Analysis of the Indentation Size Effect in the Microhardness Measurements inB₆O

Abstract

The Vickers microhardness measurements of boron suboxide (B6O) ceramics prepared by uniaxial hot-pressing was investigated at indentation test loads in the range from 0.10 to 2.0 kgf. Results from the investigation indicate that the measured microhardness exhibits an indentation load dependence. Based on the results, we present a comprehensive model intercomparison study of indentation size effects (ISEs) in the microhardness measurements of hot-pressed B6O discussed using existing models, that is, the classical Meyer's law, Li and Bradt's proportional specimen resistance model (PSR), the modified proportional specimen resistance model (MPSR), and Carpinteri's multifractal scaling law (MFSL). The best correlation between literature-cited load-independent Vickers microhardness values, the measured values, and applied models was achieved in the case of the MPSR and the MFSL models.

Hardness of Alumina/Silicon Carbide Nanocomposites at Various Silicon Carbide Volume Percentages

“…As expected, maximum scattering, typically 7-8% of the hardness value, occurred in the fracture-prone unreinforced Al 2 O3 and is particularly prevalent at the lower load ranges. As recommended 3,20 , in order to alleviate variance, each of the plotted data points is an average of at least 5 measurements. The typical conditions of the indents measured are presented in the SEM images in Fig.…”

“…Whilst a number of comparative studies conducted on several single-crystal and polycrystalline ceramics have remained inconclusive as to the ascendancy of each model 6,12,13,16,17,18,19,20 speculations concerning the cause of the ISE and the physical meaning associated with the "true hardness" have been widespread.…”

“…19,20,30,31 with some concluding that it is only logical to reject "true hardness" values that are below experimental measurments 44 . (c) MPSR model…”

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“…The parameter c 2 is the measure of the load-independent microhardness (plastic properties). The ratio a 1 /a 2 or c 1 /c 2 may be treated approximately as a measure of the residual stress due to machining and polishing [11,20]. Hays and Kendall proposed that there exists a minimum load W (N) necessary to initiate plastic deformation and below which only elastic deformation occurs.…”

Multiresponse Optimization of a Compliant Guiding Mechanism Using Hybrid Taguchi-Grey Based Fuzzy Logic Approach

“…Via finite element simulations, the pile-up on accuracy of sharp indentation test was demonstrated [4]. The Vickers microhardness of boron suboxide ceramics was measured via indentation [5]. The microindentation for human tooth enamel and dentine was performed [6].…”