Lead is used in roof flashings but is subject to metal creep - Leaving Cert Engineering - Question (i) - 2018

Metal creep refers to the gradual and permanent deformation of a metal under constant stress over time. This phenomenon is most prominent at elevated temperatures where the applied stress is below the material's yield strength.

Creep occurs due to the motion of dislocations within the metal's crystal structure, which gradually leads to a change in shape. The process is influenced by several factors, including:

• Stress Level: Creep typically happens under prolonged exposure to high stress levels, particularly those that do not exceed the yield strength of the metal.
• Temperature: Increased temperatures can accelerate creep, as they allow atoms within the metal to move more freely, facilitating the deformation process.
• Time: As time progresses, the gradual accumulation of strain leads to noticeable changes in the material properties, impacting its structural integrity.

In conclusion, metal creep is a critical consideration in the design and application of metal components, especially in environments subject to sustained loads and elevated temperatures.