2005 Volume 91 Issue 2 Pages 285-291
Circumferentially notched and smooth round tension tests were conducted at room temperature with or without compressive prestrain in hotrolled ferrite-pearlite SM490B steel. And the effects of compressive prestrain and notch acuity on plastic deformation limit were investigated. Plastic deformation limit was defined as the termination point in the true stress-true strain relationship, caused by ductile or cleavage fracture. The average stress-true strain relationship was varied with prestrain and notch acuity, but the true stress-true strain relationship was not. The true strain at the onset of plastic instability was determined by the work hardening exponent, regardless of prestrain and notch acuity. On the other hand, the plastic deformation limit in terms of true strain was varied with prestrain and notch acuity. It was found that the plastic deformation limit can be estimated by the axial stress criterion. The axial stress at plastic deformation limit was about 1300 MPa, regardless of ductile and cleavage fracture.