Creep, relaxation and shrinkage

Why study time-dependent deformation of materials?

• materials may continue to deform through the time under constant load

• materials may deform through the time due to changes in their moisture content

What is Creep?

time-dependent deformation of a material under a constant load or constant stress, typically at medium or high temperatures

What does the typical creep curve show?

The typical creep curve for metals (under constant stress) shows how strain changes over time at medium or high temperatures

What is Creep Recovery?

the partial or complete recovery of strain that occurs in a material after the removal of a constant load or stress applied during creep

What is Relaxation?

• opposite of creep

• time dependent loss of stress due to constant strain

What is Shrinkage?

Deformation due to loss of moisture (drying shrinkage)

Time-dependent loss of stress due to constant strain in

viscoelastic materials is called …

stress relaxation

Is drying shrinkage of concrete reversible or irreversible?

Briefly justify your answer.

Irreversible: drying shrinkage occurs when moisture evaporates from concrete, causing permanent volume reduction. Once water is lost, the concrete cannot fully regain its original dimensions, even if moisture is reabsorbed