Dissipative energy: monitoring microstructural evolutions during mechanical tests
Fatigue characterization is an expensive operation commonly undertaken in industry. Some authors thus developed experimental measurement methods based on the materials thermomechanical behaviour to provide faster fatigue limit estimations. Yet, the physical ground of these methods needs to be understood. In this work, it has been assumed that heat dissipation phenomena are related to dislocation movements in the material lattice (internal friction); changes in the dislocation characteristics (through plastic straining for example) will affect the material dissipative behaviour.
The dissipative energy characteristics of a Dual-Phase 600 grade (DP600) have been experimentally estimated during traction-traction cyclic loadings on thin sheet specimens. The specimens surface temperature variations have been recorded using an infrared camera and analysed using the heat balance equation. Each dissipative energy measurement has been performed for a specific microstructural state of the material (no macroscopic plasticity occurs during the measurement).
The effect of different loading sequences on the material dissipative behaviour has been tested and interpreted using the commonly used specific damping capacity. The dissipative energy (the dislocation mobility) has been proved to increase with the macroscopic plastic strain and to be affected by aging periods at ambient temperature.
KeywordsFatigue Convection Cold Work Kato
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- 1.H.F. Moore, J.B. Kommers, Fatigue of metals under repeated stresses, Chemical and Metallurgical Engineering 25, 1141–1144, (1921)Google Scholar
- 5.D. Caillard, J.L. Martin, Thermally activated mechanisms in crystal plasticity, Pergamon, Amsterdam London 85–123, (2003)Google Scholar
- 6.A. Granato, K. Lücke, Theory of mechanical damping due to dislocations, Journal of Applied Physics, 27:6, 583–593, (1956)Google Scholar
- 7.T. Tanaka, S. Hattori, Initial behavior of hysteresis loop of low carbon steels under repeated load (theoretical treatment on the multiplying model of dislocations), Bulletin of the JSME, 21:161, 1557–1564, (1978)Google Scholar
- 8.C. Déprés, M. Fivel, L. Tabourot, A dislocation-based model for low-amplitude fatigue behaviour of face-centred cubic single crystals., Scripta Materialia, 58:12, 1086–1089, (2008)Google Scholar
- 10.P. Lukáš, L. Kunz, Cyclic plasticity and substructure of metals, Materials Science and Engineering A, 322:1–2, 217–227, (2002)Google Scholar
- 11.H. Mughrabi, F. Ackermann, K. Herz, Persistent slipbands in fatigued Face-Centered and Body-Centered Cubic metals, ASTM Special Technical Publication, 675, 69–105, (1979)Google Scholar
- 12.C. Doudard, Détermination rapide des propriétées en fatigue à grand nombre de cycles à partir d'essais d'échauffement. PHD Thesis, ENS Cachan, (2004), in FrenchGoogle Scholar
- 13.C. Mareau, Modélisation micromécanique de l'échauffement et de la microplasticité des aciers sous solliciations cycliques, PHD Thesis, ENSAM, (2007), in FrenchGoogle Scholar
- 14.N. Connesson, F. Maquin, F. Pierron, Experimental Energy Balance During the First Cycles of Cyclically Loaded Specimens Under the Conventional Yield Stress, Experimental Mechanics, 51 :1, 23–44, (2010)Google Scholar
- 15.B. Lazan, A study with new equipment of the e®ects of fatigue stress on the damping capacity and elasticity of mild steel, Transactions of the ASM, 42:499–558, (1950)Google Scholar