On Plastic Notch Effects in Quenched and Tempered Steels

Pasquale Russo Spena, Donato Firrao, Paolo Matteis

Materials Science and Chemical Engineering department, Politecnico di Torino, Torino, Italy..
Production Systems and Business Economics department, Politecnico di Torino, Torino, Italy..

DOI: 10.4236/jmmce.2010.96035                

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.

Keywords

Notch effects; Elastic-plastic numerical simulation; Steel

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	D. Firrao, J.W. Spretnak, 1971, "An evaluation of the Gerard-Papirno ductility ratio characterization of notch ductility in high strength AISI 4340 Steel", Ohio State University Research Foundation Report No. COO-2048-2 to the U.S. Atomic Energy Commission, Columbus, OH, U.S.A., pp. 1-73.
[2]	D. Firrao, J.W. Spretnak, 1971, "Characterization of notch ductility", abstract in Proceedings of the International Conference on Mechanical Behavior of Materials (ICM) – Kyoto, Japan, Vol. 3, pp. 987-988.
[3]	D. Firrao, B. De Benedetti, 1997, "Influenza della posizione e dell'acutezza dell'intaglio sulla resistenza a trazione di provini piatti di acciaio da bonifica al Ni-Cr-Mo", Atti V° Convegno Nazionale A.I.A.S., Bari, Italy, pp. 36.1-36.22.
[4]	J.W. Spretnak, D. Firrao, 1980, "Considerazioni sul ruolo dell'instabilità plastica nella formazione di fratture di tipo duttile", Metallurgia Italiana, No. 72, pp. 525-534.
[5]	J.R. Dixon, 1960, "Stress distribution around a central crack in a plate loaded in tension; effect of finite width of plate", Journal of the Royal Aeronautical Society, No. 64, pp. 141- 145.