NODE-BASED SMOOTHED POINT INTERPOLATION METHOD: A NEW METHOD FOR COMPUTING LOWER BOUND OF NATURAL FREQUENCY

A meshfree method called node-based smoothed point interpolation method (NS-PIM) is proposed for static analysis of cantilever beam and dynamic analysis of rotating flexible beam for the first time. Gradient smoothing technique is utilized to perform the numerical integration required in the weakened weak (W2) form formulation. The shape functions are approximated using linear interpolation functions, which can be used to solve the 4th order differential equation. In static problems, the cantilever beams with two loading conditions are analyzed, and the results are compared with the analytic solution, which shows a high accuracy of this method even if using linear shape functions. A further study shows that if more than 9 modes were used in the assumed mode method, the result will be divergent. In dynamic problem, the natural frequencies of a rotating flexible beam are analyzed. Simulation results of the NS-PIM are compared with those obtained using finite element method (FEM) and assumed modes method (AMM). It is found that NS-PIM can provide unique lower bounds of natural frequencies, while FEM and AMM can provide upper bounds of natural frequencies. That means we can get more accurate results for the problems by using FEM and NS-PIM in case that exact solution can't be obtained. The NS-PIM has easier shape functions and less independent variable than FEM, and can provide lower bounds of natural frequencies, with a great value of application and dissemination.