In this work, a theoretical model is developed to address the effect of primary creep on the relationship between indentation and uniaxial creep tests. By considering the expansion of a spherical cavity in the materials following the primary creeping law, a general expression of the conversion factor is deduced during the primary creep stage. For creep tests with spherical and flat punch indenters

Tensegrity is a kind of efficient structural system that is composed of continuous cables in tension and discontinuous struts in compression. Although the studies on tensegrity have been carried out by many researchers, there are few methods for assembling large-span tensegrity by multiple units. Inspired by the similarities between reciprocal units and tensegrity units, we present a novel method for

This paper details the nonlinear design of adaptive lattices by determination and enhancement of compliant modes and optimizing the designed structure for delivering high amplitude actuation. The particular focus is the kagome lattice geometry — a pattern with some unique and useful actuation properties. Developing a novel design tool, the stiffness matrix of the beam assembly is calculated using a

The Parametric High-Fidelity-Generalized-Method-of-Cells (PHFGMC) micromechanical model is extended to include a local cohesive formulation for simulating discontinuities in multiphase composites. The nonlinear PHFGMC governing equations are obtained from a virtual work principle applied to both the local and far-field variables and solved using a new incremental-iterative formulation. The nonlinearity

The paper presents a novel mathematical model of coupled hygro-thermo-mechanical processes in a porous material, partially saturated with liquid water and exposed to temperatures below the freezing point of pore water. Water – ice phase change is modelled by means of a non-equilibrium approach considering both water supercooling and a hysteresis of ice content during freezing and thawing of moist porous

Functionally Graded Materials (FGMs) are characterized by the distribution in composition and structure gradually over volume, which were recently designed and developed as a key component of a multifunctional building envelope for the high performance of energy efficiency. It was realized by mixing aluminum particles and fine High-Density Polyethylene (HDPE) powders through a vibration-sedimentation

A new ductile fracture criterion motivated by dislocation theory and void evolution is proposed to predict fracture initiation of high-strength steels, which also considers size effect. In this model, the maximum shear stress is the driving force of the dislocation movement. The high shear stress contributes to metal plastic deformation. The equivalent maximum normal stress accelerates void growth

The Heavy Elastica problem is a classical issue and has been addressed by many authors. The only analytical approach applied is the perturbative method, and the expansion through Taylor's series is the most recurrent technique. This transforms the nonlinear differential problem into a system of nonlinear (trigonometric) algebraic equations to compute the expansion coefficients. The main disadvantage

The aim of this study is to experimentally seek a unification of brittle fracture by an atomic-level criterion. In situ fracture experiments are carried out in transmission electron microscope by using notched nano-cantilever specimens of single-crystal silicon. On the basis of atomic fracture mechanics, the critical atomic energy release rate GAFMC at fracture is experimentally determined by combining

As a consequence of shearing, wing cracks can emerge from pre-existing fractures. The process involves the interaction of sliding of the existing fracture surfaces and the tensile material failure that creates wing cracks. This work devises a numerical model to investigate how wing cracks emerge, propagate and connect pre-existing fractures under shear processes. A mathematical and numerical model

The damage rule of concrete is theoretically analyzed and discussed from the aspects of the stiffness degradation and the cohesive strength degradation. Further, the stress-strain relationship and the multiaxial damage rules of concrete are studied by 21 groups of tests under true triaxial compressive cyclic conditions. The analysis of the test results shows that the relationship between the damage

Pre-assembled scissor structures can be transformed from a compact bundle of elements to a fully deployed configuration, offering a considerable volume expansion. Intended geometrical incompatibilities during transformation can be introduced as a design strategy to obtain bistability, which allows instantaneously achieving some structural stability in the deployed state. Because of these incompatibilities

Snapping mechanical metamaterials have garnered significant interest in recent years because of their ability to achieve extremely large strains and shape/configuration changes or recoveries via elastic buckling instability. For 1D snapping 2D periodic structures with planar topological configurations, the snapping mechanisms have been deeply studied. In this article, 1D multistable cylindrical metastructures

Critical drawback of poor stiffness in traditional auxetic materials limits them to be applied where negative Poisson’s ratio behavior and excellent load-bearing capacity are simultaneously desired. In this work, a general prescription for designing auxetic lattice structures with high stiffness and controllable isotropic/anisotropic elastic properties is proposed. Based on it, we rationally design

A deployable M cross section thin-walled boom (M boom) can be flattened and coiled elastically around a hub; and can then be self-deployed by releasing the stored strain energy. The M boom has been proposed as the key member of membrane deployable structures. First, the covariant base vectors of geometrical relation of the single type I tape spring were analyzed by establishing three coordinate systems

This work provides an analytical method for determining the time-dependent effective constitutive response of linear viscoelastic composites with particulate microstructures by means of a differential-algebraic system (DAS) of equations. By making use of differential equations instead of difference equations and utilizing, as primary variables, the variances of the field fluctuations instead of the

In this work we propose to model the mechanical and fracture response of semi-crystalline low-density polyethylene (LDPE) films exposed to accelerated ultraviolet (UV) ageing using a physically based visco-hyperelastic–viscoplastic approach. UV irradiation induces an alteration of the chemical and structural properties of the semi-crystalline polymer, which affects significantly its mechanical behavior

The structural stiffness of a tensegrity is dominated not only by the material stiffness, but also by its internal forces. The deployment of tensegrities with member length actuation is investigated with an emphasis on the variation in the structural load-carrying stiffness. The relationship between the driving elongation of members and the structural displacement is established. The analytical incremental

A discrete-to-continuum transformation to model 2-D discrete lattices as energetically equivalent 1-D continuum beams is developed. The study is initiated in a classical setting but results in a non-classical two-scale micropolar beam model via a novel link within a unit cell between the second-order macrorotation-gradient and the micropolar antisymmetric shear deformation. The shear deformable micropolar

Multilayer two-dimensional (2D) material assemblies (MLMs) with a staggered architecture are widely applied to transfer exceptional properties of 2D materials into their 3D counterparts. However, the quantitative relation between interlayer shear and structural deformation, significant for the design of high-performance MLMs, has not been fully understood due to the inadequacy of existing theoretical

We investigate the complex band structure and forced response of flexural waves propagating in an elastic metamaterial thick plate. Mindlin-Reissner thick plate theory is considered. We study the influence of periodic arrays of spring-mass resonators attached to the surface of a homogeneous thick plate on the formation of Bragg-type and locally resonant band gaps. The plane wave expansion and extended

In this work a considerable development of the time-fractional damage model for hyperelastic body is presented. The novel model is implemented for full spatial configuration (AceFEM software). A patient-specific 3D computational model is elaborated to mimic the abdominal aortic aneurysm (AAA) phenomena. The considerations include the initial spatially inhomogeneous degradation of mechanical properties

We establish the existence of an internal uniform hydrostatic state of stress inside a coated non-parabolic open elastic inhomogeneity when the surrounding matrix is subjected to a concentrated couple and uniform remote in-plane stresses. The proof of existence is accomplished through analytic continuation and the introduction of a specialized form of the conformal mapping function containing an infinite

Constitutive models that describe anisotropic mechanical behaviour have generally focused on incompressible materials such as metals. However, many cellular materials such as foams and wood are compressible, and their mechanical response is both direction- and rate-dependent. To describe the anisotropic behaviour of these compressible cellular materials, a rate-sensitive constitutive model is proposed

In this paper, we present a method for simulating the structural properties of curved-crease origami through the use of a simplified numerical method called the bar and hinge model. We derive stiffness expressions for three deformation behaviors including stretching of the sheet, bending of the sheet, and folding along the creases. The stiffness expressions are based on system parameters that a user

The present research is an effort to enhance and control locally resonant bandgaps in periodic metamaterials of hexagonal and triangular topologies by introducing spider-web and snowflake-inspired hierarchies to the conventional geometries. Due to their low connectivity number, hexagonal lattice structures are unable to exhibit locally resonant bandgaps. By introducing the spider-web hierarchy, the

The two-scale asymptotic homogenization method is used to find closed-form formulas for effective properties of periodic multi-phase fiber-reinforced composites where constituents have complex-valued transport properties and parallelogram unit cells. An antiplane problem relevant to linear elasticity is formulated in the frame of transport properties. The application of the method leads to the need

The goal of this paper is to investigate the propagation of two-dimensional elastic Bloch waves in helical periodic structures, obeying two discrete screw symmetries about the same axis. First, a three-dimensional coordinate system is built from the two helical directions of periodicity of the problem and the radial coordinate originating from the symmetry axis. The existence of Bloch waves in bi-helical

Understanding the mechanical behavior and failure mechanisms of stretchable electronics is key in developing reliable and long-lasting devices. In this work a micron-scale stretchable system consisting of an aluminum serpentine patterned interconnect adhered to a polyimide substrate is studied. In-situ experiments are performed where the stretchable sample is elongated, while the surface topography

Fretting analysis may be of critical importance in the design of mechanical structural components when the contact interfaces are subjected to cyclic tangential loading. Indeed, fretting damage may induce various mechanisms of failure, such as wear, but may also lead to fretting fatigue through the early development of embryo cracks than can result in a significant decrease in fatigue performance.

Stress redistribution and damage phenomena in the vicinity of the first-fibre break in unidirectional composites under longitudinal tensile loads are investigated by means of high-fidelity computational micromechanics based on experimentally characterised material constituents. In this framework, periodic microstructures with statistically representative random fibre packings are analysed, and transient

The nonlinear response of straight, constant cross-section beams is investigated by means of a two-level finite element solution procedure. The higher level model is built starting from the Hellinger–Reissner principle, with the normal stress resultant and moment resultant as additional unknowns field beside the beam reference line position and orientation field. A lower-level nonlinear cross-section

Two-dimensional materials with self-similar second-order hierarchy are considered. The microstructure with fourfold cubic symmetry is generated by a periodic system of voids in brittle parent material, in one case, macrovoids are filled by a microvoided phase, and in the second one, this phase surrounds hollow macrovoids. A crack is embedded in a rectangular periodic domain subjected to the K-field

Initial fibre misalignment is recognised to be one of the precursors leading to longitudinal compressive failure in fibre-reinforced composites. Thus, to properly model their mechanical behaviour, an accurate spatial representation of the fibrous reinforcements must be assured. This work presents a three-dimensional micromechanical framework that is capable of analysing in detail the longitudinal tensile

The present study is on the analytical solution for the elastic field due to a cuboidal inclusion of uniform eigenstrain within a transversely isotropic full-space material, and a numerical method to model inclusions of any arbitrary shapes and with any eigenstrain distributions as the integration of a set of such cuboidal inclusions. The fast Fourier transform (FFT) is applied for efficient computation

In this paper, a strain gradient viscoelastic theory is proposed strictly, which can be used to describe the cross-scale mechanical behavior of the quasi-brittle advanced materials. We also expect the theory to be applied to the description for the cross-scale mechanical behavior of advanced alloy metals in linear elastic deformation cases. In the micro-/nano-scale, the mechanical properties of advanced

The work presents a thermomechanical model for polycrystalline NiTi-based shape memory alloys developed within the framework of generalized standard solids, which is able to cover loading-mode dependent localization of the martensitic transformation. The key point is the introduction of a novel austenite-martensite interaction term responsible for strain-softening of the material. Mathematical properties

Thanks to scale-bridging fabrication techniques, truss-based metamaterials have gained both popularity and complexity, ultimately resulting in structural networks whose description based on classical discrete numerical calculations becomes intractable. We here present a framework for the efficient and accurate simulation of large periodic three-dimensional (3D) truss networks undergoing nonlinear deformation

The aim of this study is to design a two-dimensional solid structure with embedded inertial amplification mechanisms that shows an ultrawide stop band (band gap) at low frequencies. First of all, a unique compliant inertial amplification mechanism is suggested. The compliant (flexure) hinge connections are designed and the topology of the beams in the unit cell mechanism are optimized to achieve the

An analytical approach based on multiscale homogenization is proposed to enable efficient and accurate characterizations of fiber-reinforced composites with imperfect interfaces. Micromechanical formulations are developed to evaluate transversely isotropic properties of a microscale representative volume element (RVE) consisting of a fiber, the surrounding matrix and their interfaces. We utilized the

A generalized Reissner theory for axisymmetric problems of thin circular and annular plates is applied to various problems. The plates are assumed to be linearly elastic, and shear deformation is neglected. Large deflections, rotations, and strains are allowed. The plate edges may be clamped or simply supported, movable or immovable. The types of loading considered are uniform pressure, central concentrated

Variable Angle Tow (VAT) composite panels, whereby fibre angle distributions vary continuously in-plane, have more scope for tuning structural properties than traditional straight fibre laminated composite materials. Currently, the geometrically non-linear response of such structures is typically modelled using path-following methods implemented in commercial finite element analysis. However the high

Scaled experimentation continues to play a significant role in process, product design and testing for metallic components and products but for hot forging in particular is recognized to suffer pronounced scale effects with physical behaviour changing with scale. This paper is concerned with an assessment of a new scaling approach called finite similitude that has appeared in the recent literature

This paper proposes to take into account the influence of some morphological fluctuations – often observed in unidirectional composite materials – on the modelling of the elastic behaviour of such materials. This work relies on a Generalized Self-Consistent Scheme coupled with a Morphologically Representative Pattern based approach. An analytical model is proposed to deal with “non-percolated” or trapped

Damage due to freeze-thaw cycles is a major problem for asphalt mixtures. Considering the complexity of the damage process in asphalt mixtures, characterization of the process and its effect on the material behavior is not straightforward. This paper therefore develops a thermodynamics-based model which includes viscoelasticity, damage due to freeze-thaw cycles, and temperature dependent damage due

Fiber-reinforced composites are materials that display a great potentiality in many applications for their multifaceted features. The employment of curved fibers contributes to enhancing this already wide range of possibilities further. In this paper, we propose two particular fiber arrangements with the intention of realizing ultra-stiff and ultra-soft composites. For this purpose, we explore the

We quantitatively analyze the dynamic fracture of a glass tube under bending and model the associated generation of acoustic emissions. In our experiments, precisely controlled dynamic fracture is induced by focusing flexural waves. High-speed videos show the crack propagating rapidly through 85% of the cross section, before slowing down considerably. The resulting acoustic emissions are modeled by

This paper presents an analytical description of frictional contact hysteresis behavior between two flat rough surfaces in partial and gross slip. Couplings between shear and normal forces in the contact interface are included by considering spherical asperities in oblique contact. In the oblique contact, the relation between shear and normal interface forces is determined using asperities tangential

This paper presents a study of the elastic buckling behavior of Triangular Rollable And Collapsible (TRAC) booms under pure bending. An autoclave manufacturing process for ultra-thin composite booms is presented and the behavior of three test samples is investigated experimentally. Two regimes are observed, a pre-buckling regime and a stable post-buckling regime that ends when buckling collapse is

The post-buckling behavior of a compressed, simply supported, shearable elastic rod on a nonlinear elastic foundation is studied. For the critical values of auxiliary parameter the eigenvalues are double so that the Liapunov-Schmidt method leads to two bifurcation equations. These equations describe the post-buckling behavior for the values of auxiliary parameter near the critical ones. The occurrence

Clay concrete is the main material of the embankment dam impervious wall, and its linear elastic property has significant influence on safe operation of dam impervious system. To deeply study the linear elastic property of clay concrete, this paper combines the multi-scale and multi-phase structure characteristics of the material and proposes a multi-scale analyses method to conduct the material research

In the present paper, we develope a 3-D Msrf-integral to evaluate the surface energy that is corresponding to formation of multiple surface cracks. The Msrf-integral is formulated by modifying the conventional 3-D M-integral with deliberate origination of the coordinate system and proper delimitation of the integral surface. The integral is demonstrated to be surface-independent in a modified manner

The wear volume is known to keep increasing during frictional processes, and Archard notably proposed a model to describe the probability of wear particle formation upon asperity collision in a two-body contact configuration. While this model is largely adopted in the investigations of wear, the presence of wear debris trapped between the surfaces changes the system into a three-body contact configuration

The introduction of prismatic dislocation loops in the interface between a misfitting spherical particle and its semi-infinite matrix has been theoretically investigated. The equilibrium position of one isolated loop has been first determined from an energy variation calculation and a shifting effect on the dislocation position relative to the particle equatorial plane has been identified due to the

This work presents a new return mapping, which can be an essential part in the numerical integration of the equations of motion of multibody systems involving impact events. For such systems, each unilateral constraint introduces a boundary hypersurface within the original configuration manifold, restricting the allowable motions on one side of this hypersurface only. When an impact is detected during

Two-scale models for reinforced concrete, where the large-scale problems are defined in terms of Euler–Bernoulli beam and Kirchhoff–Love plate models, are constructed. The subscale problem on the Representative Volume Element (RVE) is correspondingly outlined as finding the response of the three-dimensional RVE comprising plain concrete continuum, reinforcement bars and the bond between them. The boundary