In situ ultrasonic fatigue with a cyclic frequency of 20 kHz was employed in an environmental scanning electron microscope (ESEM) to characterize fatigue crack formation and growth in the near alpha titanium alloy Ti–6242S. The role of environment on small fatigue crack initiation and growth was investigated in vacuum and in variable pressures of saturated water vapor, as well as in laboratory ...

Title: Crack Growth During Brittle Fracture in Compression. Author: Bartlett W. Paulding, Jr. Submitted to the Department of Geology and Geophysics February 9, 1965 in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology. Photoelastic analysis of several two-crack arrays predicts that compressive fracture is initiated at cra...

OBJECTIVES The objective of this in vitro study was to evaluate the fatigue crack growth properties of the dentin/resin adhesive interface. METHODS Compact tension (CT) specimens were prepared from coronal dentin, resin composite, and dentin bonded to resin composite using Optibond Solo Plus adhesive. All specimens were then subjected to cyclic Mode I loading while fully hydrated at a stress ...

We have carried out systematic fracture experiments in a single edge notch geometry over a range of stretch rates on dual crosslink hydrogels made from polyvinyl alcohol chains chemically crosslinked with glutaraldehyde and physically crosslinked with borate ions. If the energy release rate necessary for crack propagation was calculated conventionally, by using the work done to deform the sampl...

The mechanisms of fatigue-crack propagation in ceramics and intermetallics are examined through a comparison of cyclic crack-growth behavior in ductile and brittle materials. Crack growth is considered to be a mutual competition between intrinsic mechanisms of crack advance ahead of the crack tip, which promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip, which ...

Continuum mechanics predicts that the propagation speed of non-equilibrium information in solids is limited by the longitudinal wave speed, so is crack propagation. However, solids are essentially discrete systems. In this paper, via theoretical analysis and numerical simulations, it is demonstrated in a straightforward way that nonequilibrium disturbance (e.g. force, displacement, energy, and ...

Minimum energy paths for unit advancement of a crack front are determined by reaction pathway sampling, thus providing the reaction coordinates for the analysis of crack tip mechanics in ductile and brittle materials. We compare results on activation energy barrier and atomic displacement distributions for an atomically sharp crack in Cu, where one observes the emission of a partial dislocation...

This paper deals with the quasistatic crack growth of a homogeneous elastic brittle thin film. It is shown that the quasistatic evolution of a three-dimensional cylinder converges, as its thickness tends to zero, to a two-dimensional quasistatic evolution associated with the relaxed model. Firstly, a Γ-convergence analysis is performed with a surface energy density which does not provide weak c...

structural health monitoring of cracked structures is one of beloved subject of researchers recently. consider of crack behavior in the water and energy pipeline is important because of environmental problems. in this paper consider of crack parameters in the underwater pipe subjected to mechanical transient load is investigated. for this purpose, three- dimensional parametric model of cracked ...