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Sound insulation performance of plates with interconnected distributed piezoelectric patches

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Chinese Journal of Aeronautics 2017年第1期30卷 99-108页

作者： Yi Kaijun Li Lin Mohamed Ichchou Manuel Collet laboratory of tribology and systems dynamics Ecole Centrale de Lyon School of Energy and Power Engineering Beihang University

This paper deals with the sound insulation performance of a thin plate with interconnected distributed piezoelectric patches. Piezoelectric patches are periodically bonded on the surfaces of the plate in a collocated fashion, and are interconnected via an inductive circuit network. This piezoelectric system is termed as piezo-electromechanical（PEM） plate in the *** methods are involved under a sub-wavelength assumption to analytically develop the dynamical equations for the PEM plate. The dispersion relationships and energy densities of the wave modes propagating in the PEM plate are studied; the sub-wavelength assumption is verified for the simulations in this paper. The coincidence frequency of the PEM plate is researched, and results show that the coincidence frequency of the PEM plate will disappear at certain circumstances; mathematical and physical explanations are made for this phenomenon. The disappearance of the coincidence frequency is used to optimize the value of inductance, for the purpose of improving the sound transmission loss of the PEM plate.

关键词： Coincidence frequency Homogenization Piezoelectric material Sound transmission loss Wave propagation

Application of Fractal Contact Model in Dynamic Performance Analysis of Gas Face Seals

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Chinese Journal of Mechanical Engineering 2018年第2期31卷 137-147页

作者： Song-Tao Hu Wei-Feng Huang Xiang-Feng Liu Yu-Ming Wang State Key laboratory of tribology Tsinghua University State Key laboratory of Mechanical system and Vibration Shanghai Jiao Tong University

Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face?contacting conditions. Structure?Function method is adopted to handle the surface profiles of typical carbon?graphite rings, proving the fractal con?tact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar?Bhushan(MB) fractal model and the Chang?Etsion?Bogy(CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D(nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.

关键词： Fractal theory Asperity contact Gas face seal Dynamic performance

Investigation of dynamics of discrete framed structures by a numerical wave-based method and an analytical homogenization approach

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Chinese Journal of Aeronautics 2017年第1期30卷 66-74页

作者： Zhou Changwei Sun Xiangkun Mohamed Ichchou Abdel-Malek Zine Jean-Pierre Lainé Stephane Hans Claude Boutin laboratory of tribology and systems dynamics Ecole Centrale de Lyon Ecully 69134 France Institut Camille Jordan Ecole Centrale de Lyon Ecully 69134 France laboratory of tribology and systems dynamics Ecole Nationale des Travaux Publics de l'Etat Vaulx-en-Velinx 69518 France

In this article, the analytical homogenization method of periodic discrete media（HPDM）and the numerical condensed wave finite element method（CWFEM） are employed to study the longitudinal and transverse vibrations of framed structures. The valid frequency range of the HPDM is re-evaluated using the wave propagation feature identified by the CWFEM. The relative error of the wavenumber by the HPDM compared to that by the CWFEM is illustrated in functions of frequency and scale ratio. A parametric study on the thickness of the structure is carried out where the dispersion relation and the relative error are given for three different thicknesses. The dynamics of a finite structure such as natural frequency and forced response are also investigated using the HPDM and the CWFEM.

关键词： Framed structures Homogenization method Periodic structures Wave finite element method Wave propagation

Two material removal modes in chemical mechanical polishing:mechanical plowing *** bonding

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Friction 2024年第5期12卷 897-905页

作者： Yuan WU Liang JIANG Wenhui LI Jiaxin ZHENG Yushan CHEN Linmao QIAN tribology Research Institute State Key Laboratory of Rail Transit Vehicle SystemSouthwest Jiaotong UniversityChengdu610031China

With the rapid development of semiconductors,the number of materials needed to be polished sharply *** material properties vary significantly,posing challenges to chemical mechanical polishing(CMP).Accordingly,the study aimed to classify the material removal *** on the CMP and atomic force microscopy results,the six representative metals can be preliminarily classified into two groups,presumably due to different material removal *** the tribology perspective,the first group of Cu,Co,and Ni may mainly rely on the mechanical plowing *** adding H_(2)O_(2),corrosion can be first enhanced and then suppressed,affecting the surface mechanical ***,the material removal rate(MRR)and the surface roughness increase and *** comparison,the second group of Ta,Ru,and Ti may primarily depend on the chemical bonding *** H_(2)O_(2)can promote oxidation,increasing interfacial chemical ***,the MRR increases,and the surface roughness decreases and levels *** addition,CMP can be regulated by tuning the synergistic effect of oxidation,complexation,and dissolution for mechanical plowing,while tuning the synergistic effect of oxidation and ionic strength for chemical *** findings provide mechanistic insight into the material removal mechanism in CMP.

关键词： Chemical mechanical polishing corrosion wear material removal mode mechanical plowing chemical bonding

The spreading behaviour of perfluoropolyether droplets on solid surfaces

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Chinese Physics B 2008年第3期17卷 1094-1100页

作者：郭晓燕李欣胡元中王慧 State Key laboratory of tribology Tsinghua University

The spread of perfluoropolyether （PFPE） droplets on solid surfaces has been measured from the top-down view through a microscope system. Effects of substrates, molecular weight and end-group functionality on spreading of the PFPE droplets have been studied experimentally and the results were compared with those by molecular dynamics （MD） simulations. Silicon wafer and diamond-like carbon （DLC） substrates were used to study the effect of substrates on spreading. Two types of PFPE, Z-dol and Z-tetraol, with the same chain structure and various molecular weights （2000 and 4000 g/mol） were employed in experiments. Effect of molecular weight has been investigated through comparing the spreading of Z-dol 2000 and Z-dol 4000, and it is found that the increase of molecular weight will decrease the mobility of PFPE. Comparison between spreading of Z-dol and Z-tetraol of the same molecular weight proved that functional end group plays a significant role on the spreading of PFPE, which confirmed the MD simulation results.

关键词： perfluoropolyether spreading thin lubricant films hard disk driver

Analysis of the Caratheodory's Theorem on Dynamical system Trajectories Under Numerical Uncertainty

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IEEE/CAA Journal of Automatica Sinica 2018年第4期5卷 787-793页

作者： Pavel Osinenko Grigory Devadze Stefan Streif Automatic Control and system dynamics laboratory Technische Universitat Chemnitz09107 ChemnitzGermany IEEE

The current work proposes a new and constructive proof for the Caratheodory's theorem on existence and uniqueness of trajectories of dynamical systems. The key concern is the numerical uncertainty, i.e., the discrepancy between mathematical proofs, algorithms, and their implementations, which may affect the correct functioning of a control system. Due to growing demands on security and compliance with specifications,correctness of the control system functioning is becoming ever more important. Since in both dynamical systems and many control design approaches, one of the central notions is the system trajectory, it is important to address existence and uniqueness of system trajectories in a way which incorporates numerical uncertainty. Constructive analysis is a particular approach to formalizing numerical uncertainty and is used as the basis of the current work. The major difficulties of guaranteeing existence and uniqueness of system trajectories arise in the case of systems and controllers which possess discontinuities in time,since classical solutions to initial value problems do not *** issue is addressed in Caratheodory's theorem. A particular constructive variant of the theorem is proven which covers a large class of problems found in practice.

关键词： Constructive analysis Caratheodory’s theorem dynamical systems

A Novel Model for Describing Rail Weld Irregularities and Predicting Wheel-Rail Forces Using a Machine Learning Approach

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Computer Modeling in Engineering & Sciences 2025年第1期142卷 555-577页

作者： Linlin Sun Zihui Wang Shukun Cui Ziquan Yan Weiping Hu Qingchun Meng State Key laboratory of High-Speed Railway Track system China Academy of Railway Sciences Corporation LimitedBeijing100081China Railway Engineering Research Institute China Academy of Railway Sciences Corporation LimitedBeijing100081China School of Aeronautic Science and Engineering Beihang UniversityBeijing100191China

Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed *** can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and *** researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry ***,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric *** this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to *** vertical dynamic forces in the time and frequency domains were compared under different running *** forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed ***,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is *** results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the *** ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.

关键词： Rail weld irregularity high-speed railway vehicle-track coupled dynamics wheel/rail dynamic vertical force artificial neural networks

Wafer back pressure control and optimization in the CMP process

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Journal of Semiconductors 2011年第12期32卷 153-160页

作者：门延武张辉周凯叶佩青 State Key laboratory of tribology Tsinghua University

Chemical mechanical polishing （CMP） is the most effective wafer global planarization technology. The CMP polishing head is one of the most important components, and zone back pressure control technology is used to design a new generation of polishing head. The quality of polishing not only depends on slurry, but also depends on the precise control of polishing pressures. During the CMP polishing process, the set pressure of each chamber is usually not the same and the presence of a flexible elastic diaphragm causes coupling effects. Because of the coupling effects, the identification of multi-chambers and pressure controls becomes complicated. To solve the coupling problem, this paper presents a new method of multi-chamber decoupled control, and then system identification and control parameter tuning are carried out based on the method. Finally, experiments of multi- chambers inflated at the same time are performed. The experimental results show that the presented decoupling control method is feasible and correct.

关键词： CMP zone pressure control technology decoupling control

Discriminative Features of Abnormities in a Spiral Groove Gas Face Seal Based on Dynamic Model Considering Contact

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Chinese Journal of Mechanical Engineering 2022年第2期35卷 135-149页

作者： Yuan Yin Weifeng Huang Decai Li Songtao Hu Xiangfeng Liu Ying Liu State Key laboratory of tribology Tsinghua UniversityBeijing 100084China State Key laboratory of Mechanical system and Vibration Shanghai Jiao Tong UniversityShanghai 200240China

It is a difficult task to root the cause of the failure of a gas face seal because different causes may result in similar *** the work being presented,the discrimination of multiple types of abnormities in a spiral groove gas face seal is studied.A dynamic model is employed to analyze groups of cases in order to uncover the dynamic behaviors when the face contact is induced by different mixtures of abnormities,whose discriminative features when motion and contact are monitored are studied and uncovered.A circumferential-pattern-related oscillation phenomenon is discovered,which is extracted from contact information and implies the relative magnitude of the moment on stator and the rotor *** experimental observation shows consistent *** means that the grooves(or other circumferential patterns)generate useful informative features for *** results provide guidance for designing a monitored gas face seal system.

关键词： Gas face seals dynamics tribology Nonlinear system