USE OF ROUND BAR SPECIMEN IN FRACTURE TOUGHNESS TEST OF METALLIC MATERIALS

摘要

The fracture toughness of high strength metallic materials is determined by standard test methods like ASTM E 399, ASTM E-1820 using standard specimen geometries such as Compact tension (CT) or Single edge notched bend (SENB) specimens. This paper explains a simple test methodology based on fracture mechanics approach using circumferentially cracked round bar (CCRB) specimen. Specimen preparation and fatigue precracking is quite simple, consuming less material and machining time. This CCRB, being small scale specimen is widely useful in situations where large volume of specimen material is not easily available. The test material used in this work is 6082-T6 aluminum alloy. Observations of fractured surfaces using Scanning Electron Microscope (SEM) were also done. This test methodology is simple, reliable, rapid and cost effective results in a valid fracture toughness value quite close to the true fracture toughness. CCRB specimen geometry can be considered as a standard test specimen in fracture toughness test.