Anelasticity hysteresis

Figure 8.17 Hysteresis loop shown by the stress-strain curve of an anelastic solid...

Figure 8.17 shows a hysteresis loop for an anelastic solid subjected to an oscillating stress. If the amplitude of the stress is a0, find the shape of the hysteresis loop ... 

Time-dependent hysteresis effects can also occur in crystalline materials and these lead to mechanical damping. Models, such as the SLS and the generalized Voigt model, have been used extensively to describe anelastic behavior of ceramics. It is, thus, useful to describe the sources of internal friction in these materials that lead to anelasticity. The models discussed in the last section are also capable of describing permanent deformation processes produced by creep or densification in crystalline materials. For polycrystalline ceramics, creep is usually considered from a different perspective and this will be discussed further in Chapter 7. 

A small hysteresis between tensile loading and unloading curves was detected. The total strain is regained. Those processes are defined as anelastic ones. A temperature change occurs during deformation (adiabatic process). Thus, anelastic processes should depend on the strain rate, e, but this was not found in the experiment. This point cannot be explained. 

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