力学进展

Theory of electroelasticity accounting for biasing fields: Retrospect, comparison and perspective

WU Bin, ZHANG Chunli, ZHANG Chuanzeng, CHEN Weiqiu

2016, 46(1) doi: 10.6052/1000-0992-15-020

Abstract(2708)

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Abstract:
The nonlinear continuum theory of solids with electromechanical coupling was first developed in the 1950s, and matured in the 1970s. In the late 1980s and early 1990s, it gained new impetus for further elaboration and drawn wider attention due to the rapid development of intelligent materials and structures. However, research priority was given to linear analysis in applications. Since the early twentieth century, electromechanical soft ma-terials have inspired many research interests because of their potential application prospect. On account of the large deformation that is inevitably involved, the mathematical model-ing of problems and the subsequent quantitative analysis must be carried out within the general framework of nonlinear continuum mechanics. Consequently, the nonlinear theory of solids with electromechanical coupling has received great attention and many new and seemingly different versions of the theory have appeared. Based on the general framework of the nonlinear continuum theory, the aim of this paper is to review in detail the theory of electroelasticity that accounts for biasing fields by adopting both Lagrangian description and the updated Lagrangian description based on three configurations. We attempt to iden-tify the similarities and differences between different versions of the theory in order to clear the confusions in the current literature and provide a theoretical guidance for the related research in the future. The current and future research focus and development trend of the electromechanical biasing field theory in different areas are also brie°y summarized and discussed.

Developments of numerical methods for linear and nonlinear fluid-solid interaction dynamics with applications

Jing Tang XING

2016, 46(1) doi: 10.6052/1000-0992-15-038

Abstract(2454)

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Abstract:
This paper presents a review on some developments of numerical methods for linear and nonlinear fluid-solid interaction (FSI) problems with their applications in engineering. The discussion covers the four types of numerical methods: (1) mixed finite element (FE)-substructure-subdomain model to deal with linear FSI in a finite domain, such as sloshing, acoustic-structure interac-tions, pressure waves in fluids, earthquake responses of chemical vessels, dam-water couplings, etc.; (2) mixed FE-boundary element (BE) model to solve linear FSI with infinite domains, for example, very large floating structure (VLFS) subject to airplane landing impacts, ship dynamic response caused by cannon/missile fire im-pacts, etc.; (3) mixed FE-finite difference (FD)/volume (FV) model for nonlinear FSI problems with no separations between fluids and solids and breaking waves; (4) mixed FE-smooth particle (SP) method to simulate nonlinear FSI problems with F-S separations as well as breaking waves. The partitioned iteration approach is suggested in base of available fluid and solid codes to separately solve their gov-erning equations in a time step, and then through reaching its convergence in coupling iteration to forward until the problem solved. The selected application examples include air-liquid-shell three phases interactions, liquefield natural gas (LNG) ship-water sloshing; acoustic analysis of air-building interaction system excited by human foot impacts; transient dynamic response of an airplane-VLFS-water interaction system excited by airplane landing impacts; turbulence flow-body interactions; structure dropping down on the water surface with breaking waves, etc. The numerical results are compared with the available experiment or numeri-cal data to demonstrate the accuracy of the discussed approaches and their values for engineering applications. Based on FSI analysis, linear and nonlinear wave energy harvesting devices are listed to use the resonance in a linear system and the periodical solution in a nonlinear system, such as flutter, to effectively harvest wave energy. There are 231 references are given in the paper, which provides very useful resources for readers to further investigate their interesting approaches.

Mechanical behaviors and constitutive models of polycarbonate amorphous polymers

YU Peng, YAO Xiaohu, ZHANG Xiaoqing, HAN Qiang

2016, 46(1) doi: 10.6052/1000-0992-15-016

Abstract(2528)

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Abstract:
Polycarbonate is a kind of glassy amorphous polymer materials.Due to the excellent performance in resisting heat and impact, it is widely used in defense, military and engineering fields.In this paper, we introduce experimental investigations on mechani-cal behaviours of polycarbonate amorphous polymer materials, and discover the mechanical behaviors of such materials from a phenomenological point of view.Then we discuss re-searches on constitutive models for these materials, including the developments, physical mechanisms, mechanical characteristics and application range.Finally, we sketch the ap-plications of various constitutive models in polycarbonate amorphous polymer materials, and further discuss their descriptions for mechanical behaviors from the engineering appli-cation aspect.Meanwhile, some open key scientific problems in experimental and theoretical studies are raised, and prospects for future research are provided.

Stability and evolution of liquid-gas interfaces on superhydrophobic surfaces

LV Pengyu, XUE Yahui, DUAN Huiling

2016, 46(1) doi: 10.6052/1000-0992-15-043

Abstract(3452)

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Abstract:
Microstructured superhydrophobic surfaces have broad applications such as anti-fouling and drag reduction.The performance of such surfaces strongly depends on the stability of liquid-gas interfaces, which affects physical processes including wetting transition, restoration and bubble evolution.Various physical factors including pressurization and gas diffusion may destabilize the liquid-air interfaces, and lead to evolution in different manners.In this paper, we first summarize the three types of interfacial stability problems for liquid-gas interfaces.Relying on external stimulations, the liquid-air interface may evolve into different stages and exhibit different morphologies.The recent progress of research on the stability and control of liquid-air interfaces in both droplet systems and submersion circumstances has been reviewed.Based on this review, remaining challenges for future research have been given.

Theory and experiment of space electrodynamic tether systems

YU Bensong, WEN Hao, JIN Dongpingy, CHEN Ti

2016, 46(1) doi: 10.6052/1000-0992-15-029

Abstract(2619)

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Abstract:
This paper focuses on electrodynamic tether systems having conductive property in space.The complex dynamics and potential applications of electrodynamic tethers have gained more and more attention from academic researchers.The paper summarizes recent progress of space electrodynamic tether systems, including the principle of electro-dynamic tethers, mechanics modeling, dynamic behaviors, dynamics control, applications, orbital and the ground-based experiments.Some challenges in the fields are put forward for further studies.

Mechanical problems in momentous projects of aerospace engineering

MENG Guang, ZHOU Xubin, MIAO Jun

2016, 46(1) doi: 10.6052/1000-0992-15-018

Abstract(5619)

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Abstract:
With the vigorous development of the momentous projects in aerospace en-gineering field, new mechanical problems emerge continuously. Therefore, the research on engineering mechanics plays a prominent role in the developments of the space technol-ogy. The launch and operation environment for spacecraft is becoming more stringent as the spacecraft nowadays is developing on the track of super high speeds, deep space explo-ration and multifunction. Large-area and large flexible structure equipped on the spacecraft has proposed new challenges on the dynamics of deployment in orbit, modal identification and rigid-flexible coupling dynamics. Meanwhile, high-precision and high-resolution earth-observing request leads to new problems of micro-vibration control and thermally induced vibration control in orbit. All these problems urge more accurate methods for ground sim-ulations and experiments. In this paper, we outline the new mechanical problems arising from the launch of spacecraft, in orbit operation, ground simulations and experiments, etc. We focus on coupled dynamics, aerodynamics, multi-body dynamics, structure dynamics and experimental mechanics. The new problems and development directions of engineering mechanics are discussed in the end.

Medical image based hemodynamic analysis

Yu CHEN, Rui LI, Xuemei ZHAO, Donghai LI, Wenjuan XU, Aihua LIU, Sheau Fung SIA, Winston CHONG, Yu ZHANG

2016, 46(1) doi: 10.6052/1000-0992-15-042

Abstract(2190)

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Abstract:
Computed tomography (CT) and magnetic resonance imaging (MRI) are widely used in clinical practice for diagnose of vascular diseases, such as artery stenosis, aneurysm and vascular malformation. Besides static images, the newly developed phase-contrast magnetic resonance imaging (PCMRI) is able to capture hemodynamic parameters from timesequenced scanning; these parameters include velocity magnitude and directions. However, long time scanning is usually required for data collection. Alternatively, hemodynamic parameters can be obtained by image based computational fluid dynamics (CFD), this only demands normal scan of CT or MRI images for 3-D construction. This report will compare both methods, present examples of hemodynamic analysis in clinical application, and discuss the future directions of hemodynamic research.

Physical mechanics investigations of moving contact lines

Quanzi YUAN, Wenhao SHEN, Yapu ZHAO

2016, 46(1) doi: 10.6052/1000-0992-16-006

Abstract(3220)

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Abstract:
Moving contact line (MCL) is the triple-phase region (TPR) formed by two impermeable fluids moving on a solid surface. TPR covers multiple scales, where the interactions among phases influence the dynamic behaviors of the entire fluid field. Owing to its significant applications and rapid development in the fields of energy, aerospace, biology, etc., new challenges emerge in MCL problems. Scaling analysis is an important tool to characterize self-similar expansion of the MCL. Focusing on the scaling relations of MCLs, we review the progresses of physical mechanics investigations under "mechano-electro-thermalchemical" multifield coupled conditions for MCL on rigid/flexible solid surfaces with complex geometries, including hydraulic interior corner, micro-pillar-arrayed surface, dissolvable surface, lag zone in hydraulic fracturing, etc. Through a combined study of multiscale experiments, large-scale molecular dynamics simulations, molecular kinetic theory and hydrodynamics, new phenomena were discovered, such as solid-like precursor film, single-file water-molecular precursor chain, and zigzag MCL. From the interface structure at atomic level to the flow characteristics at continuum level, we discuss the scaling laws of self-similar expansion, and the physical mechanisms and dynamic rules, such as driving source, energy dissipation, boundary conditions, etc. We explore the answers to the "Huh-Scriven paradox" under multifield circumstance, and outlook the prospects and applications of MCL.

Pentamode material for underwater acoustic wave control

CHEN Yi, LIU Xiaoning, XIANG Ping, HU Gengkai

2016, 46(1) doi: 10.6052/1000-0992-16-010

Abstract(3615)

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Abstract:
Pentamode materials, made of conventional solids through microstructure de-sign, may have acoustic property of complex fluid. Its superior capacity for underwater acoustic wave manipulation stimulates recently an intense research activity. In this review, pentamode materials and their recent progress are explained from di?erent angles: basic concept, microstructure design, acoustic applications and fabrication technology, in order to provide an overall view on this kind of special material.

Progress in thermal-mechantical effects induced by laser

SONG Hongwei, HUANG Chenguangy

2016, 46(1) doi: 10.6052/1000-0992-15-025

Abstract(2234)

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Abstract:
In this paper we review several recent progresses in laser-induced thermal-mechanical effects, including constitutive model under high temperature and high temperature rise rate, laser damage behaviors of typical structures like thin plate and cylinders, and laser damage behaviors of multi-layered materials. We describe analytical model and mechanism study on the laser damage behavior including phase transformation and ablation, numerical modeling on the thermal-fluid-structure coupling behavior, and the shock effect and damage behavior induced by short pulse laser.

Modeling and analysis of functionally graded carbon nanotube reinforced composite structures: A review

SHEN Hui-Sheny

2016, 46(1) doi: 10.6052/1000-0992-16-007

Abstract(2124)

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Abstract:
Functionally graded carbon nanotube reinforced composite (FG-CNTRC) is a new generation of advanced composite materials, where carbon nanotubes (CNTs) are used as the reinforcements in a functionally graded pattern. The mechanical behavior of FG-CNTRC has emerged as one of the recent hot research topics in materials science and engineering. This paper presents a review of the developments in the modeling and analysis of FG-CNTRC structures. The emphasis are put on the linear and nonlinear bending, buckling and postbuckling, and free and forced vibration of FG-CNTRC beams, plates, shells and shell panels under various loading, boundary and environmental conditions. The presented progresses lay foundation for future studies in the area of FG-CNTRC structures. Some critical aspects for further explorations are highlighted.

Fragmentations of solids under impact tension

ZHENG Yuxuan, ZHOU Fenghua, HU Shisheng, YU T.X.

2016, 46(1) doi: 10.6052/1000-0992-16-004

Abstract(2553)

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Abstract:
Materials usually break into many pieces (fragments) under high strain-rate tension. Understanding the fragmentation properties of solids is important to the researchers in fields of physics, mechanics, aerospace and defense engineering. In this paper, we reviewed the researches on tensile fragmentation undertaken since 1940s. Recent advances in the fragmentation studies from theoretical analysis, experimental investigation, and numerical simulation are addressed. Some suggestions were provided for the future development in this field.

Shock wave propagation and interactions

YANG Jimingy, LI Zhufei, ZHU Yujian, ZHAI Zhigang, LUO Xisheng, LU Xiyun

2016, 46(1) doi: 10.6052/1000-0992-16-009

Abstract(3124)

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Abstract:
The propagation of a shock wave depends not only on the conditions that it is generated, but also on the media where it propagates. Variations in driver condition, boundary condition and/or physical/chemical properties of the media may alter the behav-iors of the shock wave propagation, while the flowfield also varies along with the shock wave motion. Although shock wave propagation and interactions exist widely in the nature and human activities, there is still a long way to go for a better understanding of its complex mechanism, for theoretical descriptions of the phenomena, as well as for enrichment of the application. In this paper, we review the shock wave interactions and related analyses, and further discuss several hot topics, including shock/shock interaction, shock/boundary layer interaction, shock/turbulence interaction, shock focusing/ignition and instability of shocked interface.

2016 Vol. 46, No. 1

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