Mechanics and Design Stress-Strain Relations: Plastic and Anisotropic Behavior SNU School of Mechanical and Aerospace Engineering Idealizations of Stress-Strain Curves ㆍDifferent materials often have quite dissimilar stress-strain relations and no simple mathematical equation can fit the entire stress-strain curve of one of the materials. ㆍBecause we wish the mathematical part of our analysis to be as simple as possible, consistent with physical reality, we shall idealize the stress-strain curves into forms which can be described by simple equations.