Force elongational

Mooney-Rivlin correction. In the 1940 s, Mooney and Rivlin showed that, generally, the basic force-elongation relationship must be corrected by a term proportional to the reciprocal extension ratio ... 

Work, R.W. "Dimensions, birefringences, and force-elongation behavior of major and minor ampullate silk fibers from Orb-Web-Spinning Spiders - Effects of wetting on these properties". Text. Res. ]. 47(10), 650-662 (1977). 

Typical force-elongation curves of some manufactured and natural staple fibers and textile-type manufactured filaments are shown in Figs 12.1 and 12.2. Table 12.1 gives the values of some of the physical and tensile properties of textile fibers. 

Fig. 12.1. Force-elongation curves of natural and manufactured staple fibers at standard conditions of 70°F and 65 percent humidity.

High Speed Movie and Tensile Testing. High speed force—elongation material properties were measured on a model 581 Plastechon high speed tester. Experimental details have been describd previously (10). Figure 1 shows a typical force-elongation trace obtained for this class of materials. 

The tensile test shows a steady course of the tensile force-elongation curve, where a linear relationship exists only at low tensile forces. There are only small deviations from a linear course at approximately half-rupture. The tensile strength increases with increasing density. The degree of heat-sealing has an effect here also. 

The raw data from a tensile test (Fig. 11-20) are obtained in terms of force and corresponding elongation for a test specimen of given dimensions. The area under such a force-elongation curve can be equated to the impact strength of an isotropic polymer specimen if the tensile test is performed at impact speeds. Show that this area is proportional to the work necessary to rupture the sample. 

The viscoelastic character of stratum corneum is further demonstrated by the dependence of elastic modulus on strain rate (Figure 32). Even the dry corneum 10 wt % H2O) showed significant viscoelastic behavior over the narrow range of strain rates studied. In the case of hydrated membranes, there is also a change in shape of the force-elongation curve (6, 85). 

The force elongating the specimen may be separated into that of the unbroken specimen, and the reduction, Pc, due to the presence of a crack. The former is calculated as follows ... 

Owing to the experimental procedure, the force in the system, F, can be related to the forced elongation speed of the pili, L, and the bond opening rate, dlVe/dt, according to... 

For operation in the hard mode, one selects the appropriate full-scale values of force, elongation, and the time to strain the sample. This predetermined strain rate signal is compared with an ac differential three-... 

The initial portion of the virgin force-elongation curve is approximately linear, and the crystals support compressional forces. 

However, when the applied force is expressed in terms of the linear density of the fiber at the commencement of the test and the elongation is expressed in terms of the percentage elongation of the fiber, the true story emerges, as shown in Fig. 17 where the force/ elongation curve is transferred from Fig. 16. 

Figure 19 Force elongation curve illustrating work factor.

A is the area under the force-elongation curve in cm S is the full-scale load in gf R is the cross-head speed in cm/min G is the (corrected) effective specimen length in cm IV is the chart width in cm L is the chart speed in cm/min... 

The force-extension relation derived previously from statistical considerations does not agree well with experimental data at small extensions. As an example, a plot of unixial force-elongation data for natural rubber falls below the curve calculated from the theoretical equation (equation 7.48) in the region between 1.1 to 2.0 elongation... 

The force-elongation curves of the radial and spiral threads prepared from... 

Fig. 4.41 Force-elongation curves of the radial and spiral threads prepared from an Argiope bruennuichii spider with a weight of 0.949 g. Stretching velocity 3.3 X10 m/s.

Here, F is the force applied to the dragline, S is the cross sectional area of the double filament, L is the initial length of the dragline, and AL is the elongation of the dragline when the F is applied. The F and AL are determined from the force-elongation curve within the elastic limit point and the S from the electron scanning microscopy. 

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