Different Types Of Deformation Research Articles

On the behavior of rotating thick-walled cylinders made of hyperelastic materials

This paper focuses on the behavior of rotating thick-walled cylinders made of the rubber-like materials. These materials are characterized by high deformability which their stress-stretch curves are arranged in the range of S-shaped to J-shaped forms. Here, it is considered an Ogden-type model with only integer powers to give a satisfactory correspondence with experimental results over wide ranges of different types of deformation. This type of constitutive model is mathematically simple and can provide the foundation of existence of a closed-form solution for the boundary value problems in the finite deformation elasticity. In this study, as an application, the Ogden-type strain energy density with only integer powers is applied to a rotating thick-walled cylinder made of the hyperelastic materials. It is shown that this constitutive model gives a closed-form solution, not involving the integral form, for the stress distribution through the wall thickness. Also, the results predicted from classic strain energy density models (Mooney-Rivlin, Neo-Hookean and Varga) and the Ogden-type model are compared for (i) a solid circular cylinder under rotation, (ii) a rotating circular cylinder with a concentric circular rigid inclusion, (iii) a rotating cylinder shrink-fitted to a rigid spindle and (iv) an unconstrained cylinder under rotation. These comparisons are done in order to investigate the accuracy of the simplification carried out by applying the well-known classic models instead of the Ogden-type model. It is concluded that this simplification is allowable if the classic models can follow the test data to some acceptable extent. While, the classic models are not capable to analyze an unconstrained rotating cylinder when experiences large deformations. Finally, influence of different parameters such as wall thickness, presence of the axial pre-stretch and form of mechanical behavior or strain-stiffening behavior of the rubber utilized in cylinders examined on stability of an unconstrained rotating cylinder.

Graphene for flexible lithium-ion batteries: Applications and prospects

With the advent of flexible electronics, flexible lithium-ion batteries (LIBs) have attracted great attention as a promising power source in the emerging field of flexible and wearable electronic devices. Flexible LIBs are generally LIBs that can operate within the normal elastic range. When the external force is unloaded, it can completely restore its original state without any remaining plastic deformation. According to the different types of deformation, most of the as-reported flexible LIBs are referred to as bendable LIBs. This review summarizes the recent developments in the application of graphene in bendable LIBs. Graphene has superior electronic conductivity. Thus, graphene can act as a type of conductive phase to form composite films containing polymers, paper and cloth. In this structure, graphene has a conductive network and the substrates provide a flexible support. Because of its unique two dimensional structure and rich functional groups, graphene can form composites with other active materials. Graphene-based materials can work as flexible electrodes and can effectively improve the overall energy density of LIBs, making them highly anticipated in the near future. This review also introduces methods to characterize the mechanical and electrochemical properties of flexible LIBs. In this review, the trends of flexible LIBs are also included. Future flexible LIBs will be stretchable, enabling them to work under different conditions. Newly developed flexible LIBs should also have self-healing abilities and should be able to be charged at high rates. Although there are still many problems to overcome, the ubiquitous applications of flexible LIBs with superior electrochemical and mechanical properties in flexible electronic devices are highly anticipated in the near future.

Влияние различных видов деформации на физико-механические свойства ГПУ- и ГЦК-металлов и сплавов

Влияние различных видов деформации на физико-механические свойства ГПУ- и ГЦК-металлов и сплавов

Interpreting atomic force microscopy nanoindentation of hierarchical biological materials using multi-regime analysis.

We present a novel Multi-Regime Analysis (MRA) routine for interpreting force indentation measurements of soft materials using atomic force microscopy. The MRA approach combines both well established and semi-empirical theories of contact mechanics within a single framework to deconvolute highly complex and non-linear force-indentation curves. The fundamental assumption in the present form of the model is that each structural contribution to the mechanical response acts in series with other 'mechanical resistors'. This simplification enables interpretation of the micromechanical properties of materials with hierarchical structures and it allows automated processing of large data sets, which is particularly indispensable for biological systems. We validate the algorithm by demonstrating for the first time that the elastic modulus of polydimethylsiloxane (PDMS) films is accurately predicted from both approach and retraction branches of force-indentation curves. For biological systems with complex hierarchical structures, we show the unique capability of MRA to map the micromechanics of live plant cells, revealing an intricate sequence of mechanical deformations resolved with precision that is unattainable using conventional methods of analysis. We recommend the routine use of MRA to interpret AFM force-indentation measurements for other complex soft materials including mammalian cells, bacteria and nanomaterials.

Study of the nonlinear instability of confined geometries

The discovery of a ``weakly turbulent'' instability of anti--de Sitter spacetime supports the idea that confined fluctuations eventually collapse to black holes and suggests that similar phenomena might be possible in asymptotically flat spacetime, for example in the context of spherically symmetric oscillations of stars or nonradial pulsations of ultracompact objects. Here we present a detailed study of the evolution of the Einstein-Klein-Gordon system in a cavity, with different types of deformations of the spectrum, including a mass term for the scalar and Neumann conditions at the boundary. We provide numerical evidence that gravitational collapse always occurs, at least for amplitudes that are three orders of magnitude smaller than Choptuik's critical value and corresponding to more than ${10}^{5}$ reflections before collapse. The collapse time scales as the inverse square of the initial amplitude in the small-amplitude limit. In addition, we find that fields with nonresonant spectrum collapse earlier than in the fully resonant case, a result that is at odds with the current understanding of the process. Energy is transferred through a direct cascade to high frequencies when the spectrum is resonant, but we observe both direct- and inverse-cascade effects for nonresonant spectra. Our results indicate that a fully resonant spectrum might not be a crucial ingredient of the conjectured turbulent instability and that other mechanisms might be relevant. We discuss how a definitive answer to this problem is essentially impossible within the present framework.

A principal axis formulation for nonlinear magnetoelastic deformations: Isotropic bodies

In this work a new set of principal axis invariants is proposed in order to study the problem of considering large magneto-elastic deformations, for bodies that are isotropic in the un-deformed configuration when no external magnetic induction is applied. The new set of invariants has clear physical meanings and may have an experimental advantage over the standard invariants used in many previous works in this area. The principal axis invariant formulation is also shown to be more general. Some simple boundary value problems are solved, such as the simple shear, and the biaxial extension of a slab, where with the use of these new invariants, it is possible to study in a much simpler manner the effect of different types of deformations on the response of the material. An illustrated simple specific constitutive equation is proposed which compares well with experiment. • A new set of invariants are proposed to be used in the modelling of magneto-active elastomers. • The new set of invariants has clearer physical meanings than the standard set of Rivlin and Spencer. • Some simple boundary value problems are solved considering the new formulation. • A general form for the total energy function has been proposed.

Capabilities of the New Element of the Stress-Strain Model

Stress-strain model is an appliance for research of the strength and deformations. It can be used to solve technological problems in the production of materials. Rheological element is a part of stress-strain model. There are some disadvantages of existing rheological elements. They can’t be applied for research of the material strength and some experimental facts which are observed for many materials. The aim of the new element is to eliminate these disadvantages. The new rheological element includes the matrix and the puncheon. It differs from its analogues by configuration and characteristics of its parts. If the value of the friction coefficient between the matrix and the puncheon is not zero and greater than the tangent of the angle between the axis and the matrix on the section with the variable cross-section, the puncheon is jammed by frictional force under loading. When unloading and subsequent loading the puncheon retains a permanent deformation until the load exceeds the maximum value during the previous cycle. If the above-mentioned angle matrix is equal to zero, displacement of the puncheon does not require increasing of the load within this section. The plastic flow is observed. Deformation can be accompanied by strengthening on the section where the value of the friction coefficient is greater than the above-mentioned tangent. Fragmentation of the element is possible on this section. Thereby the new rheological element permits to relate different types of deformations of simulated solid. In other words, it allows researching the strength of material.

Two-dimensional model of a double-well potential: Proton transfer upon hydrogen bond deformation

Proton tunneling in a hydrogen bond can only take place if the potential energy surface has two minima; this is known as a double-well potential. The aim of this work was (i) to present a simple enough 2D model of H-bond double-well potential in harmonic approximation and (ii) to assess how proton transfer therein is affected by H-bond deformations (shifts and turns such as result from conformational motion of molecular structures carrying the donor and the acceptor). It is shown that even small stretching of the H-bond and reorientation of its covalent part (‘bending’) increase the characteristic time of proton tunneling by orders of magnitude. On the other hand, the model, being two-dimensional, demonstrates that different types of deformation not only can aggravate each other but in some cases can be mutually compensatory in terms of proton transfer efficiency. The properties of the model and some implications of the results are discussed.

Global geometric torsion estimation in adolescent idiopathic scoliosis

Several attempts have been made to measure geometrical torsion in adolescent idiopathic scoliosis (AIS) and quantify the three-dimensional (3D) deformation of the spine. However, these approaches are sensitive to imprecisions in the 3D modeling of the anatomy and can only capture the effect locally at the vertebrae, ignoring the global effect at the regional level and thus have never been widely used to follow the progression of a deformity. The goal of this work was to evaluate the relevance of a novel geometric torsion descriptor based on a parametric modeling of the spinal curve as a 3D index of scoliosis. First, an image-based approach anchored on prior statistical distributions is used to reconstruct the spine in 3D from biplanar X-rays. Geometric torsion measuring the twisting effect of the spine is then estimated using a technique that approximates local arc-lengths with parametric curve fitting centered at the neutral vertebra in different spinal regions. We first evaluated the method with simulated experiments, demonstrating the method's robustness toward added noise and reconstruction inaccuracies. A pilot study involving 65 scoliotic patients exhibiting different types of deformities was also conducted. Results show the method is able to discriminate between different types of deformation based on this novel 3D index evaluated in the main thoracic and thoracolumbar/lumbar regions. This demonstrates that geometric torsion modeled by parametric spinal curve fitting is a robust tool that can be used to quantify the 3D deformation of AIS and possibly exploited as an index to classify the 3D shape.

Achnanthidium minutissimum (Bacillariophyta) valve deformities as indicators of metal enrichment in diverse widely-distributed freshwater habitats

In the presence of different environmental stressors, diatoms can produce frustules presenting different types of deformities. Metals and trace elements are among the most common causes of these teratological forms. Metal enrichment in water bodies can be attributed to the geological setting of the area or to pollution. The widespread benthic diatom Achnanthidium minutissimum (ADMI) is one of the most metal-tolerant species. In the present study, ADMI teratologies were defined from samples taken from eight very diverse, widely-distributed inland-water habitats: streams affected by active and abandoned mining areas, a metal-contaminated stream, a spring in an old chalcopyrite mine, a mineral-water fountain, and a sediment core taken from a lake affected by metal contamination in the past. Deformed frustules of ADMI were characterised mainly by one (sometimes two) more or less bent off ending, conferring to the specimens a cymbelloid outline (cymbelliclinum-like teratology, CLT). Marked teratologies were distinguished from slight deformities. Hydrochemical analyses, including metals and trace elements, were carried out and enrichment factors (EF) relative to average crustal composition were calculated. To improve our knowledge on the potential of different metals and trace elements to trigger the occurrence of ADMI CLT, we carefully selected 15 springs out of 110 (CRENODAT dataset) where both ADMI and above-average metal or metalloid concentrations occurred, and re-analysed these samples. The results from the eight widely-distributed core sites as well as from the 15 selected CRENODAT springs led to the hypothesis that two metals (copper and zinc) and a metalloid (antimony) were the most likely triggers of ADMI CLT formation. From a quantitative point of view, it is worth noting that the lowest concentrations triggering ADMI CLT can be fairly low, particularly in the case of copper contamination. The antimony-rich site was characterised by a marked-teratology variant where both ends of ADMI were bent off.

Towards modeling quasi-periodic oscillations of microquasars with oscillating slender tori

Context. One of the often discussed models for X-ray binaries high-frequency quasi-periodic oscillations is the oscillating torus model that considers oscillation modes of slender accretion tori. Aims. Here, we aim at developing this model by considering the observable signature of an optically thick slender accretion torus subject to simple periodic deformations. Methods. We compute light curves and power spectra of a slender accretion torus subject to simple periodic deformations: vertical or radial translation, rotation, expansion and shear. Results. We show that different types of deformations lead to very different Fourier power spectra and therefore could be observationally distinguished. Conclusions. This work is a first step in a longer-term study of the observable characteristics of the oscillating torus model. It gives promising perspectives on the possibility to constrain this model by studying the observed power spectra of quasi-periodic oscillations.

Morphological evolution of oriented clay-containing block copolymer nanocomposites under elongational flow

We have studied the effects of elongational flow on the morphology of nanocomposites of polystyrene-b-poly(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymers – with aligned cylindrical morphologies – containing organoclays. These nanocomposites were elongated along two perpendicular directions at varied Hencky strain rates. Small angle X-ray scattering measurements indicate that the different types of deformation induce very different microstructural changes during the elongation processes. When elongated along the direction parallel to the extrusion direction, pure copolymers under low strain rates exhibit an increasing alignment of the cylinder axes while under high strain rates a disorientation effect prevails. When elongated at low strain rates along the transversal direction, the axes of the cylinders rotate an angle close to 90°, thus becoming parallel to the elongation direction, while under high strain rates the rotation is incomplete. The addition of clay causes different effects on the final morphology after elongation depending on the sizes and degree of clay dispersion and on the predominant interactions between clay and copolymer domains.

Mechanical coupling in homogeneously deformed single-wall carbon nanotubes

We developed a full symmetry implementing method, based on classical molecular dynamics with the Brenner–Tersoff potential, for determining the optimal configuration of homogeneously deformed infinitely long single-wall carbon nanotubes. All nanotubes with diameter less than 1.3 nm are studied. Systematic analysis of the coupling between different types of deformation shows that, in the tubes with chiral angle close to zero and 30°, the torsion-induced circumferential strain is opposite to the induced axial strain. Also, torsion in zigzag tubes induces larger circumferential strain, but in armchair tubes it yields a larger axial strain. The influence of diameter on axial-stretching-induced torsion becomes significant only for narrow tubes. Finally, significant deviation from the linear dependence of axial-strain-induced radial deformation is found for zigzag tubes. The presented results are important for the calculation of electro-optical properties of nanotubes under strain.

Spinal deformities in a wild line of Poecilia wingei bred in captivity: report of cases and review of the literature

ObjectiveTo describe the occurrence of various spinal deformations in a captive-bred wild line of Poecilia wingei (P. wingei). MethodsFish belonging to a wild line of P. wingei caught from Laguna de Los Patos, Venezuela, were bred in an aquarium home-breeding system during a period of three years (2006-2009). The spinal curvature was observed to study spinal deformities in P. wingei. ResultsOut of a total of 600 fish, 22 showed different types of deformities (scoliosis, lordosis, kyphosis), with a higher incidence in females. Growth, swimming and breeding of deformed fish were generally normal. ConclusionsPossible causes for spinal curvature in fish are discussed on the basis of the current literature. While it is not possible to determine the exact cause(s) of spinal deformities observed in the present study, traumatic injuries, nutritional imbalances, genetic defects or a combination of these factors can be supposed to be involved in the pathogenesis of such lesions.

Nanoscratch characteristics and interfacial adhesion energy of SiN/GaAs film/substrate bilayer systems

Deformation characteristics and interfacial adhesion property of silicon nitride/gallium arsenide film/substrate systems were investigated by use of nanoscratch. During scratching, three different types of deformation, elastic, elastoplastic and fracture, were discovered. The critical loads for film failure were obtained. The critical loads, together with the other scratch parameters, were used to determine the interfacial adhesion energies. The practical adhesion energies per unit area of the bilayers obtained were 2.72 and 3.73 Joules/m2, respectively. The tensile stress developed just behind the contact area and at the interface was attributed to the film failure. It was also found that residual compressive stress strengthened, but tensile stress weakened the interfacial adhesion.

An Influence of Step Cyclic Loading due to Torsion on Tensile Curve Variation

The paper presents experimental results of tests carried out at room temperature on power engineering steel: 10H2M (11CrMo9-10) using thin-walled tubular specimens under biaxial stress state. The loading programme comprised different types of deformation, i.e. monotonic tension and cyclic torsion in the form of symmetric or asymmetric step-increasing strain amplitude. The main task of the paper was focused on investigation of an influence of the cyclic loading parameters on tensile curve variations. The magnitudes of axial strain and cyclic shear strain amplitude were small and did not exceed 1%. An analysis of the results showed a significant reduction of the axial stress (even equal 90% for the torsional amplitude ±0.8%, in both cases of cyclic loading). An influence of torsion frequency on the tensile stress curve was discovered within the range from 0.005Hz to 0.5Hz.

High temperature single impact studies on material deformation and fracture behaviour of metal matrix composites and steels

To exploit the full potential of materials used at elevated temperatures, it is crucial to understand their deformation and fracture mechanisms. High Temperature Single Impact Studies were performed to evaluate deformation mechanisms at different energy and momentum levels and their correlation to temperature. The limitations of materials regarding their impact resistance, the resulting deformation and fracture mechanisms were investigated. NiCrBSi based Metal Matrix Composites (MMC), reinforced with TiCNiMo or Cr3C2Ni particles, manufactured by Plasma Transferred Arc Cladding along with two different types of steels were tested and compared to study different types of deformation and fractures. Results indicate more ductile deformation behaviour of the investigated steels, while the MMCs show brittle behaviour at several temperatures. Critical impact loadings were determined at elevated temperatures to limit the range of use in impact dominated high temperature environment. Results show that the influence of different momenta at constant impact energy levels cannot be neglected.

Relative motion across the eastern Tibetan plateau: Contributions from faulting, internal strain and rotation rates

A kinematic model comprising 14 rotating, elastic–plastic blocks is used to represent the modern deformation of eastern Tibet and neighboring regions. Block rotations, fault slip rates and permanent strain rates within the blocks are constrained by inverting GPS velocities, slip vector azimuths derived from earthquakes, and fault slip rates derived from geology. The calculated internal strain rates of blocks in eastern Tibet amounts to 10 to 30×10−9/yr, in contrast to relatively low rates (<5×10−9/yr) in adjacent blocks including the south China, Alxa and Thailand blocks. F-test statistics show that neither the internal strain rates nor the spins of the blocks can be neglected in describing the surface deformation of eastern Tibet. Furthermore, slip on the main faults verifies that the use of deformable blocks can also predict strain localization and strike-parallel variations in slip rates. In terms of east–southeast motion of the eastern Tibetan plateau relative to the Eurasian plate, the net relative velocity contributed by internal strain rates in the blocks amounts to ~10mm/yr, about half of that due to the faulting. In terms of N–S shortening of plateau, however, the internal strain rises to a first order factor west of 95°E, contributing approximately 10mm/yr, nearly two times larger than that from faulting. The kinematics in eastern Tibet shows that different types of deformation, i.e., NW–SE shear and N–S compression, are taken up by faulting on major faults and distributed contraction, respectively.

Effect of hot rolling by screw mill on microstructure of a Ti-6Al-4V titanium alloy

The constitute analysis of stress–strain state by the finite element method was carried out by using LS-DYNA software for the axis and surface points of bars of titanium alloy Ti-6Al-4V with lamellar microstructure state, which were processed by screw rolling at a temperature of 940°C with reduction in area of 1.25 and 1.56. The features of screw rolling method that promoted workability of material were investigated. The rolling was performed with 6 passes. Rolling bar was reheated to rolling temperature between each passes for 5 min. The microstructure changes were assessed by light and scanning electron microscopy and quantitative microscopy analysis after each pass of rolling. The different types of deformations (monotonic and cyclic) having the strong influence on microstructures of considered points in the rolled bars are explained. The kinetic of globular structure formation during rolling to total reduction in area of 3.8 was clarified in cross section of bar.

Survey on model-based manipulation planning of deformable objects

A systematic overview on the subject of model-based manipulation planning of deformable objects is presented. Existing modeling techniques of volumetric, planar and linear deformable objects are described, emphasizing the different types of deformation. Planning strategies are categorized according to the type of manipulation goal: path planning, folding/unfolding, topology modifications and assembly. Most current contributions fit naturally into these categories, and thus the presented algorithms constitute an adequate basis for future developments.