Effective Factors for Crack Propagation under Varying Load Conditions

抄録

To clarify the effective factors for the crack propagation under varying load conditions, crack propagation is investigated using V-notched specimens and radial holed ones of 0.55% carbon steel and the following results are obtained. (1) The most important effective factor for the crack propagation under high-low type varying load condition is the essential increase of the stress at the crack tip for the opening of cracked surface caused by the repeated compressive plastic deformation. (2) In the case of steel specimens, there is no effect for the crack propagation under varying load condition caused by structural changing and it is also possible to estimate the crack propagation quantitatively considering the effect of crack opening. (3) It is also possible to estimate almost all the experimental results under varying load conditions qualitatively considering the effect of crack opening and existence of incubation period. (4) The effect of crack opening appears in the case of reversible stress condition but does not appear in the case of pulsating tension stress condition. This can be predicted by the calculation of the actual stress at the crack tip under varying load conditions.