Aerodynamic behavior of the bridge of a capacitive RF MEMS switch

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The present paper proposes a coupled 3D multi-physics model and presents the results of its transient simulation, for a RF MEMS capacitive switch of bridge-type. The fluid structure interaction (FSI) simulation sustains time-varying viscous damping and modified time response of the bridge deflection compared to the actuation modulation above closing of the switch. Complex 3D geometries of the bridge were rarely taken into account in viscous damping assessment much less in the simulation of the full flow around the bridge of the switch. The final goal of the paper is to obtain the dependency of an equivalent damping coefficient with respect to time, to be used in subsequent reduced order models for the switch, that include the aerodynamic behaviour of the switch

Failure analysis of dissimilar single-lap joints

Single-lap joints made of aluminium and carbon fibre adherends of different thickness are tested to understand better the behaviour of such dissimilar joints. The overlap length and the thickness of the adhesive are kept constant. Local deformation fields are monitored by using the digital image correlation method. Peeling and shearing strains are investigated, emphasizing that peeling is important in the region where failure is initiated, towards an extremity of the overlap region. The use of only carbon fibre adherends is not recommended for a smaller thickness as an additional interface failure is produced and compromises the integrity of the lap joint. However, a dissimilar joint (aluminium-carbon) with smaller thickness adherends succeeds to maintain the stiffness of the assembly, but its strength is diminished. The obtained results are suggesting that a complete monitoring of the failure processes in the overlap region can be fully understood only if local deformation measurements are possible

Efektywny i ekonomiczny układ sieci piezoelektryków do detekcji i lokalizacji uszkodzeń słabo zakrzywionych paneli

The paper presents results obtained in creating an efficient inspection technique, based on the Lamb wave method, by using a powerful central signal generator, a network of receivers and a simple triangulation algorithm for detecting and localizing a defect/damage in metallic or composite panels. This is intended to be done in two variants: (i) with a fixed central PZT patch able to blast powerful omnidirectional waves of the desired frequency, shape and duration and (ii) with a variable angle mobile actuator able to generate powerful guided waves. The first variant is aimed for online monitoring, while the second, for field inspections. At this stage, only numerical simulations of the first variant have been made, with promising results in metallic panels.W artykule zaprezentowano rezultaty badań dotyczących opracowania efektywnej metody inspekcji materiałów opartej na zastosowaniu fal Lamba wytwarzanych silnym centralnym generatorem sygnału oraz układem sieci czujników umożliwiającym wprowadzenie algorytmu triangulacji do wykrywania i lokalizowania uszkodzeń w pa- nelach metalicznych i kompozytowych. Zbadano dwa warianty realizacji tego celu: (i) poprzez naklejenie centralnego wzbudnika piezoceramicznego pozwalającego wygenerować wielokierunkową falę o zadanej częstotliwości, kształcie i czasie trwania, (ii) poprzez użycie mobilnego aktuatora o sterowanym kącie działania zdolnego do wytworzenia silnej fali prowadzonej. Pierwszy wariant jest przewidziany do ciągłego monitoringu konstrukcji, drugi do badań w terenie. Na obecnym etapie zrealizowano jedynie badania symulacyjne dla pierwszego wariantu, otrzymując obiecujące wyniki w przypadku paneli metalicznych

Evaluation of the structural behaviour of a port chamber following damages produced in the refractory lining

The port chamber used in oil refineries is an exhaust chamber mountedafter the catalytic reactor for retaining and unifying the exhaust hot processgases. The thick steel shell has a refractory lining made of refractorycement called gunite or shotcrete. Damages produced in the refractorylining have serious effects on the thermal generated stresses in the steelshell. The research work aimed to find the level of these stresses in anumerical/experimental approach and to evaluate its consequences onthe service life of this important component of the oil refinery. A complexsequentially coupled physics thermal-structural analysis was performedusing the ANSYS code in order to get the stresses generated by a deepcrack in the shotcrete layer. The results concerning the thermal mappingwere based on previous inspections made with infrared thermography(IRT) and made possible an estimation of the remained service life of theport chamber