Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2015, 31 (5)   Published: 20 November 2015
Preface: Frontiers and current applications in elasticity
Heng Xiao

The elasticity, viz., the deformation recoverability without energy dissipation, is known as a basic aspect in various deformation behaviors of solid materials. Typical examples are small and large elastic deformations characteristic of hard solids (e.g., metals) and soft solids (e.g., elastomers), respectively. The theory of elasticity for both small and finite deformation cases plays basic roles not only in the study of elastic behavior in its own right but also in modeling various inelasti...

Some recent advances in 3D crack and contact analysis of elastic solids with transverse isotropy and multifield coupling Hot!
Wei-Qiu Chen

Significant progress has been made in mixed boundary-value problems associated with three-dimensional (3D) crack and contact analyses of advanced materials featuring more complexities compared to the conventional isotropic elastic materials. These include material anisotropy and multifield coupling, two typical characteristics of most current multifunctional materials. In this paper we try to present a state-of-the-art description of 3D exact/analytical solutions derived for crack and contact...

Swelling and instability of a gel annulus Hot!
Xiaoyi Chen, Hui-Hui Dai

We study the swelling of a gel annulus attached to a rigid core when it is immersed in a solvent. For equilibrium states, the free-energy function of the gel can be converted into a strain energy function, and as a result the gel can be treated as a compressible hyperelastic material. Asymptotic methods are used to study the inhomogeneous swelling in order to obtain the leading-order solution. Some analytical insights are then deduced. Because of the compressive hoop stress in this state, at ...

A multiaxial elastic potential with error-minimizing approximation to rubberlike elasticity Hot!
Zhi-Xiang Gu, Lu Yuan, Zheng-Nan Yin, Heng Xiao

This study is concerned with a new, explicit approach by means of which forms of the large strain elastic potential for multiaxial rubberlike elasticity may be obtained based on data for a single deformation mode. As a departure from usual studies, here for the first time errors may be estimated and rendered minimal for all possible deformation modes and, furthermore, failure behavior may be incorporated. Numerical examples presented are in accurate agreement with Treloar's well-known data....

Effect of strain-gradients of surface micro-beams on frequency-shift of a quartz crystal resonator under thickness-shear vibrations Hot!
Ling-Cheng Kong, Yuan-Tai Hu

With introduction of the first-order strain-gradient of surface micro-beams into the energy density function, we developed a two-dimensional dynamic model for a compound quartz crystal resonator (QCR) system, consisting of a QCR and surface micro-beam arrays. The frequency shift that was induced by micro-beams with consideration of strain-gradients is discussed in detail and some useful results are obtained, which have important significance in resonator design and applications.

Bi-stable states of initially stressed elastic cylindrical shell structures with two piezoelectric surface layers Hot!
Bin Wang, Guo-Hua Nie

A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric layers. The condition for existence of bi-stability of the shell structural system is presented and analytical expressions for corresponding rolled-up radii of the stable shell are given based on the principle of minimum strain energy. The resulting solution indicates that the shell system may have two stable configurati...

Multiple bifurcations and local energy minimizers in thermoelastic martensitic transformations Hot!
Chen Xuan, Shurong Ding, Yongzhong Huo

Thermoelastic martensitic transformations in shape memory alloys can be modeled on the basis of nonlinear elastic theory. Microstructures of fine phase mixtures are local energy minimizers of the total energy. Using a one-dimensional effective model, we have shown that such microstructures are inhomogeneous solutions of the nonlinear Euler-Lagrange equation and can appear upon loading or unloading to certain critical conditions, the bifurcation conditions. Ahybrid numerical method is utilized...

Nonlinear analysis of photo-induced wrinkling of glassy twist nematic films on compliant substrates Hot!
Dong Yang, Ling-Hui He

A kinetics approach is developed for the geometrically nonlinear analysis of photo-induced wrinkling of glassy twist nematic films on soft elastic substrates. In this way, the problem is reduced to finding the steady state of an overdamped evolution system according to a kinetic law, rather than directly solving the coupled nonlinear equations. This enables one to account for the complicated director distribution and obtain the precise wrinkling morphology of the film. Though the approach pro...

Recasting theory of elasticity with micro-finite elements Hot!
Wennan Zou

In the classical theory of elasticity, a body is initially modeled as a homogeneous and dense assemblage of constituent "material particles". The kernel concept of elastic deformation is the displacement of the particle that associates the current configuration with the reference one. In this paper, we exploit an alternative constituent "micro-finite element", and use the stretch of the element as the essential quality to recast the theory of elasticity. It should be reali...

On the degradation of granular materials due to internal erosion
Xiaoliang Wang, Jiachun Li

A new state-based elasto-plastic constitutive relationship along with the discrete element model is established to estimate the degradation of granular materials due to internal erosion. Four essential effects of internal erosion such as the force network damage and relaxation are proposed and then incorporated into the constitutive relationship to formulate internal erosion impacts on the mechanical behavior of granular materials. Most manifestations in the degradation of granular materials,...

Uncertainty analysis of flow rate measurement for multiphase flow using CFD
Joon-Hyung Kim, Uk-Hee Jung, Sung Kim, Joon-Yong Yoon, Young-Seok Choi

The venturi meter has an advantage in its use, because it can measure flow without being much affected by the type of the measured fluid or flow conditions. Hence, it has excellent versatility and is being widely applied in many industries. The flow of a liquid containing air is a representative example of a multiphase flow and exhibits complex flow characteristics. In particular, the greater the gas volume fraction (GVF), the more inhomogeneous the flow becomes. As a result, using a venturi ...

Surface stress effect on the vibration and instability of nanoscale pipes conveying fluid based on a size-dependent Timoshenko beam model
R. Ansari, R. Gholami, A. Norouzzadeh, M. A. Darabi

Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale pipes. To this end, the nanoscale pipe is modeled as a Timoshenko nanobeam. The equations of motion of the nanoscale pipe are obtained based on Hamilton's principle and the Gurtin-Murdoch continuum elasticity incorporating the surface stress effect. Afterwards, the generalized differential quadrature method is employed to discretize t...

Study on the influences of interaction behaviors between multiple combustion-gas jets on expansion characteristics of Taylor cavities
Xiaochun Xue, Yonggang Yu, Qi Zhang

The purpose of this study is to investigate means of controlling the interior ballistic stability of a bulk-loaded propellant gun (BLPG). Experiments on the interaction of twin combustion gas jets and liquid medium in a cylindrical stepped-wall combustion chamber are conducted in detail to obtain time series processes of jet expansion, and a numerical simulation under the same working conditions is also conducted to verify the reliability of the numerical method by comparing numerical results...

Development of efficient and accurate skeletal mechanisms for hydrocarbon fuels and kerosene surrogate
Fengquan Zhong, Sugang Ma, Xinyu Zhang, Chih-Jen Sung, Kyle E. Niemeyer

In this paper, the methodology of the directed relation graph with error propagation and sensitivity analysis (DRGEPSA), proposed by Niemeyer et al. (Combust Flame 157:1760-1770, 2010), and its differences to the original directed relation graph method are described. Using DRGEPSA, the detailed mechanism of ethylene containing 71 species and 395 reaction steps is reduced to several skeletal mechanisms with different error thresholds. The 25-species and 131-step mechanism and the 24-species an...

Effects of geometric configuration on droplet generation in Y-junctions and anti-Y-junctions microchannels
Zhao-Miao Liu, Li-Kun Liu, Feng Shen

Droplets generation in Y-junctions and anti-Yjunctions microchannels are experimentally studied using a high speed digital microscopic system and numerical simulation. Geometric configuration of a microchannel, such as Y-angle (90°, 135°,-90° and -135°), channel depth and other factors have been taken into consideration. It is found that droplets generated in anti-Y-junctions have a smaller size and a shorter generation cycle compared with those in Yjunctions under the same ex...

Feasibility study on buoyancy-weight ratios of a submerged floating tunnel prototype subjected to hydrodynamic loads
Xu Long, Fei Ge, Youshi Hong

The research progress of a novel traffic solution, a submerged floating tunnel (SFT), is reviewed in terms of a study approach and loading scenario. Among existing publications, the buoyancy-weight ratio (BWR) is usually predefined. However, BWR is a critical structural parameter that tremendously affects the dynamic behaviour of not only the tunnel tube itself but also the cable system. In the context of a SFT prototype (SFTP) project in Qiandao Lake (Zhejiang Province, China), the importanc...

Dynamic thermo-mechanical coupled simulation of statistically inhomogeneous materials by statistical second-order two-scale method
Zihao Yang, Junzhi Cui, Yufeng Nie, Zhiqiang Huang, Meizhen Xiang

In this paper, a statistical second-order twoscale (SSOTS) method is developed to simulate the dynamic thermo-mechanical performances of the statistically inhomogeneous materials. For this kind of composite material, the random distribution characteristics of particles, including the shape, size, orientation, spatial location, and volume fractions, are all considered. Firstly, the representation for the microscopic configuration of the statistically inhomogeneous materials is described. Secon...

Different effects of economic and structural performance indexes on model construction of structural topology optimization
G. L. Yi, Y. K. Sui

The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper. The influences of their different roles in model construction of structural topology optimization are also discussed. Furthermore, two structural topology optimization models, optimizing a performance index under the limitation of an economic index, represented by the minimum compliance with a volume constraint (MCVC) model, and optimizing an ec...

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