A Study of Rotary Swaging for the Tubes with Non-Uniform Wall Thickness in Inner Diameters

• Main Authors: Shu-Ming Hu, 胡書銘
• Other Authors: 許源泉
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/q8u9jz

碩士 === 國立虎尾科技大學 === 創意工程與精密科技研究所 === 98 === Special-shaped tubes, which feature extensive uses and a variety of shapes, can be achieved with rotary swaging process (RSP). Current studies of rotary swaging process focused largely on the forming of outer diameter, rarely on inner diameter, therefore, this study explored the RSP of the tubes with non-uniform wall thickness in inner diameters, aiming to learn further about the characteristics of and the trends in the RSP of inner diameter. First, AL-6063 was adopted for material properties analysis. Then, compression tests with different compression ratios and rotary swaging tests were conducted. The hardness value and the distribution between the compression workpiece and the formed tube were obtained. Meanwhile, compression test and the rotary swaging were simulated with the finite element software, in corresponding with the effective strain value of the relative location of hardness distribution, so as to establish the prediction model of hardness and effective strain value. Then, a rotary swaging process simulation was conducted for validation, comparing the differences between the simulations through axial and radial directions. In addition, this study explored the die inlet angle, thickness ratio, and the friction factors, and analyzed their influences on the effective strain value, hardness, buckling and circular stress of the special-shaped tubes, to have deeper understanding about the influences of the RSP parameters. With the results, the current study successfully established the prediction model of the hardness-effective strain of inner diameter rotary swaging in special-shaped tubes. The range of the effective strain fell between 0.1 ~ 1.8, while the predicted hardness value were slightly higher than the actual hardness value. However, in the effective strain ranging from 0.4 to 1.8, the difference between the predicted and the actual hardness was HV2. In terms of the influence of the effective strain on the special tube rotary swaging, the larger the die inlet angle was, the bigger the difference between the effective strain of inside and outside walls would be, with the angle of 10° being the better angle. Besides, the lower the friction factor was, the lower the outer strain was, and the outer strain was higher than the inner strain, whose friction factor was high. Therefore, reducing the friction factor is beneficial for the formation of the inner diameter. Finally, higher thickness ratio resulted in higher strain, but when the outside diameter reached 43mm, the impact was limited. In terms of hardness, the various process parameters have similar influences to those of effective strain. In the hardness distribution from inner to the outer walls, it ranged roughly from HV80 to 82, with the effective strain from 0.1 to 1.8. This showed that rotary swaging could improve the hardness evenly, and avoid the work hardening. In the buckling analysis, conditions for buckling were mainly the radial displacement and radial velocity. When inlet angle was bigger, the radial displacement and radial velocity increased significantly. Reducing the friction factor could also reduce the radial displacement and radial velocity. If the pipe thickness ratio increased, it had similar influences on the radial displacement, radial velocity and the friction factor. In the circular stress, buckling will lead to uneven distribution of the tension and compression stresses in outer walls. Besides, die inlet angle and friction had significant impacts on the tension stress, and thickness ratio on compression stress. In short, through the finite element simulation analysis, tests of the fundamental characteristics of materials, and rotary swaging tests, the influence of the RSP parameters on the formation of inner diameter of tubes with non-uniform wall thickness can be explored. This could not only save the production cost of dies and increase the time effectiveness, but also amend the defects generated in the forming process, so as to enhance the quality and reduce need for die repairment.