Effects of Pearlite morphology on Fatigue crack growth resistance in ferritic-Pearlitic steels

摘要

Effect of pearlite morphology on fatigue crack growth (FCG) behavior in ferritic-pearlitic structural steels was investigated. Fatigue crack growth test was carried out by using a standard compact tension (CT) specimen with 6 mm thickness and a single edge cracked plate tension (SECT) specimen with 1.5 mm thickness. To understand the effect of pearlite morphology on crack growth behavior in the Paris regime in detail, FCG test at constant-AK with in-situ SEM observation were also carried out. Crack closure behavior of the steels was monitored. The results revealed that the uniformly distributed pearlite microstructure had a FCG resistance higher than the islands of pearlite colonies microstructure. From in-situ observations, tortuous crack path was found in the uniformly distributed pearlite microstructure. Thin specimen indicated lower fatigue crack growth rate compared to thick specimen, which resulted from the difference of crack closure behavior.