| Abstrakt: |
In industrial metal shearing operations, the profile geometry of knives has an important effect on the quality of the parting edge and the amount of shearing force involved. Compared to matching profiles (closed or open), inclined knife profile offers a lower shearing force and improves greatly the distortion at the parting edge. The degree of inclination cannot be chosen arbitrarily. Limited to certain optimum size, profile inclination is beneficial. The optimum size of inclination is dependent on the coefficient of knife-metal interface friction. In order to calculate coefficient of friction and also to facilitate the selection of other shearing parameters, evaluation of hydrostatic pressure at shear plane and interface contact pressure is of extreme importance. The evaluation of hydrostatic pressure and contact pressure necessitates a critical study of preshear deformation. In this paper, preshear deformation in an ideal shearing model has been briefly studied, using the slip line field concept, and corresponding hydrostatic pressure, contact pressure, and coefficient of friction have been evaluated. Formulae to obtain optimum size of inclination have been derived for shearing different shapes. Also, effects of section size and cutting speed are discussed. |
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