13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- 4. Experimental study changes in temperature during elastic deformation. Analysis of thermal effects at the crack tip is complicated by the fact that during normal loading to the plane of the crack propagation, its trajectory is not always strictly linear. The appearance of an inflection point on the trajectory of crack leads to a significant heat release on its banks (Fig. 4).Apparently, the edges of the crack are shifted relative to each other and cause the appearance of zones of friction and/or plastic deformation, which corresponds to the hypothesis of crack closure, is used in some models of linear fracture mechanics. Fig. 4 The temperature distribution at the top and on the banks of the fatigue crack propagation under cyclic deformation Figure 5 shows the change in the maximum temperature at the crack tip, stress and crack opening during loading with the stress amplitude 212 MPa, average stress 212 MPa and frequency of 5 Hz. Data from displacement sensor mounted on the crack faces, allows to suggest that the disclosure of the crack varies in phase with the applied stress. Fig.5. Changing the maximum temperature at the crack tip (1), stress (2), and the crack opening (3) in the process of cyclic loading with the amplitude of stress 212 MPa, average stress 212 MPa and frequency of 5 Hz. Analysis of temperature data allows asserting, that the maximum of applied stress and the maximum of intensity of heat in the top of the fatigue crack does not match in time. At the beginning of the experiment the sample is loaded by middle stress and in a state of thermodynamic
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