# Advanced Structural Analysis/Part I - Theory/Materials/Properties/Elasticity

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# Introduction[edit]

All solid materials display an approximately linear response to moderate loads. This is manifested in Hooke's law:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "/mathoid/local/v1/":): {\displaystyle \epsilon_x = \frac{\sigma_x - \nu (\sigma_y + \sigma_z)}{E} }

Where:

the normal stress

the elastic modulus (Young's modulus)

the normal tension

The figure below illustrates the stress-strain curve of some material. Hooke's law is valid in the linear interval marked "Elastic region". The term elastic, as in elastic deformation, refers to the absence of energy dissipation and permanent deformation. Elastic deformations retract upon unloading.