This paper reported the designed approaches of cycloidal mechanisms, studied its dynamic forces and failure characteristics using finite element methods (FEM). A simplified cycloidal mechanism (CM) is constructed to fulfill dynamic analysis and reliability evaluation. The studied results show that the loads of the mechanism are shared mainly by a half of the outer rollers and the inner pins. The possible failures of the mechanism will occur at the inner pins caused by the bending stress, and at the cycloid disc induced by the contacting stress. The failure of the inner pins will dominate the damage of the mechanism. A method of evaluating stress variation is proposed for fulfilling reliability design. The stress variations are derived according to the data in dynamic analysis by regression analysis. The methods of design modification are reported for improve the reliabilities. The allowable loads of the CM can be decided accordingly based on the analyzed information.
