Constant rate period stresses

Constant conduction heat pipes, 13 227 Constant failure rate, 13 167 Constant-field scaling, of FETs, 22 253, 254 Constant-modulus alloys, 17 101 Constant of proportionality, 14 237 Constant pressure heat capacity, 24 656 Constant rate drying, 9 103-105 Constant rate period, 9 97 23 66-67 Constant retard ratio (CRR) mode, 24 103 Constant slope condition, 24 136-137 Constant stress test, 13 472 19 583 Constant-voltage scaling, of FETs, 22 253 Constant volume heat capacity, 24 656 Constant volume sampling system (CVS), 10 33... 

TABLE 14.6 Drying Stresses for the Constant Rate Period... 

For the constant rate period in the preceding problem, determine the tensile stress at the surface of the green body. 

Figure 10. Illustration of drying process (24). Capillary tension develops in liquid as it stretches to prevent exposure of the solid phase by evaporation, and the network is drawn back into liquid (a). The network is initially so compliant that little stress is needed to keep it submerged, so the tension in the liquid is low, and the radius of the meniscus (rc) is large (b). As the network stiffens, the tension rises as rc decreases. At the critical point, the radius of the meniscus becomes equal to the pore radius the constant rate period ends and the liquid recedes into the gel (c). (Reproduced with permission from reference...

Figure 5.25 Illustration of microscopic model during the constant rate period, meniscus has same radius of curvature for pores of aU sizes after the critical point, the largest pores are emptied first. The capillary tension compressing the smaller pores causes local stresses that crack the network. (After Ref. 39.)...

There are other more complicated experimental situations where viscoelastic behavior can also be predicted in terms of the relaxation and retardation spectra or other functions. These include deformations at constant rate of strain and constant rate of stress increase, stress relaxation after cessation of steady-state flow, and creep recovery or elastic recoil, all of which were mentioned in Chapter 1, as well as nonsinusoidal periodic deformations. In referring to stress a, strain y, and rate of strain 7, the subscript 21 will be omitted here although it is understood that the discussion applies to shear unless otherwise specified. 

Critical stress intensity. See Stress intensity Critical temperature, 501-505, 534 Crosslink, 5, 422 CRP. See Constant rate period Crystal, colloidal, 831 Crystal growth. See Crystallization Crystalline materials, sintering. See Diffusive sintering Crystalline xerogels, 599-609 Crystallinity of sol, 255 Crystallization, 272, 279, 289, 363-364, 370-372, 840... 

The relation between dr)dng process and stress formation is shown in Fig. 8.21. In accordance with drying theory in porous membrane layers a constant drying rate period (CRP) and a falling rate period (FRP) can be distinguished. The transition between them is sharper with increasing thickness. A clear explanation has not been presented but is probably related to the width of the drying zone (see Fig. 8.7) which increases with width w of the pore size distribution. 

Stress-strain curves are often measured by monitoring the tensile stress as a sample, originally at rest, is subjected to a constant tensile strain rate starting at t = 0. Show that, at any subsequent time during the constant-strain-rate period, the slope of the stress-strain curve is the tensile stress relaxation modulus ... 

These ideas can now be applied to the drying of lumber boards, which is assumed to be stress-free at the beginning. At the beginning of drying (constant drying-rate period),... 

Four criteria factors used in the Strongly Implicit Procedure package in MODFLOW for solution are 1. the error criterion is set at 0.001 2. the acceleration parameter is 1.0 3. the maximum number of iterations equals 50 4. a seed of 0.001 is specified for use in calculating the iteration parameter. The well is pumped at a constant rate of 2,450 mVd for a one-day stress period. 

---