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Milano, Italy

Bagherifard S.,Poilitecnico di Milan | Guagliano M.,Poilitecnico di Milan
Applied Surface Science | Year: 2014

Fatigue life prediction for notched components is an essential step within the design process of machines. In the past years different fatigue criteria have been applied for fatigue behaviour assessment of notched components subjected to shot peening treatment. However, due to complexity of the phenomenon, still an agreed set of standard methods for predicting fatigue endurance of shot peened notched parts is not available. In this work a series of recognized fatigue strength evaluation methods are applied on two notched shot peened specimens under different fatigue loading. After having considered the approaches based on fracture mechanics (see Part 1), now the local stress methods and the FKM guideline (which includes both a nominal stress approach and a local stress one) are considered. The results allow evidencing the criteria able to better consider the effect of SP and to underline the critical points related to the application of the mentioned criteria to shot peened parts. In this regard the FKM guideline and the approach based on critical distance theory are found to provide more accurate results. © 2013 Elsevier B.V.

Bagherifard S.,Poilitecnico di Milan | Colombo C.,Poilitecnico di Milan | Guagliano M.,Poilitecnico di Milan
Applied Surface Science | Year: 2014

Fatigue strength assessment of notched components is an essential step within their design process. It is well known that shot peening strongly increases the fatigue strength of mechanical structures. However, the contribution of shot peening to fatigue strength is generally underestimated by engineering design codes. This is due to the difficulty of defining a general fatigue design approach that is able to correctly and quantitatively consider the effect of shot peening, in terms of residual stresses, surface work hardening and surface roughness alteration. This work critically evaluates the criteria available in the literature that have been applied to shot peened notched specimens. The entire work is divided in two parts. In the first part, fatigue strength evaluation methods based on fracture mechanics concepts are applied to notched shot peened specimens tested under different fatigue loading conditions. The second part, on the other hand, studies two recognized local stress approaches. Comparison of the results highlights the restrictions of each approach and the field in which it can be successfully applied; where possible, appropriate corrections were introduced in order to obtain a better agreement with the practical condition and the experimental data. © 2013 Elsevier B.V.

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