August 2019 Volume 1

FORGING RESEARCH

Figure 2-21: Maximum strain when ID=30mm

Table 2-2: Influence of Tubular Blank IDs on Forming Loads

Load of the Upsetting Operation (ton)

Load of the Flanging Operation (ton)

ID=20 mm ID=25 mm ID=30 mm

215 206 198

677 712 783

2.6. Concluding Remarks There are currently numerous process techniques which can be used to produce hollow shafts. The focus of this investigation, however, is to develop a cost effective process which can utilize conventional and readily available forging equipment. A three step differential heating based process was developed to produce hollow axle shafts from tubular blanks. The first step is to partially heat the tube so that the material can be divided into hot, warm and cold regions. This makes the flow stress of material spatial varying. When the forging process takes place, the cold region of the blank serves as pseudo dies thus plastic deformation takes place on the heated section of the blank. The next step in the process is to upset the hot section of the tube to make a solid section. Once the center hole is closed the material is further upset into a flanged shape in a manner identical to conventional forging of a solid shaft. The feasibility of this techniques was investigated and verified using DEFORM 2D. The differential heating-based process is feasible and valid for production of hollow axle shaft, because the maximum effective strain induced is within acceptable range of hot forging. And the forming loads obtained are within the capabilities of forging presses

currently used in industry. It was also found that the differential heating based-forging process is good at maintaining a uniformwall thickness along the longitudinal axis of the axle shaft. Parametric analysis, where the inner diameter is selected as the independent parameter, showed weight reduction of the axle shaft manufactured by the process can reach 19.4% if the inner diameter increases to 30 mm. The parametric analysis also showed: a) the formability of the process is reduced by an increasing inner diameter, and b) the forming load of the upsetting operation decreases with increase in inner diameter, while the forming load in the flanging operation increases with increase in the inner diameter. The hollow shafts manufactured by the differential heating-based process exhibit a uniformwall thickness along the axis.The uniform wall thickness along the axis enhances dynamic balance and lessens vibration in high-speed rotation. Heat treatment may be needed after forging as the flange part is hot forged, whereas the hollow section remains cold and does not undergo plastic deformation. The full article can be accessed by following the link listed below: https://www.forging.org/uploaded/content/media/Final Report_ Hollow Shaft_FIERF_ NCSUNgaile May 13(1).pdf

FIA MAGAZINE | August 2019 63