Use of fluorocarbons in the cooling of LHC experiments

Perfluorochemicals sold by 3M under the trade name 3M Fluorinert Electronic Liquids have been used for many years as heat transfer media in a variety of industries. The suitability of these liquids for the cooling of LHC experiment originates from their high dielectric strength as well as from their chemical stability under ionizing radiation. The Fluorinerts are clear, colorless, non-flammable with low toxicity and low corrosiveness. Additionally, they offer low global waming potential – GWP – and zero ozone-depletion potential – ODP. Some examples of fluorinert application in the cooling of LHC experiments will be presented : (a) the ATLAS Inner detector C3F8 evaporative cooling system (b) the ATLAS TRF C6F14 monophase cooling system and (c) the ALICE SPD “active heat pipe” C4F10 evaporative cooling system. A brief comparison of evaporative and monophase cooling systems will be outlined

Formulaçao de um elemento finito de cabo incorporando o efeito do atrito (Elemento de cabos escorregando)

O trabalho apresenta a formulacáo geometricamente exata e a implementaçao computacional de um elemento finito de cabo que permite o escorregamento em presenca de atrito. O novo elemento fornece procedimentos naturais para simular o processo de montagem e a resposta aos carregamentos de estruturas de cabos em geral, além de ter campos promissores de aplicaçáo no modelamento de estruturas de concreto protendido e no estudo de oscilaçoes auto-excitáveis. Resultados de exemplos elementares sáo discutidos.Peer Reviewe

A computationally-efficient micromechanical model for the fatigue life of unidirectional composites under tension-tension loading

Failure of fibre-reinforced composites is affected by fatigue, which increases the challenge in designing safe and reliable composite structures. This paper presents an analytical model to predict the fatigue life of unidirectional composites under longitudinal tension-tension. The matrix and fibre-matrix interface are represented through a cohesive constitutive law, and a Paris law is used to model fatigue due to interfacial cracks propagating from fibre-breaks. The strength of single-fibres is modelled by a Weibull distribution, which is scaled hierarchically though a stochastic failure analysis of composite fibre-bundles, computing stochastic S-N curves of lab-scaled specimens in less than one minute. Model predictions are successfully validated against experiments from the literature. This model can be used to reduce the need for fatigue testing, and also to evaluate the impact of constituent properties on the fatigue life of composites