Introduction to Mechanical Characteristics in Polymeric Solids: Lecture 1 Stress and Strain

This article provides a foundational understanding of the mechanical behavior of polymeric solids through the lens of continuum mechanics. Key concepts such as stress, strain, and their constitutive relations are introduced, with emphasis on Hookean behavior under infinitesimal deformation. Different strain measures and stress definitions (nominal vs. true) are discussed, followed by treatments of uniaxial tension, shear, and volumetric deformation. The derivation of three-dimensional Hookean constitutive equations is included. The lecture concludes with a thermodynamic interpretation of deformation and a distinction between energy and entropy-based elastic responses, particularly relevant to rubbers and elastomers.