共查询到20条相似文献,搜索用时 109 毫秒
1.
An expression for the dynamic energy release rate of a spreading circular fracture pattern in an uniformly stretched plate is derived from a path-independent energy integral. This is equivalent to the energy dissipated in an incremental growth of a constant velocity circular locus in which the radial tension is zero. The relationship to rapid fracture and multiple crack division becomes apparent as the arc distance separating adjacent crack tips becomes small relative to the radius of the circular locus. The condition at some small fixed distance behind the closely spaced crack tips is then well-stimulated by that of zero radial tension on a circular locus. Experiments could be carried out to establish the accuracy of the analytical dynamic energy release rate expression for multiple crack division. 相似文献
2.
E.E Gdoutos 《Theoretical and Applied Fracture Mechanics》1985,3(2):141-150
The problem of failure of a plate containing a circular inclusion and a crack is studied. The crack is oriented along a diameter of the inclusion and the plate is subjected to a remote uniaxial stress perpendicular to the crack axis. The process of slow stable crack growth from initiation to termination is studied by the strain energy density theory. The crack growth is simulated by predicting finite increments of crack extension when material elements near the crack tip absorb a critical amount of strain energy density level,
. Unstable crack growth occurs when the strain energy density factor S reaches a critical value
where rc is the critical size of the final crack increment prior to instability. The stress at crack initiation and the critical stress and crack length at failure are determined. The influence of the mechanical properties of the plate and the inclusion, the relative position of the inclusion and the crack and the crack length on the characteristic quantities of stable crack growth is analyzed. The dependence of the stable crack growth process on the loading rate is also investigated. Results are displayed in graphical form. 相似文献
3.
轴对称压—弯下圆板中圆脱层的后屈曲扩展 总被引:1,自引:1,他引:1
本文分析了周边承受轴对称压一弯载荷的圆板中薄圆脱层的后屈曲扩展.运用基于四阶龙格-库塔积分公式的打靶法得到无量纲形式Von Karman非线性方程组的单参数解族.利用与路径无关的M积分导出能量释放率表达式并给出相应的数值解.文中还探讨了分叉、跳跃及扩展的可能性. 相似文献
4.
为了研究内爆炸薄圆板的失效与作用载荷特性,在双圆筒装置内开展了铝质、钢质薄圆板内爆炸实验,分析了圆板破坏模式及比冲量载荷特性,并基于相同变形下载荷相等原理,得到了钢质圆板极限变形下的有效比冲量及作用时间,提出了该工况下圆板变形的预估模型。结果表明:在内爆炸载荷作用下,薄圆板的夹持边界和几何中心是应力集中区,产生了塑性大变形、拉伸撕裂、剪切断裂3种破坏模式;圆板的比冲量载荷由初始的波浪式增长逐渐转化为线性增长,30~80 g某温压装药使1 mm厚钢质圆板产生极限变形的有效比冲量作用时间在2.26~2.93 ms之间,经验证,圆钢板变形预估模型得到的装药质量与实验装药质量偏差小于13.3%。 相似文献
5.
6.
Delamination of a symmetric circular plate made of viscoelastic composite is studied. It is assumed that the plate has a penny-shaped crack whose edges have a minor axisymmetric imperfection. The lateral surface of the plate is clamped and is compressed by uniform radial normal forces through a rigid body. The studies are made using the exact geometrically nonlinear equations of the theory of viscoelasticity. The delamination criterion is assumed unrestrained growth of the initial imperfection. The Laplace transform and FEM are employed. In particular cases, the results are compared with those for elastic composites 相似文献
7.
H. Djeridi M. Braza R. Perrin G. Harran E. Cid S. Cazin 《Flow, Turbulence and Combustion》2003,71(1-4):19-34
The present study investigates the turbulent properties of the flow around a circular cylinder in the near-wake and in the near-wall upstream region at the Reynolds number 140,000. A detailed cartography of the mean and turbulent velocity fields using a moderate blockage and aspect ratio is provided in order to use the present results for direct comparisons with realisable 3D Navier-Stokes computations. The flow structure is analysed by means of two experiments using respectively the LDV and the PIV techniques, both providing a refined grid of measurement points. The dynamics of the separation region, the growth and decay of turbulence in the near wake, as well as the spatial growth of the organised mode are analysed. 相似文献
8.
9.
《International Journal of Solids and Structures》1999,36(25):3779-3797
A composed circular cylinder, formed by a core circular cylinder, containing a crackand enclosed by a layered hollow circular cylinder, is investigated in regard to the evaluation ofstress intensity factors. Analytic solutions to the problem are provided, with which the upper andlower bounds of stress intensity factors in a cracked circular cylinder, the stress distribution in alayered hollow circular cylinder, and the stress intensity factors for a crack in the composedcircular cylinder can precisely be determined. Numerical materials, demonstrating the discretevalues of the stress intensity factors, as well as the general pattern according to which the stressintensity factors vary with the material and geometric constants, are presented. The solutions aredeveloped based on a simplified and modified solution to the Hilbert problem, and the matrixpresentation and manipulation of functions and variables, used in the circuit theory. 相似文献
10.
The boundary layer growth on a circular cylinder embedded to a wedge, when the motion is started impulsively from rest, is discussed using the method of inner and outer expansions. The equation for the time of separation involving the Reynolds number and the wedge angle is obtained. A uniformly valid solution is also found for the entire flow field. It is found that separation first occurs at the points where the cylinder meets the wedge. Also, the time of earliest separation decreases with increase in the Reynolds number and with increase in the wedge angle. 相似文献
11.
The problem of long-term fracture of an aging reinforced composite array having hexagonal symmetry and weakened by a flat
circular macrocrack is considered based on the Boltzmann-Volterra principle and the theory of long-term fracture of viscoelastic
bodies. The array is under the action of stationary tensile forces applied at infinity and normal to the crack plane. The
Maslov-Arutyunyan operator is used to describe the aging strain properties of the array. The irrational functions of integral
Volterra operators obtained during the solution are determined by expanding them into continued fractions. The crack growth
equations derived are numerically solved for a specific material (ferroconcrete). Curves of the rupture life of the composite
array, kinetics of crack growth, and safe loading are presented.
S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika,
Vol. 35, No. 12, pp. 72–79, December, 1999. 相似文献
12.
《International Journal of Solids and Structures》1999,36(12):1799-1821
Some closed-form equations for the coupling problem of buckling and growth of circular delamination are derived by recourse to the moving boundary variational principle. The axisymmetric buckling of a circular delamination subjected to an equal bi-axial compression is analysed by using high-order perturbation expansion. The axisymmetric buckled delamination has the following properties : under a certain residual pressure, there exist two characteristic radii, namely the critical radius Rc and growing radius Rg; for a certain interface toughness, the blister has three configuration of stationary, stable growth and unstable growth with increasing the loads. Under a higher edge thrust, the nonaxisymmetric secondary buckling will occur on the base of axisymmetric buckling and then the toughness and the driving force of the interface crack will be different along the delamination front. So the growth of circular delamination will not be self-similar. Without any assumption regarding the delamination front, the configurations of the blister with several nonaxisymmetric buckling modes n = 2, 3, 6, 8 are simulated. The nonaxisymmetric growth process for the nonaxisymmetric buckling mode n = 2 is simulated also under a sequence of loads. 相似文献
13.
Summary A problem of partial sliding along a planar crack with a local drop in frictional resistance is investigated. A sliding zone initiates in the area of reduced friction, and then propagates as the applied shear load is monotonously increased. The problem is formulated in general terms, and then solved for the case when sliding spreads as a penny-shaped zone. Conditions under which the front of the zone stays circular during sliding are analyzed. It is observed that the axisymmetry of the profile of frictional resistance does not necessarily guarantee uniform propagation of sliding in the radial direction. The circular shape becomes the most favorable growth condition only if the shear modes are related in a certain way. The problem is studied based on the criterion of propagation that stress intensity factors(SIFs) for II and III modes vanish on the boundary of the sliding zone. The singular integrals in expressions for the SIFs are reduced to non-singular ones. Analytical solutions are derived for a number of special cases where the radius of the sliding zone is related to the applied shear load.This work is supported by the National Science Foundation through grant DGE-0209543 to the University of New Mexico. 相似文献
14.
We study the reinforcement of an infinite elastic plate with a circular hole by a larger eccentric circular patch completely covering the hole and rigidly adjusted to the plate along the entire boundary of itself. We assume that the plate and the patch are in a generalized plane stress state generated by the action of some given loads applied to the plate at infinity and on the boundary of the hole. We use the power series method combined with the conformal mapping method to find the Muskhelishvili complex potentials and study the stress state on the hole boundary and on the adhesion line. We consider several examples, study how the stresses depend on the geometric and elastic parameters, and compare the problem under study with the case of a plate with a circular hole without a patch. In scientific literature, numerous methods for reinforcing plates with holes, in particular, with circular holes, have been studied. In the monographs [1, 2], the problem of reinforcing the hole edges by stiffening ribs is solved. Methods for reinforcing a circular hole by using two-dimensional patches pasted to the entire plate surface are studied in [3, 4]. The case of a plate with a circular cut reinforced by a concentric circular patch adjusted to the plate along the boundary of itself or along some other circle was studied in [5, 6]. The reinforcement of an elliptic hole by a confocal elliptic patch was considered in [7]. 相似文献
15.
提出了一个平面弹性体多裂纹疲劳扩展模型. 它主要涉及到复合型加载情况下多裂纹尖端疲劳扩展的数学模型及杂交位移不连续法(一种边界元法). 在数值模拟中, 对每一裂纹扩展增量分析时,在其先前的边界上增添裂纹扩展增量, 且只对新增添的裂纹扩展增量划分单元, 同时, 按照这种边界元法的实施方法对一些单元特征进行调整, 就可以方便地模拟裂纹扩展. 用这种数值方法模拟了巴西圆盘试样中心斜裂纹疲劳扩展轨迹,数值结果说明了预报模型的有效性, 揭示了裂纹体几何对疲劳扩展的影响. 相似文献
16.
V. V. Sil'vestrov A. Yu. Zemlyanova 《Journal of Applied Mechanics and Technical Physics》2004,45(4):605-611
The stressed state of a thin elastic infinite plate with a circular hole covered by a circular patch of a greater radius is considered. The center of the hole coincides with the center of the patch. The patch is attached to the plate along its entire boundary. Stresses are prescribed at infinity on the plate and at the hole boundary. Complex Muskhelishvili potentials are found by the method of power series, and the behavior of stresses on the patch–plate interface and at the hole boundary is studied. 相似文献
17.
The problem of crack initiation and growth in contact problems is studied by the strain energy density theory. This is accomplished by considering each point of the body as a possible source of crack initiation. The direction of crack initiation is determined by calculating the minimum value of the strain energy density function along a circular core area surrounding the point. The crack initiates from the point with the maximum of the local minimum values of the strain energy density function. Considered is a circular disc subjected to two equal and opposite forces and a circular cylindrical body pressed by a cylindrical punch. The stress field for the first case is obtained from the classical elasticity solution, while a finite element code is used for the second case. The locations of fracture initiation and the subsequent fracture trajectories for fast unstable fracture are determined. 相似文献
18.
Forced vibration of a thickening circular plate is studied within the framework of the small deformation theory. The plate
material is assumed to be elastic and isotropic and the plate thickness to be continually increasing due to influx of material
from outside. It is also assumed that the plate thickness varies with time but is independent of the space coordinates. Moreover,
in the process of growth, the midsurface position does not change, which suggests that the plate grows symmetrically on both
its surfaces. 相似文献
19.
The method of matched asymptotic expansions is employed for investigating the growth of the free convection boundary-layer on a horizontal circular cylinder which is embedded in a porous medium. It is assumed that the Rayleigh number is large, but finite, and the time of investigation is short. It is shown that the solution contains terms that are absent from the solution based on the boundary-layer approximation and that vortices form at both sides of the cylinder. The development of the plume region near the top of the cylinder, as well as the local and average Nusselt numbers, are evaluated and presented in graphical form. 相似文献
20.
This paper presents a numerical approach of fatigue growth analysis of cracks emanating from a hole in infinite elastic plate
subjected to remote loads. It involves a generation of Bueckner’s principle and a hybrid displacement discontinuity method
(a boundary element method) proposed recently by the senior author of the paper. Because of an intrinsic feature of the boundary
element method, a general crack growth problem can be solved in a single region formulation. In the numerical simulation,
for each increment of crack extension, remeshing of existing boundaries is not necessary. Crack extension is modeled conveniently
by adding new boundary elements on the incremental crack extension to the previous crack boundaries. As an example, fatigue
growth process of an inclined crack in an infinite plate under uniaxial cycle load is modeled to illustrate the effectiveness
of the numerical approach. In addition, fatigue growth of cracks emanating from a circular hole in infinite elastic plate
subjected to remote loads is investigated by using the numerical approach. Many numerical results are given 相似文献