Delayed under constant load

The measurements reported by Bach (56) apparently were not under constant temperature conditions. Strain recovery after loading in the plasticized state is small. The longer the loading period the smaller the recoverable strain. This suggests plastic flow under load and a conversion of delayed elastic strain into an irreversible deformation. 

Delayed Fracture under Increasing Load Constant Stress Rate Tests... 

Even if a soil is not over-consolidated and ageing occurs under a constant load, it shifts along the vertical undergoing delayed compression . Upon further loading the soil will demonstrate behaviour similar to an over-consolidated soil even when it, in reality, was never loaded to a higher stress level. 

For a viscoelastic material under a constant applied stress, the strain e(t) shows a delay in response to the applied stress see Fig. la(4). When the load is removed at t = t, a viscoelastic liquid will recover partially its deformation at t = over a period of time. Some deformation remains permanently. In contrast, for a viscoelastic solid, on load removal, the deformation recovery over time is relatively faster, and almost all the deformation may be recovered over a sufficiently long period of time. 

Figure 6.21 Burger solid and its response to a constant applied stress. On loading under tq an instantaneous elastic strain yi, a delayed elastic strain ya and a viscous strain ya appear. On unloading only elastic strain y-, and delayed elastic strain ya recover.

---