The Computing Of Micro Slip In Planet Carrier’s Interference Fit Joints

On wind power generation planet carrier flange, interference connection is used. Under wind loads, a small relative sliding is produced on the contact surface of the interference connection. This phenomenon is called micro-slip. Micro slip will result in surface wear, crack initiation and may even produce fretting fatigue failure. This paper is based on the finite element software Workbench, considering the initial assembly and work load, establishes the finite element model of the structure, writes post-processing program, calculates results before and after the micro-slip, and analyzes the slip reason to explore the structure and shape parameters on the micro-slip effects, finally proposes improvement program.First, we define the correct contact algorithm. Interference fit is typical of the contact problem so we can use the commercial finite element software to solve it. After introducing the definition of the contact and the friction model, this paper starts from the algorithm principles and examples, and compares the contact algorithm differences in the calculation of the slip.Secondly, in accordance with the finite element analysis process is the gradual establishment of the finite element analysis model of the structure. It includes:model simplification, ignoring the unnecessary structural features; bearing equivalent, the structure is of a larger size and its structural rigidity is close to the bearing stiffness, as a result, front and rear bearings are no longer regarded as a rigid constraint. The spring equivalent is used instead; meshing, high-end units are selected, and fine grid is arranged in the area of interference connection; the entire analysis process is divided into three analysis steps:the assembly, pretension and load. Actual working conditions of the original structure are simulated; mesh size sensitivity analysis.Thirdly, post-processing program is written to calculate the slip field for different load steps. Workbench software output is based on the synthetic slip of the initial state so we need to write post-processing program to calculate the slip vector, whose main process:extraction of micro slips of the contact elements in the natural coordinate system, after the coordinate transformation and node average results, slip results in the global coordinates are attained, and then according to the shape function interpolation, the slip field of the contact area is attained. Adopting the post-processing, we analyze three analytical steps one by one:the interference of the assembly step, the nut preload step and load step. The slip field and the micro slip of each analysis step are calculated and effects of different unit sizes on values of the slip are analyzed. Finally, causes and factors of the slip are analyzed, and then the improvement program is put forward. From the perspective of structure, the form of load and slip results, we analyze the cause of the back-end slip, and propose structure and shape parameters affecting the micro-slip, design finite element examples to analyze the impacts separately. We analyze the results based on affecting factors, and propose structural improvements method. Compared with the original structure, the maximum slip amplitude of the back-end interference is reduced from40.0uμm to8.8μm.