TITLE:
On Plastic Notch Effects in Quenched and Tempered Steels
AUTHORS:
Pasquale Russo Spena, Donato Firrao, Paolo Matteis
KEYWORDS:
Notch effects; Elastic-plastic numerical simulation; Steel
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.9 No.6,
June
20,
2010
ABSTRACT: In 1971, Firrao and Spretnak performed a large experimental campaign to assess the elasticplastic
stress concentration factor at fracture as a function of the elastic stress concentration
factor and of the tempering temperature, by using 25.4 mm wide, 1.14 mm thick AISI 4340
quenched steel sheet tensile specimens with variable tip radius central notches. The availability
of finite element methods allows now to re-examine those results and overcome the simplifying
assumptions that were originally used to evaluate notch stresses. The elastic stress concentration
factors are obtained by three-dimensional solutions, which also evidence the gradual evolution
from plane-stress to plane-strain that occurs by decreasing the notch radius while keeping the
thickness constant. Moreover, both the actual stress state and the stress concentration factor in
the notch immediately before the failure are evaluated by elastic-plastic solutions. Finally, the
original conclusions on the notch sensitivity of the examined steel are re-assessed and reinterpreted.