Consolidation time

Figure 7.18 shows the consolidation time versus consolidation pressure for unidirectional and cross-ply interply interfaces. As can be seen from both figures, the consolidation time decreases rapidly as pressure increases. Above 1000 kPa for T300/P1700 and 500 kPa for APC-2, increases in the consolidation pressure do not significantly decrease consolidation time. 

A comparison between the times required for consolidation of unidirectional and cross-ply lay-ups can be observed in Figure 7.18. The consolidation times required for the cross-ply lay-up are almost an order of magnitude higher than that required for the unidirectional lay-... 

Figure 7.18 Consolidation time (tc) versus consolidation pressure for T300/P1700 and APC-2 Batch II prepregs. (a) Unidirectional lay-up. (b) Cross-ply lay-up...

The time that elapses from point D to point F is known as the consolidation time. This is the time interval when a force is detectable at the upper punch. The contact time is the period when the upper punch is in contact with the original particles or the tablet (point D to point H). The residence time is the period when a force is detected at the lower punch (point D to point J), which ends on tablet ejection. 

Munoz-Ruiz, A. Jiminez-Castellanos, M.R. Cunningham, J.C. Katdare, A.V. Theoretical estimation of dwell and consolidation times in rotary tablet machines. Drug Dev. 

For deep deposits, the consolidation times may be long—months or even years. Drains can be used effectively to shorten the times, and are used universally with deep deposits. Sand drains can be put in place using the same method as for sand piles. A hollow steel shell is driven, cleaned out if necessary, and filled from the surface with a narrowly graded sand. Contrary to a sand pile, the sand fill is not compacted as the shell is withdrawn. The capacity of a sand drain to carry water depends primarily upon the drain diameter. Drains may become clogged over a period of time,... 

Disturbance and remolding occurs to some extent both with sand drains and wicks. It is probable that the coefficient of consolidation in the remolded zones is somewhere between the vertical and horizontal values. This will result in actual consolidation times greater than those gotten from computations using Ch. 

The unconfined yield strength of a bulk solid is the main property associated with arching and rathole formation. In fine or sticky powders, arching can result from cohesive forces, while in the case of coarse bulk solids, arching is caused by either the interlocking or the frictional force of single particles. Consolidation time is crucial in both cases, especially in rathole formation. A rathole can collapse if the stress imposed on the material exceeds its yield strength. 

One-dimensional consolidation Compression Time-settlement curve Consolidation time (tsortgo)... 

Unconsolidated undrained Remolded Undisturbed Stress-strain curve Undrained shear strength (C) Young s modulus (E) Consolidation time (t t,nn)... 

Consolidated undrained Shear stress-strain curve Consolidation curve Drained strength parameters (Cd,d) Consolidation time ((50, f,oo)... 

The shear strength of non-free-flowing (cohesive) materials is not a unique function of the normal stress. The shear strength of these materials increases with pressure. The YL is a function of consolidation pressure and consolidation time. Thus, the shear strength has to be described by a series of yield loci, each curve representing a certain consolidation pressure and time. These curves can often be described by ... 

The consolidation phase exists for t s 15000 s such that values of the consolidation time are given by = t-15000 s (V is shown in Column (6) of Table 4.5)). Corresponding values of the consolidation ratio are shown in Column (7) as determined by equation (4.52)... 

The consolidation index, v, can be obtained graphically which requires values of the dimensionless consolidation time (T ) to be determined according to equation (4.53) where... 

Figure 4.14 A plot of equation (4.54) showing the variation of the consolidation ratio with (dimensionless consolidation time) and the behaviour index v. Experimental data from Example 4.5 are superimposed onto this plot to estimate the value of v (which may alternatively be calculated using the curve fitting procedure described in Section 4.5.6).

Vertical line cursors are used to identify a linear or transition region on the Characteristic Plot and these are initially positioned by FDS. However, the user has facility to interact with the software and move the cursors as appropriate in order to overcome their potential misplacement due to data scatter. In this way the analysis can be amended as many times as required and optimised. During the analysis of a jar sedimentation test a third, horizontal line cursor is used to specify the final height of sediment, which is particularly useful when a test is not continued to equilibrium. In the case of a piston press analysis, and in accordance with the recommend procedure described in Section 5.5, additional representations of test data are shown for the filtration and consolidation phases to check the choice of transition between the two. For example, in Figure 5.12 the correct transition has been identified on the Characteristic Plot such that the resultant tjIVj vs. Vf plot is linear throughout and the consolidation ratio U vs. (consolidation time, exhibits an initial linear portion. In Figure 5.13 the transition point has been deliberately chosen too far to the left on the Characteristic Plot such that the vs. plot exhibits an incorrect S shape. 

Dimensionless consolidation time Depth of recess in a plate from a filter press, m Distance moved by a diaphragm, m Superficial velocity, m m s ... 

Fluidized beds produce porous granules because the consolidation time is limited to granule drying time, which is of the order of seconds, rather than minutes. 

Experiments were performed using the same humid salt as used in [2], sheared in an annular ring shear tester. We present here a temporal study of its yield locus and of its cohesion. Two types of experiments have been performed, using the classical procedure of Jenike [1] where the shear stress is removed during the consolidation time, and relaxation experiments without removing the shear stress. In both cases, the dilatancy of the powder has been recorded in order to follow its compaction. 

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