Some Class I CANDU heat exchanger tubesheets experience very high in-plane thermal gradients under Level A/B transients. If the thermal stresses exceed the ratcheting limit of the ASME Boiler and Pressure Vessel Code, shakedown has to be demonstrated by an elastic-plastic analysis. The choice of the plasticity model and its parameters must ensure that shakedown is predicted only if it occurs in reality. Differences to uniaxial modeling are discussed, and a conservative way of predicting shakedown is presented. The perforated region of the tubesheet is replaced by an equivalent solid plate with anisotropic yield properties (Hill’s yield criterion). A lower-bound shakedown limit for this material is derived. An example analysis is presented that has been performed using a commercial finite element code. [S0094-9930(00)00303-6]

Issue Section:
Technical Papers
Keywords:
thermal stresses, pressure vessels, finite element analysis, elastoplasticity, transients, plastic deformation
Topics:
Cycles, Finite element analysis, Plasticity, Stress, Transients (Dynamics), Deformation, Anisotropy, Modeling, Heat exchangers, Thermal stresses, Hardening
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