nonelastic

Nonelastic refers to the property of materials or systems that do not return to their original shape after the removal of an applied force. In materials science and engineering, nonelastic behavior encompasses plastic deformation, viscous flow, and time-dependent deformation, and it is often described as inelastic. Elastic behavior is fully reversible; nonelastic behavior is characterized by permanent deformation or delayed response.

The term covers several mechanisms. Plastic deformation occurs when stress exceeds the material's yield strength; the resulting permanent shape change persists after unloading. Viscous or time-dependent deformation, such as creep, gradually deforms under sustained load and may continue slowly even after the load is removed. Some materials exhibit viscoelastic behavior, combining elastic and nonelastic responses; the nonrecoverable portion is considered nonelastic.

In practice, nonelastic behavior is quantified with concepts like yield strength, plastic hardening, and creep rate. Metals often show plastic deformation; ceramics can fracture with minimal plastic deformation; polymers may display significant viscoelastic nonelastic deformation at elevated temperatures or long times.

Engineering implications: nonelastic deformation leads to residual stresses and permanent deformation, influencing design limits, fatigue life, and failure modes. In structural applications, allowances are made to accommodate expected nonelastic strains, while in precision applications, materials are chosen to minimize nonelastic effects.