Investigating the effect of Texture Intensity on the Forming Limit Diagram of Magnesium Microtubes used in Stents using Crystal Plasticity Finite Element Modeling

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Document Type : Article

Authors

1 Master's student, Faculty of Mechanical Engineering (Sharif University of Technology)

2 Department of Mechanical Engineering, Payam Noor University, PO Box 3697-19395, Tehran, Iran

3 -

Abstract

Metal microtubes are usually made using the extrusion method, which eventually creates a special texture in the tube. The way of creating tissue in the microtube has a great effect on its mechanical properties, which is very effective in the quality of the fabricated stents. In this research, the effect of texture intensity caused by the extrusion process to make magnesium microtubes is extracted using the crystal plasticity finite element simulation process. First, in order to validate the modeling, the hydroforming process for aluminum has been simulated in Abaqus finite element software and compared with similar results in the literature. After confirming the modeling process, using the criterion of the second derivative of the maximum large strain for the hydroforming process, the forming limit diagram is drawn for magnesium without texture intensity. In order to confirm the modeling of crystal plasticity, the representative volume element was subjected to tension and compression and the strain stress curve in tension and compression was compared with the experimental strain stress curve. Then, the representative volumetric element was subjected to tension in three directions of extrusion, perpendicular to extrusion and forty-five degrees, and by calculating the ratio of transverse strain to thickness strain, the anisotropy coefficient for the random state in these three directions was obtained. In the following, the anisotropy coefficient was obtained in three different tissue intensities as in the random state. The results show that the relative activity range of hard slip systems such as pyramidal slip and prismatic slip is greater in the direction of extrusion than in other directions, so the anisotropy coefficient obtained in the direction of extrusion is greater than in other directions. As the texture intensity decreases, the anisotropy coefficients approach one and the formation limit curve increases, and as the texture intensity increases, the formation limit curve shows a lower safe zone.

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Sharif Journal of Mechanical Engineering

Articles in Press, Accepted Manuscript
Available Online from 20 December 2024

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