Indian Institute Of Technology



MHRD Govt. Of India


CREEP...


Creep is progressive i.e. permanent and time dependant deformation of a material at a constant stress below the yield strength of the material. Creep is seen in all types of materials and is observed to be severe in materials that are utilized in applications involving high operating temperatures for long periods of time. The deformation caused by creep need not always be catastrophic i.e. if a component is deformed by creep beyond the tolerable limits of the application, the application as a whole may fail even though the component has not actually fractured. Also it is not always an undesirable property, e.g. concrete has inbuilt tensile stresses which may lead to its fracture however, due to some moderate creep these stresses get relieved and the structure is saved. It is important to note that the words "permanent" and "time dependant" are very important since the deformation is not an elastic one nor is it a brittle one.The strain keeps on building over a period of time. Creep though dependant on various factors is generally observed to increase with rise in temperature.It is particularly important for metals whose operating temperature is greater than 0.4Tm and even amorphous polymers are sensitive to creep.