Abraded Glass Strength: An Ad Hoc Fitting Protocol Based on the Change of Variable Theorem

This work tackles the problem of finding a suitable statistical model to describe relevant glass properties, such as the strength under tensile stress. As known, glass is a brittle material, whose strength is strictly related to the presence of microcracks on its surface. The main issue is that the number of cracks, their size, and orientation are of random nature, and they may even change over time, due to abrasion phenomena. Consequently, glass strength should be statistically treated, but unfortunately none of the known probability distributions properly fit experimental data, when measured on abraded and/or aged glass panes. Owing to these issues, this paper proposes an innovative method to analyze the statistical properties of glass. The method takes advantage of the change of variable theorem and uses an ad-hoc transforming function to properly account for the distortion, on the original probability distribution of the glass strength, induced by the abrasion process. The adopted transforming function is based on micromechanical theory, and it provides an optimal fit of the experimental data.

Flexural strength of glass using Weibull statistic analysis

Purpose: The aim of the study is to measure the flexural strength of glass by proposed experimental procedures. In addition, step-by-step guidelines for the strength data analysis using a two-parameter Weibull distribution are given. Design/methodology/approach: Twelve glass samples of three series were tested by three-point bending with horizontal ‘3PB(H)’ and vertical ‘3PB(V)’ orientation of samples. A two-parameter Weibull distribution was applied as an appropriate model to describe three strength data sets for glass. Findings: The experiments performed on nominally identical glass specimens revealed a wide range of flexural strength values, from 39.77 MPa to 171.71 MPa at a loading rate of not more than 1.05 MPa/s. 3PB(V) samples with vertical orientation demonstrated the flexural strength similar to that of 3PB(H) samples with horizontal orientation. The Weibull modulus, which is the measure of flexural strength variation, was between 2.04 and 5.23 at the coefficient of determination R2 greater than 90% for all series. The characteristic values of the glass strength, corresponding to the 5% fractile value, in accordance with the test evaluation procedure were 23.71 MPa, 31.98 MPa, 53.43 MPa for the first, the second and the third test series, respectively. Research limitations/implications: The maximum flexural strength of glass highly depends on the surface condition, and therefore the strength of the glass of different batches is variable whatever the case may be. For the guaranteed strength of glass used for structural purposes it is necessary to conduct strength tests of the glass from each batch under conditions that closely correspond to actual operating conditions. Practical implications: The obtained strength data is needed for designing glass load bearing constructions subjected to actual operating conditions (e.g. multilayered glass plates working on bending under static loading). Originality/value: A comprehensive overview of the existing methods for glass strength testing was presented. The features of the used flexural tests and the statistical analysis of the measured strength data were described. The results may be of a particular interest to the specialists in the modern design of load bearing glass constructions.