Fracture property Evaluation using Indentation Impact test

Reliability and safety evaluation for components in heavy industries, such as nuclear power facilities, gas pipelines and oil tankers, is of course extremely important, and small defects can cause serious system failures. In particular, it is of great interest to evaluate the fracture property of metallic materials, generally defined as Charpy V notch (CVN) energy and fracture toughness However, conventional methods of measuring this fracture property for materials have many limitations: they require a standard specimen dimension and geometry, the specimen must be fractured in each test and the testing procedure is somewhat complicated. For these reasons, it has been proposed to use indentation impact testing (IIT) to determine the fracture property because it requires neither specific specimen dimensions and geometry nor specimen fracture, and is also simple to conduct. Indentation impact energy (II energy) derived from indentation impact testing is the energy absorbed during crack history (initiation, enlargement, propagation), which is conceptually similar to CVN energy in its relation to absorbed energy to fracture. Based on similarities in geometry, the stress distribution ahead of crack tip and crack history, an attempt to relate II energy to CVN energy has been made. However, although II energy during crack initiation and crack enlargement is calculated based on the strain rate criterion, a limitation exists in defining II energy with crack propagation since indentation impact testing does not have an end point determined by fracture end point and it is determined by algorithm. II energy values evaluated for more than 15 different metallic materials were compared to those from standard Charpy V notch impact test. The results showed good agreement within ±20% error range. This indicates that indentation impact testing may be an alternative testing method to CVN testing, especially in situations where testing must be non-destructive.