Growth of small fatigue cracks in Incoloy-908.

摘要

Incoloy-908 was designed as a structural alloy for the conduit of cable-in-conduit superconductors. The conduit is a thin-wall tube that encloses superconducting cables. Since the conduit may be as thin as 3 to 12 mm in thickness and is subject to cyclic loads, fatigue crack growth behavior at liquid helium temperature, especially in the small crack regime, is a critical issue for magnet design. Because it is difficult to perform small fatigue crack propagation tests at 4.2 K, we have studied mechanisms of small crack propagation at room temperature and 77 K, and use the results to propose a feasible method for estimating small crack propagation at 4.2 K.