A New Approach to Determine the Quasi-Static and Dynamic Fracture Toughness of Engineering Materials

Abstract

There are well developed standard techniques that can be used to determine the fracture initiation toughness of materials under quasi-static loading. One of the drawbacks on the conventional methods to determine the fracture toughness of materials, even under quasi-static loading, is the sample size requirement to get an acceptable accuracy. The ASTM standard test methods used to determine the fracture toughness of material required a certain sample thickness and volume to ensure the plan-strain condition ahead of the crack tips. This limits the use of the conventional fracture toughness test methods to a certain material that their properties are size independent. On the other hand there are no standard testing methods to determine the dynamic fracture properties of materials. There is a need to design a new technique, which avoid the sample size requirement, to determine the fracture toughness of material under quasi-static and dynamic loading. In this paper a new approach, a spiral notch sample loaded under pure torsion, is proposed to determine the fracture toughness of different engineering materials. The fracture toughness of different engineering materials has been investigated and demonstrated by the proposed approach. The proposed experimental approach is extended to the dynamic fracture toughness investigation of engineering materials.KeywordsFracture intensity factorDynamic fractureSpiral notched-grove sampleTorsional loading