| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系碩士班 === 101 === The shearing and drawing processes of sheet metals are common techniques to produce metal components. The processes involve complex forming behaviors. It is difficult to predict the forming limit of sheet metals. Therefore, it is widely interested in developing methods which are able to accurately predict the facture. This study used a finite element package, DEFORM, to simulate micro shearing and micro drawing processes of pure titanium sheets. By comparing the simulated results with experimental ones, the critical values were estimated for three damage criteria which are Normalized Cockcroft and Latham, Rice and Tracey, and Ayada criteria.
This study used titanium sheets with different thicknesses of 0.05 mm, 0.1 mm and 0.25 mm in the experiments and simulations of micro shearing and micro drawing processes. The sections of the sheared sheets were examined by an optical scope and analyzed by imaging software. The ratio of burnished land to thickness was used as a reference for estimating the critical values of the damage criteria. In the case of the micro drawing process, the stroke at the fracture was employed to estimate the critical values.
The results show that the used damage criteria are able to predict the fracture profiles in the micro shearing processes and the fracture locations in the micro drawing processes. However, their critical values vary with the thickness of the sheet and the type of the forming process. The results imply that the facture is highly associated with the initial conditions of materials and the path of deformation.
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