RESTRICTIONS on the quasi-static extension, or healing, of Griffith cracks are developed in the framework of irreversible thermodynamics. It is emphasized that thermodynamics requires that (G 2r)I > 0, where i is crack speed, G the Irwin energy release rate, and 2y the work of reversible separation of the surfaces to be fractured. Implications for ‘lattice trapping’ models of cracks and for the...

The effects of HF/NH4F, wet chemical etching on the morphology of individual surface fractures (indentations, scratches) and of an ensemble of surface fractures (ground surfaces) on fused silica glass has been characterized. For the individual surface fractures, a series of static or dynamic (sliding) Vickers and Brinnell indenters were used to create radial, lateral, Hertzian cone and trailing...

In the southwest U.S., cracks in alluvial fan surface clasts have a preferred orientation independent of rock fabric and shape. In this paper, we show that differential insolation of incipient cracks of random orientations predicts a distribution of crack orientations consistent with field observations. In this model, crack growth by hydration and/ or thermal weathering is primarily a function ...

Ultrasonic is one of the most common uses of a non-destructive evaluation method for crack detection and characterization. The effectiveness of the acoustic-ultrasound Structural Health Monitoring (SHM) technique for the determination of the depth of the surface crack was presented. A method for ultrasonic sizing of surface cracks combined with the time domain and frequency spectrum was adopted...

Since the depth of surface-breaking cracks often determines the remairring life of a part, the characterization of surface-breaking cracks is a key problern in nondestructive evaluation. Eddy currents have been used for this purpose [1]. However, traditional eddy current methods have poor success when the dimensions of the crack are small compared with the inner radius of the eddy current probe...

Measurement and analysis of cracks on the surface of reinforced concrete can be an effective key for diagnosing quake-proofness of a construction or measuring material fatigue. The conventional method of diagnosis is to analyze cracks using a sketch manually produced by inspection engineers, however it takes a fairly long time and lacks quantitative objectivity. This paper proposes an automatic...

The phenomenon of ageing structures has focused attention on the problem of multiple-site damage (MSD) and wide spread fatigue damage (WFD). In isolation each ̄aw or crack may be safe. However, the cumulative e€ect of multiple, interacting cracks may signi®cantly degrade the damage tolerance of the structure. This paper presents an overview of a new ®nite element alternating technique algorithm...

A new particle-based method, the material point method (MPM), has recently been extended to handle explicit cracks in a new algorithm called CRAMP or “CRAcks with Material Points.” This new method has several advantages for numerical work on fracture. Compared to finite element analysis, CRAMP can handle cracks with similar algorithmic efficiency, but is better at handling crack surface contact...

This paper deals with the basic mechanisms of fatigue damage in materials exposed to service and a series of nondestructive techniques for the early detection of this damage. For all materials with reasonably high fracture toughness it is the organized motion of dislocations that either forms extrusions/intrusions (surface roughness) or the piling up of dislocations at grain boundaries or inter...

The study of brittle or fatigue fracture that involves contact along the crack faces is difficult for several reasons. On the one hand, material data pertaining to the growth of cracks in a compressive environment are scant, and, on the other, frictional stresses may be transmitted across the contacting crack faces. The analysis of cracks under these conditions is complicated. Nevertheless, sol...