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Journal of Materials Science & Technology 2002年第3期18卷 257-260页

作者： Guozheng KANGDepartment of Applied Mechanics and Engineering, southwest jiaotong university, chengdu 610031, ChinaChuan YANG and Jixi ZHANGDepartment of Materials Engineering, southwest jiaotong university, chengdu 610031, China [ Manuscript received Janu Dept. of Appl. Mech. and Eng. Southwest Jiaotong Univ. Chengdu 610031 China

Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of AI2O3 short fiber reinforced AI-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally, the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideration of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300℃) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.

关键词： Fracture A12O3 Al-Mg alloy Composite

MOTION TYPES AND CHAOS OF MULTI-BODY SYSTEMS VIBRATING WITH IMPACTS

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Acta Mechanica Sinica 1991年第4期7卷 369-375页

作者： Shu Zhongzhou southwest jiaotong university,chengdu 610031,China southwest jiaotong university Chengdu China

In this paper,the limit sets theory for an autonomous dynamical system is generalized to a multi-body system vibrating with *** discover that if every motion of the system is bounded,it has only four different types:periodic motion 7 t,non-periodic recurrent motion γ2,and non-Poisson stable mo- tions γ3 and γ4 approaching γ1 and γ2, respectively.γ2 is the source of *** is very interesting that cha- otic motions seem stochastic but possess the character of *** way of example,we discuss chaotic motions of a small ball bouncing vertically on a massive vibrating *** result obtained by us is different from that obtained by Holmes.

关键词： multi-body impact vibrations recurrent motion chaos

Cracking Behaviour of Al_2O_3 Short Fibre/Al-5.5Zn Composite in TEM

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Journal of Materials Science & Technology 1997年第3期13卷 235-237页

作者： Xiyan ZHANG Tianxin TAN Wenyi PENG and Qing GAO (southwest jiaotong university, chengdu 610031, China) southwest jiaotong university Chengdu 610031 China

The micromechanical behaviour of Al2O3 short fibre reinforced Al-5.5Zn matrix composite has been in-situ studied by using TEM. The results show that in the composite the nucleation and propagation of cracks take place mainly in the matrix, as well as in the region near the fibre/matrix interface. It has been also observed that the microcracks can close during *** the fracture property can be characterized by crack open displacement (COD). The cracking characteristic may result from the large strength difference between the matrix and fibre.

关键词： Cracking Behaviour of Al2O3 Short Fibre/Al-5.5Zn Composite in TEM Al Zn

ELASTIC-PLASTIC FINITE ELEMENT ANALYSIS OF THREE-DIMENSIONAL CONTACT-IMPACT AT RAIL JOINT

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Chinese Journal of Mechanical Engineering 2003年第4期16卷 411-416页

作者： Wen ZefengJin XuesongZhang WeihuaNational Traction Power Laboratory,southwest jiaotong university,chengdu 610031, China southwest jiaotong university National Traction Power Laboratory Chengdu 610031

Using the finite element code ANSYS/LS-DYNA, a dynamic finite element modelwith an elastic-linear-kinematic-hardening plastic material is established to analyzeelastic-plastic stresses in the railhead in the impact process of wheel and rail occurring at thegap of rail joint. The model is based on the discrete elastic support condition of the rails, whichis suitable for the actual situation of wheel/track rolling contact. In the analysis the influencesof axle load, yield stress and tangent modulus of rail material on the stresses and strains areinvestigated in detail. The distribution of stresses and strains in the jointed railhead are *** is found that the axle load, yield stress and tangent modulus of rail material greatly affect thestresses and strains in the railhead during impacting. The study provides a reliable method anduseful datum for the further research on fatigue and wear of railhead and improving the rail jointmode.

关键词： Wheel/rail Rail joint Elastic-plastic Contact-impact Finite elementmethod

STUDY ON DYNAMIC CURVING BEHAVIOR OF TILTING PASSENGER CARS

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Chinese Journal of Mechanical Engineering 2002年第4期15卷 360-365,371页

作者： Liu Hongyou Zeng Jing National Traction Power Laboratory, southwest jiaotong university, chengdu 610031, China National Traction Power Laboratory Southwest Jiaotong University Chengdu 610031 China

By using tilting carbodies, train can negotiate at a higher speed withoutreducing the passenger's ride quality. This is a good method to allow a significant increase inspeed at existing track to improve the railway transportation capability, and to enhance thecompetition ability of railways with other transportation systems. With the increase of the curvenegotiation speed, the wheel-rail lateral forces and wheel-rail wear of the tilting train willincrease. The self-steering radial bogie is an effective way to solve the problem. The dynamic modelof the tilting passenger car with self-steering bogies is established in detail, and the curvingperformance of the car is investigated.

关键词： tilting passenger car self-steering bogie dynamic curving behavior wheel-rail interaction

Tensile Elastic Modulus, Strength and Fracture of δ-Al_2O_(3f)/Al Alloy Composites

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Journal of Materials Science & Technology 2000年第5期16卷 475-480页

作者： GuoZheng KANG+, Qing GAO and Jixi ZHANG (Department of Applied Mechanics and Engineering, southwest jiaotong university, chengdu 610031, China) Department of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China

Based on the experimental and theoretical analysis, the tensile elastic modulus, strength and fracture characteristics of squeeze casting δ-Al2O3/Al alloy composites were studied. The fracture characteristics of composites were observed by SEM. The elastic modulus was predicted by the finite element method based on the energy equivalence principle, and the strength was predicted by the statistical integration average method using the maximum energy criterion of composite strength. In the prediction, the distribution density functions of the fiber's. orientation and length were considered. These functions were gained by experimental measurement. It is shown that the predicted results are in agreement with the experimental values well and the microstructure feature of composites controls the fracture characteristics.

关键词： Tensile Elastic Modulus Al2O

Semantic theory of finite lattice-valued propositional logic

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Science China(Information Sciences) 2010年第10期53卷 2022-2031页

作者： PAN XiaoDong 1,2 & XU Yang 2 1 School of Maths, southwest jiaotong university, chengdu 610031, China 2 Intelligent Control Development Center, southwest jiaotong university, chengdu 610031, China School of Maths Southwest Jiaotong University Chengdu China Intelligent Control Development Center Southwest Jiaotong University Chengdu China

Based on the methodology of Pavelka’s fuzzy propositional logic, in this paper, by combining L-fuzzy set and classical two-value propositional logic theory, a kind of graded semantic theory in lattice-valued propositional logic based on finite lattice implication algebras is established. The notions of L-tautology and L-contradiction are introduced, and several theorems about the relations among different kinds of L-tautologies are given. From the viewpoint of uncertainty reasoning, the notion of satisfiability with certain level for a set of formulas is also defined. On this basis, the semantic consequence operation concerning a set of formulas is proposed, and the properties of semantic consequence operation and the consistency of fuzzy information are discussed.

关键词： lattice-valued propositional logic semantic theory L-tautology consistency lattice implication algebra

Experimental study of CT test on the failure of acrylate spray-applied waterproof layer in the groundwater environment

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Science China(Technological Sciences) 2010年第2期53卷 512-518页

作者： YANG QiXin, XU Peng & ZHENG ShangFeng 1 School of Civil Engineering, southwest jiaotong university, chengdu 610031, China School of Civil Engineering Southwest Jiaotong University

In this study the computerized tomography (CT) was first used to quantitatively analyze the failure of acrylate spray-applied waterproof membrane in the groundwater environment. The results of the CT tests show that it is feasible to use the CT to quantitatively analyze the failure of the waterproof membrane and the CT method has the advantages of speediness and accuracy that can eliminate the fussy operation process in routine tests. The main conclusions summarized from the study are as follows. First, there are two combined-indexes that can be used to decide the failure of the spray-on waterproof layer: one is that the reduced percentage of the CT number of the spray-on waterproof layer is less than 40.0% and the other is that the variance of the CT number decreases first and then increases. Second, the applicability for the spray-on waterproof layer in the groundwater environment is the SO 24-concentration ≤ 1%, the Cl-concentration ≤ 7.5% and the pH value ≤ 12.0 of the groundwater, respectively.

关键词： spray-on waterproof layer scan CT number failure groundwater environment

Centroid-based semi-fragile audio watermarking in hybrid domain

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Science China(Information Sciences) 2010年第3期53卷 619-633页

作者： WANG HongXia & FAN MingQuan School of Information Science and Technology, southwest jiaotong university, chengdu 610031, China School of Information Science and Technology Southwest Jiaotong University Chengdu China

Many previous (semi-) fragile audio watermarking schemes adopt binary images as watermarks, which reduce the security of watermarking systems. On the other hand, the content-based or feature-based second generation digital watermarking has limited applicability, and its partial feature points may be damaged by watermarking operations and various common signal processing. To overcome these problems, in this paper, a novel centroid-based semi-fragile audio watermarking scheme in hybrid domain is proposed. The theoretical lower limit of signal to noise ratio (SNR) for objective evaluation of the imperceptibility of watermarked audio signal is deduced, and the watermark embedding capacity and the tamper detection ability are theoretically analyzed. In the proposed scheme, first, the centroid of each audio frame is computed, then Hash function is performed on the obtained centroid to get the watermark, after that, the audio sub-band which carries centroid of audio frame is performed with discrete wavelet transform (DWT) and discrete cosine transform (DCT), and finally the encrypted watermark bits are embedded into the hybrid domain. Theoretical analysis and experimental results show that the proposed scheme is inaudible and applicable to different types of audio signals. Furthermore, its ability of tamper detection and tolerance against common signal processing operations are excellent. Comparing with the existing schemes, the proposed scheme can effectively authenticate the veracity and integrity of audio content, and greatly expand the applicability of the content-based audio watermarking scheme.

关键词： semi-fragile audio watermarking centroid inaudibility tamper detection

CYCLIC VISCOPLASTIC DESCRIPTION FOR THE MEAN STRAIN EFFECT

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Chinese Journal of Aeronautics 1995年第2期8卷 111-117页

作者： Yang Xianjie(southwest jiaotong university)chengdu,China,610031

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关键词： strain rate effects cyclic viscoplasticity constitutive equations