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tensile stress

Sanghoon Park, Yura Kim, Hyosub Jung, Jun-Young Park, Naesung Lee, Yongho Seo
In this study, we investigated an energy harvesting effect of tensile stress using piezoelectric polymers and flexible electrodes. A chemical-vapor-deposition grown graphene film was transferred onto both sides of the PVDF and P(VDF-TrFE) films simultaneously by means of a conventional wet chemical method. Output voltage induced by sound waves was measured and analyzed when a mechanical tension was applied to the device. Another energy harvester was made with a metallic electrode, where Al and Ag were deposited by using an electron-beam evaporator...
December 11, 2017: Scientific Reports
Nicholaus Meyers, Julian Schülke, Anita Ignatius, Lutz Claes
BACKGROUND: Distraction osteogenesis is a procedure widely used for the correction of large bone defects. However, a high complication rate persists, likely due to insufficient stability during maturation. Numerical fracture healing models predict bone regeneration under different mechanical conditions allowing fixation stiffness optimization. However, most models apply a linear elastic material law inappropriate for the transient stresses/strains present during limb lengthening or segment transport...
2017: PloS One
Elizabeth H Stephens, Jiho Han, Emma A Trawick, Elena S Di Martino, Hemanth Akkiraju, Lewis M Brown, Jennifer P Connell, K Jane Grande-Allen, Gordana Vunjak-Novakovic, Hiroo Takayama
BACKGROUND: Aortic regurgitation is a prevalent, detrimental complication of left ventricular assist devices (LVADs). The altered hemodynamics of LVADs results in aortic valves (AVs) having distinct mechanical stimulation. Our hypothesis was that the altered AV hemodynamics modulates the valve cells and matrix, resulting in changes in valvular mechanical properties that then can lead to regurgitation. METHODS: AVs were collected from 16 LVAD and 6 non-LVAD patients at time of heart transplant...
December 6, 2017: Annals of Thoracic Surgery
Guorong Zhu, Changbo Yuan, Guilan Di, Meng Zhang, Leyi Ni, Te Cao, Rongting Fang, Gongguo Wu
Eutrophication and hydrodynamics determine the final distribution patterns of aquatic macrophytes; however, there is limited available knowledge regarding their interactive effects. Morphological and biomechanical responses to eutrophication and hydrodynamic stresses were assessed by sampling five abundant and dominant species, Potamogeton maackianus, P. pectinatus, P. lucens, Ceratophyllum demersum and Myriophyllum spicatum, in three macrophyte beds in Lake Erhai, Yunnan Province, China: one exposed to eutrophication and moderate southeast (SE) wind; one with mesotrophication, but sheltered by the lakeshore, with weak wind disturbance; and one with meso-eutrophication and strong SE wind...
December 5, 2017: Science of the Total Environment
Collin B Eaker, David C Hight, John D O'Regan, Michael D Dickey, Karen E Daniels
We identify and characterize a new class of fingering instabilities in liquid metals; these instabilities are unexpected due to the large interfacial tension of metals. Electrochemical oxidation lowers the effective interfacial tension of a gallium-based liquid metal alloy to values approaching zero, thereby inducing drastic shape changes, including the formation of fractals. The measured fractal dimension (D=1.3±0.05) places the instability in a different universality class than other fingering instabilities...
October 27, 2017: Physical Review Letters
Li Li, Peipei Shi, Li Hua, Jianing An, Yujiao Gong, Ruyi Chen, Chenyang Yu, Weiwei Hua, Fei Xiu, Jinyuan Zhou, Guangfa Gao, Zhong Jin, Gengzhi Sun, Wei Huang
A wearable and shape-memory strain sensor with a coaxial configuration is designed, comprising a thermoplastic polyurethane fiber as the core support, well-aligned and interconnected carbon nanotubes (CNTs) as conductive filaments, and polypyrrole (PPy) coating as the cladding layer. In this design, the stress relaxation between CNTs is well confined by the outer PPy cladding layer, which endows the fibriform sensor with good reliability and repeatability. The microcracks generated when the coaxial fiber is under strain guarantee the superior sensitivity of this fibriform sensor with a gauge factor of 12 at 0...
December 6, 2017: Nanoscale
Grzegorz Ludwik Golewski
The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters...
December 6, 2017: Materials
Sophie Belin, Kristen L Zuloaga, Yannick Poitelon
Schwann cells are the glial cells of the peripheral nervous system (PNS). They insulate axons by forming a specialized extension of plasma membrane called the myelin sheath. The formation of myelin is essential for the rapid saltatory propagation of action potentials and to maintain the integrity of axons. Although both axonal and extracellular matrix (ECM) signals are necessary for myelination to occur, the cellular and molecular mechanisms regulating myelination continue to be elucidated. Schwann cells in peripheral nerves are physiologically exposed to mechanical stresses (i...
2017: Frontiers in Cellular Neuroscience
Pauline Vitry, Claire Valotteau, Cécile Feuillie, Simon Bernard, David Alsteens, Joan A Geoghegan, Yves F Dufrêne
Bacterial pathogens that colonize host surfaces are subjected to physical stresses such as fluid flow and cell surface contacts. How bacteria respond to such mechanical cues is an important yet poorly understood issue. Staphylococcus aureus uses a repertoire of surface proteins to resist shear stress during the colonization of host tissues, but whether their adhesive functions can be modulated by physical forces is not known. Here, we show that the interaction of S. aureus clumping factor B (ClfB) with the squamous epithelial cell envelope protein loricrin is enhanced by mechanical force...
December 5, 2017: MBio
A Jungwirth-Weinberger, F Grubhofer, M A Imam, E Bachmann, S Wirth
To avoid infections and wound healing disorders Triclosan coated sutures have been invented. Little is known of these sutures regarding their tensile properties. Three different Triclosan coated sutures (Vicryl 1 plus, PDS 0 plus, Monocryl 3-0 plus) were tested at several time points over 42 days regarding load to failure, strain and stiffness compared to their non-coated versions (Vicryl 1, PDS 0, Monocryl 3-0). Four different measurement points were made. Suture loops were fixed in a material testing machine over two metal bars which were moved apart creating a stress to the fiber...
December 2, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
Gurcan Aral, Md Mahbubul Islam, Adri C T van Duin
Highly reactive metallic nickel (Ni) is readily oxidized by oxygen (O2) molecules even at low temperatures. The presence of the naturally resulting pre-oxide shell layer on metallic Ni nano materials such as Ni nanowires (NW) is responsible for degrading the deformation mechanisms and related mechanical properties. However, the role of the pre-oxide shell layer on the metallic Ni NW coupled with the complicated mechanical deformation mechanism and related properties have not yet been fully and independently understood...
December 5, 2017: Physical Chemistry Chemical Physics: PCCP
Lorenzo Zanelli, Silvia Todros, Emanuele L Carniel, Piero G Pavan, Piero G Pavan
PURPOSE: In this work, the mechanical behavior of two block copolymers for biomedical applications is studied with particular regard to the effects induced by a steam sterilization treatment that biomedical devices usually undergo in healthcare facilities. This investigation is aimed at describing the elasto-plastic behavior of the stress-strain response, determining a functional dependence between material constitutive parameters, to obtain an optimal constitutive model. METHODS: The mechanical properties of these polymers are analyzed through uniaxial tensile tests, before and after the sterilization process...
2017: Acta of Bioengineering and Biomechanics
Marziyeh Khodadoust, Davod Mohebbi-Kalhori, Nafiseh Jirofti
In spite of advances have been made during the past decades, the problems associated with small-diameter vascular grafts, including low patency and compliance mismatch and in consequence of that thrombosis, aneurysm and intimal hyperplasia are still challenges. To address these problems, net polyurethane (PU) and poly (ethylene terephthalate) (PET) polymers and hybrid PU/PET were electrospun to create three different types of small-diameter vascular scaffolds due to their unique physicochemical characteristics: PU, PET, and novel hybrid PU/PET scaffolds...
December 1, 2017: Cardiovascular Engineering and Technology
A Abdelgaied, J Fisher, L M Jennings
A more robust pre-clinical wear simulation framework is required in order to simulate wider and higher ranges of activities, observed in different patient populations such as younger more active patients. Such a framework will help to understand and address the reported higher failure rates for younger and more active patients (National_Joint_Registry, 2016). The current study has developed and validated a comprehensive combined experimental and computational framework for pre-clinical wear simulation of total knee replacements (TKR)...
November 17, 2017: Journal of the Mechanical Behavior of Biomedical Materials
David E Hanson, John L Barber
From quantum chemistry simulations using density functional theory, we obtain the total electronic energy of an eight-atom sulfur chain as its end-to-end distance is extended until S-S bond rupture occurs. We find that a sulfur chain can be extended by about 40% beyond its nominally straight conformation, where it experiences rupture at an end-to-end tension of about 1.5 nN. Using this rupture force as the chain failure limit in an explicit polymer network simulation model (EPnet), we predict the tensile failure stress for sulfur crosslinked (vulcanized) natural rubber...
December 1, 2017: Physical Chemistry Chemical Physics: PCCP
Joana M Silva, Luísa C Rodrigues, Simone S Silva, Rui L Reis, Ana Rita C Duarte
The development of versatile tubular structures is a subject of broad interest in tissue engineering applications. Herein, we demonstrate the production of tubular structures based on chitosan through a combination of dipping, freeze-drying and supercritical technology approaches. The combination of these techniques yields versatile tubes with a perfectly defined hollow imprint, which upon chemical cross-linking with genipin acquire enhanced mechanical properties (Young Modulus ( E) and ultimate tensile stress (σmax)), as well as improved stability in wet conditions...
January 1, 2017: Journal of Biomaterials Applications
Yi Sun, Hong Kai Yap, Xinquan Liang, Jin Guo, Peng Qi, Marcelo H Ang, Chen-Hua Yeow
Soft pneumatic actuators (SPAs), as novel types of motion drivers for robotic devices, excel in many applications, such as rehabilitation and biomimicry, which demand compliance and softness. To further expand their scope of utilization, the SPAs should be customizable to meet the distinctive requirements of different applications. This article proposes a novel perspective on the SPA working mechanism based on stiffness distribution and then presents a versatile method called stiffness customization and patterning (SCP) for SPA body stiffness layout as a novel attempt to customize SPAs with distinctive properties...
September 2017: Soft Robotics
Wen Luo, Zdeněk P Bažant
Nacre, the iridescent material of the shells of pearl oysters and abalone, consists mostly of aragonite (a form of CaCO3), a brittle constituent of relatively low strength ([Formula: see text]10 MPa). Yet it has astonishing mean tensile strength ([Formula: see text]150 MPa) and fracture energy ([Formula: see text]350 to 1,240 J/m2). The reasons have recently become well understood: (i) the nanoscale thickness ([Formula: see text]300 nm) of nacre's building blocks, the aragonite lamellae (or platelets), and (ii) the imbricated, or staggered, arrangement of these lamellea, bound by biopolymer layers only [Formula: see text]25 nm thick, occupying [Formula: see text] of volume...
November 27, 2017: Proceedings of the National Academy of Sciences of the United States of America
Davide Apicella, Tim Joda, Gianni Bonadeo, Roberto Sorrentino, Marco Ferrari
PURPOSE: To apply a design optimization strategy to dental prostheses machining to verify whether this approach can detect flaws occurring in the CAD process and to estimate the influence of the type of material on the occurrence of fractures in restorations. METHODS: The stereo lithography interface format of a 4-unit (from canine to first molar) fixed dental prosthesis designed by a conventional dental CAD process was converted into a Finite Element Analysis (FEA) model...
December 2016: American Journal of Dentistry
Laís Rani Sales Oliveira Schliebe, Stella Sueli Lourenço Braga, Renata Afonso da Silva Pereira, Aline Arêdes Bicalho, Crisnicaw Veríssimo, Veridiana Resende Novais, Antheunis Versluis, Carlos José Soares
PURPOSE: To compare flowable and regular paste bulk-fill resin composites with old and new generation conventional composites that use incremental filling techniques for direct restoration of endodontically-treated teeth. METHODS: Four resin composites produced by the same company (3M-ESPE) were used: two conventional resin composites (old formulation, Z100, and new nanofilled formulation, Filtek Supreme XT); and two bulk-fill resin composites (flowable composite, Filtek Bulk-fill Flowable associated with Filtek Supreme, and regular paste, Filtek Bulk-fill Posterior)...
December 2016: American Journal of Dentistry
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