Patent ID: 7487051
Filing Date: 2009-02-03
Classification: G01N

Abstract:
1. A method of evaluating the fracture toughness of a material using a continuous indentation technique, said continuous indentation technique continuously measuring an indentation load and an indentation depth while a continuous indentation test with an indenter repeatedly applies the indentation load to and removes the indentation load from the material and then evaluates properties of the material using a relationship between the indentation load and the indentation depth, the method comprising the steps of: measuring a stress coefficient, a strain hardening modulus and a yield stress using the continuous indentation technique and calculating a reduced elastic modulus (E calculating an effective elastic modulus (E determining an initial elastic modulus (E setting a void volume fraction (f) to a specific value within a range from 0.13 to 0.17 when a fracture type of the material is a I-type fracture type, and setting the void volume fraction (f) to a specific value within a range from 0.23 to 0.27 when the fracture type of the material is a II-type fracture type; calculating a damage parameter (D) from the void volume fraction using an equation calculating a critical elastic modulus (E*) using the damage parameter; calculating a characteristic fracture initiation point (h*) of the indentation depth using the critical elastic modulus; and calculating the fracture toughness (K wherein 2ω