Which property is a measure of how steel resists permanent deformation under load?

Which property is a measure of how steel resists permanent deformation under load?

• A. Ductility
• B. Elastic Modulus
• C. Yield Strength
• D. Toughness

Answer: (C)

Understanding how steel behaves under load starts with the idea of elastic versus plastic deformation. The property that marks the onset of permanent, non-recoverable deformation is the yield strength—the stress level at which steel begins to yield and deform plastically. This is why it best measures resistance to permanent deformation: a higher yield strength means the material can carry more load before any irreversible distortion remains after unloading. Ductility describes how much plastic deformation the material can undergo before fracture, not when permanent deformation starts. Elastic modulus tells you stiffness and the amount of elastic strain before yielding, but it doesn't define permanent deformation. Toughness measures the total energy a material can absorb before fracture, combining strength and ductility, not specifically the onset of permanent deformation. In practice, keeping service stresses below the yield strength helps prevent long-term distortions in bridges and other steel structures.

Understanding how steel behaves under load starts with the idea of elastic versus plastic deformation. The property that marks the onset of permanent, non-recoverable deformation is the yield strength—the stress level at which steel begins to yield and deform plastically. This is why it best measures resistance to permanent deformation: a higher yield strength means the material can carry more load before any irreversible distortion remains after unloading. Ductility describes how much plastic deformation the material can undergo before fracture, not when permanent deformation starts. Elastic modulus tells you stiffness and the amount of elastic strain before yielding, but it doesn't define permanent deformation. Toughness measures the total energy a material can absorb before fracture, combining strength and ductility, not specifically the onset of permanent deformation. In practice, keeping service stresses below the yield strength helps prevent long-term distortions in bridges and other steel structures.