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: 0.887
Citation: Acta Mech. Sin.
Frequency: Bimonthly
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Acta Mechanica Sinica--2016, 32 (2)   Published: 20 March 2016
THEMED ARTICLE ON CURRENT RESEARCH PROGRESS ON MECHANICS OF HIGH SPEED RAIL - II
Research on the mechanics of high speed rails Hot!
Yujie Wei
Abstract

In order to develop a comprehensive understanding about the dynamics and long-term durability of HSR systems, there is a prevailing need for new research from multidisciplinary groups. The theme articles published in this issue are the result of our continual endeavors to introduce cutting-edge research on the mechanics of HSR, from researchers of different backgrounds and working on different aspects of the system. One focus of the theme articles is on the aerodynamic design of high speed tr...

Influences of affiliated components and train length on the train wind Hot!
Dilong Guo, Keming Shang, Ye Zhang, Guowei Yang, Zhenxu Sun
Abstract

The induced airflow from passing trains, which is recognized as train wind, usually has adverse impacts on people in the surroundings, i.e., the aerodynamic forces generated by a high-speed train's wind may act on the human body and endanger the safety of pedestrians or roadside workers. In this paper, an improved delayed detached eddy simulation (IDDES) method is used to study train wind. The effects of the affiliated components and train length on train wind are analyzed. The results indica...

Dynamic simulation and safety evaluation of high-speed trains meeting in open air Hot!
Songyan Li, Zhijun Zheng, Jilin Yu, Chunqiang Qian
Abstract

Dynamic responses of a carriage under excitation with the German high-speed low-interference track spectrum together with the air pressure pulse generated as high-speed trains passing each other are investigated with a multi-body dynamics method. The variations of degrees of freedom (DOFs:horizontal movement, roll angle, and yaw angle), the lateral wheel-rail force, the derailment coefficient, and the rate of wheel load reduction with time when two carriages meet in open air are obtained and ...

Aerodynamic design on high-speed trains Hot!
San-San Ding, Qiang Li, Ai-Qin Tian, Jian Du, Jia-Li Liu
Abstract

Compared with the traditional train, the operational speed of the high-speed train has largely improved, and the dynamic environment of the train has changed from one of mechanical domination to one of aerodynamic domination. The aerodynamic problem has become the key technological challenge of high-speed trains and significantly affects the economy, environment, safety, and comfort. In this paper, the relationships among the aerodynamic design principle, aerodynamic performance indexes, and ...

Study on the subgrade deformation under high-speed train loading and water-soil interaction Hot!
Jian Han, Guo-Tang Zhao, Xiao-Zhen Sheng, Xue-Song Jin
Abstract

It is important to study the subgrade characteristics of high-speed railways in consideration of the water-soil coupling dynamic problem, especially when high-speed trains operate in rainy regions. This study develops a nonlinear water-soil interaction dynamic model of slab track coupling with subgrade under high-speed train loading based on vehicle-track coupling dynamics. By using this model, the basic dynamic characteristics, including water-soil interaction and without water induced by th...

Analysis of torque transmitting behavior and wheel slip prevention control during regenerative braking for high speed EMU trains Hot!
Kun Xu, Guo-Qing Xu, Chun-Hua Zheng
Abstract

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability, improving the adhesion utilization, and achieving deep energy recovery. There remain technical challenges mainly because of the nonlinear, uncertain, and varying features of wheel-rail contact conditions. This research analyzes the torque transmitting behavior during regenerative braking, and proposes a novel methodology to detect the wheel-rail...

Effect of wheelset flexibility on wheel-rail contact behavior and a specific coupling of wheel-rail contact to flexible wheelset Hot!
Shuoqiao Zhong, Xinbiao Xiao, Zefeng Wen, Xuesong Jin
Abstract

The flexibility of a train's wheelset can have a large effect on vehicle-track dynamic responses in the medium to high frequency range. To investigate the effects of wheelset bending and axial deformation of the wheel web, a specific coupling of wheel-rail contact with a flexible wheelset is presented and integrated into a conventional vehicle-track dynamic system model. Both conventional and the proposed dynamic system models are used to carry out numerical analyses on the effects of wheelse...

Multi-scale morphology analysis of acoustic emission signal and quantitative diagnosis for bearing fault Hot!
Wen-Jing Wang, Ling-Li Cui, Dao-Yun Chen
Abstract

Monitoring of potential bearing faults in operation is of critical importance to safe operation of high speed trains. One of the major challenges is how to differentiate relevant signals to operational conditions of bearings from noises emitted from the surrounding environment. In this work, we report a procedure for analyzing acoustic emission signals collected from rolling bearings for diagnosis of bearing health conditions by examining their morphological pattern spectrum (MPS) through a m...

FLUID MECHANICS
A cavitation model for computations of unsteady cavitating flows
Yu Zhao, Guoyu Wang, Biao Huang
Abstract

A local vortical cavitation (LVC) model for the computation of unsteady cavitation is proposed. The model is derived from the Rayleigh-Plesset equations, and takes into account the relations between the cavitation bubble radius and local vortical effects. Calculations of unsteady cloud cavitating flows around a Clark-Y hydrofoil are performed to assess the predictive capability of the LVC model using well-documented experimental data. Compared with the conventionalZwart's model, better agreem...

Tomographic PIV investigation on coherent vortex structures over shark-skin-inspired drag-reducing riblets
Shao-Qiong Yang, Shan Li, Hai-Ping Tian, Qing-Yi Wang, Nan Jiang
Abstract

Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect. In the present study, the effect of shark-skin-inspired riblets on coherent vortex structures in a turbulent boundary layer (TBL) is investigated. This is done by means of tomographic particle image velocimetry (TPIV) measurements in channel flows over an acrylic plate of drag-reducing riblets at a friction Reynolds number of 1...

SOLID MECHANICS
Analysis of the geometrical dependence of auxetic behavior in reentrant structures by finite elements
V. H. Carneiro, H. Puga, J. Meireles
Abstract

Materials with a negative Poisson's ratio (PR) are called auxetics; they are characterized by expansion/contraction when tensioned/compressed. Given this counterintuitive behavior, they present very particular characteristics and mechanical behavior. Geometrical models have been developed to justify and artificially reproduce such materials' auxetic behavior. The focus of this study is the exploration of a reentrant model by analyzing the variation in the PR of reentrant structures a...

Impact toughness of a gradient hardened layer of Cr5Mo1V steel treated by laser shock peening
Weiguang Xia, Lei Li, Yanpeng Wei, Aimin Zhao, Yacong Guo, Chenguang Huang, Hongxiang Yin, Lingchen Zhang
Abstract

Laser shock peening (LSP) is a widely used surface treatment technique that can effectively improve the fatigue life and impact toughness of metal parts. Cr5Mo1V steel exhibits a gradient hardened layer after a LSP process. A new method is proposed to estimate the impact toughness that considers the changing mechanical properties in the gradient hardened layer. Assuming a linearly gradient distribution of impact toughness, the parameters controlling the impact toughness of the gradient harden...

DYNAMICS, VIBRATION, AND CONTROL
The equilibrium stability for a smooth and discontinuous oscillator with dry friction
Zhi-Xin Li, Qing-Jie Cao, Alain Léger
Abstract

In this paper, we investigate the equilibrium stability of a Filippov-type system having multiple stick regions based upon a smooth and discontinuous (SD) oscillator with dry friction. The sets of equilibrium states of the system are analyzed together with Coulomb friction conditions in both (fn, fs) and (xx) planes. In the stability analysis, Lyapunov functions are constructed to derive the instability for the equilibrium set o...

Correcting the initialization of models with fractional derivatives via history-dependent conditions
Maolin Du, Zaihua Wang
Abstract

Fractional differential equations are more and more used in modeling memory (history-dependent, nonlocal, or hereditary) phenomena. Conventional initial values of fractional differential equations are defined at a point, while recent works define initial conditions over histories. We prove that the conventional initialization of fractional differential equations with a Riemann-Liouville derivative is wrong with a simple counter-example. The initial values were assumed to be arbitrarily given ...

An efficient formulation based on the Lagrangian method for contact-impact analysis of flexible multi-body system
Peng Chen, Jin-Yang Liu, Jia-Zhen Hong
Abstract

In this paper, an efficient formulation based on the Lagrangian method is presented to investigate the contact-impact problems of flexible multi-body systems. Generally, the penalty method and the Hertz contact law are the most commonly used methods in engineering applications. However, these methods are highly dependent on various non-physical parameters, which have great effects on the simulation results. Moreover, a tremendous number of degrees of freedom in the contact-impact problems wil...

BIOMECHANICS
Why a mosquito leg possesses superior load-bearing capacity on water: Experimentals
Xiang-Qing Kong, Jian-Lin Liu, Cheng-Wei Wu
Abstract

Mosquitoes possess the striking ability to walk on water because each of their legs has a huge water supporting force (WSF) that is 23 times their body weight. Aiming at a full understanding of the origins of this extremely large force, in this study, we concentrate on two aspects of it:the intrinsic properties of the leg surface and the active control of the initial stepping angle of the whole leg. Using a measurement system that we developed ourselves, the WSFs for the original leg samples ...

INTERDISCIPLINE
Acoustic emission assessment of interface cracking in thermal barrier coatings
Li Yang, Zhi-Chun Zhong, Yi-Chun Zhou, Wang Zhu, Zhi-Biao Zhang, Can-Ying Cai, Chun-Sheng Lu
Abstract

In this paper, acoustic emission (AE) and digital image correlation methods were applied to monitor interface cracking in thermal barrier coatings under compression. The interface failure process can be identified via its AE features, including buckling, delamination incubation and spallation. According to the Fourier transformation of AE signals, there are four different failure modes:surface vertical cracks, opening and sliding interface cracks, and substrate deformation. The characteristic...

ERRATUM
Erratum to: Hierarchical structure observation and nanoindentation size effect characterization for a limnetic shell
Jingru Song, Cuncai Fan, Hansong Ma, Yueguang Wei
Abstract
 
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