抄録
Circumferentially notched and smooth round tension tests were carried out at room temperature with and without compressive prestrain in a hot-rolled ferrite-pearlite SM490B steel, and the effects of the compressive prestrain and the notch on the plastic deformation limit (PDL) were investigated. The PDL was defined as a termination point in a true stress-true strain curve which was caused by a ductile or cleavage fracture. The notch caused variations in the average stress-true strain curve but did not affect the true stress-true strain curve. A true strain at the plastic instability was determined by a work hardening exponent, regardless of the notch. On the other hand, the true strain at the PDL differed according to the notch. An axial stress at the PDL was found to be about 1300 MPa, regardless of the ductile and cleavage fracture.
