An investigation on support plate of steam generator by modal analysis

Flow-induced vibration has been found to be responsible for premature failure of PWR steam generators due to wear or fretting fatigue. Based on the theory of elastic plates and shells and the concept of equivalent isotropic solid plate elaborated for perforated tubesheets and tube support plates, the new methodology to determine the effective elastic constants by modal analysis of such perforated plates is described. The computing formula of effective elastic constants for plates with hetero-diameter holes are given in terms of the stiffness superposition method. The studying results indicate that the curves for calculating effective elastic constants E* and v* adopted in the ASME are improper in non-circular hole perforated plates. By modal approach, the effective elastic constants of popular used in steam generators tubesheets and tube support plates with various perforation shapes, such as hetero-diameter holes, trefoil and quatrefoil holes are obtained. The universal relationships between the effective elastic constants and the mass fraction are established, which can be used for perforated plates with any arbitrary hole shapes.