The mechanical and thermal contact behaviour between two solids depends mainly on the contact geometry and the nature of these two solids. It is concluded that for rough surfaces in plastic contact the real contact is affected by the materials hardness, the surfaces roughness and the evolution of the mechanical contact deformation. The aim of the present study is to compare results obtained from experimental work on Vickers hardness of brass to those of the real contact pressure (RCP) obtained by numeric simulation. Hardness and RCP have been selected as physical quantities. For the numerical simulation, three three-dimensional element models are developed; firstly, we simulated Vickers assay using rigid indentor and a deformed plane surface of brass. In the second model we considered a brass indenter in contact with hard plane surface. The dimensions of the second model were changed to create the third model. The obtained results from the numeric models were in agreement with the experimental findings and confirmed the hypothesis of Abbott and Firstone. The three models of simulation may help to select the model that give the best results in short time.
This study presents a mixed numerical / semi-empirical approach that primarily aimed to estimate the thermal contact resistance between two solids. The results obtained by this mixed method were compared and validated by experimental measurements of this resistance. Three semi-empirical models were used, namely the Mikic model, the Yovanovich model and the Antonetti model. The three-dimensional finite element numerical simulation was used to estimate the contact pressure between the two solids. Then this contact pressure obtained numerically was compared to the hardness of the solids in contact. The findings indicated that the numerically obtained contact pressures were close to hardness. Therefore, the hardness, which is usually used as an input variable in semi-empirical models, was replaced by the contact pressure. The thermal contact resistance obtained by this mixed method was then compared with the experimental one. The outcomes obtained from this comparison turned out to be very conclusive and can therefore be used to reinforce our approach which can actually be viewed as a reliable and low-cost method for estimating the thermal contact resistance between solids in contact.
This research deals with the evolution of the structure of the sapphire–brass interface due to the variation of contact pressure. This evolution primarily affects the essential parameters that govern the thermal contact resistance (TCR), namely, the contact point density N, the ratio of real area of contact S*, and the distance d separating the median contact planes. The combination of three measurement techniques, namely, profilometry, imaging, and mechanical characterization, was used for the purpose of investigating the structural variation of the interface. Alternatively, the TCR, which prevails at the interface, was estimated. Thus, the object of our study is to propose an original and new experimental approach allowing at the same time the precise measurement of the TCR and the estimate of the contact parameters of the interface studied constituting input data to the theoretical models of TCR. The estimated values given by these last are then compared with those measured. Through this approach, we try to open new ways of experimentation that would tend to reinforce the effort of TCR modeling. The results obtained showed that the roughness parameters Ra and Rq are independent of loading. The roughness Rp, which is considered equal to d, is sensitive to loading and has the same decreasing behavior under the effect of loading. The determination of S*, using the hardness testing, is even more relevant when the effective hardness Hc is considered. Analysis of data for the estimation of the TCR shows that the comparisons with the reference model (Bardon) attest to the relevance of our approach.
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