Creep Quiz

What is Creep in Engineering?

• Creepy stuff

• Time-Independent strain

• Time-Dependent Strain

• Same as elasticity

Which of the following statements is true?

• Only Coble creep is controlled by diffusion

  
  

• Only Nabarro-Herring creep is controlled by diffusion

  
  

• Only dislocation creep is controlled by diffusion

  
  

• • All of the above mechanisms are controlled by diffusion

  
  

Which of the following is not an assumption that we make during the creeping coil experiment?

• Assume constant true stress when we have constant load

  
  

• Assume that the stress is uniform throughout each turn

  
  

• Assume that only steady state creep occurs throughout

  
  

• • Assume that the creep regime is the same throughout the coil

  
  

Why is creep deformation different from conventional deformation?

• Strain develops at a much slower rate in the material

  
  

• Strain produced depends on the time for which the stress is applied

  
  

• Creep cannot occur at room temperature

  
  

• • The strain produced doesn’t depend on the applied stress

  
  

What is the function of the recess in Indentation Creep Plastometry?

• It prevents tertiary creep

  
  

• It allows the stresses created during the early stages of the process to be kept relatively low (below the yield stress)

  
  

  
  

• It ensures that the indenter is located properly before indentation starts

  
  

• It removes the near-surface region, which could have different properties from the bulk

  
  

• • It eliminates primary creep, so that the steady state regime is immediately established

  
  

In the γ/γ' structure of Ni-based superalloys, why is the existence of a coherent interface important?

• It leads to lattice strains that can inhibit dislocation motion

  
  

• The ordered structure of the γ' phase inhibits diffusion

  
  

• The ordered structure of the γ' phase inhibits dislocation motion

  
  

• • All of these

  
  

Which of the following could be reasons tertiary creep is observed?

• Rising true stress can cause the strain rate to rise

  
  

• Microstructural damage such as cavitation can occur

  
  

• Rising true stress can exceed the yield stress, causing conventional plastic deformation

  
  

• • All of these

  
  

Which of the following features of Ni superalloy turbine blades helps to make them resistant to creep? (There may be more than one)

• Fine grain structure

  
  

• Single crystal

  
  

• High dislocation density

  
  

• High purity

  
  

• Order hardening due to γ' precipitates in γ matrix

  
  

Which metal creep at room temperature?

• Cast Iron

• Nickel-Based Superalloy

• Solder (37/63)

• Dough

The reason why creep is time dependent

• Because it's caused by diffusion

• Creep is stress dependent

• Because of the Miller-Norton Law

• All of the above