The Response of Chopped Circular Tubes with Different Chopped Directions under Cyclic Bending

• Main Authors: Ding-ShiuanWu, 吳定軒
• Other Authors: Wen-Fung Pan
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/57517920464534484829

碩士 === 國立成功大學 === 工程科學系 === 102 === In this thesis, the influence of different chopped directions on the mechanical behavior and fracture of chopped 6061-T6 aluminum alloy tubes subjected to cyclic bending are investigated. The material is divided into two parts, which includes experimental testing and theoretical analysis. And, the comparison between these two parts is also included. From experimental moment-curvature curve, the 6061-T6 aluminum alloy tube shows a little bit cyclic hardening under curvature-controlled cyclic bending. After a few cycles, the loop becomes stable. The chopped direction has almost no influence on the moment-curvature relationship. Next, from the experimental ovalization- curvature curve, the ovalization increases in a ratcheting manner with the number of bending cycles. The tube will fracture when the ovalization reaches a critical value. The chopped direction has a strong influence on the ovalization-curvature relationship. In addition, from experimental controlled curvature-number of cycles to produce fracture curve, a higher controlled curvature leads to a lower number of cycles to produce fracture and a higher chopped direction leads to a higher number of cycles to produce fracture. If the aforementioned relationship is plotted on a log-log scale, four straight lines can be seen corresponding to four chopped directions. Finally, by referring the theoretical equation proposed by Shaw and Kyriakides [5] and importing the appropriate factor of the chopped direction, a theoretical formulation is proposed to simulate the relationship between the controlled curvature-number of cycles to produce fracture relationship for chopped circular tube subjected to cyclic bending. Through comparison with the experimental data, the theoretical equation can reasonably simulate the experimental results.