EFFECT OF CYCLIC STRESSING ON DELAYED FRA CTURE OF HIGH-STRENGTH STEEL

The delayed fracture characteristics of a PC bar steel have been exami ned under the FIP test. Earlier fracture occurs by applying cyclic str ess compared with tile constant stress even when the maximum stress is the same. The peak temperature of desorption of hydrogen at thermal d esorption analysis is about 473K. Both the amount of diffusible hydrog en and desorption rate at room temperature of specimens just after the FIP test are irrelevant to the stress mode. After annealing the speci mens at 473K for 30min after the test and reimmersing in the FTP solut ion, the total amount of diffusible hydrogen decreases to about 2/3. T he effect of cyclic stressing appeares as the increase in the reductio n of hydrogen released up to 473K. It is discussed that the effect of cyclic stressing on the delayed fracture characteristics is through a dynamical interaction of hydrogen with defects produced by plastic def ormation.