1996 Volume 45 Issue 3 Pages 310-315
Recently, a concept of pseudo stable phenomenon (PSP) was proposed by theoretical considerations.The PSP is a phenomenon that crack extension occurs before the load reaches the maximum, Pmax, and it appears in conventional fracture toughness tests for crack-rate sensitive, perfectly brittle materials. The crack extension due to PSP depends on the initial crack length, a0, the testing machine compliance, Λ*, and the crack-rate sensitivity, m*, of crack resistance force. In the theoretical considerations, a method of numerical simulation was proposed by Nojima and Nakai.
In the present paper, a series of three point bending tests was carried out on soda-lime glass to examine the PSP experimentally. For the tests, a testing equipment with large machine compliance and specimens with different initial crack lengths were used. The experimental data were compared with the results of numerical simulation. It was found by both experiments and numerical simulations that the amount of crack extension due to PSP becomes maximum when x0≈0.16 (x0=a0/W, W: specimen width) and that the fracture toughness obtained from Pmax, and x0 is always understimated.
