FRACTURE TOUGHNESS TESTING OF A LOW ALLOY STRUCTURAL STEEL USING NON-STANDARD BEND SPECIMENS AND AN EXPLORATORY APPLICATION TO DETERMINE THE REFERENCE TEMPERATURE, T_0

摘要

This work addresses an experimental investigation on the cleavage fracture behavior of an ASTM A572 high strength, low alloy structural steel using standard and non-standard SE(B) specimens, including a non-standard PCVN configuration. One purpose of this study is to develop a fracture toughness test procedure applicable to bend geometries with varying specimen span over width ratio (a/W) and loaded under 3-point and 4-point flexural configuration. We provide a new set of plastic η-factors applicable to these non-standard bend geometries which serve to estimate the experimentally measured toughness values in terms of load-displacement records. Another purpose is to investigate the effects of geometry and loading mode in fracture tests using non-standard bend specimens. Fracture toughness testing conducted on various bend specimen geometries extracted from an A572 Grade 50 steel plate provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, J_c. The experimental results show a potential effect of specimen geometry and loading mode on J_c-values which can help mitigating the effects of constraint loss often observed in smaller fracture specimens. An exploratory application to determine the reference temperature, T_0, derived from the Master Curve methodology also provides additional support for using non-standard bend specimens in routine fracture applications.