On the frictional contact in crack analysis

Following the idea of Bowie and Freese we consider a crack in a field of pure bending. The crack is closed over part of its extent, and the two crack faces in contact are allowed to slip under frictional constraints. The solution is constructed under the assumption that the applied loading is monotonically increased. It is discovered, however, that it is possible to analyze unloading by suitably superposing the present solution and that of Bowie and Freese.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23676/1/0000645.pd

Interface disturbances caused by plane elastic pulses

In this article the work of Comninou, Dundurs and co-authors on the subject of interface disturbances caused by plane elastic pulses is briefly reviewed. Some paradoxical aspects occurring at high coefficients of friction are pointed out. Some new results are also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25028/1/0000455.pd

The interaction between a dislocation and a crack: Closure considerations

The interaction between an edge dislocation and a crack in the presence of uniform applied tension and shear is considered. Emphasis is placed on the effects of partial closure and crack-face friction. Representative results are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26659/1/0000203.pd

An overview of interface cracks

In many cases cracks leading to fracture occur at interfaces between two different constituents, e.g. a fiber and the matrix in a composite. The early solutions of such problems in the context of linear elastic fracture mechanics (LEFM) revealed the presence of an unsatisfactory behavior: rapid oscillations in the stress and displacement fields, implying the physically impossible phenomenon of interpenetration. In the late seventies two major modifications were proposed: one by Atkinson and the other by Comninou. The Atkinson modification recognizes that the interface between two different materials is almost never sharp, and provides a gradual transition which avoids the oscillatory behavior. The Comninou approach simply resolves the interface crack problem by accepting its inherently unilateral nature (presence of inequalities) and allowing for partial closure at the tips. Both solutions have received high praise and severe criticism, especially since the oscillatory behavior is absent in some, at least, classes of nonlinear materials (Knowles and Sternberg). Current emphasis is placed on numerical models of the elastoplastic behavior of interface cracks. An additional complication is the apparent presence of mixed mode crack tip fields regardless of the type of the applied loading. Valuable as these theoretical efforts may be, it is becoming increasingly imperative to perform experiments to determine the mode of propagation and critical parameters governing interface fracture. Even then, the results must be viewed with caution, because the quantities of interest can only be determined indirectly. The present paper presents an overview of the interface crack problem and describes some preliminary experimental results in the fatigue and fracture of interface cracks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28836/1/0000671.pd

The periodic array of interface cracks and their interaction

A periodic array of interface cracks is considered as a simple model for studying interface crack interaction. The novel feature of the solution is the elimination of the oscillatory singularities and of the material overlapping which is accomplished by allowing frictionless contact zones at the crack tips. The results are obtained for a combination of shear and tension-compression loads applied at infinity. It is shown that the stress intnsity factors become smaller with decreasing distance between the cracks. This indicates that the spreading of an interface crack is inhibited by the presence of adjacent cracks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23754/1/0000727.pd

Interface separation in the transonic range caused by a plane stress pulse

This is a continuation of the authors' investigation [1] of the localized separation between two contacting solids that is caused by an incident plane elastic wave of arbitrary form. The interface is taken as frictionless and incapable of transmitting tensile tractions. It is further assumed that the two solids have identical mechanical properties, and that the angle of incidence of the incoming wave is such that the disturbance propagates along the interface with a transonic speed. Moving dislocations are employed in the formulation and the problem is reduced to a singular integral equation with a Cauchy kernel. Specific results are worked out for an incident tensile stress pulse of a parabolic shape. An intriguing aspect of the results is that, in spite of the incident wave being continuous, the elastic fields are singular at the trailing edge of the separation zone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23628/1/0000591.pd

Shape of a worn slider

A slider can be expected to wear in due time to a shape that gives a uniform contact pressure and consequently uniform friction stress. Computation of the worn shape is discussed using the theory of elasticity. The results show that the trailing edge may be worn down more than the leading edge. The worn shape at a sharp corner may be either convex or concave depending on the elastic constants, the friction coefficient and the corner angle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23185/1/0000112.pd

An example for frictional slip progressing into a contact zone of a crack

We consider a crack in a linearly varying field of normal stress that is kept constant, and apply shearing tractions that increase with time. This leads eventually to slip progressing into the closed part of the crack. If the crack lies entirely in the compressive part of the normal stress field, the problem can be solved in closed form, and it is easy to get results also for shearing tractions that start to decrease and eventually lead to backslip.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23690/1/0000660.pd

Green's functions for planar thermoelastic contact problems -- Interior contact

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23713/1/0000685.pd

Interface separation caused by a plane elastic wave of arbitrary form

The paper considers the separation between two contacting solids caused by an incident elastic wave. The wave is assumed to be plane, but may have an arbitrary form. The unilateral interface between the solids is taken as frictionless and incapable of transmitting tension. If the disturbance propagates along the interface with a speed that is supersonic with respect to both solids, the problem can be solved in closed form, and simple results for the extent of the separation zones and the respective gaps are obtained. Several specific examples are included.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23656/1/0000623.pd