Stress Analysis for Interference Fitting in Air- Conditioning Compressor

• Main Authors: Rui-feng Chang, 張瑞峰
• Other Authors: Chin-Kuang Lin
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9fmrp6

碩士 === 國立中央大學 === 機械工程學系 === 106 === The objective of this study is using finite element method (FEM) to develop a computer-aided-engineering (CAE) technique for application in interference fitting of motor stator and outer shell of a rotary compressor used in household air conditioning. An FEM model is developed to simulate the reaction between the stator and outer shell under interference fit. After validation by mechanical test, the FEM modeling is applied to simulating dynamic falling and predicting the critical falling height. The effects of interference between stator and shell and number of stator layers on the deformation and stress in the stator/shell assembly are considered in the simulation. The inner radial deformation of stator, radial reaction force between stator and outer shell, and stress distribution in the stator are calculated and correlated with the given parameters. The FEM model is validated by comparing with the simulation the maximum friction force between stator and outer shell measured in mechanical test. Good agreement is found between the simulation and experiment for the maximum friction force to move the stator. In mechanical test, it is found the slope of stator and the interference are the major factors in determining the maximum static friction force. It’s observed in simulation the value of von-Mises stress at the nodes of contact corners of stator, the radial displacement of inner surface of stator, and the internal radial force between stator layer and outer shell at the top 20 layers and bottom 20 layers vary significantly and are similar for all given total numbers of layers in stator. If the stator has more than 40 layers, the stress and deformation in the middle layers do not significantly change. In addition, the maximum radial displacement of stator and the maximum static friction force at the stator/shell interface have a linear relationship with the extent of interference due to elastic deformation. The FEM model is simplified using plate elements in the middle layers and the difference in results between the original solid-element model the simplified plate-element model is acceptable in engineering application. The computational time is effectively reduced from 40-50 hours to 8 hours using the simplified plate-element model. In the dynamic falling simulation, there are three falling heights considered, namely 1, 0.5, and 0.25 m. A critical falling height of 0.5 m is predicted to separate the stator from the outer shell during falling, for a given 40-layer stator/shell assembly with 0.5-mm interference.