5. Glossary

Plastic deformation; plastic deformation

Permanent deformation of a material after mechanical loading. In uniaxial tension, plastic deformation occurs when the stress reaches the plastic flow stress.

Hardness

Resistance of a material to penetration by a pointed or spherical tool

Creep

Progressive increase in the deformation of a material after application of a mechanical load. For a viscoelastic material, this behavior is characterized in a tensile test by the creep modulus J(t) = ε(t)/σ where ε(t) is the deformation of the specimen after application during time t of the stress σ.

Relaxation; relaxation

Gradual decrease in stress in a material after application of a strain. For a viscoelastic material, this behavior...