Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2014, 30 (2)   Published: 20 March 2014
THEME ARTICLES ON MECHANICAL CHARACTERIZATION OF SOFTMATERIALS
Dynamic tensile characterization of pig skin Hot!
H. Khatam, Q. Liu, K. Ravi-Chandar
Abstract

The strain-rate dependent response of porcine skin oriented in the fiber direction is explored under tensile loading. Quasi-static response was obtained at strain rates in the range of 10-3 s-1 to 25 s-1. Characterization of the response at even greater strain rates is accomplished by measuring the spatio-temporal evolution of the particle velocity and strain in a thin strip subjected to high speed impact loading that generates uniaxial stress conditions. Thes...

FLUID MECHANICS
On the validity of the Boltzmann-BGK model through relaxation evaluation
Quan-Hua Sun, Chun-Pei Cai, Wei Gao
Abstract

The Boltzmann-Bhatnagar-Gross-Krook (BGK) model is investigated for its validity regarding the collision term approximation through relaxation evaluation. The evaluation is based on theoretical analysis and numerical comparison between the BGK and direct simulation Monte Carlo (DSMC) results for three specifically designed relaxation problems. In these problems, one or half component of the velocity distribution is characterized by another Maxwellian distribution with a different temperature....

Three dimensional simulations of penetrative convection in a porous medium with internal heat sources
A.J. Harfash
Abstract

The problem of penetrative convection in a fluid saturated porous medium heated internally is analysed. The linear instability theory and nonlinear energy theory are derived and then tested using three dimensions simulation. Critical Rayleigh numbers are obtained numerically for the case of a uniform heat source in a layer with two fixed surfaces. The validity of both the linear instability and global nonlinear energy stability thresholds are tested using a three dimensional simulation. Our r...

SOLID MECHANICS
Effect of electric boundary conditions on crack propagation in ferroelectric ceramics
F.-X. Li, Y. Sun, R.K.N.D. Rajapakse
Abstract

In this paper, the effect of electric boundary conditions on Mode I crack propagation in ferroelectric ceramics is studied by using both linear and nonlinear piezoelectric fracture mechanics. In linear analysis, impermeable cracks under open circuit and short circuit are analyzed using the Stroh formalism and a rescaling method. It is shown that the energy release rate in short circuit is larger than that in open circuit. In nonlinear analysis, permeable crack conditions are used and the nonl...

Interval finite difference method for steady-state temperature field prediction with interval parameters
Chong Wang, Zhi-Ping Qiu
Abstract

A new numerical technique named interval finite difference method is proposed for the steady-state temperature field prediction with uncertainties in both physical parameters and boundary conditions. Interval variables are used to quantitatively describe the uncertain parameters with limited information. Based on different Taylor and Neumann series, two kinds of parameter perturbation methods are presented to approximately yield the ranges of the uncertain temperature field. By comparing the ...

Quantitative assessment of the surface crack density in thermal barrier coatings
Li Yang, Zhi-Chun Zhong, Yi-Chun Zhou, Chun-Sheng Lu
Abstract

In this paper, a modified shear-lag model is developed to calculate the surface crack density in thermal barrier coatings (TBCs). The mechanical properties of TBCs are also measured to quantitatively assess their surface crack density. Acoustic emission (AE) and digital image correlation methods are applied to monitor the surface cracking in TBCs under tensile loading. The results show that the calculated surface crack density from the modified model is in agreement with that obtained from ex...

On the homogenization of metal matrix composites using strain gradient plasticity
Reza Azizi, Christian F. Niordson, Brian Nyvang Legarth
Abstract

The homogenized response of metal matrix composites (MMC) is studied using strain gradient plasticity. The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in additi...

Size effect of lattice material and minimum weight design
Jun Yan, Wen-Bo Hu, Zhen-Hua Wang, Zun-Yi Duan
Abstract

The size effects of microstructure of lattice materials on structural analysis and minimum weight design are studied with extented multiscale finite element method (EMsFEM) in the paper. With the same volume of base material and configuration, the structural displacement and maximum axial stress of micro-rod of lattice structures with different sizes of microstructure are analyzed and compared. It is pointed out that different from the traditional mathematical homogenization method, EMsFEM is...

Exact mesh shape design of large cable-network antenna reflectors with flexible ring truss supports
Wang Liu, Dong-Xu Li, Xin-Zhan Yu, Jian-Ping Jiang
Abstract

An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the generation of exact spatial parabolic mesh configurations of such reflector was proposed. By incorporating the traditional force density method with the standard finite element method, this proposed approach had taken the deformation effects of flexible ring truss supports into consid...

Frequency domain fundamental solutions for a poroelastic half-space
Pei Zheng, Bo-Yang Ding, She-Xu Zhao
Abstract

In frequency domain, the fundamental solutions for a poroelastic half-space are re-derived in the context of Biot's theory. Based on Biot's theory, the governing field equations for the dynamic poroelasicity are established in terms of solid displacement and pore pressure. A method of potentials in cylindrical coordinate system is proposed to decouple the homogeneous Biot's wave equations into four scalar Helmholtz equations, and the general solutions to these scalar wave equations are obtain...

DYNAMICS, VIBRATION AND CONTROL
Stability analysis of a thin-walled cylinder in turning operation using the semi-discretization method
Arnab Chanda, Achim Fischer, Peter Eberhard, Santosha Kumar Dwivedy
Abstract

In this work, the stability of a flexible thin cylindrical workpiece in turning is analyzed. A process model is derived based on a finite element representation of the workpiece flexibility and a nonlinear cutting force law. Repeated cutting of the same surface due to overlapping cuts is modeled with the help of a time delay. The stability of the so obtained system of periodic delay differential equations is then determined using an approximation as a time-discrete system and Floquet theory. ...

Shear deformable finite beam elements for composite box beams
Nam-Il Kim, Dong-Ho Choi
Abstract

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-...

BIO-MECHANICS
Influence of screw length and diameter on tibial strain energy density distribution after anterior cruciate ligament reconstruction
Jie Yao, Guan-Ming Kuang, Duo Wai-Chi Wong, Wen-Xin Niu, Ming Zhang, Yu-Bo Fan
Abstract

Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament (ACL) reconstruction. Interference screw, as a surgical implant in ACL reconstruction, may influence natural loading transmission and contribute to tunnel enlargement. The aims of this study are (1) to quantify the alteration of strain energy density (SED) distribution after the anatomic single-bundle ACL reconstruction; and (2) to characterize the influence of screw length and diameter on the degre...

Numerical analysis for the efficacy of nasal surgery in obstructive sleep apnea hypopnea syndrome
Shen Yu, Ying-Xi Liu, Xiu-Zhen Sun, Ying-Feng Su, Ying Wang, Yin-Zhe Gai
Abstract

In the present study, we reconstructed upper airway and soft palate models of 3 obstructive sleep apnea- hypopnea syndrome (OSAHS) patients with nasal obstruction. The airflow distribution and movement of the soft palate before and after surgery were described by a numerical simulation method. The curative effect of nasal surgery was evaluated for the three patients with OSAHS. The degree of nasal obstruction in the 3 patients was improved after surgery. For 2 patients with mild OSAHS, the up...

Multidimensional modeling of the stenosed carotid artery: A novel CAD approach accompanied by an extensive lumped model
A. Kashefi, M. Mahdinia, B. Firoozabadi, M. Amirkhosravi, G. Ahmadi, M. S. Saidi
Abstract

This study describes a multidimensional 3D/ lumped parameter (LP) model which contains appropriate inflow/outflow boundary conditions in order to model the entire human arterial trees. A new extensive LP model of the entire arterial network (48 arteries) was developed including the effect of vessel diameter tapering and the parameterization of resistance, conductor and inductor variables. A computer aided-design (CAD) algorithm was proposed to efficiently handle the coupling of two or more 3D...

A cellular scale numerical study of the effect of mechanical properties of erythrocytes on the near-wall motion of platelets
Jing Xu, Xiao-Long Wang, Yun-Qiao Liu, Xiao-Bo Gong
Abstract

The effect of mechanical properties of erythrocytes on the near-wall motion of platelets was numerically studied with the immersed boundary method. Cells were modeled as viscous-fluid-filled capsules surrounded by hyper-elastic membranes with negligible thickness. The numerical results show that with the increase of hematocrit, the near-wall approaching of platelets is enhanced, with which platelets exhibit larger deformation and orientation angle of its near-wall tank-treading motion, and th...

 
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