The objective of this work is to provide a rationale approach to de®ne the limiting conditions for high-cycle fatigue (HCF) in the presence of foreign-object damage (FOD). This study focused on the role of simulated FOD in a€ecting the initiation and early growth of small surface fatigue cracks in a Ti±6Al±4V alloy, processed for typical turbine blade applications. Using high-velocity (200±300 ...

This paper investigates the efficiency of Ultrasonic Pulse Velocity (UPV) method in detecting cracks and flaws inside the concrete. A series of concrete beams and slab specimens were cast and damaged to simulate the different mechanisms possible in a reinforced concrete deck due to mechanical loading. Two types of simulated cracks, namely, cracks perpendicular and cracks parallel to axis of bea...

Eshelby has shown that a glide dislocation can move without radiation of energy at  2 p of the shear wave speed. It is also known that the same velocity plays a special role in shear crack propagation. This result has not received wide attention in the past due to lack of experiments and numerical simulations of transonic defects. Recent experiments on transonic shear fracture and molecular ...

We solve a problem of fluid dynamics in an arbitrarSignificant progress has been made in the quantitative ily shaped fracture containing proppant. The fracture modeling of the dynamic interaction of a fracture with is embedded in an absolutely rigid solid. The fluid flow surrounding elastic rock. Using the finite-difference method, is induced by normal harmonic oscillations of fracture Chouet (...

A new mode of oscillatory fracture in brittle thin films has recently been reported in two independent experiments [1,2]. When an object is driven through a thin film clamped along its lateral boundaries, the film tears following a striking sawtooth pattern, as the crack tip propagates in an oscillatory manner. In their Letter, Ghatak and Mahadevan [1,3] make an analogy with the classical const...

-In this paper, several formulations of moving-singularity finite element procedures for fast fracture analysis are evaluated as to their accuracy and efficiency. INTRODUCTION IN REFS. [1-3] the authors have presented a "moving singular-element" procedure for the dynamic analysis of fast crack-propagation in finite bodies. In this procedure, a singularelement, within which a large number of ana...

In this paper, a piezoelectric impact hammer is designed and fabricated for generating stable repeated impact elastic waves and further for in-situ wave velocity measurements of concrete specimens. The piezoelectric impact hammer consists of a stacked multilayer PZT, a flying head system with an on-line load cell embedded and a holding fixture. To measure the longitudinal or Rayleigh waves of a...

plastic shrinkage is one of the most important parameter which must be considered in hot weather concreting. if plastic shrinkage is not prevented, cracking will be significant, especialy if silica fume is used in the mix. in this paper, the effect of silica fume in bleeding and evaporation was investigated in laboratory. the results showed that in restrained shrinkage, beside relative humidity...

A novel method for preparing and testing bending specimens in-situ the TEM has been developed. This method provides high visibility of the crack front and its associated plastic zone. This is significant because energy release rates can now be calculated at many points throughout the test based on crack tip opening displacement (CTOD), crack opening angle (COA), and crack advance. Further refin...

In this work, the plastic deformation mechanisms responsible for mechanical properties and fracture toughness in nanotwinned (NT) magnesium is studied by molecular dynamics (MD) simulation. The influence of twin boundary (TBs) spacing and crack position on deformation behaviors are investigated. The microstructure evolution at the crack tip are not exactly the same for the left edge crack (LEC)...