【作者】 黄文；

【导师】 夏源明； 汪洋；

【作者基本信息】 中国科学技术大学 ， 固体力学， 2006， 博士

【摘要】 本文的研究工作是在国家自然科学基金（高温冲击拉伸试验技术的理论与实验研究，编号10172080；多晶纯Ti高温冲击拉伸力学性能和变形机理研究，编号10472110）的资助下开展的。 对金属材料高温动态力学性能的研究是当前固体力学和材料科学研究的一个前沿课题。由于技术上的困难，高温冲击拉伸试验至今未见报导，因而阻碍了对于金属材料高温动态力学性能的研究探索。本文在拥有多个自主知识产权的冲击拉伸试验机和试验技术的基础上，采用快速接触加温技术创立和发展了一套适合于测试金属材料力学性能的高温冲击拉伸试验技术（试验温度可达1073K）。该技术能够在很短的时间内（约30秒）在试样试验段形成较均匀的温度场（温度偏差＜3％），同时有效地将杆端温升的大小和影响区域控制在一个较小的范围内，避免了杆端温升对于试验结果有效性的影响。 改进了原有的冲击拉伸加卸载试验技术，重新设计了入射杆和透射杆二次加载波吸收器（吸波器使入射杆中二次加载波的幅值降到一次加载波的1／4左右，透射杆中二次加载波的幅值降到一次加载波的1／6左右），从而得到更可靠的冲击拉伸加卸载应力应变曲线，完善了冲击拉伸复元试验技术。 对多晶纯钛在不同温度度（298K-973K）和应变率(10^-3s^-1-1400s^-1)下的拉伸力学性能进行了系统的研究，揭示了如下温度和应变率相关的力学行为：变形中孪晶密度随温度升高而锐减，使常温和高温下的硬化率出现较大差别；和已有的压缩结果相比，发现在压缩条件下更易于出现孪晶；纯钛断裂应变随温度的升高出现反复的增减，且在动静态下分别呈现出不同的规律；试验还发现纯钛的屈服行为随着应变率的升高呈现较复杂的规律，在高温高应变率下应力应变曲线在屈服之后出现多个应力振荡峰。另外，采用改进后的冲击拉伸复元试验技术得到了纯钛在常温、应变率为300s^-1下的等温应力应变曲线，发现等温变形过程中材料的强度和断裂应变明显大于绝热过程中的强度和断裂应变，冲击过程中的绝热温升促进了纯钛的破坏。 结合试验结果，在位错动力学的基础上建立了描述纯钛力学性能温度和应变率相关的本构方程，采用该本构方程拟合了多晶纯钛在不同温度和应变率下的应更多还原

【Abstract】 The present research is financially supported by the National Natural Science Foundation of China （NO. 10172080 and No. 10472110）Research on the dynamic behavior of metallic materials at elevated temperatures is one of the principal directions in the solid mechanics and material science. An understanding of tensile deformation behavior of metals over a wide range of strain rates and temperatures is very important in the design of structures. However, due to the experimental technique difficulties, few reports on tensile behavior of metals at high strain rates and elevated temperatures are available so far. In the present work, a new heating technique was proposed in a self-designed Split Hopkinson Tensile Bar （SHTB） and a high temperature and high strain-rate tensile testing system was established, which is suitable for measuring the dynamic response of metals over a wide temperature range of 298K-1073K. A thorough calibration on the testing system showed that a nearly homogeneous temperature field in the specimen （the temperature deviation <3%） can be rapidly （in 30 seconds） created, and the temperature rise in the bars of SHTB can be controlled to meet the requirement of one-dimensional experimental principle.Tensile impact load-unload experimental technique was improved by using specially designed input/output wave filter fixtures to absorb the secondary loading waves in the input/output bars. As a result, the amplitude of the secondary input/output waves can be reduced to a value of 1/4 and 1/6 of their corresponding initial waves, respectively. Owing to this improvement, a more reliable load-unload curve was obtained and the tensile impact recovery experimental technique was updated.Tensile experiments on the CP-Ti were carried out in a temperature range of 298K-973K and a strain rate range of 10^-3s^-1-1400s^-1. The testing results indicate that: 1) The density of deformation twinning decreases rapidly with increasing temperature, which leads to a noticeable difference of strain-hardening rate at room temperature更多还原