November 2020 Volume 2

FORGING RESEARCH AND TECHNOLOGY

Fig. 8. Equivalent stress (a) Conventional die (b) Tapered die design

Figure 9 shows the strain energy density for both the die configurations. The total strain energy is about 22 J in the conventional die and 105 J in the tapered die. It is clearly observed that the proposed tapered die assembly concentrate elastic strain energy in the sliding die. I.e., the sliding die exhibits higher compressive strain, thus storing more potential energy. Compared to the conventional die, the tapered die design exhibits increased elastic deformation due to frictional sliding, leading to radial compression. Correspondingly, the strain energy in the tapered die would be higher at the bottom of the insert, as seen in Fig. 9(b).

The elastic strain energy stored in the sliding tapered die provides the following potential benefits: (a) reduction or elimination of the ejection load; as the release of the stored elastic strain energy(potential energy) takes place, the die springs back thus reducing the contact pressure, (b) the reduction or elimination of residual contact pressure enhances tribological conditions as tool wear is a function of the contact pressure, (c) for hot forging operation, die thermal softening can be prevented/ minimized as the heat transfer from the workpiece to the die is reduced, and (d) potential for reduction of lubricant breakdown .

Fig. 9. Strain energy density in (a) Conventional die (b) Tapered die design

FIA MAGAZINE | NOVEMBER 2020 37