Material Response to External Loads

When a material is subjected to external forces, it responds in two fundamental ways:

1. Stress: An internal resisting force developed within the material to oppose deformation. It maintains equilibrium once external forces reach their final values.
   Stress is defined as: $$ \text{Stress} = \frac{\text{Force}}{\text{Area}} $$ Units: N/m² or Pascal (Pa)
2. Strain: The measure of deformation resulting from stress. It represents the change in dimension relative to the original dimension.
   Strain is defined as: $$ \text{Strain} = \frac{\text{Change in dimension}}{\text{Original dimension}} $$ It is a dimensionless quantity.

Types of Stress and Strain

The following sections elaborate on different forms of stress and strain, including:

• Normal (Axial) Stress and Strain
• Shear Stress and Strain
• Volumetric Strain
• Hooke’s Law and Elastic Limits