Acta Mechanica Sinica
The Journal covers all disciplines in the field of theoretical and applied mechanics, including solid mechanics, fluid mechanics, dynamics and control, and biomechanics. It explores analytical, computational and experimental progresses in all areas of mechanics. The Journal also encourages research in interdisciplinary subjects, and servess...
CN 11-2063/O3
ISSN 0567-7718(Print)
ISSN 1614-3116(Online)
Editors-in-Chief:
Professor Tianjian Lu
Professor Wei Shyy
Professor Zhigang Suo
Impact Factor: 0.832
Citation: Acta Mech. Sin.
Frequency: Bimonthly
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Acta Mechanica Sinica--2016, 32 (3)   Published: 20 May 2016
FLUID MECHANICS
Identification, characterization and evolution of non-local quasi-Lagrangian structures in turbulence
Yue Yang
Abstract

The recent progress on non-local Lagrangian and quasi-Lagrangian structures in turbulence is reviewed. The quasi-Lagrangian structures, e.g., vortex surfaces in viscous flow, gas-liquid interfaces in multi-phase flow, and flame fronts in premixed combustion, can show essential Lagrangian following properties, but they are able to have topological changes in the temporal evolution. In addition, they can represent or influence the turbulent flow field. The challenges for the investigation of th...

Study on Mach stems induced by interaction of planar shock waves on two intersecting wedges
Gaoxiang Xiang, Chun Wang, Honghui Teng, Yang Yang, Zonglin Jiang
Abstract

The properties of Mach stems in hypersonic corner flow induced by Mach interaction over 3D intersecting wedges were studied theoretically and numerically. A new method called "spatial dimension reduction" was used to analyze theoretically the location and Mach number behind Mach stems. By using this approach, the problem of 3D steady shock/shock interaction over 3D intersecting wedges was transformed into a 2D moving one on cross sections, which can be solved by shock-polar theory a...

Studying thin film damping in a micro-beam resonator based on non-classical theories
Mina Ghanbari, Siamak Hossainpour, Ghader Rezazadeh
Abstract

In this paper, a mathematical model is presented for studying thin film damping of the surrounding fluid in an in-plane oscillating micro-beam resonator. The proposed model for this study is made up of a clamped-clamped micro-beam bound between two fixed layers. The microgap between the micro-beam and fixed layers is filled with air. As classical theories are not properly capable of predicting the size dependence behaviors of the micro-beam, and also behavior of micro-scale fluid media, hence...

Fourier time spectral method for subsonic and transonic flows
Lei Zhan, Feng Liu, Dimitri Papamoschou
Abstract

The time accuracy of the exponentially accurate Fourier time spectral method (TSM) is examined and compared with a conventional 2nd-order backward difference formula (BDF) method for periodic unsteady flows. In particular, detailed error analysis based on numerical computations is performed on the accuracy of resolving the local pressure coefficient and global integrated force coefficients for smooth subsonic and non-smooth transonic flows with moving shock waves on a pitching airfoil. For sm...

Viscous fluid damping in a laterally oscillating finger of a comb-drive micro-resonator based on micro-polar fluid theory
Sahra Azma, Ghader Rezazadeh, Rasoul Shabani, Elnaz Alizadeh-Haghighi
Abstract

Viscous damping is a dominant source of energy dissipation in laterally oscillatingmicro-structures. Inmicroresonators inwhich the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator conside...

Process, mechanism and impacts of scale formation in alkaline flooding by a variable porosity and permeability model
Zhen Zhang, Jiachun Li
Abstract

In spite of the role of alkali in enhancing oil recovery (EOR), the formation of precipitation during alkaline-surfactant-polymer (ASP) flooding can severely do harm to the stratum of oil reservoirs, which has been observed in situ tests of oil fields such as scale deposits found in oil stratum and at the bottom of oil wells. On the other hand, remarkable variation of stratum parameters, e.g., pore radius, porosity, and permeability due to scale formation considerably affects seepage flow and...

Microfluidic-based single cell trapping using a combination of stagnation point flow and physical barrier
Miao Yu, Zongzheng Chen, Cheng Xiang, Bo Liu, Handi Xie, Kairong Qin
Abstract

Single cell trapping in vitro by microfluidic device is an emerging approach for the study of the relationship between single cells and their dynamic biochemical microenvironments. In this paper, a hydrodynamic-based microfluidic device for single cell trapping is designed using a combination of stagnation point flow and physical barrier. The microfluidic device overcomes the weakness of the traditional ones, which have been only based upon either stagnation point flows or physical barriers, ...

SOLID MECHANICS
Concurrent multi-scale design optimization of composite frame structures using the Heaviside penalization of discrete material model
Jun Yan, Zunyi Duan, Erik Lund, Guozhong Zhao
Abstract

This paper deals with the concurrent multi-scale optimization design of frame structure composed of glass or carbon fiber reinforced polymer laminates. In the composite frame structure, the fiber winding angle at the micro-material scale and the geometrical parameter of components of the frame in the macro-structural scale are introduced as the independent variables on the two geometrical scales. Considering manufacturing requirements, discrete fiber winding angles are specified for the micro...

An experimental study on fracture mechanical behavior of rock-like materials containing two unparallel fissures under uniaxial compression
Yan-Hua Huang, Sheng-Qi Yang, Wen-Ling Tian, Wei Zeng, Li-Yuan Yu
Abstract

Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel fissures. In the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical pr...

A new micromechanical approach of micropolar continuum modeling for 2-D periodic cellular material
Bin Niu, Jun Yan
Abstract

In this paper, we present a newunited approach to formulate the equivalent micropolar constitutive relation of two-dimensional (2-D) periodic cellular material to capture its non-local properties and to explain the size effects in its structural analysis. The new united approach takes both the displacement compatibility and the equilibrium of forces and moments into consideration, where Taylor series expansion of the displacement and rotation fields and the extended averaging procedure with a...

Modal interactions in primary and subharmonic resonant dynamics of imperfect microplates with geometric nonlinearities
Hamed Farokhi, Mergen H. Ghayesh
Abstract

This paper analyses the modal interactions in the nonlinear, size-dependent dynamics of geometrically imperfect microplates. Based on the modified couple stress theory, the equations of motion for the in-plane and out-of-plane motions are obtained employing the von Kármán plate theory as well as Kirchhoff's hypotheses by means of the Lagrange equations. The equations of motions are solved using the pseudo-arclength continuation technique and direct timeintegration method. The sy...

A stabilized complementarity formulation for nonlinear analysis of 3D bimodular materials
L. Zhang, H. W. Zhang, J. Wu, B. Yan
Abstract

Bi-modulus materials with different mechanical responses in tension and compression are often found in civil, composite, and biological engineering. Numerical analysis of bimodular materials is strongly nonlinear and convergence is usually a problem for traditional iterative schemes. This paper aims to develop a stabilized computational method for nonlinear analysis of 3D bimodular materials. Based on the parametric variational principle, a unified constitutive equation of 3D bimodular materi...

SIF-based fracture criterion for interface cracks
Xing Ji
Abstract

The complex stress intensity factor K governing the stress field of an interface crack tip may be split into two parts, i.e., K and s?iε, so that K = K s?iε, s is a characteristic length and ε is the oscillatory index. K? has the same dimension as the classical stress intensity factor and characterizes the interface crack tip field. That means a criterion for interfac...

Nanoscale strain engineering of graphene and graphene-based devices
N.-C. Yeh, C.-C. Hsu, M. L. Teague, J.-Q.Wang, D. A. Boyd, C.-C. Chen
Abstract

Structural distortions in nano-materials can induce dramatic changes in their electronic properties. This situation is well manifested in graphene, a two-dimensional honeycomb structure of carbon atoms with only one atomic layer thickness. In particular, strained graphene can result in both charging effects and pseudo-magnetic fields, so that controlled strain on a perfect graphene lattice can be tailored to yield desirable electronic properties. Here, we describe the theoretical foundation f...

Shape optimization of axisymmetric solids with the finite cell method using a fixed grid
Liang Meng, Wei-Hong Zhang, Ji-Hong Zhu, Zhao Xu, Shou-Hu Cai
Abstract

In this work, a design procedure extending the B-spline based finite cell method into shape optimization is developed for axisymmetric solids involving the centrifugal force effect.We first replace the traditional conforming mesh in the finite element method with structured cells that are fixed during the whole design process with a view to avoid the sophisticated re-meshing and eventual mesh distortion. Then, B-spline shape functions are further implemented to yield a high-order continuity f...

DYNAMICS, VIBRATION AND CONTROL
Contact dynamics of elasto-plastic thin beams simulated via absolute nodal coordinate formulation
Qing-Tao Wang, Qiang Tian, Hai-Yan Hu
Abstract

Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation (ANCF). The internal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation. A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF f...

Generalized flyby trajectories around elongated minor celestial bodies as a rotating mass dipole
Xiangyuan Zeng, Baodong Fang, Junfeng Li, Yang Yu
Abstract

The aim of this paper is to understand the common characteristics of the generalized flyby trajectory around natural elongated bodies. Such flyby trajectories provide a short-term mechanism to clear away vicinal objects or temporally capture ejecta into circling orbits. The gravitational potential of elongated bodies is described by a unified approximate model, i.e., the rotating mass dipole which is two point masses connected with a constant massless rod. The energy power is used to illustra...

The effect of waist twisting on walking speed of an amphibious salamander like robot
Xin-Yan Yin, Li-Chao Jia, Chen Wang, Guang-Ming Xie
Abstract

Amphibious salamanders often swing theirwaist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion. A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimizati...

BIOMECHANICS
Dynamic model and performance analysis of landing buffer for bionic locust mechanism
Dian-Sheng Chen, Zi-Qiang Zhang, Ke-Wei Chen
Abstract

The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are us...

 
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