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Numerical Simulation of Random Vibration Analysis for Ball Grid Array Package

IOP Conference Series: Earth and Environmental Science 2021年第3期769卷

作者： Wenhao Luo Wei Su Xianshan Dong Zhenhua Nie Agam Tomar MOE Key lab of Disaster Forecast and Control in Engineering Guangzhou China School of Mechanics and Construction Engineering Jinan University Guangzhou China Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China Faculty of Engineering and Mathematical Sciences University of Western Australia Perth Australia

This paper uses ANSYS Workbench (a finite element analysis software) to simulate BGA ceramic packing. The author models fixture, ceramic and metal steel. Then different thickness papers are laid on the BGA product. By random vibration analysis, the natural frequency and mode of the sample are obtained. According the results, the author discusses the relationship between different thickness papers and PSD-frequency curve. It provides a benefit instruction for the design of BGA packing.

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Direct Writing Supercapacitors Using a Carbon Nanotube/Ag Nanoparticle-Based Ink on Cellulose Acetate Membrane Paper

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POLYMERS 2019年第6期11卷 973-973页

作者： Guan, Xipeng Cao, Lin Huang, Qin Kong, Debin Zhang, Peng Lin, Huaijun Li, Wei Lin, Zhidan Yuan, Hong Jinan Univ Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn MOE Guangzhou 510632 Guangdong Peoples R China Jinan Univ Inst Adv Wear & Corros Resistant & Funct Mat Guangzhou 510632 Guangdong Peoples R China

In this work, we present a cellulose acetate membrane flexible supercapacitor prepared through a direct writing method. A carbon nanotube (CNT) and silver (Ag) nanoparticle were prepared into ink for direct writing. The composite electrode displayed excellent electrochemical and mechanical electrochemical performance. Furthermore, the CNT-Ag displayed the highest areal capacity of 72.8 F/cm(3). The assembled device delivered a high areal capacity (17.68 F/cm(3)) at a current density of 0.5 mA/cm(2), a high areal energy (9.08-5.87 mWh/cm(3)) at a power density of 1.18-0.22 W/cm(3), and showed no significant decrease in performance with a bending angle of 180 degrees. The as-fabricated CNT/Ag electrodes exhibited good long-term cycling stability after 1000 time cycles with 75.92% capacitance retention. The direct writing was a simple, cost-effective, fast, and non-contact deposition method. This method has been used in current printed electronic devices and has potential applications in energy storage.

关键词： Ag CNT flexible supercapacitor electrode polymer conductive film cellulose acetate membrane

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A unified and explicit approach for accurately characterizing the hardening-softening behavior of metals with a tension-compression strength asymmetry

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

作者： H F Xi L Zhan S Y Wang Z H Xu 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 unified and explicit approach is proposed for accurately characterizing a complex hardening-softening behavior of metals with a tension-compression strength asymmetry. The proposed approach provides an explicit determining of the yield strength as plastic work function and contains the following three procedures: (i) a mode invariant is introduced to express the yield strength as a sum of two uncoupled parts for the tension and the compression case; (ii) a new expression for the plastic work is derived explicitly in terms of the uniaxial stress-strain function and, then, the yield strength function can be determined jointly from the just-mentioned two functions with the axial strain as parametric variable; and, finally, (iii) the axial stress-strain function is presented for representing the hardening-softening features. With these procedures, test data over the entire hardening-softening range can be fitted independently for the tension and the compression cases by directly treating the uniaxial stress-strain function. As such, tedious trial-and-error procedures are bypassed in identifying numerous unknown parameters. Numerical examples show that accurate simulations may be achieved with the proposed approach.

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

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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 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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Coupling effects of finite rotation and strain-induced anisotropy on monotonic and cyclic failure of metals

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ACTA MECHANICA 2018年第12期229卷 4963-4975页

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

New finite-strain elastoplastic constitutive equations are proposed toward a direct approach for simulating both monotonic and cyclic failure effects of metals. Novelties in several respects are incorporated in these new equations: (a) No yield conditions need be imposed, and therefore smooth transition from an elastic to a plastic state may be ensured without involving strong discontinuities in elastoplastic tangent moduli;(b) Complex forms of usual elastoplastic equations assuming the loading-unloading conditions may be substantially simplified in a more realistic sense of representing elastoplastic behavior of metals;(c) Failure effects in a broad case of multi-axial loading conditions may be automatically predicted as inherent constitutive features, without involving any additional variables and any ad hoc failure criteria;and (d) A new evolution equation for the back stress is introduced for effective characterization of both hardening and softening effects associated with strain-induced anisotropy. A simultaneous simulation of monotonic and cyclic failure effects of metal tubes under torsional loadings is for the first time presented for both free- and fixed-end torsion with finite rotation. Results are obtained for coupling effects of finite rotation and strain-induced anisotropy. Model predictions compare well with experimental data.

关键词： Metals

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Nonlinear damage detection using linear ARMA models with classification algorithms

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SMART STRUCTURES AND SYSTEMS 2020年第1期26卷 23-33页

作者： Chen, Liujie Yu, Ling Fu, Jiyang Ng, Ching-Tai Guangzhou Univ Sch Civil Engn Guangzhou Higher Educ Mega Ctr 230 Wai Huan Xi Rd Guangzhou Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn 601 West Huangpu Ave Guangzhou Peoples R China Guangzhou Higher Educ Mega Ctr Guangzhou Univ Tamkang Univ Joint Res Ctr Engn St 230 Wai Huan Xi Rd Guangzhou Peoples R China Univ Adelaide Sch Civil Environm & Min Engn North Terrace Adelaide SA 5005 Australia

Majority of the damage in engineering structures is nonlinear. Damage sensitive features (DSFs) extracted by traditional methods from linear time series models cannot effectively handle nonlinearity induced by structural damage. A new DSF is proposed based on vector space cosine similarity (VSCS), which combines K-means cluster analysis and Bayesian discrimination to detect nonlinear structural damage. A reference autoregressive moving average (ARMA) model is built based on measured acceleration data. This study first considers an existing DSF, residual standard deviation (RSD). The DSF is further advanced using the VSCS, and then the advanced VSCS is classified using K-means cluster analysis and Bayes discriminant analysis, respectively. The performance of the proposed approach is then verified using experimental data from a three-story shear building structure, and compared with the results of existing RSD. It is demonstrated that combining the linear ARMA model and the advanced VSCS, with cluster analysis and Bayes discriminant analysis, respectively, is an effective approach for detection of nonlinear damage. This approach improves the reliability and accuracy of the nonlinear damage detection using the linear model and significantly reduces the computational cost. The results indicate that the proposed approach is potential to be a promising damage detection technique.

关键词： nonlinear damage detection time series analysis linear autoregressive moving average model vector space cosine similarity classification algorithms

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A Digital Analysis of the "Digitally-Derived Geometric Design" of the Front Wall of St. Paul's Church in Macao-A Study on the Architecture and City of Macao, No. 1-

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JOURNAL OF ASIAN ARCHITECTURE AND BUILDING engineering 2018年第2期17卷 159-165页

作者： Tang, Jian Jinan Univ Minist Educ Peoples Republ China Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China

With reference to related historical archives and literature, this study conducted research into the history, the designer and the design dimensions of St. Paul's Church in Macao. The remaining drawing of the facade merely reflects the correlation deduction of each controlling point in its geometric drawing. Through digital analysis, this study has further obtained the "digitally-derived geometric design"relations of the five-layer elevation design drawing and number-rounding adjustment of the constructing dimensions: the application of the law of equal-partition in the horizontal direction, the application of the law of upward successive-subtraction in stratification in the vertical direction, and the complicated combination of golden-rectangle controlling designs. The latter two applications are key geometrical features of Baroque Architecture.

关键词： St. Paul's Church facade geometric drawing the law of upward successive-subtraction in stratification the golden ratio

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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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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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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

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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