International Journal of Applied Mechanics

This work examines the dynamics of nonlinear large deformation of polymeric gels, and the kinetics of gel deformation is carried out through the coupling of existing hyperelastic theory for gels with kinetic laws for diffusion of small molecules. As finite element (FE) models for the transient swelling process is not available in commercial FE software, we develop a customized FE model/methodology which can be used to simulate the transient swelling process of hydrogels. The method is based on the similarity between diffusion and heat transfer laws by determining the equivalent thermal properties for gel kinetics. Several numerical examples are investigated to explore the capabilities of the present FE model, namely: a cube to study free swelling; one-dimensional constrained swelling; a rectangular block fixed to a rigid substrate to study swelling under external constraints; and a thin annulus fixed at the inner core to study buckling phenomena. The simulation results for the constrained block and one-dimensional constrained swelling are compared with available experimental data, and these comparisons show a good degree of similarity. In addition to this work providing a valuable tool to researchers for the study of gel kinetic deformation in the various applications of soft matter, we also hope to inspire works to adopt this simplified approach, in particular to kinetic studies of diffusion-driven mechanisms.

The influence of the cross-section shape on pressure driven viscous flow through a uniform channel is assessed by presenting analytical flow solutions of velocity distribution, volume flow rate and shear stress for different cross-section shapes. Next, a simplified flow model through a non-uniform constricted channel is formulated which accounts for flow inertia, viscosity and cross-section shape. The model outcome is quantified for different fluids, flows and geometrical properties relevant to physiological flows. It is seen that a commonly applied quasi-one-dimensional (1D) model is not accurate indicating the need to account for the cross-section shape.

A trigonometric shear deformation theory (TSDT) taking into account transverse shear deformation effect as well as transverse normal strain effect is presented. The inplane displacement field uses sinusoidal function in terms of thickness coordinate to include the shear deformation effect. The cosine function in thickness coordinates is used in transverse displacement to include the effect of transverse normal strain. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The results of displacements and stresses for static flexure of simply supported symmetric and anti-symmetric cross-ply laminated square plates subjected to parabolic load and line load are obtained. The results obtained by present theory are compared with those of classical, first-order and higher-order plate theories.

A systematical study of size effects and mechanical behaviors for the nanocrystalline (nc) metals is performed. The grain boundary fracture process is considered and described by the mixed-mode interface cohesive model. The grain material is characterized by the conventional theory of strain gradient plasticity. In the present investigation, the effects of five important parameters on the overall mechanical behavior are studied systematically, which include the grain size, critical separation strength, energy release rate of interface separation, mixity of separation strength, as well as the mixity of separation energy release rate. A finite element method (FEM) covering the above characteristics within the grain and on the grain boundary is developed. The present results show that the overall strength and ductility of the nc metals strongly depend on the grain boundary features described by the mixed-mode cohesive interface model, and there is a competition of deformation of grain boundary with that of grain interior.

It is well known that the friction between interfaces at bolted joints plays a major role in the damping of assembly structures. Friction can be either induced by macro-slipping or micro-slipping. The aim of this paper is to model and quantify the dissipated energy by micro-sliding down to the scale of roughness between two flat surfaces in order to compute the damping ratio. It was assumed that the coefficient of friction between two materials is constant and that friction is the only source of energy dissipation. An experimental study was conducted to measure static normal load and dynamic tangential load without any coupling between these two main directions. A rheological contact model based on the Extended Greenwood Model with micro-contacts and statistical distributions was developed and studied. Experimental results and simulations are compared in order to assess and discuss the model.

The stochastic response of base-isolated building considering the uncertainty in the characteristics of the earthquakes is investigated. For this purpose, a probabilistic ground motion model, for generating artificial earthquakes is developed. The model is based upon a stochastic ground motion model which has separable amplitude and spectral non-stationarities. An extensive database of recorded earthquake ground motions is created. The set of parameters required by the stochastic ground motion model to depict a particular ground motion is evaluated for all the ground motions in the database. Probability distributions are created for all the parameters. Using Monte Carlo (MC) simulations, the set of parameters required by the stochastic ground motion model to simulate ground motions is obtained from the distributions and ground motions. Further, the bilinear model of the isolator described by its characteristic strength, post-yield stiffness and yield displacement is used, and the stochastic response is determined by using an ensemble of generated earthquakes. A parametric study is conducted for the various characteristics of the isolator. This study presents an approach for stochastic seismic response analysis of base-isolated building considering the uncertainty involved in the earthquake ground motion.

Graphene has potential applications in a variety of fields including electronics, photonics and chemical-biosensing. In this study, we perform molecular dynamics (MD) simulations to study the interactions between graphene sheets and biomolecules. The bending behavior of graphene induced by adsorption of peptides is investigated. The influence of peptide size, number, and alignment on the deflection of graphene sheets is studied in detail. The van der Waals (VDW) interaction plays a dominant role in the interaction between peptides and graphene. Our study provides valuable information for the experimental design of nanodevices incorporating graphene with biomolecules.

In the present paper, the mechanical behavior of large deformation of a regular equilateral triangular tube under quasi-static axial crushing is reported, which is a polygon with an acute angle and odd number of sides. Based on the results from nonlinear finite element analysis (FEA), a new type of inextensional basic plastic collapse folding element is proposed to describe the plastic progressive collapse. The progressive folding around the stationary horizontal hinges and inclined traveling hinges are involved to develop the new basic folding element. Two types of inextensible deformation modes are discovered, i.e., diamond mode and rotational symmetrical mode. The average crushing load for each mode is predicted from the super-folding element theory, which was proposed from the previous investigation on the axial crushing of square columns. A rigid-plastic material model and a kinematically admissible model are involved in this theory. The results are further validated against experiments. The approximate quasi-static theoretical predictions for the mean crushing loads of triangular tubes provide reasonable agreement with the corresponding experimental results.

A new type of concrete was developed using liquid rubber (polyurethane) as binder and graded stones as aggregate. The mechanical properties of the prepared liquid rubber-based concrete (LRBC) were systematically investigated through flexural and compressive tests. The dynamic response of LRBC to impact was studied using a spit Hopkinson pressure bar system, which demonstrates a non-monotonic strain rate sensitivity of LRBC. Furthermore, three typical pavement performance tests, i.e., rutting, seepage and sanding tests, were carried out to evaluate the potential of LRBC for the applications in pavement systems. According to the experimental study, the optimum rubber-aggregate ratio was found to be 17% (weight of binder by that of aggregate). The LRBC prepared with this recipe showed the superiority in most pavement performance indicators to other three types of conventional asphalt concrete.

Some Couette flows of a Maxwell fluid caused by the bottom plate applying shear rate on the fluid, are studied. Exact expressions for velocity and shear stress corresponding to the fluid motion are determined using Laplace transform. Two particular cases of constant shear rate on the bottom plate and sinusoidal oscillations of the wall shear rate are discussed. Some important characteristics of fluid motion are highlighted through graphs.

A meshless local Petrov–Galerkin method (MLPG) based on the moving Kriging interpolation for elastodynamic analysis is presented in this paper. The present method is developed based on the moving Kriging interpolation for constructing shape functions at scattered points, and the Heaviside step function is used as a test function in each subdomain to avoid the need for domain integral in symmetric weak form. Since the shape functions constructed by this moving Kriging interpolation have the delta function property, the essential boundary conditions can be implemented easily, and no special treatment techniques are required. The discrete equations of the governing elastodynamic equations for two-dimensional solids are obtained using the local weak-forms. The Newmark method is adopted for the time integration scheme. Some numerical results are compared to that obtained from the exact solutions of the problem and other (meshless) methods. This comparison illustrates the efficiency and accuracy of the present method for solving the static and dynamic problems.