EFFECT OF STRESS CONCENTRATION ON FATIGUE CRACK GROWTH

Abstract

The present dissertation describes experimental results, which were obtained by measuring the crack propagation length when metallic specimens with different stress concentration were cyclically loaded under tension. In order to investigate the effect of stress concentration factor on crack initiation life and propagation rate, three different types• of specimen (Compact Tension, Double Edge Notched Tension and Sharp Double Edge Notched) were considered. Six different stress concentration values for each type of specimens were introduced by machining six different notch angle in Sharp Double '. Edge Notched and Compact Tension specimen. Six different notch radii were considered for Double Edge Notch Tension specimen. From experiment, it was apparent that crack initiation life was considerably influenced in all three types of specimen, i.e., for higher value of stress concentration, the number of cycles required to initiate the constant crack size of 1.5 mm, was less. Further, the crack propagation rate was very low upto the initiation stage. The crack growth rate was however found to be not varying much with stress concentration factor. To compare these experimental results, the materials fracture toughness was determined using all the three types of specimens