单脉冲载荷下伪弹性TiNi合金圆柱壳的响应特性分析

摘　要：以工程中广泛使用的基本构件－圆柱薄壳结构作为研究对象,利用改进的分离式Hopkinson压杆装置,对不同长径比的PE相变柱壳进行了较为系统的单脉冲轴向加载冲击实验。通过对相变柱壳高速CCD摄影及局部轴向应变的测试发现：不同长径比呈现出不同的屈曲模态。相变柱壳中的相变铰具有以下特点：①可回复性;②出现相变铰的时间尺度为微秒量级,与波动效应耦合在一起,变形呈现波动性;③多相变铰形成,包括周向相变铰,轴向相变铰,斜相变铰。     

Dynamic buckling of elastic-plastic complete spherical shells under step loading

The dynamic axisymmetrical behaviour of a perfect complete spherical shell made from a bilinear or work hardening material and subjected to a uniform external step pressure loading is investigated. A perturbation method of analysis leads to a Mathieu equation which gives the dynamic buckling pressure and associated mode for a complete spherical shell. The influence of the plastic parameter and damping on the dynamic buckling pressure and mode number are also discussed.     

Cracked asphalt pavement under traffic loading – A 3D finite element analysis

An asphalt pavement containing a transverse top-down crack is investigated under traffic loading using 3D finite element analysis. The stress intensity factors (SIFs) and the T-stress are calculated for different distances between the crack and the vehicle wheels. It is found that all the three Modes (I, II and III) are present in the crack deformation. The signs and magnitudes of K_I, K_II, K_III and T are significantly dependent on the location of the vehicle wheels with respect to the crack plane. The magnitude of T-stress is considerable, if compared to the stress intensity factors, when one of the wheels is very close to the crack plane.     

Dynamic buckling of functionally graded cylindrical thin shells under non-periodic impulsive loading

Summary.  This paper is concerned with the study of the amplitude of the steady-state vibration in a right finite cylinder made of a mixture consisting of three components: an elastic solid, a viscous fluid and a gas. An exponential decay estimate of Saint-Venant type in terms of the distance from one end of the cylinder is obtained from a first-order differential inequality for a cross-sectional area measure associated with the amplitude of the steady-state vibration. The decay constant depends on the excitation frequency, the constitutive coefficients and the first positive eigenvalue for the fixed membrane problem for the cross-sectional geometry. The paper also indicates how to extend the results to a semi-infinite cylinder. Received October 24, 2002 Published online: April 17, 2003     

Structural strength of electrovacuum glass in components of shells working under compressive loading

Institute of Strength Problems, Academy of Sciences of the Ukrainain SSR, Kiev, Moscow. Translated from Problemy Prochnosti, No. 2, pp. 40–47, February, 1988.     

Fracture response of externally flawed aluminum cylindrical shells under internal gaseous detonation loading

Experiments were performed to observe the fracture behavior of thin-wall and initially-flawed aluminum tubes to internal gaseous detonation loading. The load can be characterized as a propagating pressure jump with speed of 2.4 km/s and magnitude ranging from 2 MPa to 6 MPa, followed by an expansion wave. Flaws were machined as external axial surface notches. Cracks ran both in the upstream and downstream directions as the hoop stress opened up the notch. Different kinds of crack propagation behavior were observed for various loading amplitudes and flaw sizes. For low-amplitude loading and short flaws, cracks tend to run in a helical fashion, whereas for high-amplitude loading and long flaws, cracks tend to bifurcate in addition to running helically. Unless the cracks branched and traveled far enough to meet, resulting in a split tube, they were always arrested. Strain gages were used to monitor the hoop strains at several places on the tubes’ external surface. Far from the notch, tensile vibrations were measured with frequencies matching those predicted by the steady-state Tang (1965, Proceedings of the American Society of Civil Engineers 5, 97–122) and Simkins (1987, Technical Report ARCCB-TB-87008, US Army Armament Research, Development and Engineering Center, Watervliet, N.Y. 12189–4050) models. Near the notch, compressive strains were recorded as a result of the bulging at the notch. Features in the strain signals corresponding to different fracture events are analyzed.     

Ultimate load behaviour of reinforced concrete plates and shells under dynamic transient loading

This paper considers a layered thick shell finite element procedure for determining the dynamic transient nonlinear response of plates and shells. The degenerated three-dimensional isoparametric shell element with independent rotational and translational degrees-of-freedom is employed and a layered formulation is adopted to represent the steel reinforcement and to simulate progressive concrete cracking through the thickness. The dynamic yielding function is assumed to be a function of the current strain rate, in addition to being total plastic strain or work dependent. The concrete model also simulates both compressive crushing and tensile cracking behaviours and an implicit Newmark algorithm is employed for time integration of the equations of motion. Several numerical examples are presented for both slab and shell structures and the results obtained compared with those from other sources wherever available.     

Twin-characteristic-parameters analysis for elastic dynamic buckling of thin cylindrical shells under axial step loading

The relations of the critical stress and transverse inertia effect to the loading duration are investigated for the dynamic buckling of thin cylindrical shells under axial step loading. The critical stress and the inertial exponent are treated as the two characteristic parameters. The criterion of energy conservation is used to derive the supplementary restraint condition for buckling deformations at compression wave front. By use of the Galerkin method, an algebraic eigenvalue problem for the two characteristic parameters is derived from the governing equations and boundary conditions. The solution of the eigenvalue problem, which satisfies the supplementary restraint condition, gives the values of the critical stress and the inertial exponent for the dynamic buckling. The relation of critical stress to loading duration, predicted by the theoretical analysis, is in reasonable agreement with the experimental results.     

Measures to judge the sensitivity of thin-walled shells concerning stability under different loading conditions

In standard stability investigations of structures applying the finite element method usually the bifurcation and snap-through points – so-called stability points – are detected. However, for practical design purposes not only the stable state of equilibrium itself is significant but also the robustness of the state against finite perturbations in contrast to infinitesimal perturbations. The sensitivity measure, which quantifies this robustness, can be investigated by introducing perturbations at certain load levels and considering the perturbed motion. Some sensitivity studies are performed for simple stability problems as well as for realistic structures (cylindrical shells) under different loading conditions. Further scalar parameters based on Liapunov Characteristic Exponents are developed to allow a better judgment of the motion after introducing perturbations and a more efficient analysis of the complex response (see Ewert/Schweizerhof[7]).     

Buckling behavior under radial loading of orthotropic oval cylindrical shells with parabolically varying thickness

In this article, the framework of the Flügge's shell theory, the transfer matrix approach, and the Romberg integration method have been employed to investigate the buckling analysis of a radial loaded oval cylindrical shell with parabolically varying thickness along its circumference. Trigonometric functions are used to form the modal displacements of the shell and Fourier's approach is used to separate the variables. The mathematical analysis is formulated to overcome the difficulties related to mode coupling of variable curvature and thickness of the shell. Using the transfer matrix of the shell, the buckling equations of the shell are reduced to eight first-order differential equations in the circumferential coordinate and rewritten in a matrix form and solved numerically. The proposed model is adopted to get the critical buckling loads and the corresponding buckling deformations for the symmetrical and antisymmetrical modes of buckling. The influences of the shell geometry, orthotropic parameters, ovality parameter, and thickness ratio on the buckling parameters and the bending deformations are presented for different type-modes of buckling.     

温度-机械混合载荷作用下先进复合材料格栅加筋截顶圆锥壳体的屈曲分析

基于均匀化原理,推导了考虑沿格栅加筋圆锥壳体随母线变化的等效刚度阵和等效热膨胀系数,并采用前屈曲薄膜理论给出了在温度和均布外压载荷作用下格栅加筋圆锥截顶壳体稳定性分析的总势能表达式。基于最小势能原理得到了该壳体总体失稳的临界载荷值解析表达式,对典型复合材料格栅加筋截顶圆锥壳体的稳定性计算结果与有限元法所得结果相比较,验证了本文中方法的适用性。基于文中提出的方法,通过对不同温度条件下具有不同顶锥角复合材料格栅加筋截顶圆锥壳体热-力屈曲分析结果的讨论,指出温度对复合材料格栅加筋截顶圆锥壳体稳定性的影响程度将随其顶锥角增加而增大。