13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- under environment of air as well as water. In this paper, both experimental and numerical researches are taken for fretting fatigue analysis on Zr-4 tube specimen. In section 2, fretting fatigue experiment device, design and results will be introduced. In section 3, a similar structure as experiment is analysis by FEM. Initial crack nucleation can be predicted. Figure 1. Grid-to-rod assembly Figure 2. Fretting fatigue experiment device 2. Fretting Fatigue Experiment 2.1. Experiment Design An experiment device is designed and added to a MTS fatigue testing machine, as shown in Fig. 2. It is assembled by several separated parts, and every part can be replaced for different experimental conditions. Compared with the bridge-type fretting apparatus, this kind of device is supported on the MTS machine directly but not hung on the specimen. A much smaller and stable contact force could be supplied. By using this device, fretting fatigue experiments can be made directly on tube specimens. In our case, Zr-4 fuel rod cladding tubes (size Φ10mm×0.7mm×250mm) which are used in Chinese 300MWe reactors were tested as specimens. Its chemical composition is given in Table 1. As shown in Fig. 3, some necessary preventive measures were taken to make sure that there was no radial deformation neither any surface scars inside or outside the tube except the fretting point we expected. The contact force was set as 150N, and a constant amplitude displacement loading (Re= εmin/ εmax =0.1) at a frequency of 10 Hz was applied. The contact geometry is a cylinder-cross- cylinder type. The pads are made of Cr12MoV Steel. The slip displacements ( δ) between the pads and the specimen are determined by the imposed strain in specimen and the vertical motion of the pads during the tests measured by a dial indicator. For a maximum strain εmax =0.4%, the slip displacement is 200 μm.
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