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International audience; A micro-blower device, made by Murata™ Manufacturing Co. and originally designed for cooling electronic microprocessors, is used in the present study as an actuator for separation flow control. The dynamical performance of the device, working in pulsed mode, is experimentally investigated to deduce its abilities and limitations regarding active flow control. Both the device design and its dynamical characterization are addressed in the paper, paying particular attention to its ability to control flow. Both hot-wire anemometry and particle image velocimetry have been employed to investigate the dynamical evolution of the pulsed jet and allow the identification of the jet organized flow structures. The phase-averaging technique is applied to distinguish the large scale structure dynamics induced during the ejection phase. An array of active devices is also used to evaluate the flow control efficiency by forcing frequency strategy in order to reduce the separation area of a back facing step flow. Results show good performance in open loop flow control and applicability of such actuator for further closed loop flow control research.

The influence of the wall asymmetry on the flow dynamics, in two-dimensional rectangular deep cavities, is studied experimentally by combining wall-pressure and Piv measurements. Main cavity flow statistics [2] have been analyzed and they have shown that the flow features are strongly affected by the asymmetry. An emphasis is given concerning the behavior of the shear-layer oscillations that are compared to the analytical deep-cavity model prediction proposed by Block (Noise response of cavities of varying dimensions at subsonic speeds. Technical Report D-8351. NASA Technical Note, 1976 [4]). The results show that, by adjusting the convection velocity, the model seems to be still able to predict the cavity self-sustained oscillations in the case of the asymmetric cavities. Stochastic estimation of the cavity flows demonstrates that convective structures are involved downstream of the cavity along the wall and highlights the physical nature of the pressure-producing flow structures.

The fabrication activities associated with the construction of power plants envisage joints between steam pipelines operating at different temperatures and pressures. Various grades of steel are applied, depending on the operating conditions along the pipeline. The scope of the collaborative study conducted by Tenaris Dalmine, the Italian Welding Institute and Air Liquide Welding was to verify the behaviour of joints envisaging the coupling of steels corresponding to the following classifications with reference to the ASTM Standard: A335 P91–A335 P22; A335 P91–A335 P23; A335 P23–A106 Gr C. In this stage of the process, characterization envisaged the selection of weld materials consistent with lower grade steels, in accordance with standard industrial fabrication practices. The correct selection of treatment times and the chemical balance between base materials and fillers in addition to the weld parameters has yielded mechanical results completely satisfying the technical requirements.

An analytical model is first proposed for the determination of a friction-corrected flow stress in channel-die compression. A variational approach is then used for estimating the strain and strain-rate heterogeneities as well as the shape changes during deformation for two specimen geometries. The results are compared with finite element calculations. Results obtained from the two methods are in good agreement, except for the outer profiles of the deformed specimens. Finally, the various components of the powers involved in the deformation process are compared.

Torsion tests were carried out at 400°C and 0.1 s -1 on a homogenized 6060 (Al-0.48wt%Mg-0.43wt%Si) aluminium alloy. The microstructures were investigated by scanning electron microscopy and electron back-scattering diffraction (EBSD). The analyses of local misorientation distributions confirm the occurrence of continuous dynamic recrystallization, i. e., the progressive misorientation of subgrain boundaries and their transformation into high angle grain boundaries. The initially isotropic texture evolves toward the twin symmetric B/B component, i. e. {112} , for e=20. Orientation maps showing the B and B oriented grains illustrate the distribution of the grains belonging to the two orientations within the material. The various strains at which the mechanical and structural parameters reach their steady state are finally discussed.