Dynamic stress intensity factors around a rectangular crack in an infinite plate under impact load

A three-dimensional solution is presented for the transient response of an infinite plate which contains a rectangular crack. The Laplace and Fourier transforms are used to reduce the problem to a pair of dual integral equations. These equations are solved with the series expansion method. The stress intensity factors are defined in the Laplace transform domain, and they are inverted numerically in the physical space.     

Dynamic stress intensity factors around two rectangular cracks in a half space under impact load

Summary In this paper, the mixed boundary value problem for two rectangular cracks,which are embedded in a half-space, is analyzed under the action of an impact load. The cracks are situated perpendicular to the plane surface of the half space. The wave front of the incident stress impinges on the cracks at right angles to their surfaces. In the Laplace transform domain, the boundary conditions at the plane surface are satisfied using the Fourier transform technique, while those at the surfaces of the cracks are satisfied using the Schmidt method. The stress intensity factors defined in the Laplace transform domain are inverted in the physical space with the aid of a numerical method.     

Dynamic stress intensity factors around two parallel cracks in an infinite elastic plate

Summary Dynamic stresses around two parallel cracks in an infinite elastic plate are obtained. An incoming shock stress wave impinges on the cracks at right angles to their faces. The Fourier-Laplace transform technique is utilized to reduce the problem to dual integral equations. To solve these equations, the differences in the crack surface displacements are expanded in a series of functions which are zero outside the cracks. The unknown coefficients occurring in those series are solved using the Schmidt method. The stress intensity factors defined in the Laplace transform domain are inverted numerically, in the physical space.     

Dynamic stress intensity factors around three cracks in an infinite elastic plane subjected to time-harmonic stress waves

The time-harmonic problem for an infinite elastic plane weakened by three parallel cracks has been solved. In this problem, two cracks are situated symmetrically on either side of a central crack and incident stresses impinge perpendicular to the cracks. Using the Fourier transform technique, the boundary conditions are reduced to four simultaneous integral equations. To solve the equations, the differences of displacements inside the cracks are expanded in a series. The unknown coefficients in the series are solved by the Schmidt method. The dynamic stress intensity factors are calculated numerically for several crack configurations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Transient dynamic stress intensity factors around two rectangular cracks in a nonhomogeneous interfacial layer between two dissimilar elastic half-spaces under impact load

Summary Transient dynamic stresses around two rectangular cracks in a nonhomogeneous interfacial layer sandwiched between two dissimilar elastic half-spaces are examined. The material properties vary continuously in the layer within a range from those of the upper half-space to those of the lower half-space. An incoming shock stress wave impinges perpendicular on the crack surfaces. In order to solve the problem, the interfacial layer is divided into several homogeneous layers that have different material properties. Application of Laplace and Fourier transforms reduces the problem to the solution of a pair of dual integral equations. To solve the equations, the differences in the crack surface displacements are expanded into a series of functions that vanish outside the crack. The unknown coefficients in the series are solved using the Schmidt method. The stress intensity factors are defined in the Laplace transform domain and these are inverted numerically in physical space. Numerical calculations are carried out for composite materials made of a ceramic half-space and a steel half-space.     

Three-dimensional dynamic stress intensity factors around two parallel square cracks in an infinite elastic medium subjected to a time-harmonic stress wave

Summary Dynamic stresses around two parallel square cracks in an infinite elastic medium are determined. A time-harmonic stress wave impinges on the two cracks normal to their surfaces. The two-dimensional Fourier transform technique is applied to reduce the mixed boundary value conditions to dual integral equations. To solve the equations, differences of the displacements in the upper square crack are expanded using a double series of functions which are equal to zero outside the crack. Those in the lower crack are also expanded using a similar series. Unknown coefficients in the series are determined by applying the Schmidt method. Dynamic stress intensity factors are calculated numerically assuming that the shape of the upper crack is identical to that of the lower crack.     

Transient analysis of stress waves around two rectangular cracks under impact load

The three-dimensional response of two rectangular cracks in an infinite elastic medium to impact load is investigated in this paper. Fourier and Laplace transforms are applied and the problem is reduced to that of solving dual integral equations in the Laplace transform domain. To solve these equations, the crack surface displacement is expanded in a double series of functions which are zero outside of the cracks. The unknown coefficients accompanied in that series are solved with the aid of the Schmidt method. The dynamic stress intensity factors are computed numerically.     

The stress intensity factors of a star-shaped array of cracks in an infinite elastic solid

The problem of determining the stress intensity factors and crack formation energy of a radial system of line cracks in an infinite elastic solid is reduced to the solution of a singular integral equation. The equation is solved numerically for the special case in which the cracks are opened by a constant pressure.     

Dynamic stress intensity factors around two coplanar Griffith cracks in an orthotropic layer sandwiched between two elastic half-planes

Dynamic stresses around two coplanar Griffith cracks in an orthotropic layer sandwiched between two elastic half-planes are determined. To the surfaces of the cracks, an internal pressure is applied suddenly. Application of the Fourier and Laplace transforms reduces the problem to the solution of a pair of dual integral equations in the Laplace transform plane. To solve these equations, the crack surface displacement is expanded in a series of functions which are zero outside of the cracks. The unknown coefficients accompanied in that series are solved with the aid of the Schmidt method. The stress intensity factors defined in the Laplace transform plane are inverted numerically in the physical plane. Numerical calculations are carried out for the case that the layer of carbon fiber is sandwiched by the two elastic half-planes of plastic.     

Three collinear cracks in an infinite elastic medium

The plane strain problem of determining the distribution of stress in the vicinity of three cracks embedded in an infinite isotropic elastic medium is considered. The cracks are collinear, the two side cracks are equal in length and located symmetrically with respect to the middle crack. The surface tractions acting on the cracks are completely arbitrary. Some special cases of the loading are discussed in detail.     

Four co-planar Griffith cracks in an infinite elastic medium

The dynamic in-plane problem of determining the stress and displacement due to four co-planar Griffith cracks moving steadily at a subsonic speed in a fixed direction in an infinite, isotropic, homogeneous medium under normal stress has been treated. The static problem of determining the stress and displacement in an infinite isotropic elastic medium has also been considered. In both cases, employing the Fourier integral transform, the problems have been reduced to solving a set of five integral equations. These integral equations have been solved using the finite Hilbert transform technique to obtain the exact form of crack opening displacement and stress intensity factors which are presented in the form of graphs.     

Three co-planar moving Griffith cracks in an infinite elastic medium

The dynamic in-plane problem of determining the stress and displacement due to three co-planar Griffith cracks moving steadily at a subsonic speed in a fixed direction in an infinite, isotropic, homogeneous medium under normal stress has been treated. The static problem of determining the stress and displacement around three co-planar Griffith cracks in an infinite isotropic elastic medium has also been considered. In both the cases, employing Fourier integral transform, the problems have been reduced to solving a set of four integral equations. These integral equations have been solved using finite Hilbert transform technique and Cook's result [16] to obtain the exact form of crack opening displacement and stress intensity factors which are presented in the form of graphs.     

Dynamic mode II stress intensity factors of an infinite cracked medium subjected to transient concentrated forces

In this article the determination of dynamic mode II stress intensity factors of a crack embedded in an infinite medium subjected to transient concentrated line forces is investigated. The concentrated line forces act at an arbitrary distance away from the crack, including the special case when the forces act precisely on the crack surfaces. Laplace and Fourier transforms are used to reduce the mixed boundary value problem to a standard Fredholm integral equation of the second kind in Laplace transform domain, which is solved numerically. Via the numerical inversion of Laplace transform, the dynamic mode II stress intensity factors at the crack tips are obtained and presented in graphical form for various geometry parameters. It is found that the point of application of the concentrated forces, which induce the maximum value of the dynamic mode II stress intensity factors, is precisely on the crack surface for horizontal concentrated forces, whereas for vertical forces, it is at some distance away from the crack.     

Transient analysis of stress waves around two coplanar griffith cracks under impact load

The problem of determining the transient stress distribution in an infinite elastic medium weakened by two coplanar Griffith cracks is considered. To the surfaces of the cracks, an internal pressure is applied suddenly. The problem is reduced to that of solving dual integral equations in the Laplace transform domain and those are solved by a series-expansion method. The dynamic stress intensity factors are computed numerically.     

Dynamic stress intensity factors due to scattering of harmonic waves by a crack in an infinite medium

An analytical method for calculating dynamic stress intensity factors in the mixed mode (combination of opening and sliding modes) using complex functions theory is presented. The crack is in infinite medium and subjected to the plane harmonic waves. The basis of the method is grounded on solving the two‐dimensional wave equations in the frequency domain and complex plane using mapping technique. In this domain, solution of the resulting partial differential equations is found in the series of the Hankel functions with unknown coefficients. Applying the boundary conditions of the crack, these coefficients are calculated. After solving the wave equations, the stress and displacement fields, also the J‐integrals are obtained. Finally using the J‐integrals, dynamic stress intensity factors are calculated. Numerical results including the values of dynamic stress intensity factors for a crack in an infinite medium subjected to the dilatation and shear harmonic waves are presented.     

Non-symmetric extension of a crack in an infinite elastic medium under anti-plane shear stress

The dynamic problem of non-symmetric extension of a crack in an infinite elastic medium, which is initially in a state of uniform anti-plane shear, has been considered. The problem of non-symmetric extension of a crack due to cohesive traction has also been treated. The method of analysis is based on the observation that certain field quantities show dynamic similarity. The results include expressions for the stress intensity factors at the crack tips and the rate of energy flux into the crack edges for problem I. Numerical calculations are carried out to obtain stress intensity factors and the rate of energy flux into the crack tips for problem I.     

Two coplanar Griffith cracks in an infinite elastic layer under torsion

Summary We consider the problem of determining the stress distribution in an infinitely long isotropic homogeneous elastic layer containing two coplanar Griffith cracks which are opened by internal shear stress acting along the lengths of the cracks. The faces of the layer are assumed to be stress free. The cracks are located in the middle plane of the layer parallel to its faces. By using Fourier transforms, we reduce the problem to the solution of a set of triple integral equations with a cosine kernel and a weight function. These equations are solved exactly by using finite Hilbert transform techniques. Finally we derive the closed form expressions for the stress intensity factors and the crack energy. Solutions to the following problems are derived as particular cases: (i) a single crack in an infinite layer under torsion, (ii) two coplanar cracks in an infinite space under torsion, (iii) a single crack in an infinite space under torsion.