What Does Creep Failure Mean?
Creep failure is the time-dependent and permanent deformation of a material when subjected to a constant load or stress. This deformation typically occurs at elevated temperatures, although it may occur under ambient temperatures as well.
The study of creep is essential because it helps to assess the lifespan of materials or equipment in a given environment.
Corrosionpedia Explains Creep Failure
As an example of creep failure, jet engine turbine rotors and steam generators can experience creep due to increased temperature and stress exposure. At some point, failure may occur.
To understand the mechanisms behind this time-dependent deformation, a creep test is performed. During this test, a material sample is subjected to a constant load. The deformation it experiences is then plotted as a function of time.
For metals, the creep curve consists of three regions:
- The first is the primary or transient creep region, where the material experiences an increase in creep resistance or strain hardening. It is important to note that at this point, as the material is strained, deformation becomes more difficult.
- The second stage is secondary or steady-state creep. Here, the creep rate is constant and usually has the longest duration. This is due to the competing processes between strain hardening and recovery.
- Lastly is tertiary creep, where the creep occurs at an accelerated rate as the material approaches ultimate failure.
Further deformation results in creep failure.