Applied Mechanics and Materials Vol. 772

Abstract: The production high purity hydrogen by water electrolysis based renewable sources as a mean to store energy, has gained some attention in the last years due to the high specific energy of hydrogen, the potentially neutral carbon and zero emission of the usage of H₂ as fuel. However, it remains certainly necessary to develop efficient and lower cost electrolyzers. Such a situation requires the search for and the development of inexpensive and stable electrode materials, showing low polarization to hydrogen evolution reduction (HER). In this work copper and nickel oxides were studied for use as electrodes for the reduction of hydrogen in alkaline water electrolysis. The nickel and copper oxide composites coatings were deposited electrochemically as oxides/hydroxides on a stainless steel (SS) electrode and characterized using electrochemical methods such as cyclic voltammetry (CV), cathodic polarization and Tafel slops. The HER was studied using as electrolytic cathodes unmodified AISI 304 stainless steel (SS), nickel coated stainless steel (SS/Ni), copper coated stainless steel (SS/Cu), and nickel (under layer) and copper (top layer) coated stainless steel (SS/Ni/Cu) in 5 M KOH solution. It was found that, the SS/Ni/Cu electrode presents good electrocatalytic activity and stability toward the HER, compared to the SS electrodes modified by single nickel oxide layer. This behavior seems be explained by the synergistic interaction of Ni and Cu with Fe present in the stainless steel.

Abstract: Zinc oxide nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensing material due to their unique fundamental material properties. This paper presents the characterization of ZnO thin film as biosensing material by metallic strip grating structure (MSG), for the real-time detection. In this work, high quality ZnO films were grown on ITO/glass substrates by vacuum thermal evaporation method. We characterized by X-ray diffraction (XRD) the film crystalline quality and by scanning electron microscopy (SEM) the film morphology.

Abstract: Germanene, an allotrope of germanium which is a two dimensional material with sp² hybridization, has almost the same properties with graphene except for its buckled structure. In this study, germanium nanoribbon (GeNR) is use for it is still a new material for nanoscale level of research. In this paper, we investigate the effect of chirality on the thermal conductivity of zigzag GeNR (ZGeNR) and armchair GeNR (AGeNR) chiralities using equilibrium molecular dynamics with varied lengths at fixed temperature and varied temperatures at fixed length. The simulations were carried out in Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) using Tersoff potential for the Ge-Ge interactions. The thermal conductivity is calculated using Green-Kubo method. It is found that the chirality can affect the thermal conductivity of GeNR. Our results show that thermal conductivity of AGeNR is higher than ZGeNR in both increasing temperatures and lengths similar to the thermal conductivity behavior obtained in silicene nanoribbons [Int. J. Mech. Mater. Des. 9 (2013) 105].

Abstract: In order to improve both the scratch strength and the micro-hardness of (Al,Cr)N coating film, the cathode material of an aluminum/chromium/tungsten target was used in adding the tungsten (W) to the cathode material of the aluminum/chromium target. In this study, hardened sintered steel was turned with (Al60,Cr25,W15)N, (Al60,Cr25,W15)(C,N), (Al64,Cr28,W8)(C,N), (Al,Cr)N and (Ti,Al)N coated cemented carbide tools. The tool wear of the coated cemented carbide tool was experimentally investigated. The following results were obtained: (1) In cutting hardened sintered steel at the cutting speed of 0.42 m/s using the (Al60,Cr25,W15)N, the (Al60,Cr25,W15)(C,N), the (Al64,Cr28,W8)(C,N), the (Ti,Al)N and (Al,Cr)N coated tools, the wear progress of the (Al64,Cr28,W8)(C,N) coated tool became slowest among that of the five coated tools. (2) The wear progress of the (Al60,Cr25,W15)(C,N) coated tool was almost equivalent to that of the (Al64,Cr28,W8)(C,N) coated tool. However, at a high cutting speed of 1.67 m/s, the wear progress of the (Al60,Cr25,W16)(C,N) coated tool was faster than that of the (Al64,Cr28,W8)(C,N) coated tool.

Abstract: The increasingly tougher international regulations force motor vehicle designers and manufacturers to find complex solutions that should increase the protection of motor vehicle occupants. In this paper the author carries out an analysis on the energy absorption by a front strut-type structure of a motor vehicle involved in head-on collision with a rigid barrier inclined at various angles. Small overlap collisions open new challenges for car manufacturers with a view to developing structures able to absorb the impact and provide safety to the motor vehicle occupants.

Abstract: The present paper underpins a contrastive study of the driver’s behavior and the injuries suffered in frontal vehicle collision, with a focus on the analysis of head-specific injuries. Four different simulation cases have been performed by means of the LS-DYNA software, where a seated belted and/or unbelted Hybrid III 50th percentile male dummy was in turns normally-positioned and out of position. Accordingly, both the analyses as well as the numerical simulation have been completed by applying a five-component model that encompasses: the dummy, the seat, the seatbelt, the steering wheel and the airbag. The assembly’s prescribed motion has been defined following a frontal Virtual Crash software-based impact simulation of a mid-size sedan at a velocity of 50 km/h against a rigid wall. The results analysis aimed at identifying the longitudinal variation laws over time in head displacements and accelerations as well as lateral motion. Admittedly, the results analysis certified that a more controlled-oriented approach to the selection of the driver’s normal positioning is a prerequisite in compliance with typical driving particularities.

Abstract: In this paper, numerical studies have been conducted in order to evaluate the efficiency of a vertical axis wind turbine by using CFD methods. For these studies, it has been used SIMPLE type pressure-based coupled solver. The complexity and the unsteadiness character of the flow in such a machine, requires the use of unsteady RANS models. To determine the accuracy of the solution obtained by URANS models, this paper makes a comparative analysis with the same case and LES modeling. Analyses were performed with a 2D grid consisting of two regions, a rotor and a stator. The airfoil of the VAWT is a classic NACA0018. Results indicate that the poor accuracy of the URANS CFD method is mainly due to its limitation in the vortex modeling. In general the LES modeling have a better agreement with the experimental results from the wind tunnel.

Abstract: The work puts forward an analytical method for the optimal kinematic design of the wheel suspension - guiding mechanisms. The independent design variables in the optimal synthesis are the global coordinates of the joints on car body (chassis), which is fixed on ground. The design objectives relate to the variations of the toe angle, camber angle, wheel track, and wheelbase. The goal of the optimal synthesis is to minimize these variations during the wheel travel. The proposed method contains three steps: imposing finite positions for the wheel, determining the global coordinates of the joints on car body, and analyzing the guiding mechanism.

Abstract: This paper presents the preliminary results of the numerical simulation of flow and combustion in a one stage turbine combustor (turbine stage in situ combustion). The main purpose of the simulation is to assess the stability of the in situ combustion with respect to the unsteadiness induced by the rotor-stator interaction. Apart from previous attempts, the salient feature of this CFD approach is the new fuel injection concept that consisting of a perforated pipe placed at mid-pitch in the stator row passage. The flow and combustion are modelled by the Reynolds-averaged Navier-Stokes equations coupled with the species transport equations. The chemistry model used herein is a two-step, global, finite rate combustion model while the turbulence model is the shear stress transport model. The chemistry turbulence interaction is described in terms of eddy dissipation concept.

Abstract: All floating structures react different to sea currents and waves and the commonly asked question is how to understand, simplify and make distinction of structure according to the operational challenges. The main objective of this paper is to determine the response of a three column semisubmersible platform as used by WindFloat project with available CFD software: CFX and Fluent. The WindFloat created by PowerPrinciple is presented and the present study will consider only the semisubmersible.