Reducing load during partial forging of a disc specimen by applying lateral oscillation

Abstract

In recent years, the demand for plate forging has been increasing with the demand for lighter weight automotive parts. The authors developed a method to reduce the load by applying lateral oscillation during compression, and demonstrated this load reduction during the forging of cylindrical specimens. This method was applied to the partial forging of a disc in the present study. Disc specimens with diameters of 8 and 14 mm were fabricated from 3 mm thick annealed pure aluminum plates, and the outer edge of each specimen was compressed to half its thickness. A linear actuator was used to apply lateral oscillation to the lower die during the second half of compression. For the disc specimens with a diameter of 8 mm, increasing the oscillation velocity under non-lubricated conditions resulted in a greater reduction in load. In the case using the 14-mm-diameter specimens, it was found that forging with grooved dies was an effective method to reduce the load, even under a lubricated condition. Finite element analyses revealed that when the compressed region was firmly gripped, lateral oscillation produced shear stress, which reduced the axial compressive stress. Experiments and finite element analyses using grooved dies were conducted on the 14-mm-diameter specimens by varying the lateral oscillation velocity. The relationship between the ratio of lateral oscillation velocity to axial compression velocity and the load-reduction ratio was investigated, and the experimental results showed good agreement with those obtained by finite element analysis. Measurements of the cross-sectional shape of the forged region confirmed that lateral oscillation caused local elongation along the die surface when the grooved dies were used.