A B S T R A C TThe present work is devoted to the investigation of fatigue crack initiation and growth in middle-cycle fatigue (∼10 5 cycles). Smooth specimens made of 35CrMo4 quenched and tempered steel were loaded in fully reversed plane bending. Temperature field evolution in time was recorded with an infrared camera. The experimental results show that the local heating of metal under fatigue loading is a sensitive and accurate enough manifestation of small fatigue crack initiation. It is shown that the time evolution of the spatial standard deviation of the temperature field can be used to investigate the damage localization and to monitor both the crack initiation and the current location of the fatigue crack tip. This should help to investigate the behaviour of defect during cyclic loading.

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. AbstractThe infrared and structural investigations of energy dissipation processes in metals subjected to cyclic loading have given impetus to the development of a new thermodynamic model with the capability of describing the energy balance under plastic deformation. The model is based on the statistical description of the mesodefect ensemble evolution and its influence on the dissipation ability of the material. Constitutive equations have been formulated for plastic and structural strains, which allow us to describe the stored and dissipated parts of energy under plastic flow. Numerical results indicate that theoretical predictions are in good agreement with the experimentally observed temperature data.

The work is devoted to the experimental study of the energy dissipation in titanium OT‐4 under fatigue crack propagation. To investigate a spatial and time temperature evolution at fatigue crack tip, a set of experiments was carried out using specimens with pre‐grown centered fatigue crack. The temperature evolution was monitored by infrared camera. To estimate the values of heat dissipation and J‐integral for cracks with the pronounced plastic zone, an original mathematical algorithm for experimental data treatment was developed. The algorithm includes spatial‐time filtering and relative motion compensation procedures. The value of J‐integral was calculated using the HRR‐solution for stress distribution near the fatigue crack tip and an approximate equation relating the J‐integral to the value of the plastic work.

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