Secondary creep

Definition

Secondary creep is a phase of material deformation that occurs under constant stress over time, characterized by a steady and relatively low rate of strain. This phase follows the initial primary creep phase, where the rate of deformation is high but decreases as time progresses. Secondary creep is significant in understanding how materials behave under prolonged load and is particularly relevant in the study of fatigue, creep, and impact loading.

5 Must Know Facts For Your Next Test

1. Secondary creep occurs after the initial stage of primary creep and before tertiary creep, representing a period of stable deformation under constant load.
2. In secondary creep, the rate of deformation remains constant or nearly constant, making it easier to predict material behavior under long-term loading conditions.
3. The mechanisms driving secondary creep are often related to diffusion processes and dislocation movement within the material's microstructure.
4. Temperature plays a critical role in secondary creep, with higher temperatures typically resulting in increased rates of deformation due to enhanced atomic mobility.
5. Understanding secondary creep is essential for designing components that will be subjected to prolonged loads, such as in power plants and aerospace applications.

Review Questions

• How does secondary creep differ from primary and tertiary creep phases in terms of material behavior over time?
  • Secondary creep is distinct because it follows the high rate of deformation seen in primary creep, transitioning into a more stable phase where the rate of strain is relatively constant. In primary creep, the material deforms quickly but slows down as it progresses to secondary creep. Tertiary creep then occurs, marked by an accelerating strain rate leading to failure. This understanding helps predict how materials will perform under sustained loads.
• Discuss the significance of temperature on secondary creep and how it impacts material selection in engineering applications.
  • Temperature significantly affects secondary creep by influencing the atomic mobility within materials, which can either speed up or slow down the rate of deformation. At elevated temperatures, materials may experience higher rates of secondary creep due to increased diffusion processes. This understanding is crucial when selecting materials for applications like turbines or structural components exposed to high temperatures over long periods, ensuring they can withstand anticipated stresses without excessive deformation.
• Evaluate how knowledge of secondary creep can improve design strategies for components exposed to long-term loads in critical applications.
  • Knowledge of secondary creep allows engineers to design components with a better understanding of long-term behavior under sustained loads. By recognizing the stable deformation characteristics during this phase, they can select materials and design geometries that minimize risks of failure or excessive deformation over time. This evaluation leads to safer and more efficient designs in critical applications like bridges or pressure vessels, where maintaining structural integrity under continuous stress is essential.

Related terms

Creep: The gradual and permanent deformation of materials under constant stress over time, often occurring at high temperatures.

Primary Creep: The initial phase of creep where the rate of deformation decreases rapidly over time due to strain hardening or other factors.

Tertiary Creep: The final phase of creep characterized by an accelerating strain rate that eventually leads to failure or rupture of the material.