Fundamental study to manufacture thermal fatigue crack of SA106 Grade B

Thermal fatigue crack is one of the life-limiting mechanisms in nuclear power plant conditions. During the operation of a power plant thermal fatigue cracks can initiate and grow in various components (straight pipe sections, valve bodies, pipe elbows, and collector head screw holes). Causes for this are mixing, striping or stratification of hot and cold water. A typical component, where thermal fatigue cracking occurs, is a T-joint where hot and cold fluids meet and mix. The turbulent mixing of fluids with different temperatures induces rapid temperature changes to the pipe wall. The resulting uneven temperature distribution prevents thermal expansion and gives rise to thermal stresses. The successive thermal transients cause varying, cyclic thermal stresses. These cyclic thermal stresses cause fatigue crack initiation and growth similar to cyclic mechanical stresses. The aim of this study is to fulfill the need by developing an artificial crack manufacturing method, which would produce realistic cracks. The test material was used SA106 Grade B. pipes