ISSN: 0090-3973
Page Count: 8

On the Determination of JIC Using the Stretch Zone Width Method

Suresh, RKV
Osmania University,

Ramakrishnan, N
Defence Metallurgical Research Laboratory,

Srinivas, M
Defence Metallurgical Research Laboratory,

Ramarao, P
Jawaharlal Nehru Centre for Advanced Scientific Research,

(Received 15 July 1998; accepted 16 February 1999)

Abstract

The stretch zone width (SZW=1∕2CTOD, the crack tip opening displacement) method for determining JIC involves fewer specimens and lesser size restrictions compared to the con ventional J-R curve method. However, the accuracy of the SZW-based procedure depends on each term of the J-CTOD relationship, i.e., JIC=m∙σ∙CTODC. This paper presents a numerical investigation of the J-CTOD relationship, which has been carried out using a large-deformation finite element method (FEM). The slope of the blunting line (m) is computed for various combinations of yield strength-to-elastic modulus ratio (σo∕E), power law strain-hardening exponent (n), and different measures of stress (σ in the J-CTOD relationship). This work brings out the importance of the correct choice of the stress measure, and the one suggested here is the integral average of the flow stress [σ*=∫0ε*σdε/∫0ε*dε]. Also, an effective CTOD approach is numerically validated where a sharp fatigue precrack of fracture specimens can be substituted by one with a finite notch root radius without loss of accuracy in JIC.

Keywords:
finite element method (FEM), JIC, stretch zone width (SZW), crack tip opening displacement (CTOD), blunting line slope, notch root radius

Paper ID: JTE12161J
DOI: 10.1520/JTE12161J
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