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Alloys Used (alloy + used)
Selected AbstractsDynamic simulation of kinetics, heat and mass transfer during hydrogen sorption by LaNi5ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Dr Tarek Moustafa Abstract A two-dimensional transient heat and mass transfer models have been developed to investigate the dynamic phenomena of hydrogen absorption and desorption in metal hydride bed. LaNi5 has been chosen as the alloy used for hydrogen storage. The numerical simulation has been conducted to simulate the time,space evolution of temperature, fractional conversion, hydrogen pressure and velocity, in addition to metal density. A correlation for the volumetric reaction rate has been deduced. Also, comparisons have been done between various bed geometries and their influence on the average hydrogen desorbed mass. The simulation results showed that heat transfer controls the overall rate of absorption and desorption processes, and because the driving force for the hydrogen flow is the axial pressure difference; the challenge to get optimum bed geometry is in compromising between heat transfer and pressure drop limitations. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Corrosion of some selected ceramic alloys used in fixed partial dentures and their postsolder joints in a synthetic neutral salivaEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2009Pascal De March The electrochemical behavior of several alloys used in the frameworks of fixed partial dentures and their corresponding postsolders was studied in artificial saliva as a function of chemical composition. Open circuit potentials and polarization resistances were measured. The general electrochemical behaviors between the cathodic domain and the oxidation of solvent were characterized using cyclic polarization. The possible galvanic corrosion of coupled parent and postsolder alloys was also studied. The polarization resistances were high or very high. During immersion, the noblest alloys stayed in the immunity domains of their base elements, whereas Ni,Cr alloys were quickly passivated. The oxidation of the noble elements occurred only when the alloys were exposed to very high potentials solely achievable by artificial means. However, problems of galvanic corrosion may occur between an alloy and its postsolder joint if they are both exposed to saliva. Such corrosion may lead to a weakening of the framework. The parent alloy was often potentially affected by such corrosion but with low exchange currents. [source] Acceptable prior fatigue damage and failure threshold for impact loading of an aluminium alloyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2001T. Auzanneau In a competitive economic context that aims at gains in safety, some problems of combined fatigue-impact loadings are crucial, particularly in the case of light alloys used in the transport and aeronautical industries. One important challenge is to quantify the fatigue preloading effect on the residual dynamic plasticity of a 2017-A T3 aluminium alloy. From an experimental modal analysis, the change in mechanical properties of prefatigued material under impact loading allows us to define the best mechanical parameter for a limiting threshold between a no-damage state and weakened states due to fatigue predamage. For this situation a hybrid technique has been developed. A numerical model including voids (which represent surface micro-cracks produced by the fatigue preloading) is fitted to the results obtained by the modal analysis of the damaged sample. Hence, an acceptable damage threshold (i.e. a damage critical volume below which the impact toughness is not affected by fatigue preloading) and a failure threshold are established. On the basis of this methodology, it is possible to predict the energy required for the impact failure of prefatigued specimens and therefore to predict a safe or a dangerous mechanical state. [source] In vitro evaluation of the effect of a current bleaching agent on the electrochemical corrosion of dental alloysJOURNAL OF ORAL REHABILITATION, Issue 10 2002enay Canay summary, The nightguard bleaching of discoloured teeth is currently performed by using % 10 carbamide peroxide. While the material is effective on the bleaching of natural teeth, it may deteriorate crowns, bridges and amalgam restorations placed in the mouth. The purpose of the present study was to investigate the effect of 10% carbamide peroxide on the electrochemical corrosion of various dental casting alloys used for fixed partial dentures and dental amalgam. Tafel extrapolation curves were obtained by the corrosion cell that facilitated simulation of the oral enviroment and comparison of the corrosion rates of alloys and amalgam was accomplished. The results revealed that unpolished amalgam and nickel-chromium alloy samples had the most and noble alloys had the least corrosion rate. [source] Effect of cantilever length and framework alloy on the stress distribution of mandibular-cantilevered implant-supported prosthesesCLINICAL ORAL IMPLANTS RESEARCH, Issue 7 2009Letícia Borges Jacques Abstract Objectives: The purpose of this in vitro study was to analyze the stress distribution on components of a mandibular-cantilevered implant-supported prosthesis with frameworks cast in cobalt,chromium (Co,Cr) or palladium,silver (Pd,Ag) alloys, according to the cantilever length. Material and methods: Frameworks were fabricated on (Co,Cr) and (Pd,Ag) alloys and screwed into standard abutments positioned on a master-cast containing five implant replicas. Two linear strain gauges were fixed on the mesial and distal aspects of each abutment to capture deformation. A vertical static load of 100 N was applied to the cantilever arm at the distances of 10, 15, and 20 mm from the center of the distal abutment and the absolute values of specific deformation were recorded. Results: Different patterns of abutment deformation were observed according to the framework alloy. The Co,Cr alloy framework resulted in higher levels of abutment deformation than the silver,palladium alloy framework. Abutment deformation was higher with longer cantilever extensions. Conclusion: Physical properties of the alloys used for framework interfere with abutment deformations patterns. Excessively long cantilever extensions must be avoided. [source] | ||||||||||