2022 Volume 71 Issue 3 Pages 266-272
The small punch (SP) test for brittle materials is superior method compared to the three and the four point bending tests because the strength properties can be investigated from thin and small specimens. Note that the SP test can be measured the equibiaxial flexural strength. However, effects of the test conditions such as shape and thickness of specimen, and the SP diameter on the equibiaxial flexural strength have not been studied experimentally and theoretically. In this study, biaxial flexural strength characteristics of the small and thin glass specimen were theoretically and experimentally investigated via SP and modified SP (MSP) tests. First, the relationship between 1- and 2-axis strengths and effective volumes was derived on the basis of competitive risk model. Second, SP and MSP tests were performed for square and circular glass specimens. Thereafter, the F (fracture probability) – S (flexural strength) – Veff (effective volume) diagrams predicted using 1-axis bending strength data was compared with the experimental results. As the result, the predicted diagram value reasonably agreed with the experimental data of the circular specimen. In contrast, the predicted diagrams was not able to well estimated with the experimental data of the square specimen because Hertzian fracture due to the punch contact occurred during SP and MSP tests.
