Young’s modulus and stress strain diagrams

• What does the tensile test diagram illustrate?

  The tensile test diagram illustrates the relationship between stress and strain in materials.
• What occurs when there is a marked increase in extension without an increase in load?

  This phenomenon occurs in softened mild steel.
• Why is understanding the yield point important for designers?

  In-service loads should be well below the yield point to ensure safety.
• What is the typical strain specified for materials in tensile testing?

  A strain of 0.2% is typically specified.
• How is the 0.2% proof point determined on a stress-strain graph?


  It is determined by drawing a straight line parallel to the linear portion of the graph starting at a strain of 0.2%.
• What does the slope of the straight line in the stress-strain diagram indicate?

  The slope indicates the stiffness of the material.
• What is Young's modulus also known as?

  Young's modulus is also known as the modulus of elasticity.
• What are the units of Young's modulus?

  The units of Young's modulus are Pascals, often expressed as Giga Pascals (GPa).
• What is the PLEA formula used for?

  The PLEA formula is used to calculate the change in length of a material under load.
• What is the formula for Young's modulus?

  The formula is $E =$$\frac{\text{stress}}{\text{strain}} =$$\frac{P}{A} \cdot \frac{L}{\Delta L}$
• How do you rearrange the Young's modulus formula to solve for change in length?

  Rearranging gives $\Delta L =$$\frac{P \cdot L}{E \cdot A}$
• What is the significance of the area under the stress-strain curve?

  • Indicates toughness of the material
  • Represents the energy absorbed before failure
• What is the limit of proportionality in a stress-strain curve?

  • It is the point where the material stops behaving elastically.
  • It is drawn parallel to the straight line portion of the curve at 0.2% strain.
• What does the term "progressive yield" refer to in materials?

  • It refers to materials that do not have a definite yield point.
  • Instead, they exhibit a gradual increase in strain with increasing stress.
• What does the term "hardness" refer to in materials testing?

  • Hardness measures a material's resistance to deformation.
  • It is an important property for determining wear resistance.
• What is the significance of the tensile test in materials testing?

  • It determines the strength and ductility of materials.
  • It helps in understanding how materials will behave under tensile loads.