Creep behavior phenomenology

Researchers have examined the creep and creep recovery of textile fibers extensively (13-21). For example, Hunt and Darlington (16, 17) studied the effects of temperature, humidity, and previous thermal history on the creep properties of Nylon 6,6. They were able to explain the shift in creep curves with changes in temperature and humidity. Lead-erman (19) studied the time dependence of creep at different temperatures and humidities. Shifts in creep curves due to changes in temperature and humidity were explained with simple equations and convenient shift factors. Morton and Hearle (21) also examined the dependence of fiber creep on temperature and humidity. Meredith (20) studied many mechanical properties, including creep of several generic fiber types. Phenomenological theory of linear viscoelasticity of semicrystalline polymers has been tested with creep measurements performed on textile fibers (18). From these works one can readily appreciate that creep behavior is affected by many factors on both practical and theoretical levels. 

This situation becomes simplified even further if the creep behavior of the nonreacting network obeys the well known phenomenological equation (9-12) suggested by Thirion... 

In summary, it is concluded that the creep behavior of intermetallic phases can be described as that of the conventional disordered alloys given by the familiar phenomenological constitutive equations. 

The creep behavior is often analyzed in terms of the phenomenological equation... 

The phenomenological language used here is the distribution of retardation times that determines the creep compliance J(t). Various mathematical models are employed to model the observed behavior, but this is still early in the game for this approach. There is still limited good data, and it is well before the more sophisticated computer approaches of the future. 

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