Material Properties

The stress-strain curve illustration of multiple material properties. The most relevant properties on the curve include stiffness (Young’s modulus), strength, ductility, and toughness. The following examples describe when you might use these properties to select the most appropriate material to meet your patient’s functional needs^[1].

• When does stiffness matter?
  • Your initial material selection based on metal properties
• When does strength matter?
  • Selecting materials, geometries, processes compared to the anticipated loading forces/area
• When does hardness matter?
  • Selecting materials for parts that rub on one another, such as a gear or ball bearing
• When does toughness matter?
  • Selecting parts that undergo shock loading
• When does ductility matter?
  • Selecting parts if stretching and elongating are desired

Stress-strain curves for different materials look different. Metals have a unique curve as compared to plastics as illustrated here: Steel Stress Strain Curve (Nazeer A. Khan)

Stiffness is often the first material property we consider. This video explains Understanding Young’s Modulus on the stress-strain curve.

This video provides explains Material Strength, Ductility and Toughness

For a reminder of the definitions of stress and strain: An Introduction to Stress and Strain