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Tel.: + 33 4 78 02 26 85, + 33 2 98 22 41 63, + 33 3 81 66 60 12; fax: + 33 4 78 02 21 41, + 33 2 98 22 45 35, + 33 3 81 66 67 00, email address : nadege.bouchonneau@gmail.com 1 Tel.: + 33 4 78 02 26 85; fax: + 33 4 78 02 21 41. 2 Tel.: + 33 2 98 22 41 63; fax: + 33 2 98 22 45 35. 3 Tel.: + 33 3 81 66 60 12; fax: + 33 3 81 66 67 00. Abstract:Ultra-deep water (up to 3000 m) is one of the next frontiers for oil offshore exploitation. It requires the use of conduits having to resist in the long run (durability about 25 years) the mechanical and environmental requests. One of the key points is the thermal insulation of the structure to avoid the formation of hydrates and paraffin plugs inside of the steel pipe. Over the past 10 years, many studies were performed to better understand the behaviour of the syntactic foams used as thermal insulation of pipes for deepwater production, but few tests were run on industrial prototypes to reach the actual thermal properties of the systems. This paper presents the numerical and experimental characterizations of an industrial multilayered insulated pipeline tested in service conditions. Two thermomechanical finite element modellings of the coated pipeline have been developed to predict its behaviour during service condition tests. The first model considers pure conduction through the inner air inside of the structure and the second model considers convection phenomenon between the inner air and the metallic surfaces inside of the structure. In parallel, industrial pipe tests on an immersed instrumented pipeline, internally heated to temperatures up to 95 °C and subjected externally to hydrostatic pressure up to 300 bar are presented. Experimental data obtained during industrial pipe tests and related model predictions are compared and discussed. Thermal properties of the syntactic foam are determined with steady and transient states analysis. In complement, a study of the model results sensitivity to the input Poisson coefficient is presented.

Over the past 10 years, numerous studies were performed to better understand the behaviour of the glass syntactic foams used as thermal insulation of pipes for deepwater production. The obtained results outlined some specific behaviour of polymeric syntactic foams reinforced by glass microballoons in service conditions: both water uptake and mechanical stress have a key impact on thermal properties. This article focuses first on the wet behaviour of glass syntactic foams. The effect of water is investigated to better model the nature of water diffusing in syntactic foams with and without a topcoat protection. Secondly, the effect of hydrostatic pressure on coated structure is addressed by using a confined compression test. As polymer material is bonded to the steel surface, it is not submitted to pure hydrostatic loading but to non-spherical loading in the vicinity of the pipe. The confined compression test is then chosen to represent these non-spherical loadings of material. The rupture of glass microballoons is monitored by acoustic emission for different matrices and attempts are made to quantify the resulting acoustic emission signals by comparison with prior tomography results. These experimental analyses provide a better understanding of the main factors affecting the functional properties of syntactic foams.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractExternal coating systems of flowlines and risers ensure both structural and thermal insulation functions which should be efficient throughout the design life in-service, typically 25 years. In that context, the long term behaviour of thermal insulation materials is difficult to predict due to the coupled effects of three factors: hydrostatic pressure up to 300 bar, thermal gradient over 120°C between internal effluents and external sea water and the water absorption of constitutive materials. In addition, laboratory data collected on small size specimens of insulation materials are normally used to predict the thermo-mechanical behaviour of full scale systems, but laboratory testing simply do not properly simulate the service conditions, in particular the complex loading existing through the coating thickness. This paper covers the background to the development of both test facilities and models to study the thermo-mechanical behaviour of production coated steel pipe in ultra deep water conditions. This original work was launched to provide both experimental and computed data to better understand and predict the thermo-mechanical behaviour of insulation materials whilst considered as a full scale system. On the one hand, experimental data obtained on instrumented insulated pipes immersed in large scale facilities simulating ultra deep water are presented in both steady and transient states. On the other hand, a finite element model dedicated to the abovementioned insulated pipes was developed to predict their thermo-mechanical behaviour. Correlation between full scale experimental data and related model predictions are discussed to validate the predictive model taking into account the coupling between hydrostatic pressure and temperature gradient. Additional modelling developments to include the water absorption are planned to reach a suitable prediction of the whole service life.

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AA7075 aluminum alloy is widely used for several high-technology applications for its high mechanical strength to weight ratio but is still the subject of several studies seeking a further increase in its mechanical properties. A commercial powder is used, either as-received or after ball-milling. Dense AA7075 samples are prepared in one step by Spark Plasma Sintering, at 550 °C with a holding time of 15 min and a uniaxial pressure of 100 MPa. No additional heat treatment is performed. Laser granulometry, X-ray diffraction and optical- and scanning electron microscopy show that both grain size and morphology are preserved in the dense samples, due to the relatively low temperature and short sintering time used. The samples prepared using the ball-milled powder exhibit both higher Vickers microhardness and transverse fracture strength values than those prepared using the raw powder, reflecting the finer microstructure.

We synthesized (ZnO nanoparticles)/polypyrrole (ZnO_NPs/PPy) hybrid nanocomposites and used them as additives in an epoxy paint to protect SAE 1020 carbon steel from corrosion. The nanocomposites were obtained by chemical polymerization of pyrrole in aqueous solution and sodium dodecyl sulfate solution containing dispersed ZnO nanoparticles. We characterized the nanoparticles by infrared absorption spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A large disparity in the distribution of ZnO particle sizes became evident from the TEM images, which also show the formation of hybrid nanocomposites consisting of polypyrrole coated ZnO nanoparticles. Electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) tests, which were performed on SAE 1020 carbon steel plates coated with epoxy and ZnO_NPs/PPy, have shown that epoxy paints have their efficiency as anticorrosive coatings significantly improved when ZnO_NPs/PPy hybrid nanocomposites are added to them.