Types Of Mechanical Responses Research Articles

Study on the mechanical properties of cylindrical mechanical metamaterials with biomimetic honeycomb units of the diabolical ironclad beetle

In the long process of evolution in nature, the elytra of the diabolical ironclad beetle are connected in a jigsaw way, so that the overall structure of the beetle has strong pressure resistance. The study of the geometric features and interlocking effect of elytra junctions provides new ideas for the development of new bionic applications. The honeycomb structure is a new type of material structure with excellent mechanical properties, and has broad application prospects in building structure, aerospace and other aspects. Through the reasonable design and modification of the honeycomb structure, the honeycomb structure has different characteristics. Based on the concave hexagonal honeycomb structure, combined with the geometric characteristics of the diabolical ironclad beetle jigsaw connection, the concave hexagonal honeycomb structure is redesigned, and a new type of bionic honeycomb structure is proposed. Through the combination of experiments and simulations, the mechanical response of the bionic honeycomb structure of diabolical ironclad beetles was studied. Research has shown that as the connection angle increases, the curvature on both sides of the unit also increases, making the units more compact. The overall structure exhibits two types of mechanical responses under compression: "U" and "Γ". The structure with connection angle of 25° can rely on the support and buckling on both sides of the unit, thus having the best energy absorption characteristics. As the axial ratio of the ellipse (a:b) increases, the degree of concavity in the structural unit continues to deepen, resulting in three forms of deformation of the structural unit. The structural unit changes from being supported on both sides to being bent on both sides, resulting in a stacking phenomenon in structures with ratios of 2.2:1 and 2.4:1, and the overall structure has better deformation resistance.

Selective impairment of slowly adapting type 1 mechanoreceptors in mice following vincristine treatment

Loss of the sense of touch in fingertips and toes is one of the earliest sensory dysfunctions in patients receiving chemotherapy with anti-cancer drugs such as vincristine. However, mechanisms underlying this chemotherapy-induced sensory dysfunction is incompletely understood. Whisker hair follicles are tactile organs in non-primate mammals which are functionally equivalent to human fingertips. Here we used mouse whisker hair follicles as a model system and applied the pressure-clamped single-fiber recording technique to explore how vincristine treatment affect mechanoreceptors in whisker hair follicles. We showed that in vivo treatment of mice with vincristine impaired whisker tactile behavioral responses. The pressure-clamped single-fiber recordings made from whisker hair follicle afferent nerves showed that mechanical stimulations evoked three types of mechanical responses, rapidly adapting response (RA), slowly adapting type 1 response (SA1) and slowly adapting type 2 response (SA2). Vincristine treatment significantly reduced SA1 responses but did not significantly affect RA and SA2 responses. Our findings suggest that SA1 mechanoreceptors were selectively impaired by vincristine leading to the impairment of in vivo whisker tactile behavioral responses.

Visual vs. Tactile Reaction Testing Demonstrates Problems with Online Cognitive Testing

Reaction time is one of the most commonly used measures in online cognitive assessments. However, there are significant technical problems with the methods that are commonly deployed for obtaining this measure. Most online cognitive toolkits obtain reaction time measures with a visual cue and some type of mechanical response (keyboard, mouse or touchscreen). Both the hardware and software involved in the computer systems that these online cognitive tests depend on introduce significant delays and more significantly, variation in these delays. The variability that is introduced by these systems leads to inaccurate results that health care professionals have come to rely on. In this report, a comparison is made between the reaction time data collected with a tactile based device that is accurately calibrated to sub-millisecond accuracy (the Brain Gauge) to a visual reaction time test that relies on consumer grade computer systems in a manner that parallels the methods commonly used in online cognitive testing. Forty healthy controls took both the tactile based and visually based reaction time test, and the results demonstrated a significant difference in both reaction time and reaction time variability. Most significant was the difference in reaction time variability, which was 16 msec for the tactile test and 81 msec for the visual test. While the differences could be partially accounted for by tactile vs. visual biological pathways, the variability of the results from the visual task are in the range predicted by error measured from previous reports that performed robotic testing to derive differences between the two modalities of testing.

Tensile properties of mineral fibers determined with Sentmanat extensional rheometer

Within the presented research, we utilized a non-standard technique, i.e. Sentmanat Extensional Rheometer (shorter SER-tool), which can potentially provide tensile measurements (i.e. tensile strength and Young’s modulus) on relatively short and brittle fibrous materials such as slag mineral fibers. For easier transportation and fastening of the fibers, physical model of SER-tool was slightly modified. Consequently, modified technique was theoretically (through parametric error analysis) and experimentally (through mechanical characterization) evaluated on four different types of mineral fibers. Despite a fair, yet distinguishable scatter of tensile strength which cannot be theoretically evaluated due to size effect (related to thermo-mechanical histories), fiber’s weakest link (related to fiber defects), etc., mechanical response, which is universally presented by Young’s modulus, was reproducible. Parametrical error analysis, which determines the accuracy of modified SER-tool showed that the large part of the error arises from the combination of fiber diameter and error in fiber diameter, however by careful selection of fibers (related to the magnitude of the diameter and its error) the result remains within the predicted ranges. From the results different types of mechanical responses can be observed, which is related to ceramic content, i.e. SiO2+Al2O3, within the slag fiber. Utilized technique demonstrates the high performance and the capability of modified SER-tool to perform various studies, investigating the effects of thermo-mechanical histories, chemical composition and other parameters on mechanical properties of single fiber filaments.

The effect of soaking time after ultrafast heating on the microstructure and mechanical behavior of a low carbon steel

The main objective of this study is to understand the effect of the soaking time during the ultrafast heat treatment of a low carbon steel on its complex multi-phase microstructure, tensile mechanical behavior and properties of individual microconstituents. Tensile tests were performed to determine the macro-mechanical properties. Nanoindentation testing was carried out on individual microconstituents (martensite, recrystallized ferrite and non-recrystallized ferrite) identified a priori via EBSD analysis to measure their properties. It is shown that ultrafast heating combined with short soaking times results in improved macro-mechanical properties due to finer grain size and higher fraction of non-recrystallized ferrite, that has a higher nanohardness than recrystallized ferrite. Prolonged soaking times eliminate the advantages of the ultrafast heat treatment. This occurs because, even though a long soaking time promotes a higher volume fraction of martensite than a short one, it also induces substantial grain growth and complete recrystallization of the ferritic matrix. On the micro-scale, the ferritic grains show two different types of mechanical response. The recrystallized ferritic grains are prone to show pop-in events on the nanoindentation curves that are associated to dislocation nucleation events as a consequence of their low dislocation density, while non-recrystallized ferritic grains demonstrate a continuous response. The relationship between microstructure and mechanical properties on the macro- and micro-scales is discussed with respect to the microstructure, which in turn strongly depends on the applied heating rate and soaking time. A general recipe for microstructural design to improve the tensile mechanical behavior of low carbon steels implementing controlled heating and soaking conditions is outlined.

Modification of the mechanical properties of zirconium dioxide ceramics by means of multiwalled carbon nanotubes

A ceramic matrix composite based on zirconium dioxide doped with carbon nanotubes (CNTs) and metallic silver as a plastic binder was produced by hydrothermal synthesis from ceramic precursor and a CNTs suspension followed by critical point drying of the synthesized hydrogel and metallic silver deposition on ceramic composite aerogel fragments from a AgNO3 solution. Multi-indentation loading of the composite has revealed two types of mechanical response: 1) hardness decreasing with an increasing of number of cycles and 2) significant increasing of hardness with an increasing number of indentations. Local chemical composition analysis has revealed correlations between the composite hardness and the presence oxygen atoms for first type and silver and yttrium atoms for second type of mechanical response respectively.

Local Mechanical Response of Superelastic NiTi Shape-Memory Alloy Under Uniaxial Loading

In this paper, we focus on the local mechanical response of superelastic NiTi SMA at different temperatures under uniaxial loading. In situ DIC is applied to measure the local strain of the specimen. Based on the experimental results, two types of mechanical response, which are characterized with localized phase transformation and homogenous phase transformation, are identified, respectively. Motivated by residual strain accumulation phenomenon of the superelastic mechanical response, we conduct controlled experiments, and infer that for a given material point, all (or most) of the irreversibility is accumulated when the transformation front is traversing the material point. A robust constitutive model is established to explain the experimental phenomena and we successfully simulate the evolution of local strain that agrees closely with the experimental results.

Effects of sliding on rolling contact fatigue of railway wheels

ABSTRACTThis paper proposes a numerical approach based on a steady‐state algorithm to predict the rolling contact fatigue crack initiation in railway wheels in practical conditions. This work suggests taking into account the cyclic hardening of the wheel's material and one of its originality is to conduct a complete numerical approach whatever the loading level. The main stages are the characterization and modelling of the material behaviour, the determination of the stress–strain fields using a numerical steady‐state method and the application of a high cycle fatigue criterion. Computations were made with the Abaqus FE commercial software. Three cases are studied: rolling with or without sliding and skating. The numerical results give several types of mechanical responses: elastic or plastic shakedown. Otherwise, the results show that the location where the shear stress is maximal is not the same as where the risk of crack is the highest.

Chronotropic and inotropic dependence of the myocardium in patients with rheumatic heart disease before and after amiodarone treatment

Characteristic features of the electromechanical coupling of the myocardium were studied in patients with heart failure caused by rheumatic heart disease. Experiments were performed on muscle trabeculae isolated from the right atrial auricle in the course of surgical correction of a valve defect. The trabeculae displayed two types of mechanical responses, recorded in the isometric mode, to the postrest test. In the type I response, the mechanical restitution had an ascending pattern, the interval between electrical stimuli increasing. In type II, the mechanical restitution pattern was descending. Amiodarone (1 μM) treatment of the myocardium with the type I response enhanced the postrest potentiation of the mechanical response of trabeculae by more than 30%, but it had no effect on the muscles with the type II response. All patients whose biopsy material displayed the type II response had long episodes of atrial fibrillation. It is conceivable that the observed differences in the rhythm inotropic dependence of the human myocardium in rheumatic heart disease reflect different degrees of cardiomyocyte remodeling. The direction of this process is determined by the range of adaptive changes in intracellular structures, primarily, the sarcoplasmic reticulum.

Mechanical activity of frog esophagus muscle in response to electrical stimulation of intramural nerves

Microscopic observation of intramural nerves in the frog esophagus, fixed and stained with OsO(4) and ZnI(2), revealed that nerve cell bodies and bundles connecting the nerve cell bodies formed loose and irregular networks. The nerve cell bodies were mostly lying singly in the nerve bundles, with occasional observations of two closely linked nerve cell bodies. Isolated circular and longitudinal segments of esophageal muscle were spontaneously rhythmically contractile, with a frequency of 2.2-3.0 per min. This was not altered by tetrodotoxin (TTX). In longitudinal muscle segments, transmurally applied electrical stimulation produced contractile responses which were not inhibited by atropine or guanethidine, but were reduced in amplitude by TTX, suggesting a nonadrenergic-noncholinergic (NANC) excitatory innervation in the esophagus muscle. In circular muscle segments, transmural application of brief electrical stimulation evoked two types of mechanical response: a biphasic response consisting of an initial relaxation and a following contraction (type I) and a contraction alone (type II). These mechanical responses were not modulated by either atropine or guanethidine. In the type I response, TTX abolished the relaxation component, suggesting that this was produced by non-adrenergic non-cholinergic (NANC) inhibitory nerve excitation. In about half of the type II responses, the amplitude of the contraction was significantly reduced by TTX, suggesting that a part of the contraction was produced by activation of NANC excitatory nerves. Thus, the esophageal smooth muscle of the frog demonstrates myogenic activity, and is innervated by both excitatory and inhibitory NANC nerves.

Cellular adaptation to mechanical stress: role of integrins, Rho, cytoskeletal tension and mechanosensitive ion channels

To understand how cells sense and adapt to mechanical stress, we applied tensional forces to magnetic microbeads bound to cell-surface integrin receptors and measured changes in bead displacement with sub-micrometer resolution using optical microscopy. Cells exhibited four types of mechanical responses: (1) an immediate viscoelastic response; (2) early adaptive behavior characterized by pulse-to-pulse attenuation in response to oscillatory forces; (3) later adaptive cell stiffening with sustained (>15 second) static stresses; and (4) a large-scale repositioning response with prolonged (>1 minute) stress. Importantly, these adaptation responses differed biochemically. The immediate and early responses were affected by chemically dissipating cytoskeletal prestress (isometric tension), whereas the later adaptive response was not. The repositioning response was prevented by inhibiting tension through interference with Rho signaling, similar to the case of the immediate and early responses, but it was also prevented by blocking mechanosensitive ion channels or by inhibiting Src tyrosine kinases. All adaptive responses were suppressed by cooling cells to 4 degrees C to slow biochemical remodeling. Thus, cells use multiple mechanisms to sense and respond to static and dynamic changes in the level of mechanical stress applied to integrins.

Reactive blending via coordination chemistry—extraordinary mechanical response for atactic 1,2‐polybutadiene complexed with palladium chloride

AbstractExperimental evidence in solution and in the solid state suggests that atactic 1,2‐polybutadiene and palladium chloride form coordination complexes with unusual mechanical properties. Ternary phase diagrams with tetrahydrofuran as the solvent highlight regions where gelation is favored relative to precipitation. The strongest evidence for a network structure is based on the facts that (i) solid films swell in heptane, and (ii) infrared spectroscopy identifies a new absorption characteristics of three‐membered rings and dihapto coordination of the olefinic sidegroup in 1,2‐polybutadiene to the metal center in palladium chloride‐bis(acetonitrile). Carbon‐13 solid state NMR spectroscopy suggests that the polymeric palladium complex is a glass when the salt concentration is 4 mol%. NMR linewidth data together with the pulse sequence parameters suggest that the chain backbone of the polymeric palladium complex experiences a significant reduction in molecular mobility which is consistent with diamagnetic glassy materials. Most importantly, the elastic modulus of polybutadiene increases by three orders of magnitude during the transition from rubbery to glassy behavior. This type of mechanical response cannot be explained by a filler effect, crystallite reinforcement, or antiplasticization. Transition‐metal coordination concepts applied to polymeric materials suggest that the enhancement in mechanical properties is a direct consequence of ‘coordination crosslinks’ where the palladium salt bridges different polymer chains. However, palladium‐catalyzed rections of the olefinic sidegroup, generating a chemically crosslinked network, represent a second explanation of the significantly enhanced macroscopic physical properties of 1,2‐polybutadiene in the presence of the transition‐metal salt. Reactive blending via metal‐ligand coordination represents a new mechanism to compatibilize polymeric mixtures that would otherwise exhibit phase separation.

Ambient‐Temperature Mechanical Response of Alumina–Fluoromica Laminates

Flexural delamination experiments were used to evaluate the mechanical performance of thermochemically stable alumina–fluoromica laminates. Hot‐pressed, precracked laminate specimens, in which two MgAl2O4‐spinel‐coated alumina substrates were separated by a thin layer of fluorophlogopite (KMg3(AlSi3)O10F2), were tested in fourpoint flexure at room temperature. Two types of mechanical response were observed: steady‐state delamination and brittle failure. Microstructural analysis showed that the delamination response was associated with fine (≤5 μm) grains of the mica; the brittle response occurred when the mica interphase consisted of large (>30 μm) grains that bridged the interphase. The steady‐state strain‐energy release rate (Gss) measured on the graceful, delaminating beams was 9.1 ± 0.4 Jm–2 for randomly oriented ∼ 5–μm grains but only 2.8 ± 0.2 Jm–2 for ∼1–μm grains that were aligned with easy‐cleavage planes parallel to the laminate interfaces. The results suggested that debonding of the specimens occurred via cleavage of the mica grains. Observation of delamination cracks confirmed this point: propagation occurred within the fluoromica interphase rather than along the spinel/alumina or spinel/fluorophlogopite interfaces. The mechanical feasibility of laminate specimens without the protective spinel coating on the substrate containing the notch was also tested to address an issue related to the preparation of alumina fiber/mica interphase/alumina matrix composites. The delamination response again occurred for the case of a fine‐grained mica interphase.

Cellular Tensegrity: Exploring How Mechanical Changes in the Cytoskeleton Regulate Cell Growth, Migration, and Tissue Pattern during Morphogenesis

Publisher Summary This chapter focuses on the role of the intracellular cytoskeleton (CSK) in cell shape determination and tissue morphogenesis. The role of mechanical changes in the CSK during embryological development is reviewed. The chapter focuses on the mechanism by which mechanical forces are transmitted across the cell surface and through the CSK, as well as how they regulate cell shape. An analysis of the biomechanical basis of cell shape control addresses two central questions: (1) how do changes in mechanical forces alter CSK organization, and (2) how do changes in CSK structure regulate cell growth and function. The results from recent studies showing that the CSK can respond directly to mechanical stress are also reviewed. The particular type of mechanical response that living cells exhibit is consistent with a theory of CSK architecture that is based on tensional integrity and is known as “tensegrity”. Inherent to the tensegrity model is an efficient mechanism for integrating changes in structure and function at the tissue, cell, nuclear, and molecular levels. The chapter explores the possibility that CSK tensegrity may also provide a mechanical basis for cell locomotion as well as a structural mechanism for coupling mechanical and chemical signaling pathways inside the cell.