Effect of Loading Rate and Surface Conditions on the Flexural Strength of Borosilicate Glass

Abstract

This study evaluates the loading rate and surface condition dependence of the flexural strength of a borosilicate glass. The glass specimens are subjected to three different surface treatments before four-point bending tests to study the effect of surface flaws. Quasistatic (Material Test System 810) and dynamic (Kolsky bar) experiments are performed at loading rates ranging from 0.7 to 4 Â 10 6 MPa/s. The results show that the flexural strength of the borosilicate glass has a strong dependence on the loading rate. A chemically etched surface produces an enhanced flexural strength by about an order of magnitude. Scanning electron microscopy images on fracture surfaces indicate that the failure is governed by different types of flaws under different surface treatment conditions. Edge failure is also identified for samples possessing high flexural strength.

Dynamic Equibiaxial Flexural Strength of Borosilicate Glass at High Temperatures

“…It is known that glass materials are extremely susceptible to surface flaws when they are loaded in tension, which means most, if not all, of the tensile failures of glass are originated from surface located flaws due to the lack of bulk defects [27]. Previous research on the same borosilicate glass has also revealed the significant influence of surface flaws on the dynamic flexural strength by modifying the morphology of these flaws through different surface treatment methods [12,17]. Therefore, the focus of this study is to investigate how the temperature affects the characteristics of these strengthlimiting surface flaws, and how this might be related to the flexural strength of the borosilicate glass.…”

“…The flat surfaces of these disk samples were then mechanically ground and polished to a surface roughness of 20 angstroms. SEM and AFM images revealing the surface quality of the as-polished samples were given in [12]. The circumference, however, was flame polished right after cutting in order to eliminate the chips/cracks on the edge.…”

“…Although the governing mechanisms imposed by heat treatment processes that could enhance the strength of glass are still in debate, the scope has been narrowed down to the following possibilities: (1) Crack tip blunting, (2) Residual stress relaxation and (3) Crack healing, which are either associated with increasing viscosity and thus higher diffusivity in the material, or the stress assisted chemical reaction at the crack tip in a moisture environment [11]. A recent study on glass flexural strength has pointed out that different surface treatments could have significant effects on glass surface tensile strength [12]. However, the characteristics of specific surface conditions are considered to be temperature dependent, which in turn affect the tensile/flexural strength of glass at different temperatures.…”

Effects of Surface Treatment and Interfacial Strength on the Damage Propagation in Layered Transparent Armor under Impact

“…In a previous study (Nie et al, 2009), uniaxial four-point bending tests were carried out on the same material with an in-house made loading fixture in the testing section of a Kolsky bar. It was found that at a certain stress level, the fracture origins universally shifted from central surface to the edge, presumably due to the competing failure mechanisms between surface flaws and edge flaws.…”

Dynamic Behavior of Materials

“…For example, Anton and Subhash [5] used a modified bar system with a small diameter incident bar to measure dynamic Vickers hardness for brittle materials. Nie, Chen, et al [6] conducted dynamic flexural strength tests on glass through implementation of a four-point bend configuration in the Hopkinson bar. Nie and Chen also devised a ring-on-ring technique for measuring the dynamic equibiaxial flexural strength of glass at temperatures up to 750°C using non-contact specimen heating.…”