The Application of Linear Elastic Fracture Mechanics Analysis to Bluntly Notched Round Bar Specimens.(Dept.M)

Abstract

A technique has been presented which allows the use of small notched round-bar specimens without fallgue pre-cracking for the determination of the plane strain fracture toughness of engineering materials. The technique is based on the linear elastic fracture mechanics analysis and the principle of stress concentration factors at the tip of the notch. The error inherent in the fracture toughness calculations, i.e. due to the absence of very sharp crack, can be corrected from an error correction factor which is a function of the normalized notch-tip radius, r/d. The technique has been applied to two metallic alloys (bronze and steel) and the plane strain fracture toughness for the two materials were obtained. Small round-bar specimens having V-notches with different angles and tip-radii have been tested in tension. A comparison of the KIc values calculated using the present technique and those calculated in the literature indicated reasonable agreement with a difference between the two values ranging from 0 to ±5 %. It is recommended that the normalized notch-tip ratio, r/d, should not exceed about 0.14 for this difference to stay within acceptable limits. The present technique may be considered relatively fast and economic and indicating a level of accuracy adequate for many practical purposes.