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• Stress


  The force per unit area
• Strain


  A geometric quantity that measures the deformation of a body

  
• Whenever a force is applied to a body, it will tend to change the body's shape and size. These changes are referred to as deformation.
• Stress-Strain Diagram


  A graphical representation of the relationship between stress and strain

  
• Tension Test


  • Measures the relationship between stress and strain under tensile loading

  
• Compression Test


  • Measures the relationship between stress and strain under compressive loading

  
• Proportional Limit


  The upper stress limit to the linear relationship between stress and strain
• Hooke's Law


  A linear relationship between stress and strain within the elastic region
• Modulus of Elasticity (Young's Modulus)


  The slope in the elastic region of the stress-strain diagram, representing the material's stiffness

  
• Elastic Behavior


  The stress is proportional to the strain
• Elastic Limit


  The stress beyond which the material is no longer elastic
• Yielding


  The breakdown of the material and permanent deformation caused by a slight increase in stress above the elastic limit

  
• Strain Hardening


  The increase in load that can be supported by the specimen after yielding has ended, until it reaches the ultimate stress
• Ultimate Stress


  The highest stress on the stress-strain curve
• Necking


  A mode of tensile deformation where the cross-sectional area begins to decrease in a localized region of the specimen
• Fracture Stress or Rupture Stress


  The stress at which failure occurs
• True Fracture Stress


  The applied load divided by the actual cross-sectional area (the changing area with time) of the material