An international benchmark has been organized by EDF R&D during 2008–2010, gathering 11 partners. Its main objective is to quantify the confidence in numericalmodels. The built-up dynamical system considered is a pump actually in service in powerplants, considered in its work environment. Blind eigenfrequency numerical values relativeto the pump assembly fixed in concrete present a larger variability than the 5% roughvariability concerning the separate parts, essentially due to the modeling of the boundaryconditions and interfaces at macro level. For the nine first eigenmodes considered, experimental-numerical correlation shows a frequency error less than 15% for the freesub-structures and nearly 30% for the free five-component system. Though the first overallmodes are correctly identified, the frequency error is significantly larger for theclamped pump assembly, with however MAC coefficients higher than 0.9 for two modes; butthe frequency error can be reduced to less than 9% for the four first modes after updatingprocedure. A lesson to draw is that measurement information is needed to improve thequality of theoretical built-up structure. After this benchmark, a more ambitious researchprogram will follow as a FUI project, gathering the observation of numerical andexperimental variabilities, updating model improvement and numerical quantification of thetotal uncertainty.

This paper presents the comparison of results obtained from two codes with different degrees of accuracy and computational time on the case of a contra-rotating open rotor (AI-PX7). The main goal is to assess the capacity of a code based on singularity methods to predict global open rotor performance, the in-plane loads (also called 1P loads), and the blade load distribution during a full blade cycle. Moreover, installation and unsteady correction models have been implemented in this code in order to evaluate the possible improvements of initial predictions. Finally, a numerical method to quantify some of the mechanisms governing open rotor thrust and 1P loads is proposed.

An algorithm of operational modal analysis in time domain is presented for thediscrimination between structural modes, harmonic excitations and spurious modes. Aclassification factor is developed and based on the construction of the damped signal- to-noise ratio which separates the physical modes from the numerical ones. The harmonicexcitations are then recognized at very high power indexes and zero damping. Furthermore, after the modal discrimination, the harmonic spectrum and the estimated frequency responsefunction can be derived. The method can be updated in the time domain either by a shorttime sliding window or a recursive technique to provide the modal monitoring in bothstationary and non-stationary process. An industrial application on a hydro-electricalgenerator is discussed to identify the machine frequencies under operational workingconditions.

Impact wear can be defined as the wear of a solid surface due to percussion, which is arepetitive exposure to dynamic contact by another solid body. It has not been studied asextensive as other wear mechanisms and the information on causes and actual data is quitescarce. In the present work an experimental wear tester is designed and used to study theimpact wear phenomenon experimentally. It creates the consecutive impacts between ballsand flat plate. The different ball sizes (up to 30 mm), impact velocities (up to 6m.s-1) and impactangle (10°− 80°) can be tried by tester. The mass lossof plate is measured as the wear parameter. These measurements for different specimensrevealed some aspects of their wearing behaviors. The obtained results could be helpful inoptimal practical designs and explanation of some phenomena associated with impact wear.

Cleavage fracture anisotropy has been studied on a ferrite-bainite low alloy pipeline steel plate. Mechanical tests have been performed on smooth and notched bars taken along the three principal directions of the plate at temperatures between 20 °C and −196 °C, and analyzed by finite element calculations with an anisotropic plasticity model. The fracture mode of specimens tested along the normal direction differs from that of specimens taken along the two other directions, together with a lower critical cleavage stress. This difference seems to be related to microtexture anisotropy and might explain the sensitivity of this steel to delamination at low temperatures.

Laser polishing is a finishing process based on melting material, with the objective of improving surface topography. Some operating parameters must be taken into consideration, such as laser power, feed rate, offset, and overlap. Moreover, because of its dependence on the primary process, the initial topography has also an impact on the final result. This study describes a quadratic model, conceived to optimize final topography according to the primary process and laser polishing. Based on an experimental matrix, the model takes into account both laser operating parameters and the initial topography, in order to predict polished surfaces and to determine an optimal set of parameters. Furthermore, uncertainties linked to the measuring device need to be taken into consideration, as well as the process variability, in order to facilitate the interpretation of the results. After the phase of experimentation and the creation of the quadratic model, an optimal final topography is introduced, taking into account the initial surface and the laser parameters. Finally, in order to reduce the time process, it is important to study the impact of laser polishing strategy on the surface roughness.

In this study, effects of surface modification of calcium carbonate (CaCO3) nanoparticles with a single-layer of stearic acid were investigated on dispersion in polypropylene (PP) matrix. Two kinds of CaCO3 nanoparticles (monolayer-coated and uncoated) were used to investigate this effect. All combinations were mixed in a co-rotating twin screw extruder and then were injection molded. After breaking the injection molded parts in liquid nitrogen, effect of surface modification of nanoparticles on their dispersion in the PP matrix was investigated using a field emission scanning electron microscope (FESEM). The results showed good agreement between the measurements made with the TGA analysis and the existing theories. The surface modification of calcium carbonate nanoparticles using a single layer of stearic acid also had an effective influence on improving distribution and dispersion of nanoparticles in the PP matrix.

In this paper, composites based on unsaturated polyester resin reinforced with short Alfa fibers are studied in detail. Alfa fibers have been previously treated with various concentrations NaOH (1, 3, 5, 7%) during 24 h. The influence of alkali treatment on fiber morphology is analyzed. Analysis by FTIR and X-ray diffraction showed physico-chemical changes in Alfa fiber treated surfaces. SEM observations also helped to highlight these changes. The results of static tests on composites showed improvements in tensile and flexural strengths of composites reinforced with the treated fibers, particularly the composite with treated fibers at 7% NaOH. These improvements were about 30% and 50%, respectively, compared to untreated fiber reinforced composite.

The air is modeled as incompressible flow in a ribbed channel. The existence of ribs onchannel surface causes the turbulence in flow, therefore we must solve the turbulenceequations. There are previous experimentally investigations on turbulence flow in ribbedchannels. In this article, the results of numerical simulation are compared withexperimental results and the effectiveness of k−ε model in solving theproblem of micro-particle deposition with Lagrangian model is studied because ofcomplexities of turbulent flow, the problem is modeled both 2- and 3-dimensionally. Aftersolving the fluid domain, the particle equations of motion are solved separately andfinally the particle deposition on channel surface is calculated. Considering the physicand complications of turbulent flows, the results of 2-D simulation are different withexperimental results, despite of 3-D results, which are in complete accordance withexperimental results.

In this paper, we study the phenomena of thermo-chemical imbalance in a reactive mono-dimensional flow composed of a mixture of (79% nitrogen N2 and 21% oxygen O2). We are interested in modeling the physicochemical process that may be encountered in hypersonic flows, as vibrational excitation, dissociation and ionization, also the formation of chemical species to higher temperatures behind a detached strong shock. We put a special emphasis on vibrational relaxation model of CVD coupling. At these high temperatures, collisions electrons-atoms become very effective, taking in account the radiation that requires knowledge and modeling of all physicochemical processes (collisional and radiative). The mathematical model of flows at the atmospheric reentry is governed by Euler stationary equations coupled with the chemical kinetics and the radiative transfer equations. Our computational code is based on the finite differences method that used to discretize and resolve the obtained numerical model, where an appropriate mesh is selected in the relaxation zone in order to determine the flow parameters at each grid position

This paper is a numerical work to investigate thermal interactions between heat fluxes generated by electronic devices mounted on a vertical printed circuit board (PCB). In fact, the effect of some parameters such as Grashof number (Gr), the distance (S) between the heat sources and the upper exit distance (Le) was studied. The results show that a regular and uniform heat sources distribution in the inlet is very important in order to take advantage from the leading edge of the boundary layer and to obtain the necessary heat dissipation. The impact of parameters on the heat dissipation, characterized by the Nusselt number, has a different importance. For a Prandtl number Pr = 0.71, the (Gr) increases the heat exchange that is reflected by the increase of Nusselt number, and also participates to the formation of recirculation zones. The total Nusselt number Nu is increased when (Gr) is multiplied by 102. With regards to the distance (S) between the heat sources, the results show that Nu increases about 7% if the distance (S) doubles, and becomes approximately 17.8% when (S) quadruples. At the end, the heat transfer increases when increasing the distance (Le) of the upper exit length, especially on the second component. The total Nusselt number increases by 1.6% when (Le) increases by about 67%.