The evolution of the crack growthspeed in a thin, buckled strip delamina-tion is studied and two approximate solu-tions are presented. The quasi-dynamicanalysis assumes that the deflection ofthe delaminated layer is represented bythe static postbuckling solution for thecurrent delamination length. A refinedanalysis introduces an indeterminateamplitude functio...

We discuss apparent characteristic features of Rayleigh scattering of elastic waves from cracks. Interpreting these features, we propose a procedure that in some experimental situations may be useful to distinguish generally-shaped cracks from volume defects. For elliptically-shaped cracks, we propose additional procedures that in principle allow the unique specification of crack size, shape an...

We present Surface Crack Antenna Reflectometric Sensing or SCARS: a chipless RFID sensor that enables pervasive, wireless surface crack detection in structural materials. We outline the sensor design and demonstrate how crack length and orientation can be uniquely related to the backscatter signal signature of the SCARS sensor. In doing so, design techniques that improve sensor sensitivity and ...

In a continuous fiber reinforced brittle matrix composite, the transverse fracture is often dominated by the crack trapping and bridging effects as well as the fiber breakage. In this article, the toughening effect of flat fiber bundles with the cross-sectional aspect ratio, , ranging from 0.05 to 5 is discussed in the context of energy analysis. With a constant size/spacing ratio of the fiber ...

This research comprises a study of the effect of heat treatment on fatigue behavior of (A193-51T-B7) alloy steel. Two heat treatment processes were conducted, namely, annealing and quenching followed by tempering at 200C. All fatigue tests were carried out using a rotary bending machine with constant stress ratio, R=-1. The eddy current probe was used to measure the crack length propagation. Fr...

When a propagating cleavage front encounters a high-angle grain boundary it first penetrates through the grain boundary stably. With increasing penetration depth the resistance of the grain boundary rises, resulting in the well-known R-curve. When the balance between the rates of the energy release rate and the grain boundary resistance is reached, the crack advance becomes unstable and the gra...

Reliable and quantitative non-destructive evaluation for small fatigue cracks, in particular those in hard-to-inspect locations, is a challenging problem. Guided waves are advantageous for structural health monitoring due to their slow geometrical decay of amplitude with propagating distance, which is ideal for rapid wide-area inspection. This paper presents a 3D laser vibrometry experimental a...

The problem of several finite moving cracks in a functionally graded material is solved by dislocation technique under the condition of anti-plane deformation. By using the Fourier transform the stress fields are obtained for a functionally graded strip containing a screw dislocation. The stress components reveal the familiar Cauchy singularity at the location of dislocation. The solution is em...

Two levels of fidelity are used for minimum weight design of a composite bladestiffened panel subject to crack propagation constraints. The low fidelity approach makes use of an equivalent strain constraint calculated by a closed form solution for the stress intensity factor. The high fidelity approach uses the stress intensity factor directly as the constraint and computes it from the stress d...

This paper develops the extended finite element method (XFEM) to evolve patterns of multiple cracks, in a brittle thin film bonded to an elastic substrate, with a relatively coarse mesh, and without remeshing during evolution. A shear lag model describes the deformation in three dimensions with approximate field equations in two-dimensions. The film is susceptible to subcritical cracking, obeyi...