[en] Loose parts can cause component damages in nuclear power plants; thus, the mass estimation of loose parts is crucial in safety management. To accurately estimate the mass of loose parts, it is essential to precisely simulate the bending wave propagation behavior in a structure under impact loading. Lamb’s general solution for an arbitrary impact force function and Hertz impact theory have been used to identify the characteristics of the bending wave impacted by a metallic loose part. However, these approaches cannot provide accurate information on acceleration response. In this study, the bending wave propagation behavior in plate structures under impact loading by a simulated loose part (metal sphere) was modeled using the finite element analysis (FEA) technique. The impact response characteristics of the impact response signal from a metal sphere were analyzed by FEA and was verified with experimental results. In addition, the correlation between the plate thickness and characteristic length of the plate was presented