An efficient decomposition-condensation method for chatter prediction in milling large-scale thin-walled structures

In this work, an efficient decomposition-condensation method is developed to predict the in-process workpiece (IPW) dynamics for chatter prediction in finishing and semi-finishing large-scale thin-walled structures. Considering the fact that the IPW dynamics is time-varying during the milling process, the IPW is decomposed into three components, namely the machined workpiece, the initial material to be removed and the removed material. The first component is kept unchanged, while the third component is subtracted from the second one. The initial material to be removed is updated by the structural dynamic modification technique to efficiently reveal the effect of material removal. Finite element models of the first two components are further condensed and coupled using component mode synthesis method to calculate the IPW dynamics. In this way, the model order of IPW is significantly reduced and the material removal can be simulated efficiently. The proposed method is finally integrated into a dynamic model for chatter prediction of the milling process. Two thin-walled pockets with planes and curved surfaces are investigated as typical cutting tests to verify the proposed method. It is shown that numerical results agree well with the experimental ones. For the same computing accuracy, the proposed method is observed to reduce the computational burden twice more than the existing methods for chatter prediction.