A New Experimental Method for the Nonlinear Modal Parameter Identification of a Pressurized Water Reactor Fuel Assembly

Establishing a dynamic model that accurately describes realistic pressurized water reactor (PWR) fuel assembly is crucial to precisely evaluate the mechanical properties of in seismic or loss coolant accidents (LOCAs). The pluck test combined with logarithmic decrement method has been widely applied previous studies extract fundamental modal parameters calibrate models. However, most investigations focused on first cycle free vibration, which strongly affected by stiction, baseline shift, drop conditions, and high-order mode interference, leading inaccurate results. Moreover, these traditional methods cannot be used parameters. In this work, novel experimental for identifying nonlinear PWR proposed. First, two algorithms are adopted decompose vibration. Second, local linearized extracted single-degree-of-freedom fitting sliding window. Finally, summed obtain relationships between amplitude. new makes more effective use data, obtains accurate than method, capable extracting end, results fitted fractional polynomial, great value numerical simulations.