Crack growth arrester using “gourd-shaped-insert-plate”

Abstract

In accordance with aging infrastructure systems such as steel bridges, fatigue of metals becomes serious risks. Fatigue crack may lead the structure to catastrophic failure. Countermeasures against fatigue failure are required. “Crack growth arrest and retardation system” using “gourd-shaped-insert-plate” has been developed as a high performance and easy construction method against fatigue crack, by generating fatigue crack closure force and reduce crack tip opening displacement and stress concentration at the fatigue crack tip. Arrester was applied to CT (Compact Tension) specimen and also mockup of steel bridge deck, in order to validate performance of the system. Fatigue crack growth rates of the specimens with arrester were 1/10~1/2 of those without arrester. And apparent threshold stress intensity factor range was increased by about 10~20 MPa√m through using only few gourd-shaped arresters. Also the arrester was applied to the fatigue crack in a mockup of steel bridge deck. Without arrester, fatigue crack growth occurred in accordance with the increase of loading cycles, on the other hand, fatigue crack growth was arrested after installing the arrester in the mockup of steel bridge deck. And to enable quantitative fatigue life assessment in fatigue design, fracture mechanics based-crack closure model with spring elements for the arrester has been verified with good accuracy for fatigue crack growth rate in the tests using CT specimens.