13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- A New Test Method for High-Temperature Fracture of Alloys and Some Corresponding Results Shaoqin Zhang1,2,*, Wanlin Guo2,*, He Li1, Huihua Zhang1, Ying Deng1, Qiong Wu1, Qinghui Xiao1, Peng Zhou1 1 Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang HangKong University, Nanchang 330063, China 2 State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China * Corresponding author: shaoqinzhangniat@yahoo.com.cn, wlguo@nuaa.edu.cn Abstract A moiré interferometry-based experimental method is first introduced for high-temperature, mixed-mode fracture testing. The method allows real-time observation of surface deformation of cracked specimens and crack-tip plastic zone at elevated temperatures. Based on the moiré fringe patterns captured real time through image acquisition system, important fracture parameters, such as the crack open displacement, the crack initiation load, the ultimate load, etc., can be determined. With these data, the stress intensity factor, load bearing capacity, fracture ductility, strain, and stress fields near the crack-tip can be obtained. The method has been successfully applied to investigate pure mode I, I-II mixed-mode fracture performance of high temperature alloys. Furthermore, some significant thickness effects achieved by the group of researchers on the mixed-mode fracture performance of TC11 titanium alloy at high temperatures are cited and briefly introduced. Finally, three dimensional finite element simulations are performed for the tensile-shearing specimens at an elevated temperature. Simulation results are in agreement with measurements. Keywords Moiré interferometry, High temperature, Mixed mode fracture, Thickness effect 1. Introduction In industrial fields, such as aerospace, petrochemical, and dynamic transportation, there is a growing demand for high-temperature structural materials. The rising demand makes the issues of reliability design, failure analysis, and safety evaluation for high-temperature structures increasingly important [1-5]. The performance of engineering materials, especially metal materials, is always sensitive to temperature. At an elevated temperature, internal molecular motion aggravating, phase changing, cavity and micro crack emerging in materials make their fracture property significantly different from that at room temperature [3]. With the field of fracture still in development, high-temperature behavior remains one of the unresolved fundamental issues [6]. A better understanding of the fracture behavior is important. High-temperature components, such as engine turbine and blade, steam boiler and pipeline, and steam turbine bear complex loading at high temperatures. Therefore, mixed-mode fracture testing of materials from room to high temperature is necessary. By far, the research on two-dimensional (2D) cracks of single and mixed modes under room temperature (RT) becomes better and approaches perfection day by day. However, most of the previously conducted analytical and numerical investigations in fracture mechanics were focused on 2D or axisymmetric geometries, although three-dimensional (3D) effects were often acknowledged. The stress state near an actual crack tip is always 3D, and the meaning of the results obtained within the 2D theories and their relation to the actual 3D stress distribution is still not fully understood [7].
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