Internal yield locus

Construction of the Dynamic Internal Yield Locus. The dynamic yield locus represents the steady state deformation, as opposed to the static yield locus which represents the incipient failure. The dynamic yield locus is constructed by plotting on a (a, t) plane the principal Mohr circles obtained for various consolidation stresses. The dynamic yield locus will be the curve or straight line tangent to all circles, as shown in Figure 17. The dynamic angle of internal friction S and cohesion C are independent of the consolidation stress. S and Q are obtained as the slope and the intercept at er=0 of the dynamic yield locus of the powder. 

Here, [L is the coefficient of internal friction, ( ) is the internal angle of friction, andc is the shear strength of the powder in the absence of any applied normal load. The yield locus of a powder may be determined from a shear cell, which typically consists of a cell composed of an upper and lower ring. The normal load is applied to the powder vertically while shear stresses are measured while the lower half of the cell is either translated or rotated [Carson Marinelli, loc. cit.]. Over-... 

Solution The kinematic angle of internal friction can be determined from the Mohr circle, which is tangential to the yield locus at the end point. This Mohr circle yields the major consolidating stress o and minor consolidating stress <73. Thus, % is found to be 30°, either from Eq. (8.27) or from a tangent of the Mohr circle which passes through the origin, as shown in Fig. E8.1. 

Figure 22 shows a typical experimental shear stress chart, obtained for A2, using a compaction with normal stress equal to 1106.2 Pa. Figure 23 shows the corresponding yield locus from which the static angle of internal friction, cp, was worked out from the slope of the yield locus. The cohesion, C, is obtained from the intercept with the shear stress axis. 

PC/PE. In the case of PC/PE, plane strain alone does not produce significant changes in the yield stress and the deformation behavior. Its yield locus in the tension-tension quadrant is therefore either very nearly a quarter circle or similar to a Tresca locus. The exact shape of the locus can be determined only by much more elaborate biaxial tests. This material is not very notch sensitive compared with PC. The energy to break in a notched Izod impact test is 15 ft-lb/inch for Vs-inch thick bars and 11 ft-lb/inch for 4-inch bars whereas for PC the latter figure is about 2 ft-lb/inch. This reduction in notch sensitivity over pure PC appears to be related to the material s ability to void internally, probably relieving the plane strain. 

Under the hnear Mohr-Coloumb approximation, if parallel yield loci are assumed with constant angle of internal friction, and with zero intercept of the effective yield locus, the flow function is a straight line through the origin D, given by... 

As can be seen from Fig. 10, the effective angle of internal friction can be determined from just one yield locus but it is more reliable to take an average of several angles measured from a family of yield loci, each corresponding to a different state of... 

The flowability of a particulate material is determined by its shear properties. When internal shear deformation is just about to occur, the local shear stress is called the shear strength. The shear strength is a function of the normal stress this functional relationship is referred to as the yield locus (YL). For a free-flowing material, the yield locus under fully mobilized friction conditions is... 

Figure 10.14 Definition of effective yield locus and effective angle of internal friction, <5...

From it, the stress dependent effective angle of internal friction effective yield locus follows obviously [28], see Fig. 4 ... 

Therefore considering Eq.( 2), the new relation between the time dependent angle of internal friction (pi, (slope of time yield locus) and the time invariable stationary angle of internal friction yield locus) is defined as [26, 27], see Fig. 2 ... 

But if t > 0 the angle of internal friction during time consolidation decreases time yield locus is in T-o-coordinates ... 

Figure 4.6 Yield locus and Mohr s circles of studied sodium hyaluronate powder (measured at 24 °C). Determined parameters cohesion = 1.41 kPa unconfined yield strength = 5.08 kPa major principal stress Oj = 16.4 kPa friction coefficient = 3.24 angle of internal friction (p = 31.9 and effective angle of internal friction (p = 40.75 ...

Figure 12 Yield locus of tested sugar pellets with corresponding Mohr circles and parameters a-, consolidation stress a, uniaxial compression strength isostatical tensile strength cohesion (p internal friction angle

Figure 12 shows the obtained yield points and their linear approximations for the internal friction, i.e., ftiction between sugar particles. The mean wall yield locus measured using the stainless steel wall element is presented in Fig. 13. The obtained parameters are Hsted in Table 3. The investigated material has a negligible cohesion and a high friction. The mean values of the measured friction coefficients between particles is /tp.p = 0.86 it 0.07. The obtained wall fnction coefficient is //p stt.ei = 0.482 0.021. The value of flow function at ffc = 34 shows that nearly spherical sugar pellets can be characterized as free flowing.

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