Abstract: By adopting the thought of Adomian's decomposi-tion method, the common dynamic model in mechanieal systems are transformed into a standard first-order-differential-equations, and then the A-operator method (AOM) for the approximate analytic solution of nonlinear mechanieal system is developed based on the exact solution in fonn. The symbolic-numeric (S-N) method on the bases of the AOM is proposed for the first time. Finally, the dynamic responses of one-degree and tvvo-degree nonlinear cam-follower systems are investigated by using the AOM, Numerical examples show that AOM is of high accuracy and high eificiency for solving nonlinear equations. It shows that the method is of potential application value in nonlinear dynarnic analysis of mechanieal system.

Key words: A-operator method Nonlinear mechanieal system Symbolic-numeric method