130,578 research outputs found
On plastic notch effects in quenched and tempered steels
Get PDFABSTRACT: In 1971, Firrao and Spretnak performed a large experimental campaign to assess the elastic-plastic 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 reinterprete
Fatigue resistance of low pressure nitrided Cr-Mo low alloy steels
Get PDFFatigue resistance of steel parts can be improved by nitriding, the more the deeper is the layer affected by nitrogen diffusion, as stated by the Lessells-Firrao law. Low-pressure nitriding has been applied to wheel's hubs fabricated with a quenched and tempered Cr-Mo low alloy steel. N diffusion depths have been compared to similar results obtained with the same type of automotive parts subjected to classical gas nitriding. 12 h total low-pressure treatment time provided an almost 100% increase of hardened depth over 40 h gas nitrided parts. Both treatments allowed reaching an adequate fatigue life, whereas induction hardened parts did not. X-ray diffraction analysis provided phase constitution of top converted layers in both nitriding cases. A rationale based on the effect of early treatment stage top layer formation has been developed
Un modello fisico matematico dell'arrotondamento dell'apice della cricca: applicazione ad un acciaio strutturale al C-Mn
No full textInterpolazione diretta di dati sperimentali di crescita di cricca a fatica
Get PDFpresentazione orale al XX Convegno Nazionale IGF, Torino, 24-26/6/200
Valutazione della tenacità a frattura di un acciaio inossidabile bifasico austenitico-ferritico mediante l'integrale J
No full text
Minutes of the International Committee on Systematics of Prokaryotes. Subcommittee on the taxonomy of Mollicutes
No full text- …
