COMBINED DEM-FEM MODELING OF SHOT PEENING PROCESS

1 online resource (79 pages) : PDF

2018

University of North Carolina at Charlotte

Shot peening is a commonly used technique for improving the fatigue life of machine components by inducing compressive residual stresses in the surface layers. This process involves plastically deforming the surface layers by impacting the surfaces with spherical particles at high speeds. The induced residual compressive stresses resist crack propagation and thus increase the fatigue life. The intensity of shot peening, measured using the Almen test, is an essential quantity for ensuring shot peening effectiveness and repeatability. It depends on various process parameters such as the shot speed, shot size, shot material, impact direction, and flow rate. Therefore, a thorough understanding of the impact of these parameters on shot peening intensity is critical for analyzing and optimizing the process. In this thesis work, a novel computational model is developed to accurately simulate the Almen intensity tests on a Type-C strip. The model uses a coupled technique based on the discrete element method (DEM) and the conventional finite element method (FEM). The shots are generated randomly and their motion is analyzed using DEM. The interaction of the shots with the Almen strip and the deformation of the Almen strip is analyzed using FEM. The shots, spherical in shape, are treated as rigid particles while the mechanical response of the Almen strip is modeled using the Johnson-Cook constitutive model. The predicted Almen intensity values agree with analytically calculated values and are found to be within the experimentally reported range of values for Almen intensities. Results from the parametric studies conducted to analyze the influence of shot speed, impact direction and shot sizes on the Almen intensity indicate that a given Almen intensity can be obtained by many different combinations of these parameters although the residual stress fields may be different. An important conclusion from this observation is that similar Almen intensities do not necessarily mean similar values for fatigue life.

masters theses

Mechanical engineering

M.S.

Mechanical Engineering

Cherukuri, Harish

Ramaprabhu, Praveen
Ogunro, Vincent

Thesis (M.S.)--University of North Carolina at Charlotte, 2018.

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Bobba_uncc_0694N_11759

http://hdl.handle.net/20.500.13093/etd:1189