A Two-Parameter Method for Determining the Fracture Toughness of Materials from Subsized Specimens

摘要

The fracture toughness of brittle materials can be determined easily using the Linear Elastic Fracture Mechanics (LEFM) approach, and the only demand for change is the desire to decrease specimen size requirements. Specimen size effect on the normally measured K_Q and P_(MAX)/P_Q values was revisited in order to establish the suitability of a relationship between these parameters. A linear dependence was confirmed from experimental data of materials as different as isotactic polypropylene, AISI 4140 steel, a titanium alloy, and an aluminum alloy. The load ratio was interpreted as a second parameter, and thorough this dependence, K_Q values measured on subsized specimens were extrapolated to linearity conditions P_(MAX)/P_Q=1, determining a value identified as K_(1.0). When some simple conditions were met, this K_(1.0) value matched the toughness of evaluated materials. For the analyzed materials, this toughness parameter could be obtained from subsized specimens with important size reduction compared with that needed for K_(IC) valid value determination. Moreover it permitted a simple characterization of material as difficult to characterize as isotactic polypropylene, which initially motivated this study.