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In this study, a new method of backward extrusion is proposed. In this new process, a punch with a movable mandrel was designed. A hollow billet was firstly backward extruded and subsequently upset with the use of the punch after the mandrel returned. The extrusion and upsetting processes were successively executed in order for a higher effective strain to be imposed and a fibrous tissue flow direction to be controlled. In order for the capability of this process to be investigated, experimental and finite element (FE) methods were used. The effective strain of the final part prepared by both the conventional and the new process were compared along the bottom radial and wall axial direction respectively. In the results, it is shown that the plastic strain applied through the processed sample was approximately higher in twice the value of the sample processed via conventional backward extrusion. Consequently, this may improve the mechanical properties and anisotropy of the final products. The difference of the UTS and the TYS between radial and tangential at the bottom was less than 3%.This new process has proven to be promising for parts with a central hole at the bottom production in order for the parts low performance to be improved.

The effect of surface roughness on the stick-slip motion of Magnetorheological (MR) fluids under a simple linear shear mode has been experimentally reported. The shear stress of the MR fluids could be modulated by the changing of the surface roughness. The rate of energy accumulation and releasing during stick-slip motion changed with respect to the shear plates of different surface roughness. The changing of the stick-slip motion based on the different surface roughness was ascribed to the evolution of internal particle structures when shear motion was applied to the aggregates of the particles exposed to the external magnetic field.