The degree of statical indeterminacy as a fundamental property in structural mechanics is today mainly known as a property of a complete system without any information about its spatial distribution. The redundancy matrix provides information about the distribution of statical indeterminacy in the system and by this gives an additional valuable insight into the load-bearing behaviour. The derivation

Metastructures based on kirigami (the Japanese art of paper folding and cutting) have great potential for applications in stretchable electronics, bioprobes, and controllable optical and thermal devices. However, a theoretical framework for understanding the physics of their buckling behavior and to facilitate the search for ultrahigh stretchability has yet to be developed. Here, we present such a

This study utilises a third-order expansion of the strain energy density function and finite strain elastic theory to derive an analytical solution for an isolated, spherical void subjected to axisymmetric loading conditions. The solution has been validated with previously published results for incompressible materials and hydrostatic loading. Using this new solution and a homogenisation methodology

Delamination is one of the main mechanisms involved in the fatigue damage evolution in multidirectional laminates made of unidirectional plies. Typically, delamination is induced by off-axis cracks, the tips of which terminate at the interface with the adjacent layers. One of the consequences of the presence of delamination is the degradation of the apparent laminate stiffness. In this work, an analytical

Mechanical responses of cold pilgered Zircaloy-4 (Zr-4) tubes are measured under different uniaxial (tension/compression) loading directions. Tensile tests were carried out along three directions: rolling direction (RD), transverse direction (TD) and 45° to the rolling direction (45RD) at quasi static strain rate. Compression test was also performed in the RD. Texture was characterized at intermediate

This paper presents the formulation of a finite element enclosing a specific internal mechanical equilibrium in order to model cable-based structures in dynamics conditions. It is based on the concept of macro finite element which allows embedding complex mechanical systems solved inside the element boundaries. A significant advantage is to allow an easy implementation within classical commercial codes

The analysis of multiple necking phenomenon during dynamic stretching of a metallic plate is investigated. For that purpose, a new 1D linear stability analysis is proposed to capture the perturbation evolution. The multidimensional aspect of the stress field within the neck region is taken into account with a Bridgman correction factor. The novelty of the 1D approach is to let the time evolution of

The novel theoretical models for the temperature dependence of the contact mechanical properties of the particulate composites in Hertzian contact are proposed in this paper, based on an assumption of the temperature-independent constant energy storage capacity for a specific brittle particulate composite, associating with the material yielding, and the theory of Hertzian contact. The yield stress

The instability behavior of a compressive bilayer on a soft substrate is of significance for epidermal electronics adhered to human skin. Conventionally, two different wrinkling modes dependent of the modulus of intermediate layer were proposed to evolve from flat feature. Here, we uncover a new periodic pattern of secondary wrinkling feature with further compression in the case of a moderate-modulus

The configuration of a crack with respect to the multi-material fiber reinforced composite joint determines the order of singularity of the stress solutions reproduced around the crack-tip. These solutions for different configurations of crack are obtained for carbon nano-tube (CNT) reinforced CFRP composite using an innovative finite element asymptotic analysis. Micro-cracks aligned with CNTs covered

This paper deals with the fatigue of shape memory alloys considering both experimental and theoretical approaches. Initially, experimental tests are performed considering NiTi pseudoelastic wires subjected to different load conditions. Functional and structural fatigue are investigated considering situations related to phase transformations and plastic behavior. Afterward, experimental macroscopic

In Part I of this paper, a quasi-static experimental path-following method was developed that uses tangent quantities in a feedback controller, based on Newton’s method. The ability to compute an experimental tangent stiffness opens the door to more advanced path-following techniques. Here, we extend the experimental path-following method to: (i) pinpointing of critical points (limit and branching

We investigate the thermal-electric-elastic fields around two circular holes in a thermoelectric material. Solutions describing electric, thermal and elastic fields are obtained via complex variable and numerical methods. Our results show that the presence of the holes has the same effect on the effective electric and thermal conductivities but no effect whatsoever on the effective Seebeck coefficient

Failure of Thermal barrier coatings (TBCs) caused by interface oxidation directly determines the ultimate durability of TBCs. The interfacial delamination and brittle fracture will co-occur during the interface oxidation of the TBCs. To study the interaction between the two failure modes, we develop a thermodynamically-consistent coupling framework combining the phase-field model of the brittle fracture

This study presents a variationally consistent formulation of the thermo-mechanically coupled problem with non-associative viscoplasticity for glassy amorphous polymers. First, the decomposition of the equivalent plastic strain is carried out to derive the variational consistent evolution law of the shear yield strength with reference to the analogous approach taken for formulating the Armstrong-Frederick

Metamaterial with various degrees of bandgap tunability is an emerging area in manipulating elastic wave transmission characteristics for next generation phononic devices. Although several attempts are made employing multi-fields such as magnetic, electric and thermal etc., mechanical deformation based tunable bandgap is a major interest. However, achieving tunability in terms of broadening or terminating

Strong, lightweight structures are increasingly in demand for various engineering applications. Here we present a method to produce a lightweight lattice composite tube with hexagonal unit cells using a high production rate, textile-based method. A weft knitting process was employed for the first time to produce lattice preforms made of a common high-performance E-glass yarn. The lattice preforms were

Acrylonitrile Butadiene Styrene (ABS) is an inexpensive amorphous thermoplastic used for Additive Manufacturing (AM) of engineering parts. Fused Filament Fabrication (FFF) is commonly used to 3D print ABS, and it involves layer-by-layer deposition of melted thermoplastic wire through a heated nozzle along predetermined paths. The individual layers can also be configured differently and could introduce

Magnetoelectric effect is one of the most important features in multiferroic composites which is absent in either ferromagnetic or ferroelectric composites. In this paper, a two-level micromechanics model is developed to study the nonlinear magnetoelectric (ME) effects of multiferroic composites consisting both ferromagnetic (or magneto-strictive) and ferroelectric (or piezoelectric) materials. At

Using finite element analysis and analytical modeling, we investigate the strain rate sensitivity of the hardness in indentation creep (mH) and the relationship between mH and the strain rate sensitivity of the flow stress, mσ, for cone (self-similar) and spherical (non-self-similar) indenters. The present mH/mσ results extend previous results (Elmustafa et al, 2007a, b) for cones in terms of a universal

A theoretical model for thermo-chemo-mechanically coupled problems considering plastic flow at large deformation is proposed, which can be applied to predict mechanical behavior of materials under thermal and chemical environments. Different from other models in literatures, the present model derives the driving forces in the case of large deformation for reaction and diffusion: the chemical affinity

The capacity loss and cycling aging of lithium-ion batteries at high (dis)charging rate (C-rate) hinders the development of emerging technologies. To improve the performance of Li-ion batteries, it is important to understand the coupling effect of the mechanical behaviors and the electrochemical response of electrodes, as the capacity loss and cycling aging are related to the mechanics of electrodes

Void growth and morphology evolution in fcc bi-crystals are investigated using crystal plasticity finite element method. For that purpose, representative volume element of bi-crystals with a void at the grain boundary are considered in the analysis. Grain boundary is assumed initially perpendicular/coaxial with the straight sides of the cell. Fully periodic boundary conditions are prescribed in the

We derive the variational formulation of a gradient damage model by applying the energetic formulation of rate-independent processes and obtain a regularized formulation of fracture. The model exhibits different behaviour at traction and compression and has a state-dependent dissipation potential which induces a path-independent work. We will show how such formulation provides the natural framework

The double notched shear test specimen has been redesigned to test wood in structural component scale using a compression test setup. A parametric finite element method (FEM) study was performed to obtain the best specimen shape within a domain of geometrically feasible layouts. Several criteria of stress state assessment were considered to characterize the shear zone. Experiments employing DIC (Digital

This paper proposes an analytical solution for the calculation of vibrations from a twin tunnel embedded in a half-space to assess the influence of a neighbouring tunnel on the ground-borne vibrations due to underground railway traffic. Using the wave function method, the total wave field in a half-space containing two cavities is expanded as the combination of down-going plane waves from the free

In the present study, the scattering of plane elastic waves by multiple periodic arrays of interface strip-like cracks is investigated. The boundary-value problem is solved using the boundary integral equation method. The convergence of the proposed method is demonstrated for both multiple cracks and multiple periodic arrays of cracks. It is shown that the introduction of periodic arrays of strip-like

Modern numerical path-following techniques provide a comprehensive suite of computational tools to study the bifurcation behaviour of engineering structures. In contrast, experimental testing of load-bearing nonlinear structures is still performed using simple force control (dead loading) or displacement control (rigid loading). This means that established experimental methods cannot trace equilibrium

A method is presented for approximating a curved surface by a developable rigid origami; a polyhedral shape which can be developed to a plane without deformation of its facets. Form generation starts from a triangulated surface, and an optimization problem is solved to obtain a polyhedron which satisfies the geometric conditions for developability. The degrees of freedom of a rigid origami mechanism

The development of plastic strain localization in a stretching tantalum sheet in the form of necking under dynamic loading conditions was investigated by crystal plasticity simulation in the aim of evaluating the role of phenomena taking place at the scale of the material microstructure. Both equi-biaxial and plane strain stretching have been computed and two grain sizes have been considered. As expected

One of the challenges encountered in the industrialization of new single-crystal superalloys parts (like high-pressure turbine blades and vanes for aircraft engines) is to limit the mechanical stresses during the solidification and cooling of the metal. In order to accurately predict the viscoplastic flow as well as the thermo-mechanical behaviour of Ni-based superalloy during its cooling, in this

To describe the grain size dependence and rate dependence of superelastic NiTi, a constitutive model involving intrinsic material instability and thermomechanical coupling is proposed and implemented implicitly into finite element software. The material is regarded as a mixing of transformable phase and non-transformable phase. The thermodynamic driving force for martensitic transformation and the

Deep-draw experiments are performed on both glass and carbon fabric both to better understand the origin of wrinkle growth during complex forming experiments and to assess the accuracy, robustness and computational cost of forming simulations of engineering fabrics. During experiments, the shape of the deformed blanks is digitised using two different non-contact measurement techniques (Structured Light

In accordance with hyperelastic transformation theory, a range of shear-wave manipulation devices can be designed with neo-Hookean materials pre-deformed properly. However, how such devices fit the background medium remains elusive. In this study, a systematic formula is developed in terms of elastic wave transmission and reflection between un-deformed and pre-deformed hyperelastic materials. By both

Detachment of bonded tiles undermines the aesthetics, functionality, and safety of innumerable buildings world-wide. The plate-type interfacial debonding mechanisms that are the root cause of tile detachments are difficult to observe and monitor because they are hidden by opaque external layers. This invisibility, together with the brittle nature of tile detachments, raises questions regarding the

This paper presents a simple and computationally efficient multi-scale procedure to predict the macroscopic temperature dependent coefficient of thermal expansion (CTE) of any linearly thermoelastic material from isothermal mechanical simulations only. The approach relies on Levin’s demonstration that, in analytical homogenization, the effective coefficient of thermal expansion is related to the local

In this study, a computational framework is proposed for thermomechanical contact and debonding problems with proper thermal resistance at the interface. Using the Variational Multiscale (VMS) framework, we present a fully coupled thermomechanical formulation with an explicit expression of the pressure at the contact interface. The formulation considers the quasi-static balance of the momentum and

This paper presents a new general methodology to obtain an approximate analytical expression of the Saint-Venant's torsion. The shear stress in each of the principal Cartesian directions is obtained by the derivation of the stress function, whose analytical expression is obtained from the Prandtl analogy. The proposed methodology uses two variables quadratic piecewise functions to define the Prandtl

This is the second part of a two-part contribution on modeling of the anisotropic elastic-plastic response of aluminum 7079 from an extruded tube. Part I focused on calibrating a suite of yield and hardening functions from tension test data; Part II concentrates on evaluating those calibrations. A rectangular validation specimen with a blind hole was designed to provide heterogeneous strain fields

Increasing applications of laminated composite structures necessitate the development of equivalent single layer (ESL) models that can achieve similar accuracy but are more computationally efficient than 3D or layer-wise models. Most ESL displacement-based models do not guarantee interfacial continuity of shear stresses within laminates. A possible remedy is the enforcement of interlaminar equilibrium

The optimal design of the postbuckling response of variable angle tow composite structures is an important consideration for future lightweight, high-performing structures. Based on this premise, a new optimisation tool is presented for shell-type structures. The starting point is an isogeometric framework which uses NURBS interpolation functions to provide a smooth description of the deformed shapes

The application of ductile fracture criteria to shell elements yields invalid after the onset of necking and sensitivity to element size. The mesh-size regularisation strain study indicates that fracture strain modified with element dimension results in the same stress state. This phenomenon can't be accurately explained by current strain based fracture models. To fill this gap, this paper proposed

Based on the perturbation method, axisymmetric contact vibration of a rigid spherical punch on a piezoelectric half-space is studied in this paper. It is assumed that the rigid punch is a perfect insulating body with zero electric charge distribution. A compressive force composed of a static force and a time-harmonic force is applied to the spherical punch normally on the top of the surface. The variable

A rate-independent, de-cohesive damage model for the fracture modelling of large, cellular, plate-like, quasi-brittle structures is proposed. A hybrid, three-dimensional finite-discrete element method to investigate sea ice sheet fracture is then introduced, followed by three applications. The uniaxial tensile fracture of an ice sheet of varying physical sizes is examined first. The effects of both

In this contribution, a probabilistic micromechanics damage framework is presented to predict the macroscopic stress–strain response and progressive damage in unidirectional glass-reinforced thermoplastic polymer composites. Motivated by different failure modes observed experimentally, the damage mechanism in the vicinity of the fibers (namely, the interphase) is characterized by initiating and growing

The choice of model form used to represent the anisotropic yield response of metals can depend strongly on the type and amount of data available for calibration. This two-part contribution considers the calibration (part I) of three yield functions: von Mises, Hill-48 and Yld2004-18p by Barlat and co-workers. This is followed by model verification exercises (part II). The material used was a 7079 aluminum

Dimensionally reduced solids are formulated by linking the kinematics of a slender, rod-like body and a true, geometrically exact, rod. This link is enforced in such a way that the solid, where volumetric and surface loads can be applied, becomes slave of the rod, where the mechanical equilibrium is enforced. The model poses no limitations on the size of the deformations and displacements in either

Damage in oak wood museum objects under indoor climate variations (relative humidity, temperature) is studied using a thermo-hygro-mechanical model. The model incorporates the effects of moisture sorption hysteresis and discrete cracking, and is implemented within a finite element framework using a staggered update procedure. Sorptin experiments were performed in order to calibrate the moisture sorption

Equivalent plate properties are obtained for composite corrugated structures using mechanics of structure genome. The method developed in this paper interprets the unit cell associated with the corrugated structure as an assembly of plates, and the overall strain energy density of the unit cell as a summation of the plate strain energies of these individual plates. Mechanics of structure genome is

The present paper aims to show the ability of the extended overstress subloading surface EOSS theory to model the rate-dependency of metallic materials subjected to different loading conditions. The numerical results were carried out by means of Finite Elements FE simulations reproducing pure creep, stress relaxation, monotonic tensile and cyclic loading conditions. A particular emphasis is given to

The commutative-symmetrical elastic-plastic stretch-tensor product and the multiplicative Bilby-Kröner-Lee decompositions of a deformation gradient are compared to one another in particular with respect to the corresponding time derivatives and tensor rates. It turns out that these multiplicative deformation-tensor models differ with respect to the elastic response just for a Lagrangean point of view

In this paper, a lattice structure whose mechanical properties can be systematically designed is presented using tailored sub-unit structures made from curved bars. First, the stiffness of circular-arc curved bars is theoretically studied, and the effects of geometric parameters of the curved bars on the mechanical properties are analyzed. Second, sub-unit structures are designed based on the fractal

This paper develops a simple theoretical model for the adhesive contact between a rigid sphere and a circular membrane radially stretched by constant tension. The adhesive stress between the surfaces in front of the contact edge is approximated by a constant value within a finite length. The mutual relations between net external force, contact radius, and contact displacement are obtained analytically

Structures with clustered cables are widespread in many engineering applications. Most existing works involving clustered cables are based on a finite element formulation and do not address cable friction. This paper presents a novel multibody-based methodology for the mechanical analysis of systems containing clustered cable elements. The generalized coordinates of the system are chosen as configurations

In this article an “hyper-reduced” scheme for the Crisfield’s algorithm (Crisfield, 1981) applied to buckling simulations and plastic instabilities is presented. The two linear systems and the ellipse equation entering the algorithm are projected on a reduced space and solved in a reduced integration domain, resulting in a system of “hyper-reduced” equations. Use is made of the Gappy proper orthogonal

Deployable membrane structures such as inflatable stratospheric balloons are known to be sensitive to the occurrence of local instabilities such as wrinkles. The wrinkling phenomenon affects the working performances of the membrane and the occurrence of this phenomenon has to be controlled numerically in order to predict the best means of deployment during the inflation of aerospace balloons. To improve