The traditional finite element method(FEM)gives over-hard stiffness and hence provides rough upper bounds for natural frequencies
but the node-based smoothed point interpolation method(NS-PIM)gives over-soft stiffness hence provides lower bounds with temporal instability for natural frequencies. A node-based locally smoothed point interpolation method(NLS-PIM)is thus proposed. FEM is combined with NS-PIM by conducting locally gradient smoothing operation on the node-based smoothing domains based on background cells. And the stiffness can be adjusted by changing the parameter α
which is the proportion of the locally smoothed domain over each background cell. It is found that the proposed method can successfully overcome the temporal instability of NS-PIM and the inherent shortcomings of FEM and provide much tighter upper and lower bounds for natural frequencies due to the controlled model stiffness by the node-based locally gradient smoothing operation.
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references
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