Extreme Mechanics Letters最新文献

{"title":"Periodic tetrahedral auxetic metamaterial","authors":"A. Sorrentino,&nbsp;D. Castagnetti","doi":"10.1016/j.eml.2024.102214","DOIUrl":"10.1016/j.eml.2024.102214","url":null,"abstract":"<div><p>In this work, we introduce a novel three-dimensional auxetic mechanical metamaterial consisting of rotating tetrahedra connected by ideal hinges at their vertices, arranged to form a periodic framework structure. Through analytical and kinematic approaches, we evaluated the deformation behavior of the proposed idealized model, revealing Poisson’s ratios ranging between −0.36 and −2.72 and a transverse isotropic response as a result of its geometry. A specimen of the proposed metamaterial concept is designed by introducing deformable ribs between the solid units, and fabricated <em>via</em> additive manufacturing in polymeric material. Auxetic behavior of the prototype was assessed through a compression test and accurately predicted by a full-scale Finite Element model. We envisage that this new metamaterial design can have a significant impact on a wide range of engineering applications, particularly as bone substitute biomaterial.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102214"},"PeriodicalIF":4.3,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141843596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Minimal activation with maximal reach: Reachability clouds of bio-inspired slender manipulators","authors":"Bartosz Kaczmarski ,&nbsp;Derek E. Moulton ,&nbsp;Alain Goriely ,&nbsp;Ellen Kuhl","doi":"10.1016/j.eml.2024.102207","DOIUrl":"10.1016/j.eml.2024.102207","url":null,"abstract":"<div><p>In the field of soft robotics, flexibility, adaptability, and functionality define a new era of robotic systems that can safely deform, reach, and grasp. To optimize the design of soft robotic systems, it is critical to understand their configuration space and full range of motion across a wide variety of design parameters. Here we integrate extreme mechanics and soft robotics to provide quantitative insights into the design of bio-inspired soft slender manipulators using the concept of reachability clouds. For a minimal three-actuator design inspired by the elephant trunk, we establish an efficient and robust reduced-order method to generate reachability clouds of almost half a million points each to visualize the accessible workspace of a wide variety of manipulator designs. We generate an atlas of 256 reachability clouds by systematically varying the key design parameters including the fiber count, revolution, tapering angle, and activation magnitude. Our results demonstrate that reachability clouds not only offer an immediately clear perspective into the inverse problem of control, but also introduce powerful metrics to characterize reachable volumes, unreachable regions, and actuator redundancy to quantify the performance of soft slender robots.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102207"},"PeriodicalIF":4.3,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141781029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of friction and geometry in tuning the bending stiffness of topologically interlocking materials","authors":"Tracy Lu ,&nbsp;Ziran Zhou ,&nbsp;Punnathat Bordeenithikasem ,&nbsp;Norman Chung ,&nbsp;Diana Frias Franco ,&nbsp;Jose E. Andrade ,&nbsp;Chiara Daraio","doi":"10.1016/j.eml.2024.102212","DOIUrl":"10.1016/j.eml.2024.102212","url":null,"abstract":"<div><p>Topologically interlocking material (TIM) systems offer adjustable bending stiffness controlled by external pre-stress, as shown in previous studies. This study focuses on a specific TIM system comprised of truncated tetrahedral particles interconnected via tensioned wires. The fabrication process involves weaving nylon wires through 3D printed truncated tetrahedrons that have longitudinal and latitudinal through-holes. By varying the tension applied to the wires, one can systematically control the overall bending stiffness of the TIM system. We change the surface friction and the contact angle between adjacent particles at a fixed wire tension, to study experimentally how they affect the system’s bending response. We inform experiments with Level Set Discrete Element Method (LS-DEM) simulations, to correlate surface friction and contact area changes with the system’s bending modulus. The numerical model is shown to be predictive and could be used in the future to evaluate designs of TIMs.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102212"},"PeriodicalIF":4.3,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Palmitoylation enhances short polar peptide permeation across stratum corneum lipid bilayer: A molecular dynamics study","authors":"Choon-Peng Chng ,&nbsp;Lu Zhang ,&nbsp;Shikhar Gupta ,&nbsp;Changjin Huang","doi":"10.1016/j.eml.2024.102213","DOIUrl":"10.1016/j.eml.2024.102213","url":null,"abstract":"<div><p>Designing chemical molecules that target the skin for non-invasive transdermal drug delivery is of significant interest for both wound healing and skincare applications. These skin-targeting molecules must permeate the outermost protective layer of the skin, the stratum corneum (SC), which consists of dead corneocytes embedded in a lipid matrix, to fulfill their biological functions. Adsorption onto and diffusion through the lipid matrix in the SC represent two key steps for the successful permeation of a skin-targeting molecule across the SC into the underlying skin layers. Here we compare the effects of cyclization and palmitoylation on the adsorption and diffusion of a short polar peptide across a model SC lipid bilayer using molecular dynamics simulations. The cyclized peptide showed slightly better binding to the SC lipid bilayer and similar interaction energies with SC lipids compared to the unmodified peptide. In contrast, the palmitoylated peptide exhibited much stronger interaction with SC lipids via insertion of its attached fatty acid tail into the SC lipid bilayer. The average diffusivity of the cyclized peptide across the SC lipid bilayer was approximately twice that of the unmodified peptide, whereas the palmitoylated peptide’s diffusivity was about 2.7 times higher. Thus, palmitoylation appears to be a promising strategy for enhancing the binding and permeability of short polar peptides across the SC lipid matrix.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102213"},"PeriodicalIF":4.3,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Frequency-dependent electrochemical breakdown of hydrogel ionotronics","authors":"Yuechen Jiang ,&nbsp;Yuwei Han ,&nbsp;Zeyu Gao ,&nbsp;Rong Xu ,&nbsp;Kun Jia ,&nbsp;Yecheng Wang","doi":"10.1016/j.eml.2024.102210","DOIUrl":"10.1016/j.eml.2024.102210","url":null,"abstract":"<div><p>When an ionic conductor meets an electronic conductor, ions and electrons couple at the interface between ionic and electronic circuits, enabling a class of devices: ionotronics. Such a coupling gives innovations but can cause electrochemical breakdown. Rapid advances in hydrogel ionotronics, in which hydrogel serves as stretchable, transparent, ionic conductor, highlight an urgent need: a general approach and criterion to study electrochemical breakdown under AC condition. Here we study the breakdown behavior of a metal-hydrogel-metal ionotronic system subject to alternating voltages of various frequencies and amplitudes. First, we apply a sinusoidal voltage to the ionotronic system which is connected in series to a load resistor, and compare the waveforms of the applied voltage and the output voltage between the two ends of the load resistor at various frequencies and amplitudes. Electrochemical breakdown tends to take place at low frequencies and high amplitudes, and causes distortion of waveform of the output voltage. Next, we develop an electric circuit model, in which each hydrogel-metal junction is modeled as a constant phase element in parallel with a leakage resistor and the hydrogel is modeled as a resistor. Our experiments show that the electrochemical window is insensitive to the frequency and amplitude of applied voltage, as well as to the concentration of ions in the hydrogel. Through a combination of experiment and theory, we further propose a frequency-amplitude phase diagram. Different from DC condition, the breakdown behavior under AC condition depends not only on the amplitude of applied voltage, but also on the frequency of applied voltage. We also show that electrochemical reaction can be retarded by stretching the hydrogel and by increasing the frequency. It is hoped that this work will guide the development of stable and reliable hydrogel ionotronic devices.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102210"},"PeriodicalIF":4.3,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141781030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machine learning-assisted wood materials: Applications and future prospects","authors":"Yuqi Feng ,&nbsp;Saad Mekhilef ,&nbsp;David Hui ,&nbsp;Cheuk Lun Chow ,&nbsp;Denvid Lau","doi":"10.1016/j.eml.2024.102209","DOIUrl":"10.1016/j.eml.2024.102209","url":null,"abstract":"<div><p>Wood and wood-based materials, surpassing their conventional image as mere stems and branches of trees, have found extensive utilization in diverse industrial sectors due to their low carbon footprint. Nonetheless, maximizing wood utilization and advancing multifunctional wood materials face challenges due to resource-intensive conventional approaches. Integrating machine learning (ML) in wood mechanics has emerged as a promising avenue for deeper exploration of this remarkable material. By leveraging advanced computational techniques, researchers can delve into wood's intricate properties and behavior, unraveling the complex interactions between its chemical constituents, microstructures, and mechanical characteristics. Combined with imaging and sensor technologies, ML contributes to efficient, fast, and real-time health detection of wood materials. This review aims to illuminate the transformative impact of ML in unlocking the hidden potential of wood, fostering innovative applications, and facilitating sustainable engineering solutions. The basic workflow of ML and its typical applications in property prediction, defect detection, and optimized design of wood materials are discussed, thereby highlighting the challenges and the need for future research.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102209"},"PeriodicalIF":4.3,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141729249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Front cover CO1","authors":"","doi":"10.1016/S2352-4316(24)00085-3","DOIUrl":"10.1016/S2352-4316(24)00085-3","url":null,"abstract":"","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"70 ","pages":"Article 102205"},"PeriodicalIF":4.3,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352431624000853/pdfft?md5=c4c2bd59d1f2914bd0c9ee1887d691b7&pid=1-s2.0-S2352431624000853-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141637115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterizing the dielectric elastomer’s complete mechanical behavior through an electromechanical coupling method","authors":"Haopeng Liang ,&nbsp;Yong Zhao ,&nbsp;Bingxiao Du ,&nbsp;Shengxin Li ,&nbsp;Xiang Zhang ,&nbsp;Xiaoqian Chen","doi":"10.1016/j.eml.2024.102204","DOIUrl":"10.1016/j.eml.2024.102204","url":null,"abstract":"<div><p>The complete hyperelastic behavior of dielectric elastomers (DEs) refers to the large-range non-linear behavior under multiple loading modes, including uniaxial extension, biaxial extension, and triaxial-stressed deformation. Using hyperelastic models to encapsulate the complete behavior has always been hard due to not only the lack of measurement methods but also the incompleteness of the hyperelasticity theory. Among these obstacles, measuring the equi-biaxial behavior has been a crucial one as the existing methods fail to balance the measuring accuracy and the easy popularization. In this paper, an electromechanical coupling method (EMC method) is proposed to characterize the DE materials with the expectation of both a better complete-behavior coverage and a simpler experimental setup. The proposed method takes a theoretical investigation into the equi-biaxially pre-strained circular dielectric elastomer actuator (PCDEA) and deduces a special form of stress-strain relationship to bridge the gap between the easy-to-setup PCDEA experiments and model characterization. Experiments are then carried out on the classical VHB4910 acrylic film, and various hyperelastic models are evaluated with the proposed EMC characterization method on their fitting capability. Among these models, the Ogden 2-terms model fits all sets of measured data well. Validations are then carried out via DE actuators under more complex loading modes and the EMC-characterized Ogden 2-terms model provides precise behavior predictions with an average <span><math><msup><mrow><mi>R</mi></mrow><mn>2</mn></msup></math></span> of 97.2 %. Thus, this research not only offers useful insights for a more practical complete-behavior-characterization method, but also provides a hyperelastic model for VHB4910 which is worthy of reference.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102204"},"PeriodicalIF":4.3,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141623484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fully dense and cohesive FCC granular crystals","authors":"Ashta Navdeep Karuriya,&nbsp;Jeremy Simoes,&nbsp;Francois Barthelat","doi":"10.1016/j.eml.2024.102208","DOIUrl":"10.1016/j.eml.2024.102208","url":null,"abstract":"<div><p>Typical granular materials are far from optimal in terms of mechanical performance: Random packing leads to poor load transfer in the form of thin and dispersed force lines within the material, to inhomogeneous jamming, and to strain localization. In addition, localized contacts between individual grains result in low stiffness, strength and brittleness. Here we propose a granular material that simultaneously embodies three approaches to increase strength: geometrical design of individual grains, crystallization, and infiltration by an adhesive. Using mechanical vibrations, we assembled millimeter-scale 3D printed grains with rhombic dodecahedral shapes into fully dense FCC granular crystals. We then infiltrated the granular structure with a tacky, polyacrylic adhesive that is orders of magnitude weaker than the grains, but which provides sustained adhesion over large interfacial displacements. The resulting material is a fully dense, free-standing space filling granular crystal. Compressive tests show that these granular crystals are up to 60 times stronger than randomly packed cohesive spheres and they display a rich set of mechanisms: Nonlinear deformations, crystal plasticity reminiscent of atomistic mechanisms, cross-slip, shear-induced dilatancy, micro-buckling, and tensile strength. To capture some of these mechanisms we developed a multiscale model that incorporates local cohesion between grains, resolved shear and normal stresses on available slip planes, and prediction of compressive strength as function of loading orientation. The predicted strength is highly anisotropic and agrees well with the compression experiments. Once fully understood and harnessed, we envision that these mechanisms will lead to granular engineering materials with unusual combinations of mechanical performances attractive for many applications.</p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102208"},"PeriodicalIF":4.3,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141623457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-driven image mechanics (D2IM): A deep learning approach to predict displacement and strain fields from undeformed X-ray tomography images – Evaluation of bone mechanics","authors":"Peter Soar ,&nbsp;Marco Palanca ,&nbsp;Enrico Dall’Ara ,&nbsp;Gianluca Tozzi","doi":"10.1016/j.eml.2024.102202","DOIUrl":"10.1016/j.eml.2024.102202","url":null,"abstract":"<div><p>The recent advent of deep learning (DL) has enabled data-driven models to pave the way for the full exploitation of rich image datasets from which physics can be learnt. Here we propose a novel data-driven image mechanics (D²IM) approach that learns from digital volume correlation (DVC) displacement fields of vertebrae, predicting displacement and strain fields from undeformed X-ray computed tomography (XCT) images. D²IM successfully predicted the displacements in all directions, particularly in the cranio-caudal direction of the vertebra, where high correlation (R²=0.94) and generally minimal errors were obtained compared to the measured displacements. The predicted axial strain field in the cranio-caudal direction of the vertebra was also consistent in distribution with the measured one, displaying generally reduced errors in the regions within the vertebral body. The application of D²IM to lower resolution imaging in initial testing provides promising results indicating the future viability of integrating this technology into a clinical setting. This is the first study using experimental full-field measurements on bone structures from DVC to inform DL-based models such as D²IM, which represents a major contribution in the prediction of displacement and strain fields based only on the greyscale content of undeformed XCT images. In future, D²IM will incorporate a range of biological structures and loading scenarios for accurate prediction of physical fields, aiming at clinical translation for improved diagnostics.</p></div><div><h3>Data Availability</h3><p>Code for preparing dataset, training D²IM model and visualising/analysing results has been hosted on GitHub: <span><span>https://github.com/PeterSoar/D2IM_Prototype</span><svg><path></path></svg></span></p><p>The dataset used for this study can be found on Figshare: <span><span>https://doi.org/10.6084/m9.figshare.25404220.v1</span><svg><path></path></svg></span></p></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"71 ","pages":"Article 102202"},"PeriodicalIF":4.3,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352431624000828/pdfft?md5=9e6b7033d5dfa001056621424d6d7a6c&pid=1-s2.0-S2352431624000828-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141638031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}