Investigations on the Fracture Mechanical Beha viour of Ferritic Nodular Cast Iron in Dependence on the Applied Load and Temperature

Abstract

The focus of the investigations on ferritic nodular cast iron with varying graphite morphology was the determination of fracture mechanical characteristics and crack resistance curves of the J-integral and Crack Tip Opening Displacement (CTOD) concept under static and dynamic load. The experiments were performed at various temperatures down to 40 degrees below zero. The results show a close correlation between static crack initiation toughness values as well as crack resistance curves and quantitative graphite morphology parameters. The practised low-blow technique allowed the reproducible detennination of dynamic R curves of the J-integral and CTOD concept. First results of the R curve investigations under dynamic load draw attention to a correlation between crack initiation toughness and graphite morphology that is comparable to the results under static load. A comparison of static and dynamic crack initiation toughness data shows a loss of toughness with the dynamic values due to the higher loading rate. An influence of temperature on the static fracture mechanical crack resistance data in the investigated range of temperatures was found to depend on the size of the graphite nodules.