Creep (sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and generally increases as they near their melting point.

Creeping is the long term deformation of material with respect to time. For e.g. In a bar the constant load is subjected to bar which is axially due to this load with time inceasing in strain.*When you keep the cloth at constant on a rope with respect to time the elongation takes place in rope....

Creeping is the phenomenon of progressive extension of a material, where strain increases with time at a constant load. It is a common occurrence in materials subjected to high temperatures and constant stress over long periods. Creep can lead to permanent deformation and failure of the material if not properly accounted for in design and engineering.

Creeping occurs as a result of the movement of dislocations within the crystal lattice of the material. Dislocations are line defects in the crystal structure that allow atoms to move more easily. Under the influence of an applied stress, dislocations can move and rearrange, leading to the deformation of the material. This process is known as dislocation creep.

There are several mechanisms involved in the process of creep, including lattice diffusion, climb of dislocations, and grain boundary sliding. Lattice diffusion occurs when atoms move through the crystal lattice, allowing dislocations to move and contribute to the deformation. Dislocation climb involves the movement of dislocations along the stress axis, while grain boundary sliding occurs when grains in a polycrystalline material slide past each other.

Creep behavior is typically characterized by three stages: primary, secondary, and tertiary creep. In the primary stage, also known as transient creep, the strain rate is high and decreases rapidly over time. This stage is often associated with the adjustment and rearrangement of dislocations. In the secondary stage, or steady-state creep, the strain rate is relatively constant and occurs at a slower rate compared to the primary stage. This stage is dominated by dislocation motion and diffusion. The tertiary stage, also known as accelerating creep, is characterized by an increasing strain rate until failure occurs. This stage is often associated with the formation and propagation of cracks and voids within the material.

Creep can have detrimental effects on the performance and integrity of materials, especially in high-temperature applications such as power plants, gas turbines, and aerospace components. To mitigate the effects of creep, engineers often consider factors such as material selection, operating temperature, stress levels, and design considerations. High-temperature alloys and materials with enhanced creep resistance are often used in such applications. Additionally, design techniques such as proper component sizing, stress analysis, and the use of creep-resistant coatings can help minimize the effects of creep and ensure the longevity and reliability of the material.