English
Menu

Mechanical properties and fracture

Which statement about the Young's modulus of steel is correct?

  1. AWhen quenching or cold working doubles the strength, the Young's modulus also becomes roughly twice as large
  2. BIt is determined by the strength of interatomic bonding and changes little with heat treatment or working
  3. CIt is the yield stress divided by the total strain up to yielding, and represents the slope of the plastic region
Show answer and explanation

Answer: B. It is determined by the strength of interatomic bonding and changes little with heat treatment or working

Young's modulus is the ratio of stress to strain in the elastic region, E = σ/ε. It is set by the strength of interatomic bonding (the curvature of the interatomic potential) and is a structure-insensitive property. That is why it stays at around 200 GPa whether the steel is mild or quenched, and doubling the strength does not double the modulus. Yield strength and hardness are structure-sensitive properties governed by how easily dislocations move, and they change greatly with heat treatment and working. Young's modulus is the slope of the straight elastic line, distinct from the slope of the plastic region (the work-hardening rate). As temperature rises, bonding weakens and the modulus decreases gradually.

Report an error

Practice this topic Back to topic

Related calculators

Thermal Expansion and Thermal Stress CalculatorCalculate the elongation from a temperature change and the thermal stress when constrained

More Mechanical properties and fracture questions

  1. A round bar 10 mm in diameter carries a tensile load of 10 kN. Which value is closest to the engineering stress?
  2. A steel rod 2.0 m long with a Young's modulus of 200 GPa is loaded in tension to 100 MPa within its elastic range. Which value is closest to the elongation of the rod?
  3. For materials such as aluminum alloys that show no distinct yield point, which correctly describes how the 0.2% offset yield strength is determined?
  4. In a tensile test, the engineering stress was 400 MPa at an engineering strain of 0.20, before necking began. Assuming constant volume during plastic deformation, which value is closest to the true stress at this point?
  5. Which statement about the Vickers hardness test is correct?