The fatigue crack propagation, the plastic deformation at the crack tip and the acoustic emission behaviour for each cycle of crack growth were studied for a low strength steel A537 in both air and 3.5% NaCl aqueous solution. The reduction in the specimen thickness on the fracture surface was measured as a function of the crack length in order to determine the influence of corrosive medium on the plastic deformation of crack tip material. The laser speckle interferometry was used to characterize the plastic deformation behaviour on the surface of the plastic zone at crack tip in air and 3.5% NaCl solution under the hydrogen charging conditions, and the mono-direction tension behaviour of smooth specimens in two environments was examined. The results showed that acoustic emission count rate increased with the fatigue crack propagation rate in almost a linear way in both air and solution environments. The distinct effect of corrosive solution was to increase the fatigue crack propagation rate and at the same time to decrease the acoustic emission count rate. In both air and corrosive solution the fracture surface took on a morphology of ductile striations, which shows that CF crack propagation takes place due to alternative plastic blunting and resharpening of the crack tip by dislocation slip. The fact that the thickness on the fracture surface reduced with increasing crack length indicated that the plastic zone size at the crack tip increased with increasing crack length.
|Original language||English (US)|
|Number of pages||5|
|Journal||Cailiao Yanjiu Xuebao/Chinese Journal of Materials Research|
|State||Published - Feb 1994|
ASJC Scopus subject areas
- Materials Science(all)