Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2019, 35 (5)   Published: 20 October 2019
FLUID MECHANICS
Numerical study of convective heat transfer of a supersonic combustor with varied inlet flow conditions
W.H.Fan, F.Q.Zhong, S.G.Ma, X.Y.Zhang
Abstract
Characteristics of convective heat transfer of a supersonic model combustor with variable inlet flow conditions were studied by numerical simulation in this paper. The three-dimensional flow and wall heat flux at different air inlet Mach numbers of 2.2, 2.8 and 3.2 were studied numerically with Reynolds-averaged Navier-Stokes equations with a shear-stress transport (SST) k?-?ω turbulence model and a three-step reaction model. Meanwhile, ethylene was chosen as the fuel, ...
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Effects of incident wind/wave directions on dynamic response of a SPAR-type floating offshore wind turbine system
Guoqin Lyu, Huiqin Zhang, Jiachun Li
Abstract
As a promising renewable energy, offshore wind energy currently is gaining more attention, by which the economic and efficient operation of floating wind turbine systems is a potential research direction. This study is primarily devoted to the analysis of dynamic response of the NREL-5 MW reference wind turbine supported by an OC3-Hywind SPAR-type platform using a recompiled code which combines FAST with WAMIT. To verify the reliability of the recompiled code, the free decay motions of a floatin...
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Design method for an acoustic cloak in flows by topology optimization
Zhengyu Ma, Oksana Stalnov, Xun Huang
Abstract
In this paper, a design method for an acoustic cloak in the presence of background mean flows is proposed by using topology optimization, which enables the associated fabrication of the cloaking design. The density-based topology optimization method is used to allocate the designated materials, thus providing the structure of the cloak. The optimization problem is efficiently solved with the gradient-based globally convergent method of moving asymptotes, which utilizes the derivative information...
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SOLID MECHANICS
Revisiting the peridynamic motion equation due to characterization of boundary conditions
Zaixing Huang
Abstract
The peridynamic motion equation was investigated once again. The origin of incompatibility between boundary conditions and peridynamics was analyzed. In order to eliminate this incompatibility, we proposed a new peridynamic motion equation in which the effects of boundary traction and boundary displacement constraint were introduced. The new peridynamic motion equation is invariant under the transformations of rigid translation and rotation. Meanwhile, it also satisfies the requirements of total...
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Perturbation finite element solution for chemo-elastic boundary value problems under chemical equilibrium
Peter L. Bishay, Jan Sladek, Nicholas Fabry, Vladimir Sladek, Chuanzeng Zhang
Abstract
Modeling the elastic behavior of solids in energy conversion and storage devices such as fuel cells and lithium-ion batteries is usually difficult because of the nonlinear characteristics and the coupled chemo-mechanical behavior of these solids. In this work, a perturbation finite element (FE) formulation is developed to analyze chemo-elastic boundary value problems (BVPs) under chemical equilibrium. The perturbation method is applied to the FE equations because of the nonlinearity in the chemi...
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Large nonlinear deflection behavior of IPMC actuators analyzed with an electromechanical model
H. G. Liu, K. Bian, K. Xiong
Abstract
This study presents an electromechanical engineering model for the analysis of the large deflection curves of ionic polymer-metal composite (IPMC) cantilever actuators under direct current (DC) voltages. In this paper, the longitudinal normal strain performance of the material was investigated using digital image correlation on a micro-scale. The deflection of the actuator is analytically obtained with the application of an elliptic integration method based on the relationship between strain gra...
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Quadrilateral 2D linked-interpolation finite elements for micropolar continuum
Sara Grbčić, Gordan Jelenić, Dragan Ribarić
Abstract
Quadrilateral finite elements for linear micropolar continuum theory are developed using linked interpolation. In order to satisfy convergence criteria, the newly presented finite elements are modified using the Petrov-Galerkin method in which different interpolation is used for the test and trial functions. The elements are tested through four numerical examples consisting of a set of patch tests, a cantilever beam in pure bending and a stress concentration problem and compared with the analyti...
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Improved method for zero-energy mode suppression in peridynamic correspondence model
Ji Wan, Zhuang Chen, Xihua Chu, Hui Liu
Abstract
The peridynamic correspondence model provides a general formulation to incorporate the classical local model and, therefore, helps to solve mechanical problems with discontinuities easily. But it suffers from zero-energy mode instability in numerical implementation due to the approximation of deformation gradient tensor. To suppress zero-energy modes, previous stabilized methods were generally more based on adding a supplemental force state derived from bond-based peridynamic theory, which requi...
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Crystal plasticity model to predict fatigue crack nucleation based on the phase transformation theory
Lu Liu, Jundong Wang, Tao Zeng, Yao Yao
Abstract
A crystal plasticity model is developed to predict the fatigue crack nucleation of polycrystalline materials, in which the accumulated dislocation dipoles are considered to be the origin of damage. To describe the overall softening behavior under cyclic loading, a slip system-level dislocation density-related damage model is proposed and implemented in the finite element analysis with Voronoi tessellation. The numerical model is applied to calibrate the stress-strain relationship at different cy...
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Topology optimization of a 6-DOF spatial compliant mechanism based on Stewart propotype platform
Dachang Zhu, Wanghu Zhan
Abstract
To improve the global stiffness and conveniently build a model of a compliant mechanism with spatial multiple degrees of freedom (DOF), the topology optimization method, combined with the isomorphic mapping matrix, is proposed in this paper for structure synthesis of a 6-DOF spatial compliant mechanism. By using the differential approximation method, the Jacobian matrix of the Stewart prototype platform is calculated as the isomorphic mapping matrix, and its eigenvalues and eigenvectors are cons...
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SOLID MECHANICS
Model of homogenisation for analysing the effect of micrometre pore sizes on the elastic moduli of porous materials
A. F. Fedotov
Abstract
A homogenisation model for analysing the effect of micrometre pore sizes on the engineering moduli of elasticity of porous materials was proposed. In the proposed model, the engineering coefficients of localization of total strains (LTS coefficients) are considered instead of the classical strain localization tensors. For a pore, these coefficients represent the ratio of the sum of the strains in the volume of the pore to the sum of the strains in the volume of the porous body. To estimate the e...
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DYNAMICS, VIBRATION, AND CONTROL
Equivalent continuum modeling of beam-like truss structures with flexible joints
Fushou Liu, Libin Wang, Dongping Jin, Hao Wen
Abstract
The paper investigated the equivalent continuum modeling of beam-like repetitive truss structures considering the flexibility of joints, which models the contact between the truss member and joint by spring-damper with six directional stiffnesses and dampings. Firstly, a two-node hybrid joint-beam element was derived for modeling the truss member with flexible end joints, and a condensed model for the repeating element with flexible joints was obtained. Then, the energy equivalence method was ad...
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Experimental investigation of a passive self-tuning resonator based on a beam-slider structure
Liuding Yu, Lihua Tang, Tiejun Yang
Abstract
This work investigates a self-tuning resonator composed of a slender clamped-clamped steel beam and a freely movable slider. The clamped-clamped beam exhibits hardening nonlinearity when it vibrates in large amplitude, providing a broad bandwidth of dynamic response. The moving slider changes the mass distribution of the whole structure, and provides a passive self-tuning approach for capturing the high-energy orbit of the structure. In the case without inclination, adequate inertial force that ...
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Analytical approach for the design of convoluted air suspension and experimental validation
Gokul Prassad Sreenivasan, Malar Mohan Keppanan
Abstract
An improved analytical design to investigate the static stiffness of a convoluted air spring is developed and presented in this article. An air spring provides improved ride comfort by achieving variable volume at various strokes of the suspension. An analytical relation is derived to calculate the volume and the rate of change in the volume of the convoluted bellow with respect to various suspension heights. This expression is used in the equation to calculate the variable stiffness of the bell...
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BIOMECHANICS
Numerical study on dynamic mechanism of brain volume and shear deformation under blast loading
Zhijie Li, Zhibo Du, Xiaochuan You, Zhanli Liu, Jian Cheng, Chengcheng Luo, Dongyang Chu, Shaowu Ning, Yue Kang, Ce Yang, Zhuo Zhuang
Abstract
Blast-induced traumatic brain injury (b-TBI) is a kind of significant injury to soldiers in the current military conflicts. However, the mechanism of b-TBI has not been well understood, and even there are some contradictory conclusions. It is crucial to reveal the dynamic mechanism of brain volume and shear deformations under blast loading for better understanding of b-TBI. In this paper, the numerical simulation method is adopted to carry out comprehensive and in-depth researches on this issue ...
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Experimental and numerical study of the effect of pulsatile flow on wall displacement oscillation in a flexible lateral aneurysm model
L. Z. Mu, X. Y. Li, Q. Z. Chi, S. Q. Yang, P. D. Zhang, C. J. Ji, Y. He, G. Gao
Abstract
This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm. A method for constructing a flexible aneurysm model was developed, and a self-designed piston pump was used to provide the pulsatile flow conditions. A fluid-structure interaction simulation was applied for comparison with and analysis of experimental findings. The maximum wall displacement oscillation increased as the puls...
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CORRECTION
Correction to: Uniaxial experimental study of the acoustic emission and deformation behavior of composite rock based on 3D digital image correlation (DIC)
Jian-Long Cheng, Sheng-Qi Yang, Kui Chen, Dan Ma, Feng-Yuan Li, Li-Ming Wang
Abstract
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