Fracture toughness of 316L stainless steel under cyclic bending deformation

Abstract

Fracture mechanics is the field of study focused on characterizing the behavior of cracks in fracture structures which is the behavior is dependent on material, load–displacement and geometric factors. The aim of this study was to evaluate the fracture toughness of 316L stainless steel under cyclic bending deformation with load ratio, R = 0.1 in Linear Elastic Fracture Mechanics (LEFM) region by using parameter stress intensity factor, ΔK and cyclic J-integral, ΔJ. A 3-point bending testing was carried out by using Biss Fatigue machine on Single Edge Notched Bend (SENB) specimen under loading and unloading condition. By modifying the calculation of plastic area under the graph of load–displacement from ASTM E1820, ΔJ can be calculated. Parameters of the Paris Law were identified by plotting log–log crack growth rate against fracture toughness, ΔK and ΔJ. The regression for both parameter ΔK and ΔJ showing good accuracy with value of R2 are 0.995 and 0.997 respectively. Based on the results, fracture mechanics can be calculated by using ΔK and ΔJ under linear elastic condition. However, if the condition is in large scale yielding condition, ΔK is not valid and the fracture toughness should be characterized by ΔJ.