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.
KeywordsPlastic Strain Dissipative Energy Internal Friction Dual Phase Steel Material Microstructure
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