Creep

  • Understand the phenomenon of creep when a material is loaded at elevated temperature.

  • Define creep and specify the conditions under which it occurs.

  • Given the absolute melting temperature of a metal, estimate the temperature at which creep becomes important.

  • Calculate the strain rate depending upon stress, stress sensitivity and time.

Creep is the time-varying plastic deformation of a material stressed at high temperatures.
The creep rate can be calculated by the following equation:

\[\dfrac{d\epsilon }{dt} = A \sigma ^{n}e^{\frac{-Q}{RT}}\]

where
\(\displaystyle \large \epsilon\) = strain
t = time
A = Pre-exponential constant
\(\displaystyle \large \sigma\) = Applied stress
n = stress sensitivity
Creep (Thermal failure) takes place where there is stress combined with high temperature. e.g. turbine blades, nuclear reactors, etc.

Solved Examples

Solved Example:

59-1-01

Time dependent permanent deformation is called _____________ (AFCAT EKT Mech Paper I- Set 2 2016)

Correct Answer: C

Solved Example:

59-1-02

Slow plastic deformation of metals under a constant stress is known as: (CIL MT Mech 2020)

Correct Answer: A

Solved Example:

59-1-03

In which of the following cases, consideration of creep is important: (UPPSC ME Mech 2013 Paper I)

Correct Answer: D