13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Experimental study of heat dissipation process into fatigue crack tip in titanium alloys. M.V. Bannikov1*, A.I. Terekhina1, A.Y. Fedorova1, O.A. Plekhov1, O.B. Naimark1 1Institute of continuous media mechanics Russian academy of science, 614013, Perm, Russia *mbannikov@icmm.ru Abstract. Paper is devoted to investigation of initiation and propagation of cracks in titanium alloys by infrared thermography study of heat generation under cyclic loading and fractography analyses of fracture surface. Two series of experiments on cylindrical specimens and flat specimens with preliminary grown fatigue crack are carried out. Spatial and time temperature evolution into crack tip is investigated, the shape and dissipative intensity at crack process zone are estimated. Based on a result of comparative analysis of the experimental data and the linear fracture mechanics equations it is shown that the spatial distribution and character of heat dissipation zone into the crack tip doesn’t correspond to the conventional models. High-speed shooting (at a frequency of 1 kHz) allowed us to determine the intensity and shape of zone of energy dissipation caused by plastic deformation at the crack tip, as well as to compare the rate of energy dissipation for different stress levels. Fractured specimens were analyzed by interferometer microscope and SEM to verify the existing models of inelastic deformation at the crack tip and to improve methods of monitoring of damage accumulation during fatigue test. Keywords fatigue, energy dissipation, thermo elasticity effect, infrared thermography, fractography 1. Introduction The heat Dissipation caused by the evolution of the structure of the material under cyclic deformation, is the subject of intense research over recent decades. At present it is known that under cyclic deformation processes of strain localization are accompanied by intense heat generation, which makes possible early detection by infrared thermography [1]. Due to its versatility, method of infrared thermography recently been actively used at carrying out mechanical tests as to obtain detailed information about the process of nucleation and propagation of fatigue cracks [2-3] and for studying laws of conversion and energy storage during deformation [4-5]. The possibilities of the method of infrared thermography allows real-time to explore the processes of change temperature caused by thermoelasticity and localization of deformation at the crack tip, as well as the effects of friction on the crack faces during its propagation. This paper is devoted to researching thermoelastic and thermoplastic effects in the crack tip propagating under the cyclic tensile stress applied normal to the plane of the crack. Experimentally obtained cooling effects caused by the elastic deformation of the material at the crack tip, and investigate the features of the distribution of stresses at the crack tip. High-speed photography allowed us to determine the intensity and shape of the zone of energy dissipation caused by localized plastic deformation at the crack tip, and compares the rate of energy dissipation for different stress levels. 2. Experimental conditions and materials Experimental study of temperature evolution at the fatigue crack tip was carried out on the plane specimens of titanium alloy Ti-4.2Al-1.6Mn with frequencies ranging from 1 to 20 Hz in low-cycle
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