Quasi-static tensile behavior and constitutive modeling of large diameter thin-walled commercial pure titanium tube

详细信息    查看全文

• 作者：Z.Y. Zhang ; H. Yang ; ^{yanghe@nwpu.edu.cn} ; ^{zhangzhiyong555@mail.nwpu.edu.cn} ; H. Li ; N. Ren ; D. Wang
• 关键词：CP-Ti tube ; Tensile behavior ; Temperature ; Strain rate ; Constitutive modeling
• 刊名：Materials Science and Engineering: A
• 出版年：2013
• 出版时间：1 May, 2013
• 年：2013
• 卷：569
• 期：Complete
• 页码：96-105
• 全文大小：1544 K

文摘

Large diameter thin-walled (LDTW) commercial pure titanium (CP-Ti) bent tubes are widely used in the pneumatic system of commercial airplane. Understanding and modeling the temperature and strain rate dependent quasi-static tensile behaviors are fundamentals for the improvement of bending formability of LDTW CP-Ti tubes. With the LDTW CP-Ti tube of 76.2 mm¡Á1.07 mm (D¡Át, D-outer diameter, t-wall thickness, D/t=71.2) as the objective, uniaxial tensile tests were conducted under various temperatures (298-873 K) and different strain rates (10^?3-10^?2 s^?1). The major results show that: (1) The flow stress of LDTW CP-Ti tube becomes less temperature dependent at 473-573 K, and the positive effect of strain rate on the flow stress is not obvious at 523-773 K. These results are interpreted in terms of dynamic strain ageing. (2) The fracture elongation of LDTW CP-Ti tube can be greatly improved at 873 K, but the ductility decreases with the increase of temperature at 573-773 K, which is considered as ¡°blue brittle¡± phenomenon. (3) The strain hardening exponent of the LDTW CP-Ti tube increases from 0.073 to 0.155 as the temperature increases from 373 K to 573 K, and the increased strain hardening exponent has positive effect on the improvement of bending formability of the LDTW CP-Ti tube. Then, at the temperature range of 298-573 K, by introducing a quadratic function of the reciprocal of temperature and the semi-log scale of strain rate, a group of new equations for strain hardening exponent, strain rate sensitivity parameter and strength coefficient were proposed based on Fields-Bachofen(FB) equation; comparing the predicted results with the experimental data, the proposed constitutive models present a good estimate of the quasi-static flow stress for the CP-Ti tube, and the largest mean error is 3.66 % .