Metals and Metal Working

Material properties and characteristics relevant to metal selection and metal working in P&O.

Metals alloys are commonly used in P&O in endoskeletal components, aluminum uprights, and joints. Metals provide exceptional strength-to-weight ratios, particularly in structural applications. 

• Mechanical Properties
  • Strength, Toughness, and Durability: Strength measures a metal’s resistance to deformation under load (tensile, compressive, or shear), while toughness describes its ability to absorb energy before fracturing (combining both strength and ductility to resist crack propagation). Durability is the broadest concept, referring to how well a metal maintains its properties over time when exposed to real-world conditions like corrosion, fatigue, and environmental factors.
  • Malleability and Ductility: Malleability is a metal’s ability to be hammered or pressed into thin sheets without breaking, while ductility is its ability to be drawn into wires. These properties depend on the metal’s crystal structure and the mobility of atoms within it, e.g., gold is extremely malleable, while copper is highly ductile. 
    • Strong ≠ Tough: Glass is strong but not tough (brittle failure)
    • Tough ≠ Durable: Some tough steels corrode quickly
    • Trade-offs: Increasing strength often reduces toughness; optimizing durability may compromise strength
  • Work Hardening: The strengthening of metal through plastic deformation. When you bend, hammer, or otherwise deform metal, dislocations in the crystal structure multiply and tangle, making the material harder and stronger but more brittle. It is very difficult to completely straighten bent metal parts (e.g., uprights) because the metal has work hardened at the location of the bend, making that area stronger and more resistant to further deformation.
• Physical Properties
  • Density
  • Thickness
• Fabrication Properties
  • Formability: the metal’s ability to undergo plastic deformation without cracking or failure, bend radius limitations. Aluminum has higher ductility than steel – allowing tighter bends without cracking.
  • Machinability affects cutting speeds, tool life, surface finish, and dimensional accuracy during machining operations. Cutting tools (e.g., saw, drill bit) must be significantly harder than the workpiece material to maintain their cutting edge.