Validation of a fluid–structure interaction numerical model for predicting flow transients in arteries

The interaction between the flowing blood and deforming arterial wall is critical in understanding the role of hemodynamic forces such as wall shear stress (WSS) in atherosclerosis. Numerical methods have been extensively used to understand the nature of flow around atherosclerosis susceptible regions of the vascular tree in order to establish the exact role of WSS in atherosclerosis. Unfortunately, most of the numerical studies have been performed on rigid arterial geometries, which do not take into account the effect of the interaction between the flowing blood and the dynamics of the flexible arterial wall. In vivo , blood vessels are continuously deforming with every contraction and relaxation of the heart during the cardiac cycle. This paper forms the first of the two-part paper series discussing the need for fluid-structure interaction (FSI) in hemodynamic WSS analysis. The paper presents a well validated FSI based numerical model, capable of accurately predicting flow transients in arteries. The numerical model is validated using analytical solutions and experiments conducted on polyurethane mock artery, with the numerical predictions, analytical solutions and experimental data comparing very well. Numerical studies are performed using OpenFOAM, a 3D Finite Volume Method(FVM) based C++ library.Deposited by bulk impor

Modelling the fracture behaviour of adhesively-bonded joints as a function of test rate

Tapered-double cantilever-beam joints were manufactured from aluminium-alloy substrates bonded together using a single-part, rubber-toughened, epoxy adhesive. The mode I fracture behaviour of the joints was investigated as a function of loading rate by conducting a series of tests at crosshead speeds ranging from 3.33 × 10−6 m/s to 13.5 m/s. Unstable (i.e. stick–slip crack) growth behaviour was observed at test rates between 0.1 m/s and 6 m/s, whilst stable crack growth occurred at both lower and higher rates of loading. The adhesive fracture energy, GIc, was estimated analytically, and the experiments were simulated numerically employing an implicit finite-volume method together with a cohesive-zone model. Good agreement was achieved between the numerical predictions, analytical results and the experimental observations over the entire range of loading rates investigated. The numerical simulations were able very readily to predict the stable crack growth which was observed, at both the slowest and highest rates of loading. However, the unstable crack propagation that was observed could only be predicted accurately when a particular rate-dependent cohesive-zone model was used. This crack-velocity dependency of GIc was also supported by the predictions of an adiabatic thermal-heating model.Deposited by bulk importAM

A combined experimental–numerical investigation of fracture of polycrystalline cubic boron nitride

Numerical modelling of a series of experimental Single Edge V-Notched Beam tests was carried out for a number of grades of polycrystalline cubic boron nitride using the finite volume method (FV) and cohesive zone model approach. The effect of notch root radius observed experimentally was reproduced numerically via a unique CZM for each material examined. It was also found that the shape of the cohesive zone model can be signiffcant, especially when the material has a relatively high fracture energy. It was also demonstrated that the experimentally observed drop in fracture toughness with increase in test rate was not explainable in terms of the system dynamics. It was found that in order to predict the experimental fracture loads for a range of loading rates, it was necessary to modify the CZM in such a way as to preserve the micro-structural length scale information of the material embedded within the CZM.Deposited by bulk impor

A large epidemic of hepatitis B in Serbia: An integrated model for outbreak investigations in healthcare settings

We report a comprehensive approach for outbreak investigations, including cluster analysis (Bernoulli model), an algorithm to build inferential models, and molecular techniques to confirm cases. Our approach may be an interesting tool to best exploit the large amount of unsystematically collected information available during outbreak investigations in healthcare settings. © 2014 by The Society for Healthcare Epidemiology of America. All rights reserved

Arbitrary crack propagation in multi-phase materials using the finite volume method

An arbitrary crack propagation model using cell-centre nite volume based method is presented. Crack growth in an elastic solid, across an interface perpendicular to the initial crack path and into a second elastic solid is analysed. Crack initiation and the subsequent path of propagation are shown to arise naturally out of the selection of appropriate cohesive parameters. It is shown that the allowable crack propagation path is restricted by the underlying mesh. Results are presented for a number of values of interfacial strength and ratios of elastic properties between the two elastic solids. For higher values of interfacial strength, the crack is shown to propagate straight through the interface, while for lower values of interfacial strength, the crack is shown to change direction and propagate along the interface. It is shown that with careful selection of material and interface parameters it is possible to arrest a propagating crack at the interface. The method represents a useful step towards the prediction of crack propagation in complex structures.Other funderElement 6 Ltd and Enterprise IrelandDeposited by bulk importkpw7/11/1