A concurrent multi-scale computational strategy for rail surface crack initiation analysis is introduced in current paper. It attempts to take advantage of the efficiency of macroscopic models and the accuracy of the mesoscopic models. The solving procedure is , through the coupling of individual approaches, beginning from the largest scale to the smaller scale, making use of multi-body dynamic...

ID No : 43 ABSTRACT Concrete tends to crack due to its relatively low tensile strength which jeopardizes the good condition of steel reinforcement bars. Concrete cracks start at micro level and facilitate ingression of corrosive substances such as SO4 , Cl, O2. Corrosion of the rebar may result in failure of the structure. Self-healing concrete can provide crack repair immediately after crack i...

New generation jet engines are subject to severe reduced fuel consumption requirements. This usually leads to thin components in which damage issues such as thermomechanical fatigue, creep and crack propagation can be quite important. The combination of stresses due to centrifugal loads and thermal stresses usually leads to mixed-mode loading. Consequently, a suitable crack propagation tool mus...

stress-corrosion cracking (scc) tests were conducted in the near-neutral ph standard solution, ns4, and in an actual soil solution, using four-point bending at a high stress ratio and low frequency conditions very similar to those of operational pipelines. pitting incubation appeared first and then pitting initiated and grew in both solutions although there were many more pits on the specimen t...

In the present study three-point-bend impact experiments were conducted using a Modified Split Hopkinson Pressure Bar (MHPB) to better understand the correlation between impact velocity and critical dynamic energy release rate at crack initiation in linear medium density polyethylene (LMDPE). The MHPB experiments were conducted at impact velocities ranging from 1 to 7 m/s. The dynamic energy re...

Crack-growth experiments in human dentin have been performed in situ in an environmental scanning electron microscope to measure, for the first time, the crack-growth resistance curve (R-curve) for clinically relevant (<250 microm) crack extensions and to simultaneously identify the salient toughening mechanisms. "Young" dentin from donors 19-30 years in age and "aged" dentin from donors 40-70 ...

This paper presents a strategy to predict the lifetime of rails subjected to large rolling contact loads that induce ratchetting strains in the rail head. A critical element concept is used to calculate the number of loading cycles needed for crack initiation to occur in the rail head surface. In this technique the finite element method (FEM) is used to determine the maximum equivalent ratchett...

Strain-rate effects on fracture behavior of unidirectional composite materials are studied. Single-edge notched multi-layered unidirectional graphite composites (T800/3900-2) are investigated to examine fracture responses under static and dynamic loading conditions using a digital speckle correlation method. The fracture parameters for growing cracks are extracted as a function of fiber orienta...

Attached ultrasonic sensors can detect changes caused by crack initiation and growth if the wave path is directed through the area of critical crack formation. Dynamics of cracks opening and closing under load cause nonlinear modulation of received ultrasonic signals, enabling small cracks to be detected by stationary sensors. A methodology is presented based upon the behavior of ultrasonic sig...