Strain thermal contraction

Therefore, before a final wall structure can be selected, it is necessary to conduct a combined strain analysis in both the longitudinal and hoop directions. This analysis will consider thermal contraction strains, the internal pressure, and the pipe s ability to bridge soft spots in the trench s bedding. In order to do this we must know more about the inherent properties of the material we are dealing with that is a structure made up of successive layers of continuous filament-wound fiberglass strands embedded within a plastic matrix. We must know the modulus of the material in the longitudinal direction and the... 

Figure 5. Logarithm of the retractive force at 49% strain (lower curve) and sample temperature (upper curve) plotted against logarithm of time reduced to 263 K. Cross-links are introduced at log t/aT is 3 in the glassy state where the spike on the force curve is due to thermal contraction upon cooling below the glass transition temperature. Equilibrium force at 263 K after cross-linking is feQ. (Reproduced, with permission, from Ref. 27. Copyright 1981, Journal of Chemical Physics.)...

Mcaain, P. E., Kuntz, E., and Pearson, A. M. 1969. Application of stress-strain behaviour to thermally contracted collagen from epimysical connective tissues. J. Agric. Food Chem. 17 629-632. 

The resin matrix in a composite absorbs water in service. As discussed in this chapter, this process is kinetically slow, so the concentration of water in the resin will vary with time and location. Thermal cycling will tend to move the water into the strucmre. Furthermore, the absorption of the water causes the polymer to expand however, in a composite, the swelling is constrained in an analogous way to that described for thermal contraction. Thus, the process of conditioning in moist environments leads to a reduction in magnitude of the thermal strain present in the laminate. 

These differences between specimens presumably arise from varying amounts of compressive prestress, which the bronze matrix exerts on the NbaSn reaction layer (because of thermal contraction after the fabrication heat treatment). The compressive strain degrades the initial /c, so that when tension is applied to the composite, the first effect is to relieve the compressive strain on the NbsSn and increase Ic- Eventually, when enough tensile stress is applied to the composite, the... 

The influence of internal prestrains on the mechanical and Tc properties of NbaSn composite superconductors has been elucidated. Originating from differential thermal contraction in the composite wires, the prestrains amounted to a compressive load on the core and a tensile load on the bronze matrix. This effect saturated for matrix-to-core ratios exceeding 15 1, but provided for the application of tensile strains up to 1% before Tc degradation occurred. 

It has been shown that the peak positions of the Raman-active bands of carbon fibres are strain-sensitive and that Raman Microscopy can be used to follow the deformation of carbon fibres both in air and in a thermoplastic PEEK matrix. It has been demonstrated that the fibres near the surface in the carbon-fibre/PEEK composite examined are subject to a residual compressive strain of the order of 0.287o which is of the same order as that expected (19) from matrix shrinkage due to crystallisation and thermal contraction on cooling from the processing temperature. It is found that when the composite is subject to an externally-applied tensile deformation then, as expected, the change in fibre strain is similar to the applied strain as expected from simple composite theory. 

Finally, Dodds and Sanny (1978) observed the Er resonance in polycrystalline films which were deposited at room temperature onto fiised-quartz or plexiglass substrates at pressures of approximately 1 x 10" Torr. The nominal erbium concentration varied between 0.2 and 2%. The angular variation of the g-value and linewidth was measured for each sample at a fixed temperature in the liquid He range. During cooling, the difference in thermal contraction between film and substrate produced an effective uniaxial strain in the film. The contraction of the substrate forces the film to expand in the direction perpendicular to the substrate, which becomes the preferred axis and the g-value will depend on the orientation of the field with respect to this axis. In this way even in polycrystalline films an anisotropy of the g-value can be observed. The inferred orbit-lattice coefficients were somewhat smaller than those observed in insulators. They were the same for films on quartz or on plexiglass substrates. This fact supports the conclusion that the strain is macroscopically uniform in contrast to the argumentation of Arbilly et al. (1975). 

Experimeiital data on tensile actuation versus twist insertion for neat non-coded MWNT yams shows the importance of twist on thermal contraction (Fig. 8). Although only small actuation strains of less than 0.1% were observed in diese neat, non-coiled Fermat yams, a clear increase in thermal contraetion was evident in yams prepared with higher twist. With increase of inserted twist from 9,650 to... 

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