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Fatigue crack propagation of new aluminum lithium alloy bonded with titanium alloy strap

Chinese Journal of Aeronautics 2013年第3期26卷 601-605页

作者： Sun Zhenqi Huang Minghui School of Mechanical and Electrical Engineering Central South University State Key Laboratory of High Performance Complex Manufacturing Central South University

A new type of aluminum lithium alloy （Al–Li alloy） Al–Li–S–4 was investigated by test in this paper. Alloy plate of 400 mm · 140 mm · 6 mm with single edge notch was made into samples bonded with Ti–6Al–4V alloy （Ti alloy） strap by FM 94 film adhesive after the surface was treated. Fatigue crack growth of samples was investigated under cyclic loading with stress ratio （R） of 0.1 and load amplitude constant. The results show that Al–Li alloy plate bonded with Ti alloy strap could retard fatigue crack propagation. Retardation effect is related with width and thickness of strap. Flaws have an observable effect on crack propagation direction.

关键词： Aluminum lithium alloy Bonding Fatigue crack growth Fatigue life stiffness ratio

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Elastic stability of shallow pin-ended parabolic arches subjected to step loads

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Journal of Central South University 2010年第1期17卷 156-162页

作者：陈耀冯健 Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education Southeast University Engineering Research Center for Prestress of Jiangsu Province Southeast University

Buckling could be induced when shallow arches were subjected to vertical step loads. In-plane static and dynamic buckling of shallow pin-ended parabolic arches with a horizontal cable was investigated. Based on the equations of motion derived from Hamilton's principle, nonlinear equilibrium equations and static buckling equilibrium equations were deduced. Through the pseudo-static analysis, approximate solutions to the lower and upper dynamic buckling loads under step loads were obtained, for shallow parabolic arches. The results show that dynamic buckling and snap-through buckling are impossible when modified slenderness ratio λλs, where λc and λs denote critical slenderness ratios of bucking and snap-through buckling, respectively; effects of the stiffness of the horizontal cable on the dynamic buckling are significant; and the dynamic buckling loads under a equivalent central concentrated step load are lower than the loads under a distributed load appreciably.

关键词： shallow parabolic arch step load dynamic buckling modified slenderness ratio stiffness ratio

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Catastrophic destabilization of tunnel under rocks slipping in faultage

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Journal of Coal Science & Engineering(China) 2008年第2期14卷 205-208页

作者：刘海卿王学庆袁景 College of Civil Engineering and Architecture Liaoning Technical UniversityFuxin 123000China

The model of catastrophic destabilization of tunnel under rock slipping in fault zone based on catastrophic theory and the potential function of fault movement were pre- *** the basis of the results above,through Taylor series expansion of the equation of equilibrium surface,its standard form was *** show that catastrophic destabilization of tunnel will occur only when stiffness ratio between elastic sector and strain weakening sector of soft rocks was larger than or equal to *** the other hand, sliding behavior and evolution path of fault were directly affected by exogenous process, and it was a major extraneous factor which leads to catastrophic destabilization of tunnel. In the condition of system catastrophe could be generated,if external forces vary from smaller to larger,firstly,fault sticks or creeps,and secondly,when external force equal to or larger than critical value,fault turns to slip ***,if external forces vary from larger to smaller,fault smoothly slips firstly,when external force equal to or smaller than critical value,and fault turns to stick or creep suddenly.

关键词： destabilization tunnel soft interlayer cusp catastrophe stiffness ratio

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Nonlinear evolutionary mechanisms of instability of planar-slip slope:catastrophe,bifurcation,chaos and physical prediction

Nonlinear evolutionary mechanisms of instability of planar-s...

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中国科学院地质与地球物理研究所2006学术年会

作者： Jiu Jimmy Jiao Department of Earth Sciences The University of Hong KongPokfulam RoadHong KongPeople’s Republic of China

A cusp catastrophe model of landslides is presented and the necessary and sufficient conditions leading to landslides are *** sliding surface is assumed to be planar and is a combination of two media:medium 1 is elastic-brittle or strain-hardening and medium 2 is *** shear stress-strain constitutive model for the strain-softening medium is described by the Weibull’s distribution *** paper is a generalization and extension of the paper by Qin et al(2001b),in which the shear stress-strain constitutive model for medium 2 was described by a negative exponent distribution,a special case of the Weibull’s distribution *** is found that the instability of the slope relies mainly on both the stiffness ratio of the media and the homogeneity index and that a new role of water is to enlarge the material homogeneity or brittleness and hence to reduce the stiffness ratio.A nonlinear dynamical model(also called a physical forecasting model),which is derived by considering the time-dependent behavior of the strain-softening medium,is used to study the time prediction of *** algorithm of inversion on the nonlinear dynamical model is suggested for seeking the precursory abnormality and abstracting mechanical parameters from the observed series of a landslide.A case study of the Jimingsi landslide is conducted and its nonlinear dynamical model is established from the observation series using the suggested model and algorithm of *** is found that the catastrophic characteristic index |D| shows a quick rise till reaching an extremely high peak value after the slope evolves into the tertiary creep,and subsequently approaches a zero value prior to instability,which can be regarded as an important precursory abnormality *** taking into account the evolutionary characteristic of the slope being in the secondary creep,a simplified nonlinear dynamical model is proposed for studying the properties of bifurcation and *** is shown t

关键词： Cusp catastrophe Instability stiffness ratio Homogeneity index Chaos Bifurcation Physical prediction

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Instability Leading to Rockbursts and Nonlinear Evolutionary Mechanisms for Coal-pillar-and-roof System

Instability Leading to Rockbursts and Nonlinear Evolutionary...

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中国科学院地质与地球物理研究所2006学术年会

作者： Jiu Jimmy Jiao Department of Earth Sciences The University of Hong KongPokfulam RoadHong KongPeople’s Republic of China

This paper studies the unstable mechanisms of the mechanical system that is composed of the stiff hosts(roof and floor) and the coal pillar using catastrophe *** is assumed that the roof is an elastic beam and the coal pillar is a strain-softening medium which can be described by the Weibull’s distribution theory of *** is found that the instability leading to rockburst depends mainly on the system’s stiffness ratio k,which is defined as the ratio of the flexural stiffness of the beam to the absolute value of the stiffness at the turning point of the constitutive curve of the coal pillar,and the homogeneity index m or shape parameter of the Weibull’s distribution of the coal pillar.A nonlinear dynamical model,which is derived by considering the time-dependent property of the coal pillar,is used to study the physical prediction of rockbursts. An algorithm of inversion on the nonlinear dynamical model is suggested for seeking the precursory abnormality from the observed series of roof settlement.A case study of the Muchengjian coal mine is conducted and its nonlinear dynamical model is established from the observation series using the algorithm of *** important finding is that the catastrophic characteristic index D(*** bifurcation set of the algorithm of inversion) drastically increases to a high peak value and then quickly drops close to *** the viewpoint of damage mechanics of coal pillar,a dynamical model of acoustic emission(AE) is established for modeling the AE activities in the evolutionary process of the *** is revealed that the values of m and the evolutionary path(D=0 or D≠0) of the system have a great impact on the AE activity patterns and characters.

关键词： Cusp catastrophe instability stiffness ratio nonlinear physical prediction acoustic emission

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Acoustics ＆ Mechanics in Sandwich Fuselages

Acoustics ＆ Mechanics in Sandwich Fuselages

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第十三届国际复合材料会议

作者： L.A.Krakers M.J.L.vanTooren A.Beukers Technical University Delft Faculty of Aerospace Engineering Kluyverweg 1 PO Box 5058 2629 HS Delft Netherlands Technical University Delft Faculty of Aerospace Engineering Kluyverweg 1 PO Box 5058 2629 HS Delft Netherlands Technical University Delft Faculty of Aerospace Engineering Kluyverweg 1 PO Box 5058 2629 HS Delft Netherlands

＜正＞Nowadays fuselages of passenger aircraft are manufactured according to the conventional stiffened skin concept;a thin load carrying skin stiffened with frames and stringers. A new structural concept, which already has been applied successfully in small aircraft like the Beech Starship, the Extra 400 and glider planes, is the sandwich concept. A sandwich skin consists out of layers. The outer layers are called facings and are generally thin and of high density. These facings are supposed to resist most of the edgewise loads and flat-wise bending moments. The inner layer, called the core, is generally rather thick and of low density. The

关键词： stiffness ratio design requirements design strategies

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