In order to investigate the coupling characteristics between elastic deflections and rigid motions of the blades

the moderate deflection beam model was adopted to treat elastic deflections and two methods were adopted to treat rigid motions based on infinitesimal rotation and finite rotation.The impact problem of the blade droop stop was analyzed.Results show:(1) coupling of elastic deflections with rigid motions is distinctive;(2) computations of two methods are in good agreement with test data

when rotation angle is small;(3) when rotation angle is large

couplings increase distinctly and the differences between the results of the two computational methods increase;(4) the bending stiffness has evident effect on the coupling

and the coupling will increase with the decrease of bending stiffness;(5) in case of the blade is relatively soft

the calculated values of phase lag and amplitude augment based on infinitesimal rotation will exist.This phenomenon should be paid attention to

when blade dynamic response is calculated.