The rate/temperature dependent fracture behaviour of plain and glass-filled polystyrene has been investigated over the crack speed (a) range of 10 -6 to 10 -2 m sec -1 and in the temperature (7-) range of 296 to 363 K. The Kc (a, T) relationships obtained, where Kc is the stress intensity factor at fracture, are shown to follow those given by the Williams/ Marshall relaxation crack growth model...

The Brazilian Test is the most used test to determine indirect tensile strength for brittle materials like concrete. It has been observed that success of depends on cracks initiation point position and therefore arch loading angle; a crack appears in center disk when valid. To this effect, using Fast Lagrangian Continua code FLAC2D; numerical analyses were performed study impact angle initial c...

The influence of an integrated hot isostatic pressing (HIP) treatment was investigated for two single-crystalline nickel-based superalloys under very high cycle fatigue at 1000 °C in fully reversed conditions (R? = ? 1). life is improved significantly by performing heat-treatments within the HIP unit. HIP-compacted pore morphology and its impact on crack initiation considered as well. HIPed spe...

Ultra High Cycle fatigue leads to a failure initiated in the bulk material of a material. Some results on the nodular cast iron are presented: initiation occurs from the defects, located at the surface or in the bulk. It has been shown that environment plays a major role that could explain the difference between fatigue lives, for the surface and internal initiation. The influence of the defect...

Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression tes...

We study atomistically the fracture of single-crystal silicon at atomically sharp notches with opening angles of 0° ~a crack!, 70.53°, 90° and 125.3°. Such notches occur in silicon that has been formed by etching into microelectromechanical structures and tend to be the initiation sites for failure by fracture of these structures. Analogous to the stress intensity factor of traditional linear e...

To clarify the internal fatigue crack generation in a Ti-Fe-O (near a-type) alloy, microstructures, internal fatigue crack initiation sites, and dislocation structures in samples fractured during high-cycle fatigue tests at liquid nitrogen temperature were studied. The alloy contained two kinds of elongated a-phase microstructures, i.e., recovered a grains and recrystallized a grains. Untested ...

In this study, the problem of finding the limiting load in infinite plates with internal cracks is extended to the non-linear field. In particular, results concerning concrete plates in bi-axial loading are shown. The analysis is performed in discrete form, by means of the Cell Method. The discrete analysis allows us to identify the crack initiation without using the stress intensity factors. T...

This paper presents the results of a combined experimental and theoretical study of the fatigue crack initiation in LIGA Ni thin films with a thickness of 270 mm. The potential roles of surface oxide thickening and slip bands are explored for fatigue crack initiation. Surface oxides and roughness are characterized using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). T...

Based on the strain rates of 2 × 108 s−1 and 2 × 1010 s−1, molecular dynamics simulation was conducted so as to study mechanisms of crack propagation in nanoscale polycrystal nickel. The strain rate has an important effect on the mechanism of crack propagation in nanoscale polycrystal nickel. In the case of a higher strain rate, local non-3D-crystalline atoms are induced and Lomer-Cottrell lock...