Issue 27

A. Kostina et alii, Frattura ed Integrità Strutturale, 27 (2014) 28-37; DOI: 10.3221/IGF-ESIS.27.04 28 Focussed on: Infrared Thermographic Analysis of Materials Energy dissipation and storage in iron under plastic deformation (experimental study and numerical simulation) A. Kostina, A. Iziumova, O. Plekhov Institute of Continuous Media Mechanics of the Ural Branch of the Russian Academy of Sciences, 614013, Ac. Koroleva Street, 1, Perm, Russia poa@icmm.ru A BSTRACT . The work is devoted to the experimental and numerical investigation of thermodynamic aspects of the plastic deformation in Armco iron. Dissipation and stored energies was calculated from processed experimental data of the surface temperature obtained by infrared thermography. An original mathematical model describing the process of mesoscopic defects accumulation was used for numerical simulation of the quasistatic loading of iron samples and for calculation of theoretical value of the stored energy. Experimental and modeled values of the stored energy are in a good agreement. K EYWORDS . Stored energy; Infrared thermography; Mesodefect evolution; Numerical simulation. I NTRODUCTION he experimental and theoretical study of energy balance in metals under plastic deformation has a long history. The importance of this issue for understanding of nature of irreversible deformation of metals and its transition to fracture was originally shown by J. H. Lambert in 1779 in his statement concerning the energy similarity of mechanical and thermal failure processes of solids. The review of experimental works devoted to the methods of stored energy study in the material under plastic deformation and the peculiarities of this process for different material structures and load conditions is available in [1]. To analyze the thermodynamic characteristics of deformation processes in solids, it is necessary to take into account the fact that the plastic deformation work is converted into two parts: heat energy caused by the movement and annihilation of defects at various structural levels, and hidden (stored) energy of plastic deformation accumulated in the elastic fields of defects. The first part of energy can be detected by different experimental techniques and gives us information about current state of structure evolution. During the last decades the enhanced ability to detect temperature evolution during mechanical testing leads to a great interest in the application of infrared (IR) thermography to study heat dissipation process caused by defect evolution under plastic deformation in metals. The theoretical and experimental study of this problem can be useful for explanation of many phenomena of mechanics of solids such as cold work evolution, study of damage to fracture transition and crack propagation process, investigation of crack tip closure effect, validation of linear failure mechanics formula to the investigation of fatigue cracks propagation in metals under different loading conditions and so on. The aforementioned experimental results indicate the importance of further development of methods for investigation of the thermodynamics of the deformation process and develop adequate theoretical models of plastic deformation describing the energy balance in metals under plastic deformation. This work is devoted to investigation of energy dissipation in Armco iron under quasistatic tension. It was shown experimentally [2] that from macroscopic point of view the deformation process of Armco iron can be divided into homogeneous and heterogeneous parts. As a first step of T