Elastic Bending Research Articles (Page 1)

Abstract This study outlines the design, testing, and optimization of a soft actuator featuring variable stiffness based on the principle of chain mail jamming. The variable stiffness actuator was designed for a wearable exosuit for spinal rehabilitation. It enables the exosuit to apply and adjust varying forces in response to muscle activity, allowing for adaptive support during therapy. The jamming effect occurs when negative pressure is applied on the edges of a soft cover, causing particles inside to entangle. Finite Element Analysis (FEA) was conducted to evaluate the performance of the variable stiffness element in terms of the elastic bending modulus E at different particle parameters, such as length and diameter. Then, Response Surface Methodology (RSM) was applied to analyze the change of parameters and optimize them to get the optimal performance samples, which showed an improvement in stiffness and reduction in weight. Then, we manufactured the optimized sample using 3D printing to validate the simulation results. An experimental setup was used to conduct a three-point bending test, allowing an analysis of the actuator under different pressures. Finally, we customized, fabricated, and tested a wearable exosuit using the optimized variable stiffness element and compared it with the standard exosuit with fixed stiffness support.

Synthesis of organic crystals with elastic bending ability and optical waveguide behavior by crystal engineering

Abstract As adaptive organic crystals emerge as a new platform for flexible nonlinear optical (NLO) materials, understanding of the relationship between their deformation and their NLO properties is becoming critically important for the design of efficient organic optics. This study reports an organic crystalline compound that integrates a variety of mechanical properties, such as elastic bending, plastic bending, and twisting with strong second‐harmonic generation (SHG). The SHG intensity of the material, a chiral Schiff base, was found to vary across the bent region of its elastically bent crystals, with the intensity of the emission from the inner arc being stronger than that from the outer arc. On the contrary, the SHG intensity distribution in a plastically bent crystal does not appear to follow a regular trend. Density Functional Theory (DFT) calculations point out to the close molecular packing in the elastically bent region as the reason for the enhanced SHG activity of its inner arc. This study not only provides insights into the relationship between crystal deformation and the SHG activity, but it may also lead to approaches for spatial control of nonlinear optical (NLO) properties in flexible organic crystalline materials.

The aim of the manuscript is to study the effect of volume fraction on the bending properties of selected thermoplastic cellular structures (Primitive, Diamond, and Gyroid) from a mechanical and energy absorption perspective, with a view to their promising prospects and use not only for bumpers, but also for various vehicle and aircraft components, or other applications. Samples belonging to the group of so-called complex structures with Triply Periodic Minimal Surfaces, dimensions of 20 × 20 × 250 mm, and volume fractions of 30, 35, 40, 45, and 55%, were prepared by PTC Creo 10.0 software and produced using the Fused Filament Fabrication technique from Nylon CF12 material, while the basic cell size of 10 × 10 × 10 mm was maintained for all samples and the volume fraction was controlled by the wall thickness of the structure. Experimental bending tests were performed on a Zwick 1456 machine and based on recorded data; in addition to the maximum forces, the stiffness, yield strength, and effective modulus of elasticity in bending were evaluated for individual structures and volume fractions. Furthermore, the amount of energy absorbed until reaching the maximum force and until failure was compared, as well as the ductility indices μd and μU (derived from deformation and absorbed energy, respectively), as an important dissipation factor in absorbers, based on which it is also possible to predict which of the structures will have better damping.

Mitochondrial networks exhibit remarkable dynamics that are driven in part by fission and fusion events. However, there are other reorganizations of the network that do not involve fission and fusion. One such exception is the elusive "beads-on-a-string" morphological transition of mitochondria. During such transitions, the cylindrical tubes of the mitochondrial membrane transiently undergo shape changes to a string of "pearls" connected along thin tubes. These dynamics have been observed in many contexts and given disparate explanations. Here, we unify these observations by proposing a common underlying mechanism based on the biophysical properties of tubular fluid membranes, for which it is known that, under particular regimes of tension and pressure, membranes reach an instability and undergo a shape transition to a string of connected pearls. First, we use high-speed light-sheet microscopy to show that transient, short-lived pearling events occur spontaneously in the mitochondrial network in every cell type we have examined, including during T-cell activation, neuronal firing, and replicative senescence. This high-temporal data reveals two distinct classes of spontaneous pearling, triggered either by ionic flux or cytoskeleton tension. We then induce pearling with chemical, genetic, and mechanical perturbations and establish three main physical causes of mitochondrial pearling: 1) ionic flux producing internal osmotic pressure, 2) membrane packing lowering bending elasticity, and 3) external mechanical force increasing membrane tension. Pearling dynamics thereby reveal a fundamental biophysical facet of mitochondrial biology. We suggest that pearling should take its place beside fission and fusion as a key process of mitochondrial dynamics, with implications for physiology, disease, and aging.

The curve of a river bed creates a difference in the speed of water flow inside and outside this curve, indicating that plants growing along the river experience differential water-flow stresses during sudden floods caused by heavy rains. In this study, we conducted morphological, anatomical, and mechanical analyses using Osmunda x intermedia (Honda) Sugim. (Osmundaceae), a hybrid of Osmunda japonica Thunb. and the rheophytic O. lancea Thunb., growing inside and outside the river curve to elucidate the plant traits influenced by differential water-flow stresses. The external morphological analysis revealed that the O. x intermedia populations growing both inside and outside the river curve exhibited values intermediate between those of the parent species. However, the results of the anatomical and mechanical analyses of the petioles of the hybrid species did not necessarily reveal values intermediate between those of the parent species; however, in the hybrid species, the cell wall volume per unit volume was related to petiole strength, and the cell wall volume per unit volume of the hybrid population growing inside the river curve was significantly higher than that in the parent species or the hybrid population outside the river curve. In addition, the flexibility of petioles in the hybrid population growing outside the curve was associated with a lower cell wall density in the sterome than in that inside the curve, which may cause elastic bending that bends the cells further because of thinner cell walls. The results obtained in our study revealed that O. x intermedia adapts to different water-flow stresses through complex anatomical and mechanical changes that cannot be determined from external morphology alone.

Scarcity of specialized titanium alloy wires impedes wire‐arc directed energy deposition adoption in industry. Additionally, wire manufacturing on an experimental level is elaborate. Herein, a novel, physical simulation approach is presented, aimed to accelerate and economize titanium alloy development by generating wire‐arc directed energy deposition conditions in the microstructure without using wire as prematerial. An adjustable plasma torch mounted on a KUKA robot (re‐)melts the bar‐shaped samples, mimicking the wire‐arc directed energy deposition process first stages, creating a microstructure near identical to a wire‐arc directed energy deposited one. Ti–6Al–4V sheet, as‐built wire‐arc directed energy deposited material, and both after plasma remelting are characterized using various microscopy techniques, electron backscatter diffraction, microhardness tests, and four‐point bending. Results demonstrate congruence between wire‐arc directed energy deposited and plasma remelted material, including process‐specific phenomena like columnar grain growth and crystallographic texture, which results in orientation dependent elastic bending moduli. This method may offer a new tool for rapid alloy development for wire‐arc directed energy deposition applications since the approach eliminates the need for costly wire production and permits the use of any small bar‐shaped casting.

Visual-mechanical classification for evaluating the characteristic value of tensile strength parallel to grain and the modulus of elasticity in static bending of Pinus taeda wood beams

Introduction. Environmental improvement involves the recycling of man-made materials for product recovery with high performance characteristics. However, in general, energy-intensive and uneconomical materials have no alternative in construction. Literary information on the problem is insufficient and uncompiled. The presented article is intended to fill this gap. The research objective is to study mono-reinforced and hybrid-reinforced fibergeopolymers. For this purpose, two problems are solved: design of polymers and analysis of beams made from them using the finite element method.Materials and Methods. The binding base for the production of fibergeopolymers was sintered particles (beads) extracted from basalt wool waste — technogenic fibrous materials (TFM). The fiber was made from metal cord, basalt wool waste and polypropylene. Beams made from hybrid-reinforced fibergeopolymers were studied under bending and shear in the ANSYS 16.1 software environment.Results. Two types of geopolymers were obtained: – mono-reinforced (fiber from metal cord, polypropylene fiber, and TFM – fiber from waste from basalt wool production); – hybrid-fiber-reinforced (metal cord + polypropylene, metal cord + TFM, polypropylene + TFM). High values of elastic modulus (more than 25 GPa), bending strength (up to 10.19 MPa) and compression strength (up to 46.67 MPa) were defined. The ratio of bending and compression strength for the studied and traditional materials was 1:4 and 1:10, respectively. The simulated and experimental indicators of beam deflections under loads from 5 to 72 kN were compared. It was found that finite element modeling allowed designing structures from the developed materials and predicting their performance characteristics.Discussion. The cases of the smallest discrepancy between the modeling and experimental data were established. For FGP-1, it was 8% (load — 35 kN), for FGP-2 — 11% (50 kN), for FGP-3 — 7% (38 kN), for FGP-1 (1%) — 3% (30 kN). Among the hybrid-reinforced fibergeopolymers, the best compliance was that of HFGP-3. At a load of 55 kN, the discrepancy was 0.80% (theory — 4.98 mm, experiment — 5.02 mm). For HFGP-1, the best indicator was 1.85% (72 kN, 5.85 mm, 5.96 mm), for HFGP-2 — 9.12% (63 kN, 5.58 mm, 6.14 mm). The applied value of the results was confirmed by their visualization – the similarity and coincidence of the curves on the graphs.Conclusion. The advantages of the proposed innovative components for the production of building materials are proved. They are environmentally friendly and show sufficient workability. Design of hybrid-reinforced fibergeopolymers makes it possible to obtain high values of bending and compression strength (significantly higher than that of unreinforced concrete). The modulus of elasticity of more than 25 GPa proves good resistance of the material to deformations. The results of the modeling are adequate to the results of the experiments.

The wrapping of nano- and microparticles is a fundamentally important pathway for their cellular uptake and depends on the physicochemical properties of both particle and membrane. Polymeric gels are a versatile class of materials whose elastic properties can be tuned in a wide range from ultrasoft to hard by changing the density of cross-linkers. Using spring networks for the microgels and triangulated surfaces for the membranes, we study microgel wrapping with computer simulations. The interplay of microgel and membrane deformation is controlled by the competition between microgel elasticity and membrane bending rigidity. Compared with hard particles, the range of adhesion strengths for which partial-wrapped states are stable is enlarged. Volume and surface area of partial-wrapped microgels can be significantly reduced compared with those of free microgels. Understanding microgel wrapping can help us to design polymeric particles for biomedical applications, e.g., as membrane markers and targeted drug delivery vectors.

Introduction. The composite materials (4P+2C) and (4P+4C) that are used in manufacturing the below knee prostheses socket were subjected to mechanical tests tensile and bending constant and variable loading at stress ratio R = -1 and room temperature (RT25-30°C ). During the gait cycles, fatigue tensile and compression stress are induced. Methodology. The thickness and weight of the fatigue samples were 2 and 2.7 mm, 2.954 and 3.42 (gm) respectively. The increase in thickness and weight showed an increase in (UTS)tensile (UTS) bending, ET modulus of elasticity in tensile and Eb modulus of elasticity in bending by 18.84% 7.72%, 36.36% and 15.06% respectively. Results: While this increase improved the fatigue strength at 106 cycle and fatigue life at 60 MPa applied stress by 82.9% and 78.88% respectively. Increasing and decreasing fatigue variable program was carried out for the two composites. Discussion. Applying Miner rule to the obtained experimental results showed that Miner theory is not capable to predict safe fatigue life and its overestimated the fatigue properties. Conclusions. Proposed non-linear fatigue model was suggested and it applied to the experimental data. The fatigue results obtained from this model have a good agreement with those obtained experimentally

The development of snake venom-based therapeutics and antivenoms is closely linked to understanding how snake venoms modulate the physicochemical properties of biological membranes. In this study, we investigated the effects of Macrovipera lebetina venom on the surface electrical characteristics of rat liver mitochondrial membranes in vitro. A combination of electrokinetic and mechanical techniques was employed, including measurements of mitochondrial electrophoretic mobility and the bending elasticity of phosphatidylcholine membrane models. Exposure to Macrovipera lebetina venom significantly increased the net surface charge of mitochondria, while adenosine triphosphatase (ATPase) activity remained unchanged. Morphological alterations and vesicle aggregation, observed via light scattering and fluorescence microscopy, indicated reduced binding of α-D-mannosyl and α-D-glucosyl residues to the outer mitochondrial membrane in the presence of venom. In addition, malondialdehyde assays revealed elevated levels of oxidized lipid species in venom-treated mitochondria. A pronounced softening of model phosphatidylcholine membranes was also observed, likely associated with lipid oxidation induced by the venom. It states that the effect of the venom of the Macrovipera lebetina on the surface electrical charge of rat liver mitochondria is being studied in vitro. The surface charge is a physicochemical characteristic of the mitochondrial membrane.

The size and stability of micelles and vesicles determine the uptake capacity of guest molecules, thereby influencing potential applications in drug/gene delivery, bioreactors, and templates for nanoparticle synthesis. Polyethylene glycol (PEG) and polydimethylsiloxane (PDMS) are commonly used in these applications. We discovered that PEG-PDMS-PEG triblock copolymers can assemble into micelles and vesicles, making them valuable for dynamic studies to derive the bending elasticity,κη, which governs the stability these objects. We analyzed the structure using cryogenic transmission electron microscopy and small-angle neutron scattering. We investigated the dynamics through dynamic light scattering and neutron spin echo spectroscopy. By varying the number of repeating units in the hydrophilic block, we created micellar (PEG28-PDMS15-PEG28) and vesicular systems (PEG14-PDMS15-PEG14). For the vesicle, membrane rigidity was determined from experiments to beκη=(16±2)kBT, wherekBTis the thermal energy (kBBoltzmann's constant andTis the temperature). According to Zilman and Granek's concept, membrane rigidity reflects height-height fluctuations within the membrane layer. Compared to polymers at the oil-water interface of a microemulsion, the membrane rigidity in polymersomes is over an order of magnitude higher, indicatingsignificantly enhanced stability. This value closely aligns with that of liposomes, suggesting similar stability between polymersomes and liposomes.

Abstract Flexible crystals are finding increased applications in optoelectronics. The mechanism of elastic and plastic bending and thermal expansion in 9, 10‐dibromoanthracene (DBrA) crystals is determined. In addition, the X‐ray radiation luminescence performance of DBrA elastoplastic crystals is investigated and successfully prepare a flexible composite film (DBrA‐PMMA) for X‐ray radiation imaging by dispersing the crystal in polymethyl methacrylate (PMMA). This work provides new insights for the applications of elastoplastic crystals in the field of flexible optoelectronics.

The protective shell, or capsid, of many spherical viruses is formed via a self-assembly process whose underlying physical principles have not yet been fully elucidated. In this article, we analyze the role of elastic bending energy in the in vitro self-assembly of a spherical capsid in the limit where such energetic contribution dominates over compression stress. The model predicts that the capsid closes prematurely, and its final size is completely determined by a dimensionless constant fr, which is the ratio of the bending modulus to the line tension of the edge. In addition, we compute the critical size, the nucleation barrier, and the assembly rate of capsids and compare our results with those previously obtained by the original classical nucleation theory of viral capsids, where the elastic energy was neglected. Our model suggests that the competition between line tension and bending energy accelerates the rate of capsid nuclei production and causes capsids to close at suboptimal sizes, suggesting that capsomers have optimal bending angles that differ from the values measured in native viruses.

The bulk elastic behavior of a nematic liquid crystal (LC) is commonly described by three elastic constants, involving splay (K11), twist (K22), and bend (K33) director deformations. While the elastic properties of thermotropic nematic LCs are well-understood, knowledge of the elasticity of lyotropic liquid crystals (LLCs) is still quite limited. In particular, for micellar systems, which represent the largest and most ubiquitous class of LLCs, no systematic measurements of all three elastic constants have been reported so far. By means of light scattering, this study presents the concentration and temperature dependence of the three elastic moduli and their corresponding viscosities (ηsplay, ηtwist, and ηbend) for a lyotropic nematic LC, formed by the surfactant N,N-dimethyl-N-ethylhexadecyl-ammonium bromide (CDEAB) and the cosurfactant 1-decanol (DOH), assembling in water into disk-shaped micelles. At increasing surfactant concentration, a pretransitional increase in the twist and bend viscoelastic parameters is found, indicating a strong divergence near the transition to the higher ordered lamellar phase. In contrast, the splay viscoelastic coefficients show an overall increasing, yet noncritical, behavior. Furthermore, all three elastic constants and viscosities decrease linearly with an increasing temperature. These findings, which add new insights into the viscoelasticity of micellar LLCs, are compared with experimental results on both thermotropic and other classes of lyotropic nematic phases and discussed in light of existing theoretical concepts.

Abstract A universal formula for bending/curling of ultra-thin nanofilm is derived within the uniform curvature approximation. Current model includes the surface elastic effect and the size dependent surface stress effect reasonably. The derived formula is valid for anisotropic misfit strain and any types of surface stress configuration, and this formula consist of two terms, respectively, the Timoshenko term and the Stoney term. The Timoshenko term is bending of bilayer films due to the lattice mismatch, prestress or magnetostriction etc., and the Stoney term is due to the surface stress imbalance. Therefore, current model can be used to describe the bending or curling characteristics of free standing single layer and bilayer thin films. The model calculations for prestressed Si/Si and InAs/GaAs bilayer thin films proved the validity of current model. More importantly, the materials parameters such as surface Young’s modulus, size dependent surface stress are physically reasonable and fit well with available experiment. Therefore, current model can make good prediction to bending of ultrathin nanofilms (a few monolayers) with arbitrary stress load or misfit strains.

We present an experimental setup designed to investigate the statistical properties of extreme events in random elastic bending waves induced by an electromagnetic shaker on a thin stainless steel plate. In this setup, the standard statistical criteria used to define extreme events, such as rogue waves in the sea, are not sufficiently restrictive. Therefore, we introduce a new, more restrictive criterion to quantify the occurrence of rare events, similar to those observed in wave tanks [G. Michel et al., J. Fluid Mech. 943, A26 (2022)10.1017/jfm.2022.436]. Using this refined criterion, we explore correlations between the amplitude of extreme events and other wave characteristics, such as slopes, energy, and periods of the waves. We find that extreme events in our setup are correlated to the longest wavelength of the plate, which corresponds to the plate's mode. We also observe that the steepness and kinetic energy of these events reach their time-averaged value, as expected for these slow-varying modes of the plate. The study raises questions about the purely statistical characterization of statistically rare events and rogue waves.

To endure extreme conditions, silica fiber aerogels are expected to maintain ultralow thermal conductivity at high temperatures. However, the weak infrared extinction capacity of SiO2 fiber aerogels fails to effectively suppress thermal radiation, resulting in high thermal conductivity at high temperatures. Here, SiO2-air-SiC fibers with high extinction shells, air interlayer, and amorphous core are fabricated by low-pressure carbothermal reduction. Owing to low pressure conditions that reduce Gibbs free energy of the reaction and increase the diffusion rate of the gas molecules, the reaction can occur in seconds. With the mitigation of thermal radiation by the incorporation of SiC shell with high extinction capacity and the weakening of gas-phase heat conduction in air interlayer generated by reaction below the mean free path of gas (70nm), the aerogel shows ultralow thermal conductivity in a wide temperature range (the thermal conductivity at 1000°C is 0.108W m-1 K-1). Meanwhile, the ultra-fast reaction rate ensures the amorphous structure of silica core, which can maintain the flexibility of the aerogel by triggering the shear band (up to 80% elastic compressive strain and bending recovery property). The combination of high-temperature thermal insulation and high flexibility shows good potential for thermal insulation applications under extreme conditions.

A new theory of pure bending of a workpiece in the theory of elasticity is developed. Using the calibration method, the parameters of the strain-stress state of the workpiece are calculated using the example of elastic bending of a pipe on a rolling machine or in a stamp. CAD/CAE modeling are used to study the deformations, stresses and forces acting on the workpiece from the rolls or stamp tools. A new equation of plasticity in deformation formulation is developed. The criteria for crack formation, low accuracy and excessive springback of the part after processing are determined, and recommendations for their elimination are given. Keywords bending, theory of elasticity and plasticity, equation of plasticity in deformations, stamping, billet, billet bending, roller machine, stamp, CAD/CAE modeling dr_zharkov_v_a@mail.ru