Quenching is a heat treatment process for the rapid cooling of a metallic workpiece in water, oil or air to obtain certain desired material properties. The accurate determination of resulting residual stress and distortion of a large aerospace aluminum part is challenging due to the nature of fast transient thermal process that includes the coupling of thermal, metallurgical, and mechanical interactions. The use of heat transfer coefficients (HTCs) in empirical tools requires an extensive testing matrix to calibrate these HCTs based on measured temperature data at selected locations of the workpiece. The use of a thermal multi-phase FSI tool is essential for the rational design of the flow rate quenchant with agitation to reduce the quenching residual stress by decreasing the thermal gradient from the center of the work piece to the surface. Given the temperature and phase profiles predicted from the Fluid Structure Interaction (FSI) based heat transfer module, a residual stress and distortion prediction module is developed by including fields mapping, temperature and phase dependent property evolution, and a user-defined material model for Abaqus. The fatigue performance of a quenched T-stiffener is evaluated in the presence of quenching induced residual stress under different dipping orientations.
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Subcritical crack growth of nuclear components is a current concern in operating light water nuclear reactors. Weld residual stresses (WRS) can drive stress corrosion crack growth, affect fatigue crack growth, lead to reheat cracking issues if the components are operated in the creep regime, and can affect the fracture response of components. This paper provides several examples where crack growth, driven by weld residual stress fields, has led to safety concerns in several nuclear components. This is especially true for the dissimilar metal welds that are present in most PWR reactors. Mechanical mitigation examples are also discussed which are used to reduce the WRS fields or alter them to compression which can mitigate stress corrosion cracking.
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