantifying the evolution and complexity of materials is of importance in many areas of science and engineering, where a central open challenge is developing experimental complexity measurements to distinguish random structures from evolved or engineered materials. Assembly Theory (AT) was developed to measure complexity produced by selection, evolution and technology. Here, we extend the fundamentals of AT to quantify complexity in inorganic molecules and solid-state periodic objects such as crystals, minerals and microprocessors, showing how the framework of AT can be used to distinguish naturally formed materials from evolved and engineered ones by quantifying the amount of assembly using the assembly equation defined by AT. We show how tracking the Assembly of repeated structures within a material allows us formalizing the complexity of materials in a manner accessible to measurement. We confirm the physical relevance of our formal approach, by applying it to phase transformations in crystals using the HCP to FCC transformation as a model system. To explore this approach, we introduce random stacking faults in closed-packed systems simplified to one-dimensional strings and demonstrate how Assembly can track the phase transformation. We then compare the Assembly of closed-packed structures with random or engineered faults, demonstrating its utility in distinguishing engineered materials from randomly structured ones. Our results have implications for the study of pre-genetic minerals at the origin of life, optimization of material design in the trade-off between complexity and function, and new approaches to explore material technosignatures which can be unambiguously identified as products of engineered design.

Lintao Wu, Kaicheng Zhang, Rui Yu et al.

António J. Arsénio Costa, João F. P. Fernandes, Paulo J. Costa Branco

This paper analyzes the viability of different solutions to passively augment the axial stiffness of a horizontal axis radial levitation passive magnetic bearing (PMB) with a previously studied topology. The zero-field cooling (ZFC) of high-temperature superconductor (HTS) bulks promotes higher magnetic impulsion and levitation forces and lower electromagnetic losses than those with field-cooling (FC) but, on the other hand, the guiding stability is much lower than those with FC. Because of stability reasons, FC was adopted in most superconducting maglev systems. The trend of this research group has been to develop a horizontal axis HTS ZFC radial levitation PMB presenting notable levitation forces with reduced electromagnetic losses, defined by a topology that creates guiding stability. Previous work has shown that optimizing the bearing geometry to maximize magnetic guidance forces might not be enough to guarantee the axial stiffness required for many applications. First, the extent to which guidance forces are augmented by increasing the number of HTS bulks in the stator is evaluated. Then, the axial stiffness augmentation by passively adding two limiting permanent magnet (PM) rings is evaluated. The results show that the axial stiffness is highly augmented by adding limiting PM rings with no significant additional investment. This change enables the use of the studied ZFC superconducting PMB in high-precision axial stability applications, such as precision gyroscopes, horizontal axis propellers, and turbines.

Dongsheng Wen, Victoria Tucker, Michael S. Titus

Abstract Atomistic simulations are crucial for predicting material properties and understanding phase stability, essential for materials selection and development. However, the high computational cost of density functional theory calculations challenges the design of materials with complex structures and composition. This study introduces new data acquisition strategies using Bayesian-Gaussian optimization that efficiently integrate the geometry of the convex hull to optimize the yield of batch experiments. We developed uncertainty-based acquisition functions to prioritize the computation tasks of configurations of multi-component alloys, enhancing our ability to identify the ground-state line. Our methods were validated across diverse materials systems including Co-Ni alloys, Zr-O compounds, Ni-Al-Cr ternary alloys, and a planar defect system in intermetallic (Ni1−x , Co x )3Al. Compared to traditional genetic algorithms, our strategies reduce training parameters and user interaction, cutting the number of experiments needed to accurately determine the ground-state line by over 30%. These approaches can be expanded to multi-component systems and integrated with cost functions to further optimize experimental designs.

Fernando Suárez, Javier Fernández-Aceituno, Jesús Donaire-Ávila

The main aim of this work is to study two relevant experimental setups designed for studying shear fracture and see if any of them allows studying the evolution of fracture under Mode II conditions, not only inducing a shear stress state at the onset of fracture. Two tests have been selected, a standardised test described by a Japanese standard, here referred to as the JSCE test, and the push-off test. These tests have been carried out on fibre-reinforced gypsum specimens with increasing proportions of polypropylene fibres and monitored by means of digital image correlation (DIC). The results show that fracture under Mode II conditions is relatively easy to induce with both tests, but once fracture begins, it is extremely difficult to induce a fracture process under Mode II. In general, Mode II has an important role at the onset on fracture, but Mode I predominates afterwards.

Alessandro Chiari, Sara Mantovani, Andrea Berzaghi et al.

In this work, three-units monolithic fixed dental prostheses (FDPs) have been analysed and a novel model for reliable testing has been proposed. Such model is based on a new design of the polymeric base of the FDP, realised via additive manufacturing (AM) - a solution that conveys at the same time quick manufacturability, low cost, custom-ability, and design freedom. By means of this new model, the load-bearing capability of three-units monolithic FDPs has been thoroughly tested; in particular, three different analyses were performed: (i) analytical with a beam-like model, (ii) numerical, using non-linear three-dimensional Finite Elements (FE) models and (iii) experimental, by static bending test. The FDPs considered in this work were manufactured using a fourth-generation zirconia, namely 4Y-TZP. The findings demonstrated the undoubted advantages of the new base configuration, which minimized the effect of the base (which as a matter of fact is absent in in-vivo conditions) on the stress state of the connectors in the FDPs, and increased the repeatability and reliability of the experimental bending tests, able to determine the load bearing capability of the 4Y-TZP FDPs.

Ahmad Wadee, Pete Walker, Nick McCullen et al.

Daga Alessandro Paolo, Garibaldi Luigi, Cuvato Damiano et al.

Hydropower generation units (HGUs) are electromechanical systems meant to transform the potential energy of flowing water (i.e., a renewable energy source) into electrical energy. Thanks to their high manoeuvrability and green footprint, nowadays, HGUs are mission-critical assets for grid operators, as the global energy policy is pushing for a more ecological and healthier energy production. Condition monitoring becomes then a fundamental task for fostering safety while optimizing the maintenance regime of such HGUs. In this regard, this work is meant to improve an ISO20816-based vibration monitoring system by proposing further rotor health indicators based on orbital analysis. The proposed improvement is implemented on a real HGU of the Signayes hydroelectric power plant from C.V.A. S.p.A. − Compagnia Valdostana delle Acque − Compagnie Valdôtaine des Eaux.

Gang Wang, Hongyuan Wen, Jun Feng et al.

The application of robots reduces repetitive and dangerous tasks for humans, especially the spraying robot, because many spraying materials are corrosive, toxic, and harmful. This paper designs the motion trajectory planning of the material spraying service robot. With the increasing demand for technology, there are strict requirements for the uniformity and thickness of spraying. In view of this, this paper proposes an algorithm for modeling kinematics using a joint screw and optimizes the modeling algorithm using particle swarm optimization. This makes the industrial spraying robot more intelligent and more capable of completing high-standard tasks. The experimental results in this paper show that when the spraying radii on the large-curvature cone surface are 44.5 and 49.5 mm, respectively, the coating distribution in the intersection area of the curved surfaces can be well controlled, and the optimized algorithm can better plan the path of the spraying robot.

Lulu Sun, Kenjiro Fukuda, Takao Someya

Abstract The certified power conversion efficiency (PCE) of organic photovoltaics (OPV) fabricated in laboratories has improved dramatically to over 19% owing to the rapid development of narrow-bandgap small-molecule acceptors and wide bandgap polymer donor materials. The next pivotal question is how to translate small-area laboratory devices into large-scale commercial applications. This requires the OPV to be solution-processed and flexible to satisfy the requirements of high-throughput and large-scale production such as roll-to-roll printing. This review summarizes and analyzes recent progress in solution-processed flexible OPV. After a detailed discussion from the perspective of the behavior of the narrow bandgap small-molecule acceptor and wide bandgap polymer donor active layer in solution-processed flexible devices, the existing challenges and future directions are discussed.

Marta D'Elia, Hang Deng, Cedric Fraces et al.

The "Workshop on Machine learning in heterogeneous porous materials" brought together international scientific communities of applied mathematics, porous media, and material sciences with experts in the areas of heterogeneous materials, machine learning (ML) and applied mathematics to identify how ML can advance materials research. Within the scope of ML and materials research, the goal of the workshop was to discuss the state-of-the-art in each community, promote crosstalk and accelerate multi-disciplinary collaborative research, and identify challenges and opportunities. As the end result, four topic areas were identified: ML in predicting materials properties, and discovery and design of novel materials, ML in porous and fractured media and time-dependent phenomena, Multi-scale modeling in heterogeneous porous materials via ML, and Discovery of materials constitutive laws and new governing equations. This workshop was part of the AmeriMech Symposium series sponsored by the National Academies of Sciences, Engineering and Medicine and the U.S. National Committee on Theoretical and Applied Mechanics.