Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2015, 31 (4)   Published: 20 September 2015
Molecular tagging techniques and their applications to the study of complex thermal flow phenomena Hot!
Fang Chen, Haixing Li, Hui Hu

This review article reports the recent progress in the development of a new group of molecule-based flow diagnostic techniques, which include molecular tagging velocimetry (MTV)and molecular tagging thermometry (MTT), for both qualitative flow visualization of thermally induced flow structures and quantitative whole-field measurements of flowvelocity and temperature distributions.The MTV and MTT techniques can also be easily combined to result in a so-called molecular tagging velocim...

Multi-scale modeling of hemodynamics in the cardiovascular system Hot!
Hao Liu, Fuyou Liang, Jasmin Wong, Takashi Fujiwara, Wenjing Ye, Ken-iti Tsubota, Michiko Sugawara

The human cardiovascular system is a closedloop and complex vascular network with multi-scaled heterogeneous hemodynamic phenomena. Here, we give a selective review of recent progress in macro-hemodynamic modeling, with a focus on geometrical multi-scale modeling of the vascular network, micro-hemodynamic modeling of microcirculation, as well as blood cellular, subcellular, endothelial biomechanics, and their interaction with arterial vessel mechanics.We describe in detail the methodology of ...

Strain gradient plasticity: energetic or dissipative? Hot!
N. A. Fleck, J. R. Willis

For an infinite slab of strain gradient sensitive material subjected to plane-strain tensile loading, computation established and analysis confirmed that passivation of the lateral boundaries at some stage of loading inhibits plastic deformation upon further loading. This result is not surprising in itself except that, remarkably, if the gradient terms contribute to the dissipation, the plastic deformation is switched off completely and only resumes at a clearly defined higher load, correspon...

Indentation of elastically soft and plastically compressible solids Hot!
A. Needleman, V. Tvergaard, E. Van der Giessen

The effect of soft elasticity, i.e., a relatively small value of the ratio of Young's modulus to yield strength and plastic compressibility on the indentation of isotropically hardening elastic-viscoplastic solids is investigated. Calculations are carried out for indentation of a perfectly sticking rigid sharp indenter into a cylinder modeling indentation of a half space. The material is characterized by a finite strain elastic-viscoplastic constitutive relation that allows for plastic as wel...

Refraction characteristics of phononic crystals Hot!
Sia Nemat-Nasser

Some of the most interesting refraction properties of phononic crystals are revealed by examining the anti-plane shear waves in doubly periodic elastic composites with unit cells containing rectangular and/or elliptical multiinclusions. The corresponding band structure, group velocity, and energy-flux vector are calculated using a powerful mixed variational method that accurately and efficiently yields all the field quantities over multiple frequency pass-bands. The background matrix and the ...

Mechanical buckling induced periodic kinking/stripe microstructures in mechanically peeled graphite flakes from HOPG Hot!
Manrui Ren, Ze Liu, Quan-shui Zheng, Jefferson Zhe Liu

Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. In this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfol...

Mechanisms for non-ideal flow in low-power arc-heated supersonic nozzles
Cheng-Kang Wu, Wen-Xia Pan, Xian Meng, Hai-XingWang

The flow in a low-powered arc gas heater combined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quantitative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flowcharacteristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference betwe...

Active control of turbulence for drag reduction based on the detection of near-wall streamwise vortices by wall information
Mingwei Ge, Chunxiao Xu, Gui-Xiang Cui

The spatial relations between the measurable wall quantities (streamwise shear stress τwx, spanwise shear stress τwz, and pressure fluctuations p'w) and the near-wall streamwise vortices (NWSV) are investigated via direct numerical simulation (DNS) databases of fully developed turbulent channel flow at a lowReynolds number. In the standard turbulent channel flow, the results show that all the wall measurable...

Analytical and numerical studies on a single-droplet evaporation and combustion under forced convection
L. X. Zhou, K. Li

Existing droplet evaporation/combustion models in computational fluid dynamics (CFD) simulation of spray combustion are based on simplified 1-D models. Both these models and recently developed 3-D models of singledroplet combustion do not give the conditions for the different existing droplet combustion modes. In this paper, droplet evaporation and combustion are studied both analytically and numerically. In the analytical solution, a 2-D axisymmetric flowsurrounding an evaporating and combus...

Nanoindentation of soft solids by a flat punch
G. F. Wang, X. R. Niu

Measuring the surface tension and elastic modulus of soft materials and biological tissues under different physiological and pathological conditions is of significance for understanding various phenomena associated with deformation. In this paper, the nanoindentation of a circular flat punch on a soft solid is analyzed with the influence of surface tension. By solving the corresponding singular integral equation, the relation between load and indent depth is obtained. When the radius of the f...

Topology optimization design of micro-mass sensors for maximizing detection sensitivity
Zheqi Lin, Xuansheng Wang, Yiru Ren

Micro-mass sensors have attracted increasing attention in the field of biomolecular and chemical detection. It has been found that the size, shape, and geometry of the structure may affect the performance of the sensor. As a result, a topology optimization methodology is proposed in this paper for the design of micro-mass sensors. A phasefield function controlled by nodal variables and finite element shape functions is used to describe the configuration of a sensor in the constructed optimiza...

Uncertain eigenvalue analysis by the sparse grid stochastic collocation method
J. C. Lan, X. J. Dong, Z. K. Peng, W. M. Zhang, G. Meng

In this paper, the eigenvalue problem with multiple uncertain parameters is analyzed by the sparse grid stochastic collocation method. This method provides an interpolation approach to approximate eigenvalues and eigenvectors' functional dependencies on uncertain parameters. This method repetitively evaluates the deterministic solutions at the pre-selected nodal set to construct a highdimensional interpolation formula of the result. Taking advantage of the smoothness of the solution in the un...

Stability analyses of the mass abrasive projectile high-speed penetrating into a concrete target Part Ⅲ: Terminal ballistic trajectory analyses
H. Wu, X.W. Chen, Q. Fang, X. Z. Kong, L. L. He

During the high-speed penetration of projectiles into concrete targets (the impact velocity ranges from 1.0 to 1.5 km/s), important factors such as the incident oblique and attacking angles, as well as the asymmetric abrasions of the projectile nose induced by the target-projectile interactions, may lead to obvious deviation of the terminal ballistic trajectory and reduction of the penetration efficiency. Based on the engineering model for the mass loss and nose-blunting of ogive-nosed projec...

Transfer matrix method for determination of the natural vibration characteristics of elastically coupled launch vehicle boosters
Laith K. Abbas, Qinbo Zhou, Hossam Hendy, Xiaoting Rui

The analysis of natural vibration characteristics has become one of important steps of the manufacture and dynamic design in the aerospace industry. This paper presents a new scenario called virtual cutting in the context of the transfer matrix method of linear multibody systems closedloop topology for computing the free vibration characteristics of elastically coupled flexible launch vehicle boosters. In this approach, the coupled system is idealized as a triple-beam system-like structure co...

Investigation on attitude disturbance control and vibration suppression for fuel-filled flexible spacecraft
Xiao-Juan Song, Bao-Zeng Yue, Wen-Jun Wu

This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft subjected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton's principle. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacemen...

Biomechanical modeling for the response of human thorax to blast waves
Jie Zhou, Gang Tao

A simplified finite element model of a human thorax had been developed for probing into the mechanical response in simple and complex blast environments. The human thorax model was first created by CT images with blast loading applied via a coupled arbitrary Lagrangian-Eulerian method, allowing for a variety of loads to be considered. The goal is to analyze themaximum stress distributions of lung tissue and peak inward thorax wall velocity and to know the possible regions and levels of lung i...

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