materialdeformation

Material deformation is the change in shape, size, or internal structure of a solid body in response to applied forces, temperature changes, or other environmental influences. It is characterized by stress (force per unit area) and strain (relative displacement or distortion) and can be reversible (elastic) or permanent (plastic).

Elastic deformation follows linear or nonlinear reversible relationships between stress and strain; Hooke’s law describes the linear elastic region where stiffness is given by the elastic modulus. Plastic deformation occurs after yielding and involves dislocation motion, slip, twinning, or other microstructural mechanisms that produce permanent shape change. Time-dependent deformation includes creep (gradual strain under constant stress) and stress relaxation; viscoelastic materials exhibit both elastic and viscous behavior.

Deformation is quantified using tensile tests, compression tests, hardness measurements, strain gauges, and full-field optical methods. Stress–strain curves provide key parameters such as elastic modulus, yield strength, ultimate strength, and ductility. Models range from continuum descriptions (elasticity, plasticity, viscoplasticity) to constitutive laws (von Mises yield criterion, Norton creep law, Maxwell and Kelvin–Voigt viscoelastic models).

Factors influencing deformation include material composition and microstructure, temperature, strain rate, loading mode, and geometry. Understanding deformation is central to engineering design, metal forming, fatigue and fracture analysis, materials selection, and predicting service life of structures and components.