Abstract: In view of the special limitation of the numerical method commonly used in the coupling fault of rotating machinery, in order to explain the fault mechanism more deeply and widely, a modeling method of a rotor coupling fault mechanism modeling based on the deformation-motion vector analysis method is proposed. Firstly, "deformation movement" defines deformation by fault, and establishes the relationship between fault deformation and periodic signal by Fourier series; secondly, "vector analysis" analyzes fault movement in dynamic coordinate system, and establishes the relationship between fault deformation motion and periodic excitation force by using dynamic and static coordinate systems; thirdly, analytic solution is obtained by harmonic balance. The deformation motion vector analysis method is a new method of solving the analytic solution, which can make a theoretical and overall grasp of the development trend of the coupling fault of rotating machinery, it can explain mechanically how the coupling fault unfolded layer by layer and the fault structure. If the analytic solution is further rational analysis, the fault characteristics of chaos and bifurcation proposed by numerical solution as a phenomenon can be explained at the mechanism level. The fractional frequency multiplication and sum difference frequency which are difficult to explain in fault diagnosis practice are also part of the solution. Finally, the effectiveness of the modeling method and the correctness of the analytic solution are verified by engineering practice.

Key words: failure deformation node assumption, loose-rubbing coupling fault, dynamic and static coordinate systems, deformation motion vector analysis method