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An explicit simulation of arbitrarily-shaped pseudo-elastic hysteresis loops in shape-memory alloys

IOP Conference Series: Materials Science and engineering 2020年第1期770卷

作者： S Y Wang L Zhan Z H Xu H F Xi H Xiao School of Mechanics & Construction Engineering and MOE Lab for Disaster Forecast & Control in Engineering Jinan University 510632 Guangzhou China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University 710049 Xi'an China

A new and explicit approach is proposed for accurately simulating pseudo-elastic hysteresis loops of any shape in shape-memory alloys (SMAs). For this purpose, new finite strain elastoplastic J2-flow equations are established for modeling finite strain behavior of SMAs. A stress-strain loop of any given shape in each uniaxial loading-unloading cycle is derived exactly from these equations. Then, a new technique is further introduced toward integrating usual piecewise linear splines into a single smooth interpolating function in a unified form. With the proposed equations and technique, test data for SMA hysteresis loops of any shape may be automatically fitted with high accuracy based on a single-parameter identification.

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Moving force identification based on redundant concatenated dictionary and weighted l₁-norm regularization

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2018年 98卷 32-49页

作者： Pan, Chu-Doug Yu, Ling Liu, Huan-Lin Chen, Ze-Peng Luo, Wen-Feng Jinan Univ Sch Mech & Construct Engn 601 West Huangpu Ave Guangzhou 510632 Guangdong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China China Three Gorges Univ Coll Civil Engn & Architecture Yichang 443002 Peoples R China

Moving force identification (MFI) is an important inverse problem in the field of bridge structural health monitoring (SHM). Reasonable signal structures of moving forces are rarely considered in the existing MFI methods. Interaction forces are complex because they contain both slowly-varying harmonic and impact signals due to bridge vibration and bumps on a bridge deck, respectively. Therefore, the interaction forces are usually hard to be expressed completely and sparsely by using a single basis function set. Based on the redundant concatenated dictionary and weighted l(1)-norm regularization method, a hybrid method is proposed for MFI in this study. The redundant dictionary consists of both trigonometric functions and rectangular functions used for matching the harmonic and impact signal features of unknown moving forces. The weighted l(1)-norm regularization method is introduced for formulation of MFI equation, so that the signal features of moving forces can be accurately extracted. The fast iterative shrinkage-thresholding algorithm (FISTA) is used for solving the MFI problem. The optimal regularization parameter is appropriately chosen by the Bayesian information criterion (BIC) method. In order to assess the accuracy and the feasibility of the proposed method, a simply-supported beam bridge subjected to a moving force is taken as an example for numerical simulations. Finally, a series of experimental studies on MFI of a steel beam are performed in laboratory. Both numerical and experimental results show that the proposed method can accurately identify the moving forces with a strong robustness, and it has a better performance than the Tikhonov regularization method. Some related issues are discussed as well. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Moving force identification Redundant concatenated dictionary Weighted l(1)-norm regularization Structural health monitoring (SHM)

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Analytical Solutions for Bending of Nanoscaled Bars Based on Eringen's Nonlocal Differential Law

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JOURNAL OF NANOMATERIALS 2019年第1期2019卷 1-13页

作者： Li, C. Zhang, N. Li, S. Yao, L. Q. Yan, J. W. Soochow Univ Dept Vehicle Engn Sch Rail Transportat Suzhou 215131 Jiangsu Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China East China Jiaotong Univ Sch Civil Engn & Architecture Nanchang 330013 Jiangxi Peoples R China

The one-dimensional nanoscaled bar is commonly seen in current nanodevices, and it plays a significant role in nanoelectromechanical system (NEMS) and related nanotechnology. Motivated by this, the paper is concerned with the bending and stability of a nanoscaled bar especially a flexible bar subjected to vertical concentrated, vertical linearly distributed, and horizontal concentrated forces simultaneously. The theoretical model is developed by employing Eringen's nonlocal differential law. Hence, the nonlocal differential constitutions in terms of stress and bending moment at a nanoscale are applied to the classical equilibrium formulation in order to construct the nonlocal constitutive model and then determine the analytical solutions for bending of such a nanoscale bar. Subsequently, the effect of a nonlocal scale on the midpoint deflections and internal forces is shown numerically, and the internal and external characteristic length scales are also examined. It is revealed that the capacity of resisting compression decreases with increasing the nonlocal effect since the internal characteristic scale cannot be neglected by comparing with the external characteristic scale. There exists a threshold value for bending stiffness. Both the midpoint deflection and bending moment vary monotonously when the material bending stiffness exceeds the threshold value, while the mechanical quantities fluctuate when the bending stiffness is less than its threshold value, namely, for a flexible nanoscaled bar. Accordingly, two different kinds of nonlocal predictions and the related disputes are resolved in the context of Eringen's nonlocal differential law. The work is expected to be useful for the design, application, and optimization of nanoscaled bars sustaining bending with linear vertical and horizontal forces.

关键词： Bending moments

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Innovative elastoplastic J2-flow model incorporating cyclic and non-cyclic failure effects of metals as inherent constitutive features

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ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK 2019年第11期99卷

作者： Zhan, Lin Wang, Si-Yu Xi, Hui-Feng Xiao, Heng Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn West Huangpu Ave 601 Guangzhou 510632 Guangdong Peoples R China Shanghai Univ Shanghai Inst Appl Math & Mech Yanchang Rd 149 Shanghai 200072 Peoples R China

A new finite strain elastoplastic J(2)-flow model is proposed toward directly simulating cyclic and non-cyclic failure effects of metals. The main novelties of this model are as follows: The usual notion of yielding is rendered irrelevant in a more realistic sense of representing elastoplastic behaviors of metals up to failure;The thermodynamic consistency requirement from the second law may be identically fulfilled;Failure effects under cyclic and non-cyclic conditions may be automatically incorporated as inherent constitutive features, with involving neither additional variables nor ad hoc failure criteria;Hardening-to-softening effects of metals up to failure may be effectively characterized in a unified manner. (1)(2)(3)(4)Simulation results are provided and compared with experimental data for monotonic and cyclic failure effects for both uniaxial and torsional deformation modes. In particular, both the Swift effects and the failure effects of twisted metal tubes are simultaneously simulated for four cases of finite torsion, including free-end and fixed-end torsion under monotonic and cyclic loadings, and accurate agreement with finite strain data for both torsional modes is accomplished for the first time.

关键词： constrained torsion elastoplasticity finite deformation free torsion metal fatigue simultaneous simulations Swift effect

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One family of 13315 stable periodic orbits of the non-hierarchical unequal-mass triple system

arXiv

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arXiv 2020年

作者： Li, Xiaoming Li, Xiaochen Liao, Shijun MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China Department of Earth Atmospheric and Planetary Sciences Massachusetts Institute of Technology CambridgeMA02139 United States School of Civil Engineering and Transportation South China University of Technology Guangzhou510641 China Department of Engineering Science University of Oxford OxfordOX1 3PJ United Kingdom Center of Advanced Computing School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai200240 China School of Physics and Astronomy Shanghai Jiaotong University Shanghai200240 China

The three-body problem has been studied for more than three centuries1, 2, and has received much more attention in recent years3–5. It shows complex dynamical phenomena due to the mutual gravitational interaction of the three bodies. Triple systems are common in astronomy, but all observed periodic triple systems are hierarchical up till now6–8. It is traditionally believed that bound non-hierarchical triple systems are almost unstable and disintegrate into a stable binary system and a single star5, and thus stable periodic orbits of non-hierarchical triple systems are rather scarce. Here we report one family of 13315 stable periodic orbits of the non-hierarchical triple system with unequal mass. Compared with the narrow mass region (only 10−5) of the stable figure-eight solution9, our newly-found stable periodic orbits can have fairly large mass region. It is found that many of these newly-found stable periodic orbits have the mass ratios close to those of the hierarchical triple systems that have been measured by the astronomical observation. It implies that these stable periodic orbits of the non-hierarchical triple system with distinctly unequal masses can be quite possibly observed in practice. Our investigation also suggests that there should exist an infinite number of stable periodic orbits of non-hierarchical triple systems with distinctly unequal masses. Obviously, these stable periodic orbits of the non-hierarchical unequal-mass triple system have broad impact for the astrophysical scenario: they could inspire the theoretical and observational study of the non-hierarchical triple system, the formation of triple stars6, the gravitational waves pattern10 and the gravitational waves observation11 of the non-hierarchical triple system. Copyright © 2020, The Authors. All rights reserved.

关键词： Gravitational effects

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Visualization Analysis of Markov Chain Based on CiteSpace

Visualization Analysis of Markov Chain Based on CiteSpace

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作者： Songping Yang Ranni Zhang Yongyi Chen Fan Yang He Wang Ru Zhang Packaging Engineering Institute Jinan University MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University School of Marxism Jinan University School of Intelligent Science and Engineering Jinan University Electrical Engineering Institute Jinan University School of Electrical Engineering Jinan University International Business School Jinan University

Since markov chain is widely used in various fields, the relevant literatures of markov chain theories are analyzed base on CiteSpace in this paper, adopting 10,000 literatures in CNKI and 10,000 literatures in WOS as datas. The relationship among markov chain, monte carlo integral and bayesian theory is analyzed primarily. What's more, the hidden markov model, markov random field, markov decision process and grey-markov model derived from markov chain are investigated emphatically. Ultimately, we reviews the development history of markov chain, makes a visual analysis of the authors, sorts out the research status of markov chain, and makes a comprehensive review of the application of markov chain.

关键词： Visualization Monte Carlo Citespace

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An explicit high-efficiency algorithm for simulating high-cycle fatigue behavior of metals

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IOP Conference Series: Materials Science and engineering 2020年第1期770卷

作者： S Y Wang L Zhan Z H Xu H F Xi H Xiao School of Mechanics & Construction Engineering and MOE Lab for Disaster Forecast & Control in Engineering Jinan University West Huangpu Avenue 601 510632 Guangzhou China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University 710049 Xi'an China

This article presents a direct and efficient algorithm for simulating high-cycle fatigue failure effects within the framework of a recently proposed elastoplastic model, in which fatigue failure effects of metals are incorporated as inherent constitutive features. Toward bypassing very time-consuming procedures in conducting numerical integrations of the elastoplastic rate equations for extremely large number of loading cycles, from the new model it is possible to derive an explicit expression for the fatigue life directly in terms of the stress amplitude. Numerical examples show that the new algorithm thus established is much more efficient than usual direct numerical procedures and that is particularly the case in simulating fatigue failure effects with very high cycle number.

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A unified simulation of low-to-high cycle fatigue failure effects for metals with efficient algorithm

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IOP Conference Series: Materials Science and engineering 2020年第1期770卷

作者： L Zhan S Wang Z H Xu H F Xi H Xiao School of Mechanics & Construction Engineering and MOE Lab for Disaster Forecast & Control in Engineering Jinan University West Huangpu Avenue 601 510632 Guangzhou China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University 710049 Xi'an China

Within the framework of a recently established elastoplasticity model incorporating fatigue failure effects into inherent response features, a new and efficient algorithm is proposed to simultaneously treat fatigue failure effects from low to high cycle cases. From the new model it is possible to derive an explicit algorithm with which the accumulated plastic work is directly calculated by means of a recursive scheme, thus bypassing very time-consuming procedures in carrying out numerical integrations of the elastoplastic rate equations for a large number of loading-unloading cycles. Comparisons of simulation results with fatigue failure data from low to high cycle cases are presented to demonstrate the efficacy of the new algorithm.

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Analysis of the Effect of Urban Geometric Form Factors on Heat Islands in Guangzhou

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IOP Conference Series: Earth and Environmental Science 2020年第1期555卷

作者： Langtao Zheng Jian Tang Xiong Chen Guangdong Engineering Technology Research Center for Green Building Materials and Fabricated Architecture Maoming P.R. China MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University Guangzhou 510632 China

The geometric form factors of urban space include height width ratio (H/W), sky view factor (SVF) and street direction, which directly affect the incidence of solar radiation, and then affect the temperature change of the block. In this study, the representative hot island and cold island streets in Guangzhou are selected as the research objects. According to the intensity and range distribution map of Guangzhou heat island in summer of 2014-2017 issued by Guangzhou Meteorological Bureau, the intersection area with high intensity of 4-year continuous heat island is found out by two-dimensional image superposition. In the region, the typical measurement points and comparison points are selected in groups, the temperature of each measurement point is monitored, and the urban geometry data is collected for comparative analysis. The results show that under the condition of the same underlying surface factor and no significant difference in artificial heat factor, the urban geometry can alleviate the heat island effect, and the measuring points with smaller sky view factor and larger height width ratio (H/W) have lower temperature, and the temperature of each measuring point has higher correlation with the size of SVF. In addition, the direction defined by the long axis of the valley will also affect the solar radiation equivalent of the street pavement, and the reclamation open land is also easy to become a heat island area.

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Thermal-Structural Coupling Analysis of PCBA System 3

Thermal-Structural Coupling Analysis of PCBA System

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2018 3rd International Conference on Insulating Materials, Material Application and Electrical engineering, IMMAEE 2018

作者： Su, Wei Zhu, Junhua Liu, Renhuai He, Zhiyuan Scienceand Technol. on Reliability Phys. and Applic. Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China Department of Mechanics and Civil Engineering Jinan University Guangzhou China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou China

In this paper, the thermal and structural analysis of the PCBA system is provided by using the 3-D ANSYS package. The results of thermal and structural analysis for complex and simple model are compared. The paper also describes the deformation analysis of the PCBA system components, and the weak components sensitive to thermal stress are determined though thermal-structual analysis. The results of thermal analysis are helpful to the optimizing overall arrangement design of PCBA system. © Published under licence by IOP Publishing Ltd.

关键词： Thermoanalysis

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