Tese e Dissertação

Tese: Linear-elastic three-dimensional effects in notch and crack tip fields

Notches and cracks are usually treated as two-dimensional problems in most structural design and analysis tasks, employing 2D limit solutions obtained from plane elasticity theories to evaluate the severity of stress/strain concentration effects around their tips. However, due to restrictions to the Poisson strains induced by the stress gradients around such tips, these regions may be affected by important three-dimensional effects that can affect their stress/strain fields and possibly lead to non-conservative damage and life predictions if neglected. Fatigue crack initiation, plastic zone size and shape estimation, and plane stress/plane strain dominance issues on K-controlled fields are typical examples of problems sensible to such effects. Linear Elastic Finite Element techniques are used to simulate 3D effects along notch fronts, such as how the thicknessto-notch root radius Beta/Rho affects the stress and strain fields that surround them. The inuence of such 3D effects is evaluated from the structural design point of view. Then versatile submodeling techniques are used to study similar 3D effects along the fronts of short and long cracks. Finally, a stepwise remeshing routine is used to show how an initially straight crack must slightly curve its front during its propagation by fatigue.

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