Open Access Conference Proceedings

Creating of gradient structures with the grain size changing from microns to nano-scale through the thickness of processed metallic materials represents a new advanced strategy for producing a superior combination of high strength and good ductility. Severe plastic deformation with predetermined strain gradient can be considered as a mechanism of creating of gradient structures. Strain gradient through sheet thickness can be achieved by special rolling technique. A surface of work rolls consisted of small microscopic grooves with the depth of 25 µm, located in transverse to rolling direction. A ribbed surface can have certain advantages in terms of tribological use. When positioned in transverse to metal flow direction a ribbed surface of work rolls can increase the frictional force. The aim of the ribbed surface was to create high opposite frictional forces during rolling and to develop the severe plastic deformation method for producing of sheets and strips with gradient microstructure. This paper presents the distributions of the plastic strain through sheet thickness of pure aluminum processed by symmetric and asymmetric rolling. Effects of contact friction coefficient, thickness reduction per pass and rolls speed ratio were investigated by the rigid-plastic finite element analysis. Extremely high strain difference through sheet thickness was found during symmetric and asymmetric rolling. Finite element analysis of strain gradients can be used for development of the special rolling techniques for fabrication of metal sheets with gradient structures and improved properties.

Keywords: Special rolling, microscopic grooves, finite element method, strain gradient, severe plastic deformation

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