| 研究概要 |
According to the research plan, in FY2013 the experimental researches and the theoretical calculation of the equivalent plastic strain accumulated in rotating bending process of metal tubes were finished. The research achievements are summarized as follows:
1) Experimental results: To study the parameters of rotating bending process influence on the microstructure of the metal tubes, the rotating bending processes with different temperatures, rotating speeds, number of revolutions and bending radii were successfully carried out using the magnesium alloy (AZ31) tube. The microstructure of the AZ31 magnesium alloy tubes after the rotating bending processes with different parameters are presented. There were new grains formed in all samples. It means that the recrystallization occurred in high strain rate even in a relative low deformation temperature of 150oC, which made a significant contribution to the refining of grains.
2) Theoretical calculation of the equivalent plastic strain accumulated in rotating bending process of metal tubes: To determine the equivalent plastic strain accumulated in rotating bending process of metal tubes, a stress state model of the rotating bending process was proposed. The formulations for radial stress, the curvature of the bending neutral layer, the side-play amount of neutral layer are proposed based on the assumptions: i) The cross-section of tube remained unchanged before and after bending process; ii) The bending process satisfies constant volume principle of plastic deformation; iii) The equivalent stress and strain satisfy the equation.
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| 今後の研究の推進方策 |
FEM modeling:Finite element method (FEM), an effective technique to complicated problems in engineering, has provided an insight into the microstructure evolution in plastic deformation process. The 3D FEM modeling will account for elastic-plastic material behavior of metal tube during rotating bending process. A widely used commercial finite element package Deform 3D will be used to analyze the effect of rotating bending parameters on the deformation behavior and microstructure evolution of metal tubes.
Experimental verification: The experimental rotating bending process will be used to verify the simulation results. The measured bend radius, press forces of bending points and grain size will be used to verify the modeling proposed above. The simulated results obtained using this developed FEM model will be validated by obtaining experimental results. The microstructure characteristics of bent metal tubes will be evaluated by specific instruments, such as Scanning Electron Microscope (SEM) and optical microscope.
Expected results: The expected results are (1) modeling of material behavior in rotating bending process; (2) characterizing the evolution of microstructure and mechanical properties at different rotating bending process; (3) modeling of the microstructure evolution of metal tubes under the alternative compressive and tensile plastic strains; (4) optimization of process conditions for high quality bent tube with fine grain as well as good mechanical properties; (5) manufacturing high strengthened bent metal tubes.
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