Size effects on flow stress and springback behaviour in micro metal forming
- Publication Type:
- Thesis
- Issue Date:
- 2020
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The continuing trend of micro metallic devices and product miniaturization has motivated studies on micro metal forming technologies. A better understanding of material deformation behaviours with size effects is important for the design and operations of micro metal forming processes. In this dissertation, uniaxial micro tensile testing was conducted on copper specimens with characteristic dimensions to micro scales. The experimental results disclose the existence of size effects and reveal the inadequacies of the existing material models. Micro tensile experiments were carried out on copper specimens with varying grain sizes. The size effects on plastic deformation were demonstrated and were further elucidated by comparison between experimental results and the output of finite element simulations. The surface roughness assessment on tensile tested copper specimen showed the significant influences of size effects in micro metal forming process. Micro V-bending was conducted on copper foils with varying thicknesses and grain sizes. The material intrinsic length was observed and modified according to the average number of grains along the characteristic scale direction of specimen. The analytical model of springback with modified material intrinsic length was established and evaluated by employing MATLAB. This study also presents a research work aiming at the design and manufacturing of a compact UTM compatible with a 3D laser-confocal microscope for observing the deformation behaviour of materials in real-time.
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