Abstract
The work is devoted to experimental study of heat flow evolution at the fatigue crack tip during biaxial loading. The plane samples of titanium alloy Graid-2 with thick of 1 mm were weakened by notch to initiate fatigue crack at the center of samples. Infrared thermography and the contact heat flux sensor based on the Seebeck effect are used to monitor the dissipated thermal energy. During tests the samples were subjected to cyclic loading of 10 Hz with constant stress amplitude and different biaxial coefficient. The experimental results confirm the previous conclusions of authors about two regime of energy dissipation at fatigue crack tip. The heat dissipation curve can be divided in two stages. Under the first stage the power of heat flux is proportional to the multiplication of the crack rate by its length. In the second stage is characterized by classical linear relationship between crack rate and heat flux rom the crack tip. The qualitative correspondence of the energy approach to the classical representation based on the stress intensity factor was shown.
Highlights
I n the age of rapid technical progress, highly sophisticated mechanisms and technologies and ambitious projects in the field of mechanical engineering, aircraft construction, nuclear energy and space exploration much effort has been put into intensive development of many fields of science and technologies, including fracture mechanics
A comparison of heat fluxes measured by the two methods is given in Fig.5: green line - infrared thermography, red line - heat flux sensor
The experimental technique for measuring the energy dissipation during fatigue test under biaxial loading was developed based on the contact heat flux sensor and the method of infrared thermography
Summary
I n the age of rapid technical progress, highly sophisticated mechanisms and technologies and ambitious projects in the field of mechanical engineering, aircraft construction, nuclear energy and space exploration much effort has been put into intensive development of many fields of science and technologies, including fracture mechanics. In sufficiently plastic structural materials the propagation of the crack begins when the plastic deformation near its tip becomes large (of the order of 10 percent) This irreversible process is accompanied by the release and accumulation of energy, which leads to a local temperature change in the region of the crack tip and the occurrence of a heat flux. An original contact heat flux sensor was developed to record energy dissipation during crack propagation under biaxial loading and to verify the data of infrared thermography This sensor made it possible to study in details the dissipated energy evolution in metal samples (titanium alloy Grade 2) in bi-axial loading tests and to determine the relationships between the energy dissipation and the fatigue crack rate
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