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The Brazilian reduced paved road density, the increasingly demand for highways, and the lack of investment in preventive maintenance practices accelerate the occurrence of pavement distresses. This imparts for poor riding quality highways, resulting in higher fuel consumption, greater emission of pollutant gases, and increasing operational costs. In this scenario, cold recycling practices may be a cost-effective and environmental friendly alternative for pavement rehabilitation. The cold recycled asphalt mixtures (CRAMs) produced by cold recycling techniques, are comprised by reclaimed asphalt pavement (RAP), bitumen stabilized agents (asphalt emulsion or foamed asphalt), and active fillers (cement or hydrated lime). Despite the economical and sustainable benefits, the CRAMs exhibit a complex mechanical behavior since numerous variables can influence its stiffness. Therefore, the purpose of this study is to evaluate the CRAM\' stiffness dependency regarding temperature, load frequency, stress-state and moisture content variation. Four types of CRAMs were collected from the field during experimental test section construction and were evaluated by means of laboratory tests. For temperature evaluation, the CRAMs linear viscoelastic properties were investigated by means of dynamic modulus and the results were used as input data for computational simulation. It was observed that the CRAMs viscoelastic properties influence the pavement mechanical response. For moisture evaluation, triaxial resilient modulus tests were conducted at different curing conditions. In conjunction with the filter paper test and X-ray micro computed tomography, a correspondence was observed between matric suction and resilient modulus. Besides, the CRAMs stress-state dependency was evaluated by means of pavement simulation and compared with in situ measurements. It was observed that the non-linear elastic behavior of CRAMs substantially influences the pavement mechanical behavior. A baixa proporção de vias pavimentadas no Brasil, a alta demanda pelo transporte rodoviário e a falta de investimentos em manutenções preventivas aceleram o surgimento de patologias no pavimento. Tais patologias comprometem a qualidade das rodovias, aumentando o consumo de combustível, a emissão de gases poluentes e os custos operacionais. Logo, as técnicas de reciclagem a frio podem ser vistas como uma alternativa vantajosa em termos de sustentabilidade e custo-benefício para a reabilitação de pavimentos. As misturas recicladas a frio (CRAMs, do inglês cold recycled asphalt mixtures), são compostas por material fresado (RAP, do inglês reclaimed asphalt pavement) estabilizado com emulsão asfáltica ou espuma de asfalto e fíler ativo (cimento ou cal hidratada). Apesar das vantagens econômicas e ambientais das CRAM, seu comportamento mecânico é complexo, pois diversas variáveis afetam sua rigidez. O objetivo deste estudo é avaliar a influência da temperatura, da frequência de carregamento, do estado de tensão e da umidade na rigidez das CRAMs. Quatro tipos de CRAMs foram coletados do campo durante a construção de um trecho experimental e ensaiadas em laboratório. Para análise do efeito da temperatura, o ensaio de módulo dinâmico foi realizado para obtenção das propriedades viscoelásticas das CRAMs e os resultados obtidos foram utilizados como dados de entrada para simulação computacional. Observou-se que a comportamento viscoelástico das CRAMs influencia a resposta mecânica do pavimento. Para avaliar o efeito da umidade e do estado de tensão, o ensaio de módulo de resiliência triaxial foi realizado em diferentes condições de cura. Juntamente com os ensaios de papel filtro e microtomografia por raio X observou-se que a sucção mátrica está relacionadacom o módulo de resiliência desses materiais. Além disso, o efeito da dependência do estado de tensão das CRAMs foi avaliado por meio de simulação computacional e comparadas com medições in situ. Constatou-se que a elasticidade não-linear influencia significativamente o comportamento mecânico do pavimento.

In this paper, a high order mesh-free continuation for nonlinear elasticity problems is presented. This proposal consists to introduce the Weighted Least Squares (WLS) in a High Order Continuation (HOC). The WLS has been employed to create shape functions using a local support domain. The HOC permits to transform the nonlinear problems in a succession of linear problems of the same tangent matrix. A strong formulation of the problem is adopted to avoid the numerical integration and mesh generation. In this work, a numerical study has been conducted in nonlinear elasticity problems in order to study the behaviour and stability of the proposed approach. Several examples are investigated numerically in order to demonstrate the robustness and efficiency of the proposed approach. This proposed approach has shown its efficiency in management of complex geometries and irregular nodal distributions with respect to other approaches.

We exploit the possibility of deforming a solid volume, or a surface as well, by assigning a target metric. As well known, an elastic solid may change its shape under two different kinds of actions: one are the loadings, the other one are the distortions, aka, the pre-strains. Actually, a distortion prescribes the target metric sought by the solid, and the metric effectively realized is the one that minimize the distance, measured through an elastic energy, between the target metric and the actual one. The challenge of our work is to use the metric information taken from a pair of configurations X ¯ , X of a given body B x , to deform a different body B y , so that its deformation be as similar as possible to the one suffered by B x . In particular, we assess the metric change between the two configurations X ¯ , X of the template B x ; then, we use this information to build a target metric for B y , exploiting the notion of distortions: given a source configuration Y ¯ , we find a target configuration Y by minimizing an appropriate elastic energy. The proposed method is very effective in deforming solids as well as surfaces, and in reproducing similar deformations even when applied to different bodies.

Brushes formed by arm-tethered starlike polyelectrolytes may exhibit internal segregation into weakly and strongly extended populations (stratified two-layer structure) when strong ionic intermolecular repulsions induce stretching of the tethers up to the limit of their extensibility. We propose an approximate Poisson-Boltzmann theory for analysis of the structure of the stratified brush and compare it with results of numerical self-consistent field modeling. Both analytical and numerical models point to the formation of a narrow cloud of counterions (internal double electrical layer) localized inside a stratified brush at the boundary between the layers.

Light-weight origami-inspired mechanisms can provide advantages in deployable space systems and other applications. However, a significant challenge in their design is ensuring that they are sufficie...

A new multi-state HLLD (‘‘D’’ stands for Discontinuities.) approximate Riemann solver for Riemann problem of nonlinear elastic solid is developed based on the assumption that a wave configuration for the solution that consists of five waves (two slow waves, two fast waves and a contact discontinuity) separating six constant states. Since the intermediate states satisfied with the Rankine-Hugoniot relations in this approximate Riemann system are analytically obtained, the HLLD Riemann solver can be constructed straightforwardly. The Piecewise Parabolic Method (PPM) is used directly to construct high-order finite-volume schemes. Numerical tests demonstrate that the scheme PPM coupled with HLLD is robust and efficient. It indicates that the scheme PPM+ HLLD can be useful in practical applications for the non-linear elasticity.

Fibrin is a viscoelastic proteinaceous polymer that determines the deformability and integrity of blood clots and fibrin-based biomaterials in response to biomechanical forces. Here, a previously unnoticed structural mechanism of fibrin clots' mechanical response to external tensile loads is tested using high-resolution confocal microscopy and recently developed three-dimensional computational model. This mechanism, underlying local strain-stiffening of individual fibers as well as global stiffening of the entire network, is based on previously neglected nascent cohesive pairwise interactions between individual fibers (crisscrossing) in fibrin networks formed under tensile load. Existence of fiber-fiber crisscrossings of reoriented fibers was confirmed using 3D imaging of experimentally obtained stretched fibrin clots. The computational model enabled us to study structural details and quantify mechanical effects of the fiber-fiber cohesive crisscrossing during stretching of fibrin gels at various spatial scales. The contribution of the fiber-fiber cohesive contacts to the elasticity of stretched fibrin networks was characterized by changes in individual fiber stiffness, the length, width, and alignment of fibers, as well as connectivity and density of the entire network. The results show that the nascent cohesive crisscrossing of fibers in stretched fibrin networks comprise an underappreciated important structural mechanism underlying the mechanical response of fibrin to (patho)physiological stresses that determine the course and outcomes of thrombotic and hemostatic disorders, such as heart attack and ischemic stroke. STATEMENT OF SIGNIFICANCE: Fibrin is a viscoelastic proteinaceous polymer that determines the deformability and integrity of blood clots and fibrin-based biomaterials in response to biomechanical forces. In this paper, a novel structural mechanism of fibrin clots' mechanical response to external tensile loads is tested using high-resolution confocal microscopy and newly developed computational model. This mechanism, underlying local strain-stiffening of individual fibers as well as global stiffening of the entire network, is based on previously neglected nascent cohesive pairwise interactions between individual fibers (crisscrossing) in fibrin networks formed under tensile load. Cohesive crisscrossing is an important structural mechanism that influences the mechanical response of blood clots and which can determine the outcomes of blood coagulation disorders, such as heart attacks and strokes.

The ageing of human bone leads to bone diseases and the functional failure of joints. Joint replacement is effective in relieving paints and recovering functions. The mechanical properties of materials determine the performance of artificial replacements. The newly developed Ti2448 (Ti–24Nb–4Zr–8Sn-0.13O, wt.%) possesses excellent mechanical properties, especially its low modulus. Usually, metals show linear elasticity, complying with the Hooke's law. However, Ti2448 exhibits a special non-linear elastic deformation behavior, which is in contrast to most metals. While, deformation mechanisms underpinning this special non-linear elasticity is still unclear although extensive effort has been made in recent years. In this study, direct experimental evidences of stress-induced β→α″ martensitic transformation are obtained by employing in situ XRD and high-resolution transmission electron microscopy. It is found that martensitic transformation is the physical origin of the non-linear elasticity of Ti2448. The findings of this study shed light on understanding and further optimizing mechanical properties of Ti2448 and other multifunctional shape memory alloys.

Starting from constrained three-dimensional Cosserat elasticity and in a total Lagrangian framework, we derive and discuss a hierarchy of static non-linear micropolar shell models in which the thickness can stretch, and the independence of the micro-rotation on the macro-rotation is not limited to the drilling degree of freedom as in the classical six-parameter theory. If the thickness stretch is considered, unconstrained quaternions allow a singularity-free, non redundant and rational parametrization of the strain measures. Emphasis is placed in the discussion of the differences between curvatures, wryness and director deformation strains.

In this paper, using technics from asymptotic analysis, we show that the three-dimensional dynamical model for a non-linearly elastic shallow shell made of anisotropic material, with boundary conditions of generalized Marguerre–von Karman’s type, reduces to two-dimensional dynamical model.

This paper is concerned with the effect of residual stress on the elastic behaviour of materials undergoing finite elastic deformations. The theory is based on a general constitutive framework for hyperelastic materials with residual stress. Several simple problems, whose solutions are known in the situation where there is no residual stress, are analyzed in order to elucidate the influence of residual stress, and the results are illustrated for two prototype constitutive laws.

We prove non-existence of smooth solutions of a quasi-linear system suggested by Ericksen in a model of Non-linear Elasticity. This system is of mixed elliptic–hyperbolic type. We discuss also a relation of such a system to polynomial integrals of Classical Hamiltonian systems.

We model cardiac muscle contractions in the framework of finite elasticity with large distortions and couple a mechanical model with reaction–diffusion equations representing electrophysiological activity. Both models are implemented using anisotropic constitutive relations: we use stress–strain relations for fiber-reinforced materials, and anisotropic diffusion tensors for both the membrane potential and calcium ions. The effects of these choices on the electromechanical behavior are presented and discussed.

We explore theoretically the possibility of austenite-martensite transformations more complicated than those envisaged by the crystallographic theory, and make corresponding experimental predictions. The use of the Hadamard jump condition in this context is justified, and leads also to results on non-attainment of minimum energy. (C) 1999 Elsevier Science S.A. All rights reserved.

Recently, it has been shown that the class of bodies that can be called ‘elastic’ is far larger than classical Cauchy and Green elastic bodies. In order to assess the usefulness and viability of this new class of elastic bodies, it is necessary to evaluate solutions to typical initial-boundary-value problems and to see if the predictions of these models agree with observed phenomena. With this in mind, we studied members of the new class of elastic bodies within the context of a physically meaningful boundary-value problem, namely that of an infinite slab subject to a state of simple shear. Even though the problem that we consider seems very simple, we found a richness of solutions that was quite surprising. We used a non-standard semi-inverse method and looked for a special form for the solution of the problem. We found that, depending on the choice of models for the new class, this simple problem presents the most interesting outcomes: the possibility that there exists only one solution to the problem, the possibility that there exists more than one solution to the problem, and the possibility that there exists no solution, of the form sought within the context of the semi-inverse form to the problem. The non-uniqueness that is encountered is different from the traditional sense, as will be explained in the text. We were able to establish several exact solutions, which in addition to being useful solutions can also be used to check the efficacy of numerical solutions to more complicated problems. We also find the interesting possibility that solutions exhibit pronounced layers where the strain gradient is significantly larger than in the rest of the domain.

Most contemporary derivations of the linearized theory of elasticity start with the basic equations of the non-linear theory organized into kinematical, balance, and constitutive equations. The linear approximations of these equations, under the assumption that the displacement gradient is small are found, and the higher-order terms are discarded to get the basic equations of the linear theory. Consequently, determination of the range of applicability of solutions to particular linear elasticity problems has generally been based on the size of the displacement gradient. However, all solution procedures involve commingling of the basic equations, and this raises the question of whether or not the gradients of the discarded terms are small. We establish that generally they are not unless the (non-dimensionalized) second gradient of the displacement is also small. An example shows that this additional restriction on the range of applicability can be significant.

Approximative formulas for post-buckling analysis of non-linearly elastic columns made of Ludwick material are developed for free-clamp, hinge—hinge, and clamp—clamp supports. The columns have a superellipsoidal cross-section. Comparison between analytically obtained and numerical solutions showed good agreement. Additionally, post-buckling configurations for all three types of columns and materials are given in diagrams, from where the influence of material constants on the shape of the deflection curve can be examined.

This work carries out a research about the elastic behaviour of metallic powder compacts. Cylindrical specimens with different levels of density have been submitted to uniaxial compression tests with loading and unloading cycles. The analysis of the elastic loadings shows a non-linear elasticity, which can be mathematically represented by means of a potential law. Results can be explained from two different theoretical approaches: one concerns the initial compression cycles and is based on the development of an internal field of chain forces; the other concerns advanced compression stages in which forces are distributed homogeneously among the contacts between particles.

The mechanical response of an inflated spherical membrane–fluid structure in contact with rigid parallel planes is studied. The membrane is assumed to be a two-dimensional non-linear elastic and isotropic structure, while no assumption is imposed on the fluid. A numerical procedure is employed to compute the equilibrium configurations of the membrane–fluid structure. This study provides information regarding the contact force, stress distribution and pressure in the membrane and in the enclosed fluid, respectively. It was observed that a transition between unwrinkled to partially wrinkled configurations of the membrane occurs subjected to the loading conditions. Further investigation of the wrinkled configurations is presented.

A mathematical model of a nonlinear elastic medium is considered. Discontinuous solutions of the model are studied numerically for the one-dimensional case.

Myocardium generally demonstrates viscoelastic behavior. Since the stress–stain relationships of tissues are pseudo-elastic, their mechanical behavior can be defined as hyperelastic. In this work, mechanical properties of bovine heart were studied. In this study, the experimental technique for testing myocardium is explained and the experimental data are presented. First, the heart was perfused and the specimens were cut from different regions of the heart. Second, the materials preferred direction was identified. Then, a series of uniaxial, biaxial and equibiaxial test were performed on specimens taken from: left ventricle free wall (LVFW), right ventricle free wall (RVFW), left ventricle mid-wall (LVMW) and apex. Test specimens were preconditioned by applying cyclic load to reduce the viscoelastic effect. After preconditioning, the samples were tested at various stretch rates and loading conditions. Finally, a conclusion is made on the experimental data.

A peel model for nan-linear elastic tapes is presented which accounts for large deformations and for pre-straining. The large deformation setting is a new feature of modelling, which would be of interest for applications related to soft polymers and tissues. The conditions for having quasistatic-steady debonding or dynamic catastrophic debonding are determined in terms of the loading variables (peel angle and peeling force). The decohesion energy associated with a given process-zone model is included in the formulation of the peeling model. The predictions of various decohesion laws are discussed with respect to experimental results in the literature. Finally, the adhesion of a gecko is analysed and the maximum adhesion force of a single spatula is evaluated. The result correlates well with the maximum experimental pulling force reported in the literature for a gecko's seta.

An invariant (with respect to rotations) formalization of equations of linear and nonlinear elasticity theory is proposed. An equation of state (in the form of a convex generating potential) for various crystallographic systems is written. An algebraic approach is used, which does not require any geometric constructions related to the analysis of symmetry in crystals.

A mathematical model is proposed to describe the experimentally observed creep effect on the instantaneous elastic deformation of physically nonlinear elastic microinhomogeneous materials. Using a structural model of the medium, it is shown that, during unloading of a sample after creep at constant stress, the elastic strain can be both larger and smaller than the elastic strain during loading. It is shown that calculation results for a biocomposite material are in good agreement with experimental data.

This paper is devoted to a study of problems involving the propagation of one-dimensional non-linear waves of small amplitude in elastic media, using analytic and numerical methods. The equations of non-linear elasticity theory belong to the class of hyperbolic systems expressing conservation laws. For the unique construction of solutions it is necessary to supplement these equations with terms that make it possible to adequately describe actual small-scale phenomena, including the structure of the discontinuities that arise. The behaviour of non-linear waves is considered in two cases: when the small-scale processes are conditioned by viscosity, and when dispersion plays an essential role in addition to viscosity.

Non-linear elastic wave spectroscopy (NEWS) has been shown to exhibit a high degree of sensitivity to both distributed and isolated nonlinear scatterers in solids. In the case of an isolated non-linear scatterer such as a crack, by combining the elastic energy localization of time reversal (TR) with NEWS, it is shown that one can isolate non-linear scatterers in solids. The experiments reviewed here present two distinct methods of combining TR and NEWS for this purpose. The techniques each have there own advantages and disadvantages, with respect to each other and other non-linear methods, which are discussed. 2008 Published by Elsevier Ltd.

To validate earlier results for the case of arbitrary deformations and displacements in orthogonal curvilinear coordinates, kinematic and static relations of the non-linear theory of elasticity are set up which, in the limit of small deformations, lead, unlike the known relations, to correct and consistent relations. The same relations are also constructed for momentless shells of general form for the case of arbitrary displacements and deformations on the basis of which the problem of the static instability of a cylindrical shell with closed ends, made of a linearly elastic material and under conditions of an internal pressure (the problem of the inflation of a cylinder), is considered. It is shown that, in the case of momentless shells, the components of the true sheat stresses are symmetrical, unlike the three-dimensional case. All the above-mentioned relations are constructed for the loading of deformable bodies both by conservative external forces of constant directions and, also, by two types of “following” forces.

The present paper is devoted to the construction and comparative study of upwind methods as applied to the system of one-dimensional non-linear elasticity equations with particular attention to robustness and accurate resolution of delicate features such as linearly degenerate fields. Copyright © 2007 John Wiley & Sons, Ltd.

This paper presents an approach for developing a mechanical system that is similar to a musclo-skeletal system. Antagonistic driving of articulation is a key mechanism, in which at least two muscles control a single rotary axis in the antagonistic manner. It provides not only to control the joint angle but also to control the joint stiffness. The stiffness control requires for individual muscle to have a non-linear elasticity. Hence we have developed an actuator system having non-linear elasticity, which is called ANLES. It fundamentally mimics the skeletal muscle in the sense of having non-linear elasticity. This paper describes a method for designing the elastic characteristics of ANLES and shows the developed ANLES followed by the theoretical and experimental result of its non-linear elasticity. Next one rotary joint controlled by two ANLESes is introduced. The experimental result of measuring stiffness of the joint is shown. A method for controlling the joint angle is proposed, in which two ANLESes drives one rotary joint with no angular feedback. An on-line method for estimating the weight loaded at the end-point is also proposed. All of methods are evaluated and validated by the experiments.

Resume Les milieux granulaires, comme les poudres ou encore les sables, sont des materiaux formes d'une assemblee de particules. La microstructure est donc discrete par nature. Le comportement mecanique de ces derniers a ete largement traite dans la litterature, essentiellement sous l'angle experimental ou dans le cadre de simulations numeriques qui prennent en compte cette nature discrete. On aborde ici la modelisation de ces materiaux dans le cadre d'une approche micromecanique continue. Le comportement au niveau local y est modelise par une loi d'interface intergranulaire. On met en œuvre une methode d'homogeneisation non lineaire qui permet de retrouver la dependance du module de Young tangent par rapport a la contrainte moyenne observee experimentalement. Pour citer cet article : Y. Maalej et al., C. R. Mecanique 335 (2007).

The numerical modelling of non-linear electroelasticity is presented in this work. Based on well-established basic equations of non-linear electroelasticity a variational formulation is built and the finite element method is employed to solve the non-linear electro-mechanical coupling problem. Numerical examples are presented to show the accuracy of the implemented formulation. Copyright © 2006 John Wiley & Sons, Ltd.

Computer simulation of soft tissues is rapidly becoming an important aspect of medical training, pre-operative planning and intra-operative navigation. Whereas in medical training, generic models are usually employed, both planing and navigation require patient-specific modeling. However, creating a patient-specific model is a challenging task, as many of the mechanical parameters of the organ tissues are unknown. One way of addressing the issue is to extend the deterministic simulation by methods based on stochastic modeling.

This article presents a modified version of the vir-tual multi-dimensional internal bonds model. In this modi-fied model, a different approach for virtual internal bond’ strain energy is proposed, which uses the spherical stretch strain and the shear strain to calculate the bonds’ stretch energy and shear energy respectively, so as to overcome the excessive stretch energy in the virtual multi-dimensional internal bonds model. And the modified model successfully extends the limit Poisson ratio to 0.5. This new model could be applied to simulate material non-linearity behavior. DOI: http://dx.doi.org/10.5755/j01.mech.21.5.10956