Patent ID: 9702798
Date: 2017-07-11
CPC Classifications: G01N

Claim:
1. A method for measuring a fracture toughness using an instrumented indentation testing of a fracture toughness measuring device, which measures a load and an indentation depth in real time while applying a load to a specimen by an indenter having a flat punch shape, the method comprising: executing an indentation testing up to a determined indentation depth by the indenter having the flat punch shape and a determined radius to create a determined load-depth curve; converting the determined load-depth curve into a normalized curve of a stress and an indenter radius-to-indentation depth (h/a); finding a crack initiation point (P) by calculating the indenter radius-to-indentation depth and a crack initiation stress at a time point (P) at which a crack begins in the normalized curve; obtaining an adjusted radius of the indenter by calculating the crack initiation stress, the indenter radius-to-indentation depth at the crack initiation point (P), a configured radius of the indenter, or a configured indentation depth of the indenter; and creating an adjusted load-depth curve according to the indenter having the adjusted radius; wherein the converting of the determined load-depth curve into the normalized curve comprises: and the indenter radius-to-indentation depth (h/a); the method further comprising calculating the plane strain fracture toughness (J wherein J calculating the elastic-plastic stress intensity factor (K