In the present study, for the first time, a thermodynamically consistent large deformation theory is developed to model the multi physics problem of axonal swelling which is the hallmark of most of the brain diseases. To this end, the relevant axonal compartments are first explained and the corresponding model parts are introduced. Next, the problem is formulated as an open thermodynamic system and

Owing to the special arrangement of platelets, staggered composites can achieve superior fracture toughness. Nevertheless, a rigorous mathematical framework for the fracture analysis on them remains a challenge. Here, we show that by incorporating the mechanical behavior of individual unit cells, a multiscale analytical framework for a mode I crack propagation in staggered composites can be setup adopting

We present a dislocation density-based strain hardening model for single crystal copper through a systematic coarse-graining analysis of more than 200 discrete dislocation dynamics (DDD) simulations of plastic deformation under uniaxial tension. The proposed constitutive model has two components: a generalized Taylor relation connecting resolved shear stresses to dislocation densities on individual

Fungi develop structures that interact with their surroundings and evolve adaptively in the presence of geometrical constraints, finding optimal solutions for complex combinatorial problems. The pathogenic fungus Ophiocordyceps constitutes a perfect model for the study of constrained interactive networks. Modeling these networks is challenging due to the highly coupled physics involved and their interaction

Physical systems consisting of an elastic matrix permeated by fluid mixture are ubiquitous, with examples ranging from morphogenesis of a single biological cell to the migration of greenhouse gases in sediments. Recent experimental studies show that the presence of the elastic networks in these systems significantly alters their phase-separation response by imposing an energetic cost to the growth

Bacteria usually grow in populations to survive in various environments. A yet unsolved issue is how mechanical forces at the cellular level regulate the morphogenesis of bacterial population. In this paper, we combine experiments and theoretical analysis to investigate the growth of bacterial chains constituted by rod-shaped Bacillus subtilis. Our experiments show that due to cellular proliferation-induced

Emerging three-dimensional printing approaches enable cellular structures with composite walls or struts, creating new opportunities for architected materials with high specific stiffness and damping. This paper describes the damped dynamic response of composite walls comprising elastic and viscoelastic phases, and quantifies the scaling between material and structural loss factors. These descriptions

Onsager’s Reciprocal Relations between thermodynamic forces and fluxes, for which Onsager was awarded the Nobel Prize, automatically follow from Thermodynamic Extremal Principles. Thus, the principles have been up to now non-applicable for the treatment of experimentally determined or theoretically modeled non-reciprocal systems as e.g. those involving magnetic fields. Recently, we were able to demonstrate

The lungs are among the most deformable body organs, a mechanical feature that is key to the vital process of breathing. Current micromechanical constitutive models of the lung parenchyma construct the tissue response function either as strain-driven or pressure-driven. However, the lung parenchyma resembles an open-cell foam material consisting of a solid phase and a fluid phase that closely interact

Nanostructured metallic multilayers with carefully designed mechanical and functional properties are omnipresent in cutting edge technological applications. To ensure the mechanical integrity of such coatings, the Mode I critical Stress Intensity Factor KIC is used to quantify their fracture toughness in order to avoid material failure by appropriate design. In this article, we present a novel approach

Rate-dependent fracture has been observed for a silicon/epoxy interface as well as other polymer interfaces, where both the interfacial strength and toughness increase with the separation rate. Motivated by this observation, we propose a multiscale approach to modeling a polymer interface, from atomic bonds to the macroscopic specimen, considering the energetics of bond stretching, the entropic effect

The mechanical properties of brick-and-mortar composites depend on their interface fracture properties, which have not been evaluated to date, preventing a rational optimization of the microstructure and of the resulting mechanical properties. Micro-(cantilever) and macro-scale (Single Edge Notched Bending) tests on nacre-like alumina both result in crack initiation at the interface between the platelets

Manipulation by focused ultrasound is an emerging technology with much promise for non-contact handling of microscale objects. A particularly promising approach for achieving this with living cells involves incorporating standing surface acoustic waves (SSAWs) into a microfluidic device. SSAWs must be tuned to provide the necessary range of acoustic radiation force (ARF), but models enabling this tuning

Endocytosis and exocytosis are key mechanisms in cellular systems by which a cell deforms its plasma membrane to move substances in or out of the cell. Whereas these cellular processes typically rely on active mechanisms, we study here the problem of achieving encapsulation by a purely physical process. We consider an ideal system in which a rigid particle is put in contact with a spherical deformable

The swelling behavior of hydrogels, involving coupled diffusion and large deformations, makes them ideal for biomedical applications such as micro- and nano-scale drug delivery systems. Understanding the transient swelling or drying behavior of hydrogels at relevant length-scales will provide insight for the development of specialized and controlled drug release. At sub-millimeter length-scales, surface

Wear is well known for causing material loss in a sliding interface. Available macroscopic approaches are bound to empirical fitting parameters, which range several orders of magnitude. Major advances in tribology have recently been achieved via Molecular Dynamics, although its use is strongly limited by computational cost. Here, we propose a study of the physical processes that lead to wear at the

In this work, we investigate the use of pre-twisted metallic ribbons as building blocks for shape-changing structures. We manufacture these elements by twisting initially flat ribbons about their (lengthwise) centroidal axis into a helicoidal geometry, then thermoforming them to make this configuration a stress-free reference state. The helicoidal shape allows the ribbons to have preferred bending

Solid solutions are of critical importance to many technological applications. While continuum frameworks have been developed and invoked in the past for studying behavior of solid solutions, recent studies point to the importance of image stresses in finite systems, and in particular, suggest that the homogenized self-stress field of the solutes, which enter the chemical potential in the prevalent

Lower eukaryotic cells such as Schizosaccharomyces pombe employ closed mitosis for their division where the nuclear envelope remains intact despite undergoing severe deformation. However, how forces generated by growing spindle microtubules overcome resistance from the deformed nuclear membrane as well as the viscous surrounding to drive the progression of closed mitosis remains unclear. In this study

Photoactive nematic elastomers are soft rubbery solids that undergo deformation when illuminated. They are made by incorporating photoactive molecules like azobenzene into nematic liquid crystal elastomers. Since its initial demonstration in 2001, it has received increasing interest with many recent studies of periodic and buckling behavior. However, theoretical models developed have focused on describing

The detachment of material in an adhesive wear process is driven by a fracture mechanism which is controlled by a critical length-scale. Previous efforts in multi-asperity wear modeling have applied this microscopic process to rough elastic contact. However, experimental data shows that the assumption of purely elastic deformation at rough contact interfaces is unrealistic, and that asperities in contact

A scale-free phase-field model for martensitic phase transformations (PTs) at finite strains is developed as an essential generalization of small-strain models in Levitas et al. (2004) and Idesman et al. (2005). The theory includes finite elastic and transformational strains and rotations as well as anisotropic and different elastic properties of phases. The gradient energy term is excluded, and the

Microlattice structures possess properties imparted by the architected microstructure of their constituents (unit cells) and micro/nanofeatures rather than their bulk material properties. Post-processing techniques have revealed intriguing length scale effects, encompassing enhanced behavior or shape morphing of various structures. Although monolithic structures consisting of single unit cells have

Almost a century ago Onsager found a universal feature of all dissipative systems describing approach to thermodynamic equilibrium, the reciprocal relations. They hold for linear differential equations describing an evolution of macrovariables in vicinity of equilibrium states. It was assumed implicitly that underlying microdynamics is Hamiltonian and ergodic. The reversibility of Hamiltonian equations

Liquid crystal elastomers with mobile liquid crystal moieties display unique mechanical instabilities and domain patterns in the strain-induced director reorientation. Based on a continuum mechanical model, we present a complete Lagrangian description of finite element formulation of LCEs by solving the coupled displacement and director fields within the Lagrangian scheme. The nucleation of the stripe

This paper presents an investigation on the formation of adiabatic shear bands in metallic sheets subjected to dynamic shear-compression loading under plane-stress conditions. For that purpose, we have developed a theoretical model based on perturbation analysis, and have performed finite element calculations. The material behavior has been modeled with von Mises plasticity, and the evolution of the

A computational framework is presented for high-fidelity virtual (in silico) experiments on granular materials. By building on i) accurate mathematical representation of particle morphology and contact interaction, ii) full control of the initial state of the assembly, and iii) discrete element simulation of arbitrary stress paths, the proposed framework overcomes important limitations associated with

The material characterization of ultra-thin solid sheets, including two-dimensional materials like graphene, is often performed through indentation tests on a flake suspended over a hole in a substrate. While this ‘suspended indentation’ is a convenient means of measuring properties such as the stretching (two-dimensional) modulus of such materials, experiments on ostensibly similar systems have reported

The energy barrier for homogeneous cross-slip of a screw dislocation in face-centered cubic (FCC) nickel is calculated using atomistic simulations as a function of the Escaig stress on the glide plane, the Escaig stress on the cross-slip plane, and the Schmid stress on the cross-slip plane. Two cross-slip mechanisms, Friedel-Escaig (FE) and Fleischer, are examined and their energy barriers are calculated

The topologically polarized isostatic lattices discovered by Kane and Lubensky (2014, Nat. Phys. 10, 39–45) challenged the standard effective medium theories used in the modeling of many truss-based materials and metamaterials. As a matter of fact, these exhibit Parity (P) asymmetric distributions of zero modes that induce a P-asymmetric elastic behavior, both of which cannot be reproduced within Cauchy

While homogenization of periodic linear elastic structures is now a well-known procedure when the stiffness of the material varies inside fixed bounds, no homogenization formula is known which enables to compute the effective properties of highly contrasted structures. Examples have been given in which the effective energy involves the strain-gradient but no general formula provides this strain-gradient

The rate capability and lifetime of Li-ion batteries is largely dictated by the composition dynamics of the electrodes. We set forth a nanoindentation approach to probe the spatiotemporal Li profile using the functional dependence of the mechanical properties on Li composition. This mechanics-informed material dynamics allows us to measure the composition-dependent diffusivity, assess the rate-limiting

We derive a Föppl-von Kármán-type constitutive model for solid liquid crystalline plates where the nematic director may or may not rotate freely relative to the elastic network. To obtain the reduced two-dimensional model, we rely on the deformation decomposition of a nematic solid into an elastic deformation and a natural shape change. The full solution to the resulting equilibrium equations consists

The interaction between contact area and frictional forces in adhesive soft contacts is receiving much attention in the scientific community due to its implications in many areas of engineering such as surface haptics and bioinspired adhesives. In this work, we consider a soft adhesive sphere that is pressed against a rigid substrate and is sheared by a tangential force where the loads are transferred

Ferroelectric ceramics are of interest for engineering applications because of their electro-mechanical coupling and the unique ability to permanently alter their atomic-level dipole structure (i.e., their polarization) and to induce large-strain actuation through applied electric fields. Although the underlying multiscale coupling mechanisms have been investigated by modeling strategies reaching from

In this paper, a novel physically-motivated anisotropic model for growth driven by nutrient diffusion is proposed and the mathematical framework is extensively presented. Growth phenomena usually occur in living tissues under different mechanobiological stimuli. Here the growth is driven by the diffusion of a chemical substance which reflects, in fact, the extent of nutrients availability or other

Mechanical metamaterials have gained increasing interest owing to its unique properties and promising applications. However, most developed mechanical metamaterials feature a single-step pathway and/or a single deformation mode, which limits their multi-task applications. In this paper, a multi-step metamaterial (MSM) is introduced. Under compression, the MSM can translate global loading into multiple

Spiders, silks and webs are abundant and can be found in most ecosystems: in the corner of houses, on top of bushes, or even spanning rivers. They are the proof of an evolutionary success as they were able to survive and prosper for millions of years despite being subjected to environmental and human threats, such as the displacement of spider web silk attachments or impact of prey, predators, and

Using molecular dynamics (MD) we study the dependency of the contact mechanics on the sliding speed when an elastically soft slab (block) is sliding on a rigid substrate with a sin(q0x) surface height profile. The atoms on the block interact with the substrate atoms by Lennard-Jones potentials. We consider contacts with and without adhesion. The contact area and the friction force are nearly velocity

The theory of dislocation and generalized dislocation fields is developed within a second-order mechanical framework where the description of the internal state of the body and the balance equations involve the stress and hyper-stress tensors, work-conjugates to the strain and second-order distortion tensors. Consistently, the free energy density depends on the elastic strain and second-order distortion

We present a gradient-based theoretical framework for predicting hydrogen assisted fracture in elastic-plastic solids. The novelty of the model lies in the combination of: (i) stress-assisted diffusion of solute species, (ii) strain gradient plasticity, and (iii) a hydrogen-sensitive phase field fracture formulation, inspired by first principles calculations. The theoretical model is numerically implemented

Two-phase piecewise homogeneous plane deformations are examined in respect of a neo-Hookean matrix material reinforced with embedded aligned fibres characterized by a single stiffness parameter. The deformations are interpreted in terms of fibre kinking and fibre splitting. Previous work has shown that such a transversely isotropic material can lose ellipticity if the reinforcing stiffness is sufficiently

Besides being ubiquitous in engineering applications such as Polyethylene terephthalate, materials with tension-compression asymmetry can also be found in lots of biological systems, e.g., muscle and brain tissue. However, the effect of tension-compression asymmetry at finite strains has not been well studied, especially lack of theoretical model and analytical solutions. In this work, based on a bi-modulus

Water injection laboratory experiments in weak, poorly consolidated sandstones show evidence that the peak injection pressure is much larger than the one predicted by the Haimson-Fairhurst breakdown criterion. A model based on poroelasticity, fracture mechanics, and lubrication theory is constructed to simulate the laboratory experiments. It aims at computing the propagation of a bi-wing hydraulic

This work is concerned with the purely dissipative version of a well-established model of rate-independent strain-gradient plasticity. In the conventional theory of plasticity the approach to determining plastic flow is local, and based on the stress distribution in the body. For the dissipative problem of strain-gradient plasticity such an approach is not valid as the yield function depends on microstresses

We consider a two-dimensional cellular vertex model, modeling the mechanics of epithelial tissues. The energy of a planar configuration penalizes deviations in each cell from a reference perimeter P0 and a reference area A0. We study the variational limit of this model as the cell size tends to zero, obtaining a continuum variational model. For P02/A0 below a critical threshold, which corresponds to

The hydraulic circular and elliptical bulge tests have been widely used in extracting mechanical properties of sheet materials. Theoretical analysis of bulge tests usually requires the kinematic relationships between the apex strains, radii of curvatures and dome heights to be established. Most of the available analytical solutions are derived on a case-by-case basis and are often limited to circular

Spatially-varying stress fields can be obtained from atomistic simulations as weighted averages over a phase function that depends on the positions and momenta of the atoms and the interatomic forces between them. However atomistic stress fields exhibit significant nonphysical noise on atomic length scales even under uniform loading conditions. This makes it difficult to obtain accurate stress estimates

Understanding the feature-rich buckling-dominated behavior of thin elastic ribbons is ripe with opportunities for fundamental studies exploring the nexus between geometry and mechanics, and for conceiving of engineering applications that exploit geometric nonlinearity as a functioning principle. Predictive mechanical models play an instrumental role to this end. As a direct consequence of their physical

Several experiments have demonstrated the existence of an electro-mechanical effect in many biological tissues and hydrogels, and its actual influence on growth, migration, and pattern formation. Here, to model these interactions and capture some growth phenomena found in Nature, we extend volume growth theory to account for an electro-elasticity coupling. Based on the multiplicative decomposition

Biologically-derived and chemically-treated collagenous tissues such as glutaraldehyde-treated bovine pericardium (GLBP) are widely used in many medical applications. The long-term cyclic loading-induced tissue fatigue damage has been identified as one of the primary factors limiting the durability of such medical devices and an in-depth understanding of the fatigue behaviors of biological tissues

Head-to-head comparisons are made between calculations and experimental data on shock-driven pore collapse in the transparent material, poly(methyl methacrylate) (PMMA). Simulations are performed using SCIMITAR3D, an Eulerian sharp-interface multi-material code, while plate impact experiments are visualized using ultra-high speed x-ray imaging. The experiments and simulations are conducted over a wide

Bridging effects in heterogeneous composite materials are traditionally treated as tractions lumped at the crack surface. This conventional equivalence, however, may fail to reveal the fundamental mechanisms of composite toughening. Hereby, a damage-plastic multiphase model is proposed and developed which is capable of capturing the engaging bridging mechanisms of fiber reinforced cementitious composites

Macroscopic wear experiments in mid 1950s suggested an empirical wear relation: wear volume is linearly proportional to load and sliding distance. Recent asperity-level wear experiments and simulations reported a breakdown of this law at the nanoscale, posing the fundamental question: Is the macroscopic wear relation recoverable at the asperity level? Here we show that discrepant observations of wear

At low strain, geometrically necessary dislocations (GND) confined in the close vicinity of grain boundaries can be approximated as a dislocation wall structure called a GND facet. Analytical solutions derived from Field Dislocations Mechanics (FDM) theory allow calculating the stress components associated with the GND facets but are unable to account for the stress field variation induced by finite

Mylar balloons are popular in funfairs or birthday parties. Their conception is very simple: two pieces of flat thin sheets are cut and sealed together along their edges to form a flat envelope. Inflation tends to deform this envelope in order to maximize its inner volume. However, although thin sheets are easy to bend and hardly resist compressive loads, they barely stretch, which imposes non-trivial

This paper proposes an efficient contact model for a viscoelastic layered half-space where coating and substrate have different creep functions (i.e. different viscoelastic behaviours). The problem is formulated in three dimensions for an imposed pressure and shear field. The influence coefficients are calculated with the Papkovich-Neuber potentials and computation performed using Discrete Convolution

This paper investigates the problem of a radial (or a penny-shaped) hydraulic fracture propagating in a permeable reservoir. In particular, we consider the fluid exchange between the crack and ambient porous media as a pressure-dependent process. In most of the existing models, the fluid exchange process is represented as one-dimensional pressure-independent leak-off described by Carter’s law. We modify