Experimental Study on the Response and Collapse of Local Sharp-cut Circular Tubes with Different Diameter-to-thickness Ratios under Cyclic Bending

• Main Authors: WEN-YIHuang, 黃文義
• Other Authors: Wen-Fung Pan
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/92fp3x

碩士 === 國立成功大學 === 工程科學系 === 105 === This paper is mainly to study the response and collapse of 6061-T6 aluminum alloy tubes with three different diameter-to-thickness ratios and five different cut depths under cycling bending. The tube bending machine and curvature-ovalization measurement apparatus were used to control, measure and collect the experimental data. During the symmetrical cycling bending, it can be observed from the experimental moment-curvature curves that the loops exhibit a little bit cyclic hardening and become stable after a few bending cycles. For a certain diameter- to-thickness ratio, the cut depths have almost no influence on the moment-curvature curves. Next, from the experimental ovalization-curvature curves, the ovalization of the tube’s cross section increases in a symmetrical and ratcheting manner for tubes without a cut. However, a higher cut depth leads to a more asymmetrical ovalization- curvature curve. In addition, a larger diameter-to-thickness ratio causes a larger ovalization of the tube’s cross section. It is shown from the experimental controlled curvature-number of bending cycles required to produce failure relationships on a log- log scale that five nonparallel straight lines can be found for each diameter-to- thickness ratio. Finally, a theoretical formulation was proposed in this thesis to simulate the relationships between the controlled curvature and the number of bending cycles required to produce failure. By comparing the theoretical analysis with the experimental data, it is shown that the theoretical formulation can properly simulate the experimental results.