Stable Fracture in Three-Point Bending Test for Brittle Materials.

Abstract

Recently, a bending-type stabilizer for precracked ceramic specimens regulated by JIS was proposed. To investigate the behavior of crack growth in stable fracture of brittle materials, large specimens will be useful because of difficulties in accurate measurement in experiments using small specimens. In this study, therefore, a series of three-point bending tests was carried out using a newly developed large stabilizer and soda-lime glass speciments (100×20mm) with various precrack lengths. Crack extension during stable fracture was measured using video images. Numerical simulations of three-point bending for crack-rate sensitive, perfectly brittle materials were also performed using a rate constitutive equation. It was found that stable fracture was observed in the specimens with crack length larger than x0=0.36 (x0-a0/W, a0: initial crack length, W: specimen width). In stable fracture, the crack grows gradually and the stress intensity factor, Kt, increases even after a maximum load is observed. This newly observed experimental finding was also confirmed qualitatively by numerical simulations.