Contribuição da mineralogia à dureza Knoop e ao desgaste abrasivo em algumas rochas silicáticas de revestimento

Abstract:

The Knoop hardness is one of the micro indentation hardness tests, where the hardness in a surface is determined as the ratio between the area of indentation produced by a diamond indenter and the applied load. Another hardness test commonly carried out in Brazil is the Amsler abrasive wear test, which utilizes quartz sand and the wear is measured, in millimeters, as the average thickness reduction after a 1.000-meter path. Since the hardness of a material is function of several parameters in a multivariate and interdependent universe, this study applied statistical analysis following the multiple regression method. Sixteen aluminous-silicatic rocks (containing 35 % to 0 % of quartz, including granites, monzonites, gneiss and others) commercially designated as granites from São Paulo State, Brazil (Frascá, 2000), were selected for this study. The results indicated that the Knoop hardness and the Amsler abrasive wear tend towards an inverse proportionality, or as higher is the hardness, lower is the wear. In the studied samples the best correlation between the parameters of Knoop hardness and Amsler abrasive wear was 0,56 (R2), obtained by multiple linear regression. The Knoop hardness, particularly the average value, tends to higher values as the quartz content increases, but the correlation is poor (R2 = 0,35). Relatively to the quartz grain-size, it was observed a tendency to the increase of hardness, especially HK25, with the increase in the minimum size of the quartz grains (R2 = 0,37). Considering only the quartz, plagioclase and K-feldspar contents, in a multiple linear regression, the Amsler abrasive wear can be predicted with a slightly better correlation (R2 = 0,59) than Knoop hardness.


Referência:
QUITETE, Eduardo Brandau. NAVARRO, Fabiano Cabañas; FRASCÁ, Maria Heloisa Barros de Oliveira . Contribuição da mineralogia à dureza Knoop e ao desgaste abrasivo em algumas rochas silicáticas de revestimento. In: SIMPÓSIO DE ROCHAS ORNAMENTAIS DO NORDESTE, 9., 2016, João Pessoa. Anais… 10 p.  

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