Weight Reduction of Heavy Duty Truck Components Through Geometry and Quenching

6. Concluding remarks

• Currently the power transmission shafts and axles used in most HDV are solid
• Is it feasible to manufacture hollow shafts in a cost effective manner?

• Investigate the potential of forging lightweight hollow power transmission shafts for heavy duty vehicles

• The weight saving for using a 47 mm OD axle shaft with wall/diameter ratio of 0.24 is 5 5 kg ~24%
• Greater weight savings possible as shaft diameter is increased
• Minor modifications must be made to the axle housing and bearings and differential gears
• Forging may provide a practical solution to creating long hollow parts

• Axle shaft weight may be reduced by 5.6 to 7.35 kg (12.3 to 16.2
lbs)
• The input shaft weight may be reduced by 1.75 kg (3.85 lbs)
• The output shaft weight may be reduced by 1.7 to 2.2 kg (3.74 to 4.84 lbs)
• The countershaft weight may be reduced by 0.5 kg (1.1 lbs)
• A truck with a tandem rear axle and three countershafts can have its weight reduced by a total of about 38.4 kg (86.6 lbs) by using hollow shaft geometry

1. Employ existing forging technologies
2. Employ forging machine architecture
3. Employ induction heating technologies
4. Comparable cycle time to forging

• The maximum strain attained is 6.5 mm/mm which is acceptable for hot forging
• Due to oxide, the tube wall will not completely close during upsetting, thus a small through hole will have to be machined as part of the finishing operations
• Experimental verifications are needed to assess the feasibility of the process
• Induction heating and material flow can be optimized to reduce concentrated strain

Proposed Sequence
1. Open die extrusion
2. Induction heating
3. Upsetting to form a solid top part
4. Heading operation

• The maximum strain attained is 5.3 mm/mm acceptable for hot forging
• Due to oxide formation, the tube will not close during upsetting, thus a small through hole will have to be machined as part of finishing operations
• Experimental verifications are needed to assess the feasibility of the process.

• The maximum strain attained is 6.39 mm/mm which is acceptable for hot forging
• Due to oxide formation, the tube will not close during upsetting, thus a through hole will be drilled as part of finishing operations
• Experimental verifications are needed to assess the feasibility of the process
• Induction heating and material flow can be optimized to reduce concentrated strain

• Large Increase in the Residual Compressive Surface Stresses
• Reduction in the Alternating Axial Stresses (Semi-Float Axle)
• Decrease in Required Shaft Diameter (3% Weight Reduction)
• Increased Hardness and Strength in Core

• A truck with a tandem rear axle and three countershafts can have its weight reduced by a total of about 38.4 kg (86.6 lbs) by using hollow shaft geometry
• A forging sequence for hollow shaft based on differential heating of tubular billet is proposed. The sequence includes three major operations:
i. Heating a section of a tubular stock via induction heating
ii. Upset the heated section into a solid rod
iii. Shape the solid section into a flange or a desired shape by further upsetting
• The proposed forging sequence can be accomplished using conventional tooling and forging presses/equipment
• Modern heat treating techniques can be employed to improve surface stresses and reduce component weight

Students who worked on this project:
James Lowrie,  Graduate student
Hao Pang, Graduate student
Aman Akataruzzaman, Graduate student
Joseph Jonkind, Undergraduate student
Steve Henkel, Undergraduate student
Frederic Morrow, Undergraduate student
FIERF and AISI for sponsoring this project
Forging companies and truck manufacturers for providing valuable information for this
project:
Fox Valley Forge, Mid-West Forge, Sona BLW Precision Forge, GKN Sanford, Volvo
Powertrain Manufacturing at Hagerstown MD, and Cleveland Truck Manufacturing
Plant (Freightliner)

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