Subcritical Crack Growth under Sustained Loading as Affected by Stress Mode and Corrosive Environment.

摘要

Subcritical crack growth under sustained load in a Ti-4Al-3Mo-1V alloy has been investigated using compact tension specimens under constant load. Crack growth sufficient to cause failure in less than one week was observed at initial stress intensities as low as 0.45 K sub c. Subcritical crack growth was not attributable to stress corrosion;it occurred more readily in vacuum than in salt water. Since the alloy was stabilized in vacuum prior to test,metallurgical instability also appears an unlikely contributory factor. Tests of specimens of several thicknesses having variable degrees of triaxial loading across the crack front suggest that subcritical crack growth is controlled by the combined influences of creep in the uncracked surface region under plane stress loading and strain-dependent plane strain fracture in the central region and triaxial loading. (Modified author abstract)