Creep phenomena

Figure 25 shows that, in the case of a stable crack-craze growth with breakage of fibrils in the midrib, the oldest part of a fibril (the part having carried the craze stress for the longest time) is just at the middle Hence, if the breakage is due to some additional creep phenomena, it must break in the midrib. A straightforward consequence is that the life-time tq of the fibril under a load cs may be easily defined as ... 

Since many grouts and grouted soils are subject to creep phenomena, the tests must be long-term. Because strength increase due to confinement within a soil mass is an important factor, triaxial tests are indicated. 

Biswas B, Haydon DA. The rheology of some interfacial adsorbed films of macromolecules. I. Elastic and creep phenomena. Proc Royal Soc London Ser A Mathematical Phys Sci 1963 A271 296-315. 

Landform steep slope (10-15%) with diffuse soil cracks due to creeping phenomena Exposure SE Altitude 180 m Mean annual air temperature 13.6°C Mean annual precipitation —800 mm Parent material Pleistocene sediments. 

Shorten, G.G. 1995. Quasi-overconsolidation and creep phenomena in shallow marine and estuarine organo-calcareous silts, Fiji. Canadian Geotechnical Journal, 32(1) 89. 

Singh, A. 1966. Creep phenomena in soils. PhD Thesis, University of California, Berkeley, CA. 

The effect of fillers on creep phenomena (essentially the inverse of stress relaxation) is also of interest a detailed study by Nielsen (1969b) of creep in filled polyethylene is illuminating. Kaolin and wollastonite were used as fillers, both treated with a silane coupling agent and untreated. A major aim was to discover whether the major effect of a filler is due to its effect on elastic modulus, or whether a filler also changes the viscoelastic nature of the system. As reported in previous work by others, the presence of a filler did in fact reduce the creep, the relative effect being nearly independent of the applied stress. The nature of the filler and the surface treatment were also found to be important. In experiments at a constant volume fraction (0.2), kaolin was more effective than wollastonite. Silane treatment of the filler surface tended to decrease creep, especially if the specimens had been soaked in water. 

Rate-process theory n. A general theory, derived from statistical mechanics, applicable to both chemical reactions and creep phenomena in plastics. For the latter, the theory relates time-to-mpture to stress and the reciprocal of the absolute temperature. 

Since one, universal creep function can hardly fit all the experimental data, many functions were suggested to provide an empirical description of creep phenomena. As seen above, functions for logarithmic, transient and linear creep have been suggested in various forms and combinations. 

In Chap. 6, creep was discussed in general, but a considerable portion of the chapter was devoted to creep fracture and creep rupture, so these will not be reviewed here. However, since various additives do influence the basic properties of materials (e.g., second phases, fibers, whiskers), to complete this discussion on creep phenomena in ceramics, an example follows of the effect of whiskers in a... 

Typical creep curves for polyethylene (PE) and polypropylene (PP) at 23 °C are shown in Figures 18.2 and 18.3. Lin and co-workers [1] have discussed creep phenomena accuracy in reinforced polyamide (PA) and polycarbonate (PC) composites. The phenomenon of the increasing dynamic creep property and the temperature under tension-tension fatigue loading are compared between semi-crystalline and amorphous composites. 

Typical curves for polyethylene and polypropylene at 23°C are shown in Figures 2.2 and 2.3. Lin and coworkers [41] discussed the accuracy of creep phenomena in reinforced PA and polycarbonate (PC) composites. In this paper, the phenomenon in increasing dynamic creep and temperature under tension-tension fatigue loading is compared between semicrystalline and amorphous composites. 

Figure 10.2 Springs and dashpots are the basic elements in modeling stress relaxation and creep phenomena.

The rupture life of a vessel at elevated temperatures is dependent upon the history of the stre conditions and I creep phenomena. Thus, if a vessel is held at a given temperature Under a high stress, it will have a shorter life than if it is held at the sjime stress level at a lower temperature. Voorhees verified Robinson i %liebfy (212) that the... 

The need for a building material with high strength and durability afforded the development of Polymer Mortars (PM). PM show, in general, high mechanical, chemical and durability properties however, they also exhibit great sensitivity to high temperatures and creep phenomena, and mainly, deficient behaviour under fire (Ribeiro et al., 2004, 2008 Tavares et al., 2002). 

Nature of the driving force on flux creep phenomena (with J. Friedel and J. Matricon), AppI. Phvs. Lett.. 2, 199 (1963). 

Finally, one should bear in mind that the Maxwell model does not describe creep phenomena, such as those displayed in Figure 1.11b. Putting a constant stress, Go, in Equation (1.15) simply leads to a constant shear rate, y = ao t]p, as in a Newtonian liquid, without reproducing any real viscoelastic behavior. For describing creep, one has to use other approaches, such as the Kelvin or Voigt model. 

The dimensional stability under irradiation controlled by swelling and irradiation creep phenomena has to be as high as possible ... 

General insight about swelling, irradiation creep phenomena... 

In this section, the phenomena of thermal creep and its influence on the slip flow boundary condition is discussed. Let us explain the thermal creep phenomena using a simple experiment. Figure 3.10 shows the schematic of thermal creep experimental setup. The two tanks are connected with each other through an array of microchannel. The pressure relief valves are kept open, and both the tanks are initially at equilibrium with the atmosphere. Then the tanks are dipped to the fluid bath. If the continuum hypothesis is valid, the pressure will remain unchanged. If thermal creep effects are present, then pressure in the cold reservoir will decrease and hot reservoir will increase indicating the pumping action from the cold reservoir to the hot reservoir. It is possible to increase the thermal creep effects by performing the... 

For thin channel, that is, A>h, free molecular flow condition can be assumed. Here, the intermolecular collisions are negligible in comparison to the interaction of molecules with the surface. Let us assume the molecule wall interaction to be specular (o- = 0) and explain the thermal creep phenomena observed experimentally. 

Once they have been shaped into a suitable object, rubber compounds are vulcanized in such a manner that the full development of their mechanical properties is achieved, without creep phenomena that are normally exhibited by all polymer materials when on their rubbery plateau. In other terms, vulcanization extends toward infinity the rubbery plateau of the relaxation modulus function G t). Furthermore, reinforcing fillers somewhat increase the magnitude of the modulus at a given time. The combination of vulcanization and reinforcing effects induces quite complex changes in material functions of polymers, as easily demonstrated through purposely simple calculations. 

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