Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2014, 30 (1)   Published: 20 January 2014
Preface: Mechanical characterization of soft materials
Yan-Ping Cao, Yang-Tse Cheng

Determining the mechanical properties of soft materials (e.g., biological soft tissues, polymeric gels, and soft elastomers) across multiple length scales represents an activity of increasing importance in understanding the deformation behavior of soft materials under various stimuli. Much effort has been made in the past in this field. This theme issue of the Acta Mechanica Sinica contains a number of innovative papers regarding the mechanical characterization of soft materials from five dif...

Nanoscale viscoelastic properties and adhesion of polydimethylsiloxane for tissue engineering Hot!
J. Chen, K. E. Wright, M. A. Birch

It has shown that altering crosslink density of biopolymers will regulate the morphology of Mesenchymal Stem Cells (MSCs) and the subsequent MSCs differentiation. These observations have been found in a wide range of biopolymers. However, a recent work published in Nature Materials has revealed that MSCs morphology and differentiation was unaffected by crosslink density of polydimethylsiloxane (PDMS), which remains elusive. To understand such unusual behaviour, we use nanoindentation tests an...

Viscoelastic analysis of single-component and composite PEG and alginate hydrogels Hot!
Jenna M. Shapiro, Michelle L. Oyen

Hydrogels, three-dimensional hydrophilic polymer networks, are appealing candidate materials for studying the cellular microenvironment as their substantial water content helps to better mimic soft tissue. However, hydrogels can lack mechanical stiffness, strength, and toughness. Composite hydrogel systems have been shown to improve upon mechanical properties compared to their singlecomponent counterparts. Poly (ethylene glycol) dimethacrylate (PEGDMA) and alginate are polymers that have been...

Mechanical properties of double-stranded DNA biofilm with Gaussian distribution Hot!
Heng-Song Tang, Wei-Lie Meng, Neng-Hui Zhang

In microcantilever-based label-free biodetection technologies, deflection changes induced by adsorptions of double-stranded DNA (dsDNA) molecules on Au-layer surface are greatly affected by the mechanical, thermal and electrical properties of DNA biofilm. In this paper, the elastic properties of dsDNA biofilm are studied. First, the Parsegian's empirical potential based on a mesoscopic liquid crystal theory is employed to describe the interaction energy among coarse-grained DNA cylinders. The...

Separating viscoelasticity and poroelasticity of gels with different length and time scales Hot!
Qi-MingWang, Anirudh C. Mohan, Michelle L. Oyen, Xuan-He Zhao

Viscoelasticity and poroelasticity commonly coexist as time-dependent behaviors in polymer gels. Engineering applications often require knowledge of both behaviors separated; however, few methods exist to decouple viscoelastic and poroelastic properties of gels. We propose a method capable of separating viscoelasticity and poroelasticity of gels in various mechanical tests. The viscoelastic characteristic time and the poroelastic diffusivity of a gel define an intrinsic material length scale ...

Linear stability of a fluid channel with a porous layer in the center
Qi Li, Hai-Yan Lei, Chuan-Shan Dai

We perform a linear stability analysis of a Poiseuille flow in a channel inserted with one porous layer in the centre, and focus mainly on the effect of porous filling ratio. The spectral collocation technique is adopted to solve the coupled linear stability problem. We investigate the effect of permeability, σ, with fixed porous filling ratio ψ=1/3 and then the effect of change in porous filling ratio. As shown in the paper, with increasing σ, almos...

An enhanced treatment of boundary conditions in implicit smoothed particle hydrodynamics
Ya-Wei Han, Hong-Fu Qiang, Hu Liu, Wei-Ran Gao

In this work, an enhanced treatment of the solid boundaries is proposed for smoothed particle hydrodynamics with implicit time integration scheme (Implicit SPH). Three types of virtual particles, i.e., boundary particles, image particles and mirror particles, are used to impose boundary conditions. Boundary particles are fixed on the solid boundary, and each boundary particle is associated with two fixed image particles inside the fluid domain and two fixed mirror particles outside the fluid ...

Analytical solution of a double moving boundary problem for nonlinear flows in one-dimensional semi-infinite long porous media with low permeability
Wen-Chao Liu, Jun Yao, Zhang-Xin Chen

Based on Huang's accurate tri-sectional nonlinear kinematic equation (1997), a dimensionless simplified mathematical model for nonlinear flow in one-dimensional semi-infinite long porous media with low permeability is presented for the case of a constant flow rate on the inner boundary. This model contains double moving boundaries, including an internal moving boundary and an external moving boundary, which are different from the classical Stefan problem in heat conduction: The velocity of th...

The application of three-dimensional hydroelastic analysis of ship structures in Pekeris hydro-acoustic waveguide environment
Ming-Song Zou, You-Sheng Wu, Yan-Min Liu

The hydroelastic analysis and sonoelastic analysis methods are incorporatedwith the Green's function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull (SWATH) ...

Coupled extension and thickness-twist vibrations of lateral field excited AT-cut quartz plates
Ting-Feng Ma, Rong-Xing Wu, Ji Wang, Jian-Ke Du, Li-Li Yuan, Fa-Peng Yu, Chao Xie

In this paper, the coupled extension and thicknesstwist vibrations are studied for AT-cut quartz plates under Lateral Field Excitation (LFE) with variations along the x1- direction. Mindlin's two-dimensional equations are used for anisotropic crystal plates. Both free and electrically forced vibrations are considered. Important vibration characteristics are obtained, including dispersion relations, frequency spectra, and motional capacitances. It is shown that, to avoid th...

A continuous-discontinuous cellular automaton method for cracks growth and coalescence in brittle material
Fei Yan, Xia-Ting Feng, Peng-Zhi Pan, Shao-Jun Li

A method of continuous-discontinuous cellular automaton for modeling the growth and coalescence of multiple cracks in brittle material is presented. The method uses the level set to track arbitrary discontinuities, and calculation grids are independent of the discontinuities and no remeshing are required with the crack growing. Based on Griffith fracture theory and Mohr-Coulumb criterion, a mixed fracture criterion for multiple cracks growth in brittle material is proposed. The method treats ...

Nanoscale mass sensing based on vibration of single-layered graphene sheet in thermal environments
S. Ahmad Fazelzadeh, Esmaeal Ghavanloo

Based on vibration analysis, single-layered graphene sheet (SLGS) with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysupported configuration. Based on the nonlocal plate theory which incorporates size effects into the classical theory, closed-form expressions for the frequencies and relative frequency shifts of SLGS-based mass sensor are derived using the Galerkin method. The suggested model is justif...

A meshfree-based local Galerkin method with condensation of degree of freedom for elastic dynamic analysis
De-An Hu, Yi-Gang Wang, Yang-Yang Li, Xu Han, Yuan-Tong Gu

Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form for elastic dynamic analysis. In the present method, scattered nodes without connectivity are divided into several subsets by cells with arbitrary shape. Local discrete equation is established over each cell by using moving Kriging interpolation, in which the nodes that located in the cell are used for approximation. Then local discrete equations can...

Vibration analysis of axisymmetric functionally graded viscothermoelastic spheres
D. K. Sharma, J. N. Sharma, S. S. Dhaliwal, V. Walia

The present study focuses on the analysis of free vibrations of axisymmetric functionally graded hollow spheres. The material is assumed to be graded in radial direction with a simple power law. Matrix Fröbenious method of extended power series is employed to derive the analytical solutions for displacement, temperature, and stresses. The dispersion relations for the existence of various types of possible modes of vibrations in the considered hollowsphere are derived in a compact form. I...

Dynamics and adaptive control of a dual-arm space robot with closed-loop constraints and uncertain inertial parameters
Ying-Hong Jia, Quan Hu, Shi-Jie Xu

A dynamics-based adaptive control approach is proposed for a planar dual-arm space robot in the presence of closed-loop constraints and uncertain inertial parameters of the payload. The controller is capable of controlling the position and attitude of both the satellite base and the payload grasped by the manipulator end effectors. The equations of motion in reduced-order form for the constrained system are derived by incorporating the constraint equations in terms of accelerations into Kane'...

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