Will a material fail if a stress lower that its yeild point is applied again and again? (You should know about creep)

The repeated application of stress below the yield point of a material generally does not lead to immediate failure. However, if the stress is applied over an extended period, especially at elevated temperatures, a phenomenon known as "creep" can occur. Creep is the gradual deformation of a material under constant stress, and it can result in permanent and time-dependent deformation.

Here are key points related to creep:

1. Creep at Elevated Temperatures:

   • Creep is more pronounced at elevated temperatures, where atoms and dislocations in the material have increased mobility.
   • The rate of creep generally increases with temperature.

2. Below Yield Point Stress:

   • Creep can occur even at stresses below the yield point of the material.
   • Repeated application of stress below the yield point, especially at elevated temperatures, can lead to cumulative creep deformation.

3. Accumulation of Deformation:

   • While the stress may be below the yield point, the prolonged application of stress can result in the accumulation of deformation over time.
   • Creep deformation is time-dependent, and the material may exhibit increased strain even without surpassing the yield stress during each loading cycle.

4. Material Factors:

   • Creep resistance varies among materials. Some materials are more resistant to creep than others.
   • Materials that are more prone to creep may experience significant deformation over time, even at stress levels below the yield point.

5. Applications and Considerations:

   • Creep is a critical consideration in applications where materials are subjected to sustained loads, such as in high-temperature environments, power plants, and certain components in aerospace engineering.
   • Engineers must account for creep in the design phase to ensure the long-term integrity and safety of structures and components.

In summary, while a material may not fail immediately when subjected to stress levels below its yield point, the cumulative effects of creep over time can result in permanent deformation and potential failure, especially at elevated temperatures. Engineers need to carefully consider creep in the design and maintenance of components in applications where creep is a relevant factor.