The objective of this work is to model fatigue damage of the aluminium alloy AA2139 at the microscopic scale. It combines an experimental campaign and numerical simulations for a complete modelling of the alloy. Special attention is given to the reproduction of the alloy grain morphology and crystallography. Moreover, intermetallic phases are preferred sites for fatigue crack initiation in this alloy. Therefore, a method for taking into account the alloy microstructural complexity including the presence of intermetallic phases is presented. Finally, a fatigue damage model using a fatigue indicator parameter (FIP) is considered for the introduction of a crack and its propagation in simulations.
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Themes: Microstructures and Fracture in Advanced Materials
CRACK TIP TRANSFORMATION ZONE MORPHOLOGY IN SMA MATERIALS WITH TRANSFORMATION SOFTENING [Keynote]
The pseudoelastic effect due to martensitic transformation in polycrystalline shape memory alloys is simulated with a phenomenological constitutive model based on a kinematic hardening framework with a gradient enhancement to regularize moving austenite-to-martensite boundaries that arise in softening materials. This constitutive modeling framework introduces a length scale within the theory which has yet to be deteremined experimentally. Calculations are presented for the evolution of the transformation zone around a stationary crack tip. The calculations uncover the interplay between the length scale associated with the size of the transformation zone around the crack tip and the material length scale inherent to the consistutive model. The calcualtions show that localized “fingers” or “needles” of deformation emenate from the transformation zone at a specific level of the applied stress intensity, which provide a comparison to experimental observations that then can be used to quantify the sie of the material length scale.
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