Stable crack growth prediction method of a cylinder with an axisymmetrical surface crack

Watashi, Katsumi; Furuhashi, Ichiro*; Sasaki, Toshihiko*

This paper describes an experimental and analytical result of crack growth behavior from circumferential slitted-cylinders under cyclic cold transients. PNC is promoting R&D program aimed at assessment method of crack and/or defect at creep temperature for FBR application, the experiment and analysis is one item of them. The purpose of this study is to verify the applicability of the method developed recently in PNC. Test models made of 304 austenitic stainless steel are 1.5 m in hight, 70 mm in inner diameter and 30 mm in thickness, and have axisymmetrical circumferential initial machined-notches on inner surface. As a first step, five machined-notches with different depth and width were tested in Air Cooled Themal Transient Test Rig. One cycle of thermal loading is such that the model heated up tp 650 C by furnace, then air blow into the model for 5 min. This sequence caused cyclic temperature gradient in the wall of the model. The tests were continued till crack depth exceeded 20. DC potential method and precise ultrasonic examination were applied to measure the crack growth. After the test, the model were dismantled and laboratory fractured, then striation spacing was measured continuouasly in the direction of crack growth. The experimental result was summarized as crack growth rate and reliability of online monitoring measures. Thermal-inelastic finite element analysis facilitated evaluation of fracture mechanics parameters, J, for thermal fatigue. The crack growth behavior was well predicted by the analysis considering a scatter band in material crack growth character. A simple method for inelastic crack evaluation was developed in PNC. The method is based on a database of linear fracture mechanics, and includes plastic and creep/relaxation modification. Firstly the applicability of the database to present problem was damonstrated comparing with thermal-elastic finite element analysis. Then J, and the crack growth behavior ...