Fatigue Life Estimation of Local-Cut Circular Tubes under Cyclic Bending

• Main Authors: YunWang, 王筠
• Other Authors: Wen-Fung Pan
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/tanb5y

碩士 === 國立成功大學 === 工程科學系 === 103 === In this study, the finite element method software - ANSYS Workbench 15.0 was used for analyzing the mechanical behavior of local-cut 6061-T6 aluminum alloy tubes under symmetrical curvature-controlled (maximum and minimum curvatures with equal amount and opposite sign) cyclic bending. Next, according the analysis amount of the cyclic maximum stress and the number of cycles required to failure tested by Shen【9】, an appropriate fatigue theory was proposed and the related fatigue parameters were determined. The 6061-T6 aluminum alloy tubes considered were 35 mm in outside diameter and 3 mm in wall thickness. The symmetrical controlled curvature of the cyclic bending was from ±0.2 m-1 to ±1.1 m-1. The different local-cut depths were 0.4, 0.8, 1.2, 1.6 and 2.0 mm. According to the analysis results from ANSYS, for a constant cut depth, a higher controlled curvature leads to a higher amount of stress. In addition, for a constant controlled curvature, a higher cut depth leads to a higher value of stress. Due to symmetrical curvature-controlled loading, the maximum and minimum stresses of the cyclic bending were also symmetrical. Thus, the mean stress effect was not considered in this study. Finally, based on data of the stress amplitudes determined by ANSYS and the experimental number of cycles required to failure tested by Shen【9】on log-log scale, a straight line was determined by least-square method. Therefore, a simple fatigue theory was easily built and the related material parameters were determined from the slope and intercept of the line.