Materials-Young Modulus

• What does Young modulus indicate about a material?

  It indicates how stiff a material is
• What is the main purpose of a typical tensile test machine?

  To test the tensile strength of a specimen
• What is the resolution limit of a typical light microscope?

  • The resolution limit of a light microscope is 0.2 µm
• How does the tensile test machine apply force to the specimen?

  • The moving crosshead applies a pulling force to the specimen
  • This force is measured by the load cell
  • The extensometer measures the elongation of the specimen
• What are the key dimensions of a typical tensile specimen?

  • Reduced section diameter: 0.505 inches
  • Gauge length: 2 inches
  • Radius: 1 inch
• How does the total force relate to the stress and cross-sectional area?

  • The total force F carried must be equal to the stress σ multiplied by the cross-sectional area A.
  • This relationship is expressed as F = σ * A.
• If a rubber band is stretched more, what happens to the strain?

  Strain increases as it stretches further
• What device measures strain in a tensile test?

  Extensometer
• What symbol represents the stress in the equation shown in the image?

  σ
• What is the significance of measuring both stress and strain in a tensile test?

  It helps determine material properties under load
• What does the variable δ represent in the strain formula?

  It represents the extension or increase in length
• What does stress measure in a material?

  Force applied per unit area
• What is the total force carried by any cross section of the object?

  F
• How is strain defined in materials science?

  Change in length divided by original length
• What does the symbol δ represent in the equation shown in the image?

  • δ represents the change in length of the rod
• What does the variable A represent in the stress formula?

  Cross-sectional area of the specimen
• How is strain (\( \epsilon \)) calculated in a tensile test?

  Strain is calculated as $\epsilon =$$\frac{\Delta L}{L_0}$
• What does stress represent in the context of Young modulus?

  Force per unit area
• What is the relationship between force (F) and extension (ΔL) in calculating strain?

  Strain is calculated using ΔL over L₀
• How is the strain (ε) calculated from the change in length (δ) and the original length (L)?

  • Strain (ε) = Change in length (δ) / Original length (L)
  • ε = δ/L
• What is the role of the load cell in a tensile test machine?

  It measures the force applied to the specimen
• How is strain defined in the calculation of Young modulus?

  Change in length divided by original length
• If the total force F is 100 N and the cross-sectional area A is 10 cm^2, what is the stress σ?

  $\frac{100 \text{ N}}{10 \text{ cm}^2} =$$10 \text{ N/cm}^2$
• What is the purpose of the extensometer in a tensile test machine?

  To measure the elongation of the specimen
• What is the formula for Young modulus?

  $E =$$\frac{\sigma}{\epsilon}$
• What does stress (\$\sigma$) represent in the formula?


  It represents the internal resistance to deformation
• Under what conditions is Young modulus determined?

  Under static loading conditions
• What units should stress and strain be in for calculating Young modulus?

  Pascals (Pa)
• What does it mean for a material to be homogeneous in Young modulus calculations?

  It has the same properties throughout
• What is the name of the object shown in part (a) of the image?

  Rod
• What is the relationship between initial length, final length, and extension in the context of strain?

  • Initial length (L₀) is the length before force.
  • Final length (L) is the length after force.
  • Extension (δ) is the change in length: $\delta =$$L - L_{0}$
• What does Young modulus calculations assume about the relationship between stress and strain?

  It assumes a linear relationship
• What does the image in the study material illustrate?

  It illustrates the relationship between lengths and strain
• What does an extensometer monitor during a tensile test?

  Change in length of the specimen
• What is the relationship between strain (ε) and stress (σ) for a uniaxially loaded rod?

  • Strain (ε) is directly proportional to stress (σ)
  • The constant of proportionality is the modulus of elasticity (E)
  • The equation is: σ = Eε
• What must be calculated before substituting values into the Young modulus formula?

  Stress ($σ$) and strain ($ϵ$)
• What does ΔL represent in the context of a tensile test?

  Extension of the specimen
• What is the name of the object shown in part (b) of the image?

  Uniaxially Loaded Rod
• What does a higher Young modulus imply about a rubber band?

  It is stiffer and resists stretching more
• How does a load cell function in a tensile test?

  It records the force applied to the specimen