A preliminary study of the effects from age and dehydration on fatigue crack growth in human dentin was conducted. Compact tension (CT) fatigue specimens of coronal dentin were prepared from extracted molars and subjected to high cycle fatigue (10(5)<N<10(6)) under Mode I loading. Young hydrated dentin (mean age=25+/-7 years), old hydrated dentin (mean age=55+/-14 years) and young dehydrated de...

Dynamic crack propagation drives catastrophic solid failures. In many amorphous brittle materials, sufficiently fast crack growth involves small-scale, high-frequency microcracking damage localized near the crack tip. The ultrafast dynamics of microcrack nucleation, growth, and coalescence is inaccessible experimentally and fast crack propagation was therefore studied only as a macroscale avera...

The present paper explores quasi-cleavage processes driven by dislocation pileups against a Dislocation Free Zone (DFZ). The nanoscopic growth of the main crack consists of sequences of nanocrack formation in DFZ and its subsequent linkage with the main crack. Under mode I loading, the equilibrium locations of individual dislocations and the equilibrium number of dislocations are determined by ...

The crack growth resistance of human dentin was characterized as a function of relative distance from the DEJ and the corresponding microstructure. Compact tension specimens were prepared from the coronal dentin of caries-free 3rd molars. The specimens were sectioned from either the outer, middle or inner dentin. Stable crack extension was achieved under Mode I quasi-static loading, with the cr...

The objective of this investigation was to develop an innovative methodology for life and reliability prediction of hot-section components in advanced turbopropulsion systems. A set of generic microstructure-based time-dependent crack growth (TDCG) models was developed and used to assess the sources of material variability due to microstructure and material parameters such as grain size, activa...

The fatigue process is viewed as the result of the competing processes of crack growth and crack healing. The crack growth or damage proctss is ont of micrOCnlck development and growth and ultimately coalescence of microcraclc.s and propagation in the form of macrocracks. During the entire process, and especially during the period of microcrack growth, microdamage healing strongly influences th...

This paper explores the fracture process based on finite element simulation. Both probabilistic and deterministic methods are employed to model crack initiation, and several commonly used criteria are utilized to predict crack growth. It is concluded that the criteria of maximum tensile stress, maximum normal stress, and maximum Mises stress, as well as the Coulomb-Mohr criterion are able to pr...

A transient _nite element analysis is carried out to provide insight into the low temperature dynamic material toughness versus crack tip relationship for high strength structural steels under intense stress pulse loading[ The problem analyzed here is plane strain fracture of an edge cracked specimen under plane wave loading conditions[ The _nite element formulation employed accounts for the e}...

modelling of crack propagation by finite element method under mixed mode conditions is of prime importance in fracture mechanics. this paper describes an application of finite element method to the analysis of mixed mode crack growth in linear elastic fracture mechanics. crack growth process is simulated by an incremental crack-extension analysis based on the maximum principal stress criterion,...

Finite element simulations are carried out to characterize a new fracture specimen, consisting of an outer circular epoxy ring bonded to an inner circular invar plate for accelerated thermal fatigue testing. Radial cracks are introduced in the epoxy ring. The growth of these radial cracks is correlated to the applied energy release rate G. We studied the dependence of G on the crack length, the...