Suitability Of Standard Fracture Test Specimens For Low Constraint Conditions

Abstract

Test specimen selection plays a vital role in successful transformation of laboratory fracture parameter findings to the real fracture behavior of any component. The ASTM and BSI Standard test methods for measurement of fracture toughness are dominated by high constraint specimens like Compact Tension (C(T)) and Single Edge Notch Bend (SEN(B)). However, most cracks in real time structure are shallow and surrounded by low constraint. Hence, the standard specimen like Middle Crack Tension (M(T)) in ASTM and Clamped Single Edge Notch Tension (Clamped SEN(T)) specimen in BSI, yield fracture toughness value to be test specimen dependent. The Clamped SEN(T) specimen suitable for various real pipeline (low constraint conditions) application has been widely reported in literature, that however in not the case for M(T) specimen which has scarcely reported. The 3D numerical analysis of SEN(T) and M(T) specimens with an identical flaw size for fracture toughness and constraint parameters (T-stress) under linear-elastic conditions are dealt in this article. The standard specimen that emulates low constraint fracture behaviour forms the basis for recommending suitable specimen for defined real time conditions. The conservatism associated with usage of standard specimen to find fracture parameters for an application has been quantified in this work for field implementation by practitioners in fracture mechanics.