Fundamentals of Metal Forming Notes

Homework 4:
  - Topic: Metal Forming Fundamentals and Forging Fundamentals
  - Due by 11:59 PM Wednesday, March 11th
  - Individual submissions needed via Top Hat

Metal forming encompasses a broad array of manufacturing processes where plastic deformation is utilized to modify the shape of metal workpieces.
In these processes, a tool, typically referred to as a die, exerts stresses that surpass the yield strength of the metal, resulting in a new shape dictated by the die's geometry.

The stresses applied for plastic deformation are predominantly compressive.
  - Common examples include:
    - Rolling
    - Forging
    - Extrusion
Other processes may involve:
  - Tensile stress for stretching the metal
  - Combination of tensile and compressive stress for bending
  - Shear stresses in relevant operations

Desirable Material Properties:
- Low yield strength
- High ductility
Temperature plays a crucial role in altering these properties:
  - Raising temperature:
    - Increases ductility
    - Decreases yield strength
Additional Influential Factors:
- Strain rate
- Friction

Metal forming processes can be categorized into two main types:
1. Bulk Deformation Processes
2. Sheet Metal Working Processes
Classification criteria relate to the surface area and volume of the raw material utilized in the process.

Characterized by significant deformations and extensive shape transformations.
The term bulk implies workparts with relatively low surface area to volume ratios.
Typical starting shapes include:
  - Cylindrical billets
  - Rectangular bars
  - Processes include:
    - (a) Rolling
    - (b) Forging
    - (c) Extrusion
    - (d) Wire and bar drawing

Operations performed on metal sheets, strips, and coils characterized by a high surface area to volume ratio.
Commonly referred to as pressworking since they typically utilize presses for operation.
The resultant parts are known as stampings.
Typical tooling includes:
  - Punch and die
  - Processes include:
    - (a) Bending
    - (b) Deep Drawing
    - (c) Shearing
      - Steps of shearing:
        1. Punch first contacts the sheet
        2. Cutting action occurs
        - Note: Shearing does not classify strictly as a forming operation.

Temperature Influence:
  - At increased temperatures:
    - Strength and strain hardening decrease, requiring lower forces and power during forming
    - Ductility increases, allowing for enhanced plastic deformation
Temperature Ranges:
  - Cold Working: Room temperature or slightly above
  - Warm Working: Ranges from $0.3T_m$ to $0.5T_m$
  - Hot Working: Ranges from $0.5T_m$ to $0.75T_m$

Friction generally impedes metal forming processes by:
  - Reducing metal flow
  - Increasing required forces and power
  - Causing expedited tool wear
Notably, friction and tool wear issues are more pronounced in hot working.

The friction behavior in metal forming is distinct from typical mechanical systems, characterized by:
  - Low contact pressures
  - Low to moderate temperatures
  - Ample lubrication to minimize direct metal-to-metal contact
In metal forming:
  - Conditions involve:
    - High pressures between hardened tooling and softer workpieces
    - Plastic deformation of softer materials
    - High temperatures during operations
Even with lubricants, these conditions yield a high coefficient of friction.

Considerations include:
  - Type of forming process being utilized (e.g., rolling, forging, sheet metal drawing)
  - Whether the process is classified as hot or cold working
  - Chemical reactivity of lubricant with both tool and work metals
  - Ease of application
  - Cost effectiveness

Typical values and distinctions between the three categories of metal forming processes to be discussed in detail in upcoming sessions.