Effects of Cyclic Loading on the Deformation and Elastic-Plastic Fracturebehavior of a Cast Stainless Steel

摘要

Tests conducted in Japan as part of the High Level Vibration Test (HLVT) programfor reactor piping systems revealed fatigue crack growth in a cast stainless steel pipe elbow. Material property data was developed to characterize cyclic deformation, cyclic elastic-plastic crack growth and ductile tearing resistance in the pipe elbow material. The tests conducted included monotonic and cyclic tensile tests, monotonic J-R curve tests, and cyclic elastic and elastic plastic fatigue crack growth rate tests. The cyclic elastic plastic fracture behavior of the stainless steel was the primary concern and was evaluated using a cyclic J-integral approach. It was found that the cast stainless steel was very resistant to ductile crack extension. J-resistance curves essentially followed a blunting behavior to very high J levels. High cycle fatigue crack growth rate data obtained on this stainless steel was typical of that reported in standard textbooks. Low cycle fatigue crack growth rate data obtained on this material using the cyclic J integral approach was consistent with the high cycle fatigue crack growth rate and with a standard textbook correlation equation typical for this type of material. Evaluation of crack closure effects was essential to accurately determine the crack driving force for cyclic elastic-plastic crack growth in this material.