Axial Stress-Strain Curve & Modulus of Elasticity


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Axial Stress-Strain Curve & Modulus of Elasticity

  1. 1. AHSANULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY Department of Civil Engineering Presentation On Axial Stress-Strain Curve & Modulus of Elasticity Presented by Md. Nafizul Haque ID:
  2. 2. What Is Axial Stress?  A tension or compression stress created in a structural member by the application of a lengthwise axial load.  Axial stress is defined as the force per unit area of a material.  i.e. Axial stress = axial force / cross sectional area:
  3. 3. What Is Axial Strain?  Increase (or decrease) in length resulting from a stress acting parallel to the longitudinal axis of the specimen.  Axial strain is defined as extension per unit length.  Axial Strain = extension / original length
  4. 4. Universal Testing Machine
  5. 5. Axial Stress-Strain Curve for Brittle Material
  6. 6. Axial Stress-Strain Curve for Ductile Material Typical regions that can be observed in a stress-strain curve are:  Elastic region,  Yielding,  Strain Hardening,  Necking and Failure
  7. 7. Elastic behavior  If the specimen returns to its original length when the load acting on it is removed, it is said to response elastically
  8. 8. Yielding  A slight increase in stress above the elastic limit will result in permanent deformation. This behavior is called yielding for ductile materials.  The stress that causes yielding is called yield stress sy.  The deformation that occurs is called plastic deformation
  9. 9. Strain Hardening  When yielding has ended, a further load can be applied to the specimen, resulting in a cure that rises continuously but becomes flatter until it reaches a maximum stress referred to as ultimate stress, su.  The rise in the curve is called Strain Hardening
  10. 10. Necking & Fracture  After the ultimate stress, the cross-sectional area begins to decrease in a localized region of the specimen, instead of over its entire length. The load (and stress) keeps dropping until the specimen reaches the fracture point.
  11. 11. Modulus of Elasticity  The modulus of a material describes how well it resists deformation. A material with a higher modulus is stiffer and has better resistance to deformation. The modulus is defined as the force per unit area required to produce a deformation or in other words the ratio of stress to strain.  Modulus of elasticity=Stress/Strain