Cycle and Crack Length Dependence of Crack Growth Characteristics in Silicon Nitride.

Mode I Fracture Toughness of a Small-Grained Silicon Nitride: Orientation, Temperature, and Crack Length Effects

The Mode I fracture toughness (KIC) of a small-grained Si3N4 was determined as a function of hot-pressing orientation, temperature, testing atmosphere, and crack length using the single-edge precracked beam method. The diameter of the Si3N4 grains was <0.4 μm, with aspect ratios of 2–8. KIC at 25°C was 6.6 ± 0.2 and 5.9 ± 0.1 MPa?m1/2 for the T–S and T–L orientations, respectively. This differe...

Transient Fatigue-crack Growth Behavior following Variable-amplitude Loading in a Monolithic Silicon Nitride Ceramic

ÐTransient cyclic fatigue-crack growth behavior following variable-amplitude loading sequences has been investigated in a hot-pressed, monolithic Si3N4 ceramic (NTK EC-141), for which fracture toughness (resistance-curve) and cyclic fatigue properties are well characterized. Following rapid changes in the applied stress-intensity range, DK, during both low-high and high-low block-loading sequen...

Crack Deflection and Propagation in Layered Silicon Nitride/Boron Nitride Ceramics

Crack deflection and the subsequent growth of delamination cracks can be a potent source of energy dissipation during the fracture of layered ceramics. In this study, multilayered ceramics that consist of silicon nitride (Si3N4) layers separated by boron nitride/silicon nitride (BN/Si3N4) interphases have been manufactured and tested. Flexural tests reveal that the crack path is dependent on th...

Practical Methods for Crack Length Measurement and Fatigue Crack Initiation Detection Using Ion-Sputtered Film and Crack Growth Characteristics in Glass and Ceramics

CHARACTERIZATION OF TRANSVERSE CRACK AND CRACK GROWTH IN A RAILWAY RAIL

Abstract: To ensure the rail transportations safety, evaluation of fatigue behavior of the rail steel is necessary. High cycle fatigue behaviour of a rail steel was the subject of investigation in this research using fracture mechanics. Finite element method (FEM) was used for analyzing the distribution of the stresses on the rail, exerted by the external load. FEM analysis showed that the ...