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.

Although condition monitoring of centrifugal pump bearings to infer faults is common practice, the relationship between a pump’s vibration level and the unsteady flow within has not been extensively researched. The latter, however potentially provides the foundations for further developments in, pump design to increase performance, advanced predictive maintenance programs and, vibration monitoring techniques that can permit inference of pump efficiency states. This paper investigates the correlation between pump vibration and unsteady flow at different motor speeds. A test rig and a numerical CFD model were employed. It was found that flow-induced vibration in general increases with pump speed and was clearly linked to pump efficiency. It therefore seems possible to construct a model to deduce a pump’s efficiency from its pressure and vibration levels, if the efficiency curve is known a priori. However, as the vibration levels are also dependent on the system’s structural natural frequencies and modes, it seems that knowledge of these may also be needed in some instances. The work confirms that utilising a variable speed pump at lower pump speeds allows greater deviations from the design BEP without jeopardising the safety of the pump and should be considered for industrial use.

In this paper, we consider the possibilities of the stimulated infra-red thermography for local metallic sample thermal characterization. At first we introduce the measurement principle, which is based on the local measurement of the thermal diffusivity parameter. Then, using simulations, we demonstrate the feasibility of the method. We then present the experimental device implemented for the study. Finally, we show that this approach allows a good estimation of the thermal diffusivity of a metal sample.

When operational modal analysis (OMA) is conducted on operating machines or structureswithout knowing excitations and perturbations neither the number of concerned frequencies,one problem raises on the validity of modal parameters identification (especially dampingratios) and on the precision of results obtained. This paper presents an OMA methodallowing for the evaluation of uncertainties of modal parameters (frequencies, dampingratios and mode shapes). The method is based on the vector autoregressive model (VAR) formultiple numbers of measured channels. It is seen that the uncertainty of modal parametersdecreases with higher model orders; the calculation of uncertainty allows also for theconstruction of an objective criterion for the selection of computing model order based ona threshold of confidence interval. The derivation confirms also that the identificationof natural frequencies deals with a smaller uncertainty compared with the damping ratioestimation, and hence it can be conducted with a lower computing model order. Numericalsimulations and experiments on a steel plate show the feasibility and the effectiveness ofthe developed OMA method.

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.

In this paper, a Levy-type solution based on the modified couple stress theory isdeveloped to study the buckling behaviors of micro-plates. Based on this theory, lengthscale parameter is considered to capture the size effect of rectangular micro-plates.Minimum potential energy and adjacent-equilibrium criteria are exploited to obtain thestability equations and corresponding boundary conditions. Different boundary conditionswith two opposite edges simply supported and arbitrary boundary conditions along the otheredges are considered. To illustrate the new model, both uniaxial and biaxial loads areapplied and the critical buckling loads are defined for over a wide range of thickness,different length scale parameters and various boundary conditions. To show the accuracy ofthe formulations, present results are compared with available results in literature forspecific cases and a very good agreement is observed. Results reveal that the criticalbuckling load increases as the length scale parameter increases especially when thethickness of the micro-plates becomes in order of length scale parameter and this effectis more significant for free boundary condition.

In this paper, a computational investigation of thermohydrodynamic performance andmechanical deformations of a fixed-geometry thrust bearing with artificial surfacetexturing is presented. A parallel eight-pad bearing is considered; the surface of eachpad is partially textured with square dimples. Here, a CFD-based thermohydrodynamicmodeling approach, recently introduced by the authors, is used to calculate theperformance of the bearing; the THD results are then used to quantify the deformations ofthe bearing mechanical parts. The bearing is modelled as a sector-shaped channel,consisting of a smooth rotating wall (thrust collar) and a partially textured stationarywall (bearing pad). The bearing performance characteristics are computed by means ofnumerical simulations, based on the numerical solution of the Navier-Stokes and energyequations for incompressible flow, as well as on the solution of the elasticity equationsfor the bearing solid parts. Here, a reference texture geometry is considered, whileproper thermal and structural boundary conditions are implemented. For representative filmthickness values, the effect of rotational speed and collar thickness on bearingperformance is quantified, and the resulting pad and rotor deformation fields arecomputed. It is found that, due to oil heating, the load carrying capacity decreases withrotational speed for values higher that approximately 2000 rpm. The computed rotordeformation field is representative of a fixed support beam, characterized bysubstantially higher levels than those of the bearing pad. Rotor deformations increasesubstantially at low values of collar thickness.

The vibrations undergone by men are a well-known and widely studied risk factor in the industrial world. They are transmitted to the whole body or the upper limbs and they are measured, and limited, according to international standards. Disorders resulting from exposure to vibration are varied in nature: osteoarticular, muscular, vascular, and neurological. In this context, an European Directive 2002/44/EC to the protection of workers exposed to vibration, precises thresholds for vibration exposures and defines the procedure for risk prevention. Nevertheless, the effect of vibration is little studied in sports despite the ubiquity of these. Vibration can induce discomfort, degrading performance or causing musculoskeletal disorders. This paper makes an overview of the studies involving the vibrations during cycling. At first, this paper will summarize the different standards and guidelines relating vibration in humans, which present a guide for the measurement and evaluation of the vibration and exposure limits. Secondly, this paper presents a state of the art vibration effects: (i) the physiological and pathological disorders in athletes, (ii) and the performance. A third part will be devoted to the synthesis of numerical studies that represent the biodynamic response and help to predict the effects of human body vibration. Finally, new research and innovations will be discussed based on studies in other sports.

The effects of punch geometry and sample size on forming limit diagrams in expansion areinvestigated in the case of a 2024 aluminium alloy. Four configurations were selected:flat punch (Marciniak test) or hemispheric punch and decimetric vs. centimetric toolingdimensions. Both decimetric and centimetric deep-drawing devices are associated with animage correlation tool that allows identifying without any contact the deformation on thesurface of planar or non-planar specimens. Strains on the surface of the samples areobserved by means of a double numerisation in three dimensions of the sample before andafter deformation by using stereoscopic vision and triangulation. Finally, deep-drawinglimit of the four configurations are compared in expansion state and with literature.Results mainly show that hemispherical punch allows measuring higher strains and is lesssensitive to size effect than Marciniak test.

Current demands of higher damage-tolerance in the Aerospace industry resulted inresurging interest in β, or near β, titanium alloys. The combination of attractiveproperties of this class of alloys also led to the consideration of beta alloys forcastings. Such alloys, however, are more difficult to cut than α-β titanium alloys due totheir limited ability to work harden and the effect of β-stabilizers on ductility.These factors affect failure modes and active wear mechanisms of cutting inserts. Thispaper investigates some of the wear modes exhibited by WC-Co inserts when end milling theαnear-βalloy Ti-x.In addition to being of near-β composition, this alloy is characterized by a finesized microstructure (range of 1−5 μm). The study focuses on SEM and EDS observations ofthe wear patterns exhibited by two groups of inserts. The first is uncoated WC-Co, whereasthe second is coated with multi layers of TiAlN. The results of this post-mortem study arecompared to wear patterns, observed under identical conditions, while milling theα-β alloy Ti6Al4V. Results show that inserts used inmachining the Ti-x alloy exhibit wear modes that contrast thoseexhibited when machining Ti64. The paper discusses factors leading to such occurrences andstudies the influence of the alloy microstructure on tool effectiveness and failure modes.

In this paper, we present techniques for fatigue damage evaluation using spectral methodsand a model taking into account confined elasto-plastic behavior. The model is associatedwith a local fatigue approach, covering the whole endurance domain (low cycle and highcycle fatigue). It uses Neuber’s method and is valid for limited plasticity. To validatethis modeling, we perform a correlation between spectral methods, modified spectralmethods and experimental tests. Results presented here are focused on the uniaxial loadingcase.

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.

This study presents a finite element (FE) model of the human hand-arm system to derivenatural frequencies and mode shapes. The FE model is calibrated by considering modalparameters obtained from experimental vibration analyzed by using operational modalanalysis (OMA) and transmissibility. Modal and harmonic analyses of the FE model areperformed for two boundary conditions. The first one considers fixed shoulder conditionwhile the second one introduces the trunk in order to permit motion of the shoulder. Theresults show that the natural frequencies of the second model that permits shoulder motionare comparable with those determined from measurements. Especially, the natural frequencyabout 12 Hz, which is corresponding to the frequency of maximum weight in ISO-5349-1(2001), is not present in the model with fixed shoulder condition, while it appears in thesecond model. The results of the present study suggest that improved finite element modelsof the human hand-arm system may reveal hand-arm injury mechanism, the understanding ofwhich may assist in deriving appropriate frequency weightings for the assessment ofdifferent components of the hand-arm vibration syndrome.

In this work, we approach the possibilities of infrared thermography for non-destructive testing of metallic materials. We show that the passive alternative of the method makes it possible to improve detection of surface defects existing in deep-drawn parts and visible to the naked eye. We then show that active infrared thermography, in particular coupled with induction excitation, can replace in certain cases the magnetic particle inspection, allowing the detection of very fine defects in forged parts. Finally, the study of a stepped block confirms the possibilities of active infrared thermography to detect defects not open to the surface and underlying defects.

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

For qualitative prediction of chip morphology and quantitative prediction of burr size,2D and 3D finite element (FE) based turning models have been developed in this paper.Coupled temperature-displacement machining simulations exploiting the capabilities ofAbaqus® with a particular industrial turning insert and a newly proposed geometricalversion of this insert have been performed. Limitations of 2D models in defining the chipmorphologies and surface topologies have been discussed. The phenomenological findings onthe Poisson burr (Side burr) formation using 3D cutting models have been highlighted.Bespoke geometry of the turning insert has been found helpful in reducing the Poisson burrformation, as it reduces the contact pressures at the edges of tool rake face-workpieceinterface. Lower contact pressures serve to decrease the material flow towards workpieceedges (out of plane deformation). In contrast, higher contact pressures at tool rakeface-workpiece interface lead to more material flow towards workpiece edges resulting inlonger burr. Simulation results of chip morphologies and cutting forces for turning analuminum alloy A2024-T351 have been compared with the experimental ones. Finally, it hasbeen concluded that the newly proposed geometry of the insert not only decreases the burrbut also helpful in lessening the magnitude of tool-workpiece initial impact.

The measurement of the thickness of a coating layer is a traditional industrial problem. Many methods of measurement are already classically used for that purpose. However, the majority of these methods require either contact with the sample to be studied, or its destruction. These constraints limit their applicability. Photothermal radiometry is already largely used in the field of thermophysical properties measurement and for the detection and characterization of defects. This method does not impose the constraints mentioned above. It could thus be a complementary technique of the classical ones. The purpose of this work is then to approach the possibilities of this photothermal method, implemented under pulse excitation and front face analysis, for the measurement of the coating thickness. Using theoretical and experimental studies, we show that the method allows a good estimation of the thickness of chromium deposits on a steel substrate, at distance, without contact and in a non-destructive way.

The efficiency of passive methods for noise reduction decreases at low frequency. In thisfrequency range active structural acoustic control (ASAC) can reduce sound radiation ofstructures by controlling their vibration usually using piezoelectric or electrodynamictransducers. Besides its global effect on the structure, a bending nearfield is observed,depending on the actuator type. In some ASAC strategies as in the virtual impedanceapproach, actuators and sensors are collocated. Although it does not affect the radiationof the structure, the local bending strongly modifies the transfer function betweentransducers. A method is proposed in order to identify and compensate it. The global partof the vibratory field is extracted by cancelling the contribution of higher order modesapproximated as a stiffness. After compensation, the signal from the sensor is much morerepresentative of the radiation and nearly independent of the nature and the size of theactuator.

Cet article porte sur une méthode d’estimation, novatrice et non intrusive, de la conductance thermique de contact dans un mur de réacteur métallurgique. Dans le cas d’un réacteur métallurgique, il est essentiel de déterminer la conductance thermique de contact dans l’assemblage des parois. Cela permet d’identifier et de corriger les défauts de contact avant la mise en fonctionnement du réacteur métallurgique. Cette étude recourt à la méthode inverse du gradient conjugué avec un problème adjoint, pour réaliser cette estimation. La méthode a été validée à l’aide de tests numériques représentant un diagnostic du contact thermique entre une paroi réfractaire et une paroi d’acier du réacteur métallurgique avec différentes conductances thermiques de contact. Dans un second temps, des tests supplémentaires ont été réalisés pour observer l’évolution de l’erreur d’estimation en fonction de deux nombres sans dimension, le rapport de conductivité thermique et le nombre de Biot. Cela a permis de conclure qu’il faut avoir simultanément un rapport de conductivité thermique supérieur à 1 et un nombre de Biot supérieur à 0,005 pour obtenir une estimation précise dans les cas étudiés.

The main objective of this article is to study the effect of 2D coupled mode freeconvection with surface radiation on the fluid flow behavior in an air filled partitionedand shallow cavity subjected to isothermal or insulated boundary conditions. Thedimensionless governing equations under Boussinesq approximation are coupled with aradiative model through the boundaries conditions and solved by the finite volume method.The numerical results are discussed in terms of streamlines, isotherms, convective andradiative Nusselt numbers along the cover plate for various aspect ratios (a, b and c), emissivities andRayleigh number. These results highlighted the condition of the enclosure performance andrevealed among other that isothermal boundaries induce better convective heat exchangecompared to adiabatic cases. Also, it is noticed that varying aspect ratio(a) causesstrong influence on both Nusselt numbers compared to the aspect ratios (b) and (c). The increase of(ϵo) raisesNuconvand decreases Nuradslightly. Whereas, an increase of (ϵC) leads to minorchanges in Nuradwhen (b) or(c) vary,this effect becomes appreciable with increasing (a).