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Multi-parameter Sensitivity Analysis and Application Research in the Robust Optimization design for Complex Nonlinear System

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Chinese Journal of Mechanical Engineering 2015年第1期28卷 55-62页

作者： MA Tao ZHANG Weigang ZHANG Yang TANG Ting State key laboratory of advanced design and manufacturing for vehicle body Hunan University

The current research of complex nonlinear system robust optimization mainly focuses on the features of design parameters, such as probability density functions, boundary conditions, etc. After parameters study, high-dimensional curve or robust control design is used to find an accurate robust solution. However, there may exist complex interaction between parameters and practical engineering system. With the increase of the number of parameters, it is getting hard to determine high-dimensional curves and robust control methods, thus it＇s difficult to get the robust design solutions. In this paper, a method of global sensitivity analysis based on divided variables in groups is proposed. By making relevant variables in one group and keeping each other independent among sets of variables, global sensitivity analysis is conducted in grouped variables and the importance of parameters is evaluated by calculating the contribution value of each parameter to the total variance of system response. By ranking the importance of input parameters, relatively important parameters are chosen to conduct robust design analysis of the system. By applying this method to the robust optimization design of a real complex nonlinear system-a vehicle occupant restraint system with multi-parameter, good solution is gained and the response variance of the objective function is reduced to 0.01, which indicates that the robustness of the occupant restraint system is improved in a great degree and the method is effective and valuable for the robust design of complex nonlinear system. This research proposes a new method which can be used to obtain solutions for complex nonlinear system robust design.

关键词： complex nonlinear system global sensitivity analysis robust optimization design grouped variables

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Gearbox Fault Diagnosis using Adaptive Zero Phase Time-varying Filter Based on Multi-scale Chirplet Sparse Signal Decomposition

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Chinese Journal of Mechanical Engineering 2013年第4期26卷 831-838页

作者： WU Chunyan LIU Jian PENG Fuqiang YU Dejie LI Rong State key laboratory of advanced design and manufacturing for vehicle body Hunan University

When used for separating multi-component non-stationary signals, the adaptive time-varying filter(ATF) based on multi-scale chirplet sparse signal decomposition(MCSSD) generates phase shift and signal distortion. To overcome this drawback, the zero phase filter is introduced to the mentioned filter, and a fault diagnosis method for speed-changing gearbox is proposed. Firstly, the gear meshing frequency of each gearbox is estimated by chirplet path pursuit. Then, according to the estimated gear meshing frequencies, an adaptive zero phase time-varying filter(AZPTF) is designed to filter the original signal. Finally, the basis for fault diagnosis is acquired by the envelope order analysis to the filtered signal. The signal consisting of two time-varying amplitude modulation and frequency modulation(AM-FM) signals is respectively analyzed by ATF and AZPTF based on MCSSD. The simulation results show the variances between the original signals and the filtered signals yielded by AZPTF based on MCSSD are 13.67 and 41.14, which are far less than variances (323.45 and 482.86) between the original signals and the filtered signals obtained by ATF based on MCSSD. The experiment results on the vibration signals of gearboxes indicate that the vibration signals of the two speed-changing gearboxes installed on one foundation bed can be separated by AZPTF effectively. Based on the demodulation information of the vibration signal of each gearbox, the fault diagnosis can be implemented. Both simulation and experiment examples prove that the proposed filter can extract a mono-component time-varying AM-FM signal from the multi-component time-varying AM-FM signal without distortion.

关键词： zero phase time-varying filter multi-scale chirplet sparse signal decomposition speed-changing gearbox fault diagnosis

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An element decomposition method with variance strain stabilization

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Science China(Physics,Mechanics & Astronomy) 2015年第7期58卷 57-66页

作者： CUI XiangYang LIU PengWei LI GuangYao State key laboratory of advanced design and manufacturing for vehicle body Hunan University

An element decomposition method with variance strain stabilization(EDM-VSS) is proposed. In the present EDM-VSS, the quadrilateral element is first divided into four sub-triangular cells, and the local strains in sub-triangular cells are obtained using linear interpolation function. For each quadrilateral element, the strain of the whole quadrilateral is the weighted average value of the local strains, which means only one integration point is adopted to construct the stiffness matrix. The stabilization item of the stiffness matrix is constructed by variance of the local strains, which can eliminate the instability of the one-point integration formulation and largely increase the accuracy of the element. Compared with conventional full integration quadrilateral element, the EDM-VSS achieves more accurate results and expends much lower computational cost. More importantly, as no mapping or coordinate transformation is involved in the present EDM-VSS, the restriction on the conventional quadrilateral elements can be removed and problem domain can be discretized in more flexible ways. To verify the accuracy and stability of the present formulation, a number of numerical examples are studied to demonstrate the efficiency of the present EDM-VSS.

关键词： numerical methods element decomposition method variance strain stabilization one-point integration quadrilateralelement

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A New Understanding of the Dielectric Breakdown Theory from the Study of Plasma Electrolytic Oxidation of Carbon Steel

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材料导报 2019年第1期33卷 3-4页

作者：陈鼎 State key laboratory of advanced design and manufacturing for vehicle body Hunan University

Schematic illustration of the PEO of the carbon steel in 8 g·L^-1 NaAlO2+2 g·L^-1 NaH 2PO4:(a)the sample before the application of anodic current,(b)the moment after the application of anodic current,(c)the deposition of an aluminum phosphates or AAP layer on the steel surface,(d)the initiation of plasma discharges through the breakdown of the dielectric layer,(e)stable discharges at later stage of PEO.

关键词： New Understanding Dielectric Breakdown Theory Plasma Electrolytic

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Non-random vibration analysis for general viscous damping systems

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Chinese Journal of Aeronautics 2019年第12期32卷 2655-2666页

作者： Chao JIANG Long LIU Jinwu LI Bingyu NI State key laboratory of advanced design and manufacturing for vehicle body College of Mechanical and Vehicle Engineering Hunan University

The authors recently developed a kind of non-probabilistic analysis method, named as‘non-random vibration analysis’, to deal with the important random vibration problems, in which the excitation and response are both given in the form of interval process rather than stochastic process. Since it has some attractive advantages such as easy to understand, convenient to use and small dependence on samples, the non-random vibration analysis method is expected to be an effective supplement of the traditional random vibration theory. In this paper, we further extend the nonrandom vibration analysis into the general viscous damping system, and formulate a method to calculate the dynamic response bounds of a viscous damping vibration system under uncertain excitations. Firstly, the unit impulse response matrix of the system is obtained by using a complex mode superposition method. Secondly, an analytic formulation of the system dynamic response middle point and radius under uncertain excitations is derived based on the Duhamel’s integral, and thus the upper and lower response bounds of the system can be obtained. Finally, two numerical examples are investigated to demonstrate the effectiveness of the proposed method.

关键词： Complex mode Dynamic response bounds Interval process Random vibration Viscous damping system

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Fretting instability characteristics for gear shaft shoulder

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Journal of Central South University 2014年第10期21卷 3746-3752页

作者：贾国海龚金科鄂加强蔡皓王曙辉 State key laboratory of advanced design and manufacturing for vehicle body (Hunan University)

In order to solve fretting instability problem of gear shaft shoulder due to torsional vibration in mechanical system, the mathematical model of fretting instability vibration of gear shaft shoulder was established by adopting the method of combining kinematics and tribology, and the numerical analysis was applied to the fretting instability mechanism of gear shaft shoulder by introducing the friction instability damping ratio. The numerical results show that the main factors causing the unstable and vibrating gear shaft shoulder are the large tightening torque and too large static friction coefficient. The reasonable values of the static friction coefficient, the amount of interference and tightening torque can effectively mitigate the fretting instability phenomenon of gear shaft shoulder. The experimental results verify that damping plays a significant role in eliminating the vibration of gear shaft control system.

关键词： gear shaft shoulder torsional vibration kinematics fretting friction instability damping ratio

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Interval arithmetic operations for uncertainty analysis with correlated interval variables

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Acta Mechanica Sinica 2016年第4期32卷 743-752页

作者： Chao Jiang Chun-Ming Fu Bing-Yu Ni Xu Han State key laboratory of advanced design and manufacturing for vehicle body College of Mechanical and Vehicle Engineering Hunan University

A new interval arithmetic method is proposed to solve interval functions with correlated intervals through which the overestimation problem existing in interval analysis could be significantly alleviated. The correlation between interval parameters is defined by the multidimensional parallelepiped model which is convenient to describe the correlative and independent interval variables in a unified framework. The original interval variables with correlation are transformed into the standard space without correlation,and then the relationship between the original variables and the standard interval variables is obtained. The expressions of four basic interval arithmetic operations, namely addition, subtraction, multiplication, and division, are given in the standard space. Finally, several numerical examples and a two-step bar are used to demonstrate the effectiveness of the proposed method.

关键词： operations uncertainty arithmetic correlative unified transformed considering convenient subtraction illustrated

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Dislocation stability in three-phase nanocomposites with imperfect interface

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Acta Mechanica Sinica 2014年第5期30卷 693-702页

作者： Ying-Xin Zhao You-Wen Liu Qi-Hong Fang State key laboratory of advanced design and manufacturing for vehicle body/College of Mechanical and vehicle Engineering Hunan University

Interface imperfection can significantly affect the mechanical properties and failure mechanisms as well as the strength and toughness of nanocomposites. The elastic behavior of a screw dislocation in nanoscale coating with imperfect interface is studied in the three-phase composite cylinder model. The interface between inner nanoin- homogeneity and intermediate coating is assumed as perfectly bonded. The bonding between intermediate coating and outer matrix is considered to be imperfect with the assumption that interface imperfection is uniform, and a linear spring model is adopted to describe the weakness of imperfect interface. The explicit expression for image force acting on dislocation is obtained by means of a complex variable method. The analytic results indicate that inner interface effect and outer interface imperfection, simultaneously taken into account, would influence greatly image force, equilibrium position and stability of dislocation, and various critical parameters that would change dislocation stability. The weaker interface is a very strong trap for glide dislocation and, thus, a more effective barrier for slip transmission.

关键词： Nanocomposites -Dislocation Imperfect inter- face - Interface effect Complex variable method

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Real-time lane departure warning system based on principal component analysis of grayscale distribution and risk evaluation model

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Journal of Central South University 2014年第4期21卷 1633-1642页

作者：张伟伟宋晓琳张桂香 State key laboratory of advanced design and manufacturing for vehicle body (Hunan University)

A technology for unintended lane departure warning was proposed. As crucial information, lane boundaries were detected based on principal component analysis of grayscale distribution in search bars of given number and then each search bar was tracked using Kalman filter between frames. The lane detection performance was evaluated and demonstrated in ways of receiver operating characteristic, dice similarity coefficient and real-time performance. For lane departure detection, a lane departure risk evaluation model based on lasting time and frequency was effectively executed on the ARM-based platform. Experimental results indicate that the algorithm generates satisfactory lane detection results under different traffic and lighting conditions, and the proposed warning mechanism sends effective warning signals, avoiding most false warning.

关键词： lane departure warning system lane detection lane tracking principal component analysis risk evaluation model ARM-based real-time system

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Theoretical and Experimental Study on the Performance of Hermetic Diaphragm Squeeze Film Dampers for Gas-Lubricated Bearings

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 151-169页

作者： Jianwei Wang Haoxi Zhang Shaocun Han Hang Li Peng Wang Kai Feng State key laboratory of advanced design and manufacturing for vehicle body Hunan UniversityChangsha 410082China

Low damping characteristics have always been a key sticking points in the development of gas *** application of squeeze film dampers can significantly improve the damping performance of gas lubricated *** paper proposed a novel hermetic diaphragm squeeze film damper(HDSFD)for oil-free turbomachinery supported by gas lubricated *** types of HDSFDs with symmetrical structure were proposed for good damping *** considering the compressibility of the damper fluid,based on hydraulic fluid mechanics theory,a dynamic model of HDSFDs under medium is proposed,which successfully reflects the frequency dependence of force *** on the dynamic model,the effects of damper fluid viscosity,bulk modulus of damper fluid,thickness of damper fluid film and plunger thickness on the dynamic stiffness and damping of HDSFDs were *** experimental test rig was assembled and series of experimental studies on HDSFDs were *** damper fluid transverse flow is added to the existing HDSFD concept,which aims to make the dynamic force coefficients independent of *** the force coefficient is still frequency dependent,the damping coefficient at high frequency excitation with damper fluid supply twice as that without damper fluid *** results serve as a benchmark for the calibration of analytical tools under development.

关键词： Hermetic diaphragm squeeze film damper Compressibility Dynamic model Experimental studies

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