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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

A frequency domain reliability analysis method for electromagnetic problems based on univariate dimension reduction method

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Science China(Technological Sciences) 2019年第5期62卷 787-798页

作者： PING MengHao HAN Xu JIANG Chao ZHONG JianFeng XIAO XiaoYa HUANG ZhiLiang WANG ZhongHua State key laboratory of advanced design and Manufacturing for vehicle body College of Mechanical and Vehicle EngineeringHunan University Nanjing Research Institute of Electronics technology

In this paper, a class of electromagnetic field frequency domain reliability problem is first defined. The frequency domain reliability refers to the probability that an electromagnetic performance indicator can meet the intended requirements within a specific frequency band, considering the uncertainty of structural parameters and frequency-variant electromagnetic *** then a frequency domain reliability analysis method based on univariate dimension reduction method is proposed, which provides an effective calculation tool for electromagnetic frequency domain reliability. In electromagnetic problems, performance indicators usually vary with frequency. The method firstly discretizes the frequency-variant performance indicator function into a series of frequency points' functions, and then transforms the frequency domain reliability problem into a series system reliability problem of discrete frequency points' functions. Secondly, the univariate dimension reduction method is introduced to solve the probability distribution functions and correlation coefficients of discrete frequency points' functions in the system. Finally, according to the above calculation results, the series system reliability can be solved to obtain the frequency domain reliability, and the cumulative distribution function of the performance indicator can also be obtained. In this study,Monte Carlo simulation is adopted to demonstrate the validity of the frequency domain reliability analysis method. Three examples are investigated to demonstrate the accuracy and efficiency of the proposed method.

关键词： electromagnetic field frequency domain reliability system reliability random process discretization univariate dimension reduction method

Deformation simulation of low-temperature high-speed extrusion for 6063 Al alloy

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Journal of Central South University 2010年第5期17卷 881-887页

作者：王孟君何钊武星星李彩文李光耀 key laboratory of Nonferrous Metal Materials Science and Engineering of Ministry of Education Central South University State key laboratory of advanced design and manufacture for vehicle body Hunan University

The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.

关键词： 6063 Al alloy hot deformation low-temperature high-speed extrusion constitutive equation numerical simulation

Additively manufactured fiber-reinforced composites:A review of mechanical behavior and opportunities

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Journal of Materials Science & technology 2022年第24期119卷 219-244页

作者： Jiahui Li Yvonne Durandet Xiaodong Huang Guangyong Sun Dong Ruan Department of Mechanical Engineering and Product design Engineering School of EngineeringSwinburne University of TechnologyHawthornVIC 3122Australia State key laboratory of advanced design and manufacture for vehicle body Hunan UniversityChangsha 410082China

Recent developments in additive manufacturing techniques have facilitated the fabrication of fiberreinforced composite *** this paper,the mechanical properties and deformation mechanisms of discontinuous and continuous fiber-reinforced composites fabricated by various additive manufacturing techniques are comprehensively *** effects of fiber type,orientation and weight/volume fraction,printing path,and stacking sequence on the mechanical properties of additively manufactured composites are *** addition,the applications of additively manufactured composites,the main challenges of the current additive manufacturing techniques,and recommendations for future work are also presented.

关键词： Additive manufacturing Discontinuous and continuous fiber-reinforced composites Mechanical properties Deformation mechanism Applications

Improved Differential Evolution with Shrinking Space Technique for Constrained Optimization

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Chinese Journal of Mechanical Engineering 2017年第3期30卷 553-565页

作者： Chunming FU Yadong XU Chao JIANG Xu HAN Zhiliang HUANG State key laboratory of advanced design and Manufacturing for vehicle body Hunan University School of Mechanical Engineering Nanjing University of Science and Technology

Most of the current evolutionary algorithms for constrained optimization algorithm are low computational efficiency. In order to improve efficiency, an improved differential evolution with shrinking space technique and adaptive trade-off model, named ATMDE, is proposed to solve constrained optimization problems. The proposed ATMDE algorithm employs an improved differential evolution as the search optimizer to generate new offspring individuals into evolutionary population. For the con- straints, the adaptive trade-off model as one of the most important constraint-handling techniques is employed to select better individuals to retain into the next population, which could effectively handle multiple constraints. Then the shrinking space technique is designed to shrink the search region according to feedback information in order to improve computational efficiency without losing accuracy. The improved DE algorithm introduces three different mutant strategies to generate different offspring into evo- lutionary population. Moreover, a new mutant strategy called ＂DE/rand/best/l＂ is constructed to generate new individuals according to the feasibility proportion ofcurrent population. Finally, the effectiveness of the pro- posed method is verified by a suite of benchmark functions and practical engineering problems. This research presents a constrained evolutionary algorithm with high efficiency and accuracy for constrained optimization problems.

关键词： Constrained optimization - Differentialevolution Adaptive trade-off model Shrinking spacetechnique

Elastic behavior of disclination dipole near nanotube with surface/interface effect

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Chinese Physics B 2014年第3期23卷 77-90页

作者：赵迎新曾鑫陈昌萍 State key laboratory of advanced design and Manufacturing for vehicle body Hunan University College of Civil Engineering and Architecture Xiamen University of Technology

In this paper, we present an analytical solution of the interaction of the nanotube （NT） with a wedge disclination dipole in nanotube-based composites. The corresponding boundary value problem is solved exactly by using complex potential functions. The explicit expression of the force exerted on disclination dipole is given by using the generalized Peach- Koehler formula. As a numerical illustration, both the equilibrium position and the stability of the disclination dipole are evaluated for different material combinations, relative thickness of an NT, surface/interface effects, and the features of the disclination dipole. The results show that as the thickness of the NT layer increases, the NT has a relatively major role in the force acting on the disclination dipole in the NT-based composite. The cooperative effect of surface/interface stresses and the NT becomes considerable as the increase of NT layer thickness. The equilibrium position may occur, even more than one, due to the influences of the surface/interface stress and the NT thickening. The influences of the surface/interface stresses and the thickness of the NT layer on the force are greatly dependent on the disclination angle.

关键词： nanotube-based composites disclination dipole nanotube thickness surface/interface effect

Experimental research on the mechanism of non-monotonic characteristic between curing temperature and mechanical behaviors of Kevlar/epoxy composite

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Science China(Technological Sciences) 2018年第7期61卷 1012-1020页

作者： LIU Li HU DeAn ZHANG YouMin HAN Xu State key laboratory of advanced design and Manufacturing for vehicle body Hunan University key laboratory of advanced design and Simulation technology for Special Equipments Ministry of Education Hunan University School of Mechanical Engineering Hebei University of Technology

An experimental procedure is conducted to investigate the mechanism of the non-monotonic characteristic between curing temperature and mechanical behaviors of the Kevlar/epoxy composite in macro and micro levels. Different specimens are fabricated at four different curing temperatures and tested with ±45° off-axis tensile loading on a universal test machine coupled with digital image correlation(DIC). Moreover, the environmental scanning electron microscope(SEM) was used to obtain the micrographs and reveal their mechanism. The tested results show that the tensile mechanical behaviors are sensitive to the curing temperature and the relationship is non-monotonic. Also, as the temperature increases, the thicknesses of the specimens are significantly enlarged. By analyzing the SEM micrographs of the matrix grooves in the damage zone and DIC strain contours, it is concluded that the non-monotonic relationship is dominated by the properties of the Kevlar/epoxy interfaces and deformation of the distorted fibers.

关键词： Kevlar/epoxy composite mechanical behavior digital image correlation SEM micrograph non-monotonic character-istic distorted fiber

Suppression of grazing-induced instability in single degree-of-freedom impact oscillators

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Applied Mathematics and Mechanics(English Edition) 2019年第1期40卷 97-110页

作者： Shan YIN Guilin WEN Xin WU School of Mechanical and Electric Engineering Guangzhou University State key laboratory of advanced design and manufacture for vehicle body Hunan University School of Mechanical Engineering Hunan Institute of Engineering

As a typical non-smooth bifurcation, grazing bifurcation can induce instability of elementary near-grazing impact periodic motion in impact oscillators. In this paper,the stability for near-grazing period-one impact motion to suppress grazing-induced instabilities is analyzed, based on which, a control strategy is proposed. The commonly-used leading order zero time discontinuity mapping is extended to a higher order one to aid the perturbation analysis of the characteristic equation. It is shown that the degenerate grazing bifurcation can eliminate the singular term in the characteristic equation, leading to bounded eigenvalues. Based on such a precondition, the bounded eigenvalues are further restricted inside the unit circle, and a continuous transition between non-impact and controlled impact motion is observed. One discrete feedback controller that changes the velocity of the oscillator based on the selected Poincar′e sections is adopted to demonstrate the control procedure.

关键词： grazing-induced instability higher order discontinuity mapping eigenvalue perturbation degenerate grazing bifurcation

BRAIN INJURY BIOMECHANICS IN REAL WORLD vehicle ACCIDENT USING MATHEMATICAL MODELS

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Chinese Journal of Mechanical Engineering 2008年第4期21卷 81-86页

作者： YANG Jikuang XU Wei OTTE Dietmar State key laboratory of advanced design and manufacture for vehicle body Hunan University Changsha 410082 China Accident Research Unit Medical University HannoverHannover D-30623 Germany

This paper aims at investigating brain injury mechanisms and predicting head injuries in real world accidents. For this purpose, a 3D human head finite element model （HBM-head） was developed based on head-brain anatomy. The HBM head model was validated with two experimental tests. Then the head finite element（FE） model and a multi-body system （MBS） model were used to carry out reconstructions of real world vehicle-pedestrian accidents and brain injuries. The MBS models were used for calculating the head impact conditions in vehicle impacts. The HBM-head model was used for calculating the injury related physical parameters, such as intracranial pressure, stress, and strain. The calculated intracranial pressure and strain distribution were correlated with the injury outcomes observed from accidents. It is shown that this model can predict the intracranial biomechanical response and calculate the injury related physical parameters. The head FE model has good biofidelity and will be a valuable tool for the study of injury mechanisms and the tolerance level of the brain.

关键词： Skull-brain FE model Head injury Real-world vehicle accident

A meshfree-based local Galerkin method with condensation of degree of freedom for elastic dynamic analysis

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Acta Mechanica Sinica 2014年第1期30卷 92-99页

作者： De-An Hu Yi-Gang Wang Yang-Yang Li Xu Han Yuan-Tong Gu State key laboratory of advanced design and Manufacturing for vehicle body Hunan University School of Chemistry Physics and Mechanical EngineeringQueensland University of Technology

Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form for elastic dy- namic analysis. In the present method, scattered nodes with- out connectivity are divided into several subsets by cells with arbitrary shape. Local discrete equation is established over each cell by using moving Kriging interpolation, in which the nodes that located in the cell are used for approxima- tion. Then local discrete equations can be simplified by con- densation of degree of freedom, which transfers equations of inner nodes to equations of boundary nodes based on cells. The global dynamic system equations are obtained by as- sembling all local discrete equations and are solved by using the standard implicit Newmark＇s time integration scheme. In the scheme of present method, the calculation of each cell is carried out by meshfree method, and local search is imple- mented in interpolation. Numerical examples show that the present method has high computational efficiency and good accuracy in solving elastic dynamic problems.

关键词： Meshfree method Local Galerkin method Moving Kriging interpolation - Condensation of degree of freedom Computational efficiency