Procedure

Follow the steps below to conduct the virtual experiment and correlate the simulation results with the theoretical principles of cold heading.

1. Understanding the Objective: Begin the experiment by reviewing the core objective: studying the formation of bolt, hexagonal bolt, and screw heads using the cold heading process. The goal is to observe material deformation and strain distribution while the billet is shaped by the mechanical press.

2. Observation of Bolt Setup Simulation

• Action: Play the “Bolt Setup” simulation video.
• Observation: Observe the initial billet made of plain carbon steel at room temperature (20°C). Notice the arrangement of the upper die (punch), lower die, and billet.
• Analysis: Understand how the mechanical press applies force to "upset" the billet, causing it to expand and fill the die to form the bolt head.

3. Analysis of Strain in Bolt Formation

• Action: Play the “Bolt with Strain” simulation.
• Observation: Observe how strain develops in the billet during deformation. Initially, strain is zero and increases as the punch moves downward.
• Technical Note: Note the maximum strain value (approx. 3.36107). Relate higher strain regions (shown in red) to greater plastic deformation and grain refinement. Study the strain variation graph with respect to punch movement.

4. Observation of Hexagonal Bolt Formation

• Action: Play the “Hexagonal Bolt Setup” simulation.
• Observation: Observe how a round billet is converted into a hexagonal bolt head.
• Comparison: Identify the role of die geometry in shaping the hexagonal head. Compare this process with the round bolt formation observed in Step 2.

5. Strain Analysis in Hexagonal Bolt

• Action: Play the “Hexagonal Bolt with Strain” simulation.
• Observation: Observe the strain distribution across the billet. Identify high-strain regions near the corners of the hexagonal head.
• Data Analysis: Analyze the strain-mesh view and the graph plotting Punch vs. Pilot Height to understand the force required to fill the hexagonal corners.

6. Observation of Screw Head Formation

• Action: Play the “Screw Head Setup” simulation.
• Observation: Observe the formation of the screw head using a single-step cold heading process.
• Analysis: Note the deformation pattern, die arrangement, and material flow as the slot is formed in the head.

7. Strain Analysis in Screw Head Forming

• Action: Play the “Screw Head with Strain” simulation.
• Observation: Observe the evolution of strain. Identify regions of maximum strain and understand how this affects mechanical properties such as strength and durability.
• Graph Analysis: Analyze the graph showing variation between pilot height and upper die movement.

8. Comparison and Inference

1. Comparison: Compare the bolt, hexagonal bolt, and screw head forming processes in terms of deformation behavior.
2. Inference: Conclude how the cold heading process improves mechanical properties through plastic deformation and grain refinement.
3. Thread Connection: Relate the finished head to the Pitch and Lead parameters discussed in the Theory section, as the fastener would next move to the thread-rolling stage.