Consideration of Shot Peening Treatment Applied to a High Strength Aeronautical Steel with Different Hardnesses

Author:  Torres(1), Nascimento(2), Voorwald(2)
Source:  Conf Proc: ICSP-8 Sept. 16-20, 2002 Garmisch-Partenkirchen, Germany
Doc ID:  2002006
Year of Publication:  2002
Marcelo A.S. Torres(1), Marcelino Pereira do Nascimento(2), Herman Jacobus Cornelis Voorwald(2) (1) Department of Mechanics/ (2) Department of Materials and Technology -State University of Sao Paulo, 333 Ariberto Pereria da Cunha Ave., Guaratingueta, Sao Paulo, 12516-410, Brazil Introduction One of the most important components in a aircraft is its landing gear, due to the high load that it is submitted to during, principally, the take off and landing. For this reason, the AISI 4340 steel is widely used in the aircraft industry for fabrication of structural components, in which strength and toughness are fundamental design requirements [1]. Fatigue is an important parameter to be considered in the behavior of mechanical components subjected to constant and variable amplitude loading. One of the known ways to improve fatigue resistance is by using the shot peening process to induce a compressive residual stress in the surface layers of the material, making the nucleation and propagation of fatigue cracks more difficult [2,3]. The shot peening results depend on various parameters. These parameters can be grouped in three different classes according to R. Fathallah et al [4]: parameters describing the treated part, parameters of stream energy produced by the process and parameters describing the contact conditions. Furthermore, relaxation of the CRSF induced by shot peening has been observed during the fatigue process [5-7]. In the present research the gain in fatigue life of AISI 4340 steel, obtained by shot peening treatment, is evaluated under the two different hardnesses used in landing gear. Rotating bending fatigue tests were conducted and the CRSF was measured by an x-ray tensometry prior and during fatigue tests. The evaluation of fatigue life due the shot peening in relation to the relaxation of CRSF, of crack sources position and roughness variation is done.

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