PROBLEM 3 (Open Die Hot Upset Forging)
(15 marks)
At Makkah Precision Metals Ltd., a production team is tasked with performing an open die hot upset forging operation on cylindrical billets of a specialty alloy. These billets will be used in a high-strength mechanical coupler for a pipeline system. The forging is carried out on a hydraulic forging press with the following specifications:
• Maximum available force: 250 kN
• Operating efficiency: 90%
• Ram speed during forging: 10 mm/s
Each billet is initially 30 mm in diameter and 50 mm in height. The part is forged in a single blow to achieve a larger average diameter of 45 mm, as required by design. The forging is performed at elevated temperature, under the following material and interface conditions:
• The work material behaves as a perfectly plastic material (no strain hardening)
• Yield strength at forging temperature: 90 MPa
• Coefficient of friction at the die-work interface: 0.40
You are the process engineer assigned to assess the feasibility of the forging setup and ensure the machine's capability. Perform the following analyses:
(a) Calculate the final height of the billet after deformation to the target average diameter.
(b) Determine the true strain rate at the end of the process.
(c) Compute the flow stress and average flow stress of the billet during deformation.
(d) Based on the press specifications and calculated forging force, determine whether the current hydraulic forging press can operate effectively.
Note to students: Use the constant volume assumption and relevant upset forging equations for perfectly plastic materials as provided in class (e.g., Groover's manufacturing science references). Assume axisymmetric deformation and friction effects at the die interface.
