Experimental stress

Figure 4.17 Experimental stress relaxation moduli of polystyrene measured over about two orders of magnitude in time at the temperatures indicated. [Reprinted with permission from H. Fujita and K. Ninomiya, J. Polym. Sci. 24 233 (1957).]...

Appendix 6 contains requirements of experimental stress analysis. Appendix 8 has acceptance standards for radiographic examination. Appendix 9 covers nondestructive examination. Appendix 10 gives rules for capacity conversions for safety valves, and Appendix 18 details quahty-control-system requirements. 

To initiate a chemical relaxation it is necessary to perturb the system from its initial equilibrium position. This is done by applying a forcing function, which is an appropriate experimental stress to which the system responds with a shift in equilibrium configuration. Forcing functions can be transient (a sudden, essentially discontinuous Jolt ) or periodic (a cyclic stress of constant frequency). 

Test results provides the hypothesis that syntactic foam is rate insensitive and that the static uniaxial strain stress-strain curve actually represents the general constitutive relation. Disagreement between the experimental data and the predicted behavior is greatest at low stresses (1 kbar) where experimental stresses are about double those predicted analytically. The discrepancy decreases at the higher stress levels and virtually disappears at and beyond 7 kbar. This range... 

Figure 4 displays experimental stress-strain curves for ultrahigh molecular weight (UHMW) polyethylene films derived from... 

Figure 4 Experimental stress-strain curves for UHMW polyethylene (Mw = 1.5 X 10, Mn = 2 X 10 ) crystallized from the melt and from solutions of various initial polymer concentrations 0. T = 120°C and e = 500%/min.

EXPERIMENTAL STRESS-STRAIN BEHAVIOR OF VULCANIZED RUBBERS AT MODERATE ELONGATIONS... 

Fig. 96.—Theoretical and experimental stress-strain curves for simple elongation of gum-vulcanized rubber. (Treloar. )...

Anthony, Caston, and Guth obtained considerably better agreement between the experimental stress-strain curve for natural rubber similarly vulcanized and the theoretical equation over the range a = 1 to 4. KinelP found that the retractive force for vulcanized poly-chloroprene increased linearly with a — l/a up to a = 3.5. 

Contents Introduction to Materials. Manufacturing Considerations for Injection Molded Parts. The Design Process and Material Selection. Structural Design Considerations. Prototyping and Experimental Stress Analysis. Assembly of Injection Molded Plastic Parts. Conversion Constants. 

The temperature-time superposition principle is illustrated in Figure 8 by a hypothetical polymer with a TK value of 0°C for the case of stress relaxation. First, experimental stress relaxation curves are obtained at a series of temperatures over as great a time period as is convenient, say from 1 min to 10 min (1 week) in (he example in Figure 8. In making the master curve from the experimental data, the stress relaxation modulus ,(0 must first be multiplied by a small temperature correction factor/(r). Above Tg this correction factor is where Ttrt is the chosen reference... 

An example of experimental stress-relaxation data is shown in Figure 14 (160). Master stress-relaxation curves made from the experimental data on different molecular weight materials are shown in Figure 15. The temperature-shift factors used in making the master curves are shown in Figure 16. Note that the shift factors a, are the same for all molecular weights... 

The terms are arranged into sections dealing with basic definitions of stress and strain, deformations used experimentally, stresses observed experimentally, quantities relating stress and deformation, linear viscoelastic behaviour, and oscillatory deformations and stresses used experimentally for solids. The terms which have been selected are those met in the conventional mechanical characterization of polymeric materials. 

Z0337 Yamazaki, M., and H. Shirota. Application of experimental stress ulcer test in mice for the survey of neurotropic naturally occurring drug materials. Shoyakugaku Zasshi 1981 35 96—102. 

Handhook of Experimental Stress Analysis , J. Wiley, NY (1950), p 982 (Fairly comprehensive description of y-ravs technique is given) 11) K. Siegbahm, "Beta and Gamma Ray Spectroscopy , Interscience, NY (1955) 12)W.J. Price, "Nuclear Radiation Detection ,... 

Figure 7.6 NMR parameter image of a strained poly(dimethylsiloxane) rubber band with a cut and calibration curves (a) Experimental curve for T2 versus strain, (b) Experimental stress-strain relationship, (c) Calibration curve for T2 versus strain obtained from combination of curves a and b, (d) Stress image obtained by recalibration of a T2 parameter image. The stress contours range from 0 to 2.4 MPa...

Figure 13. Experimental stress-stretch curves for solithane under uniaxial straining at several ambient pressures. A positive pressure corresponds to a negative mean stress. Data are re-plotted from Quested et al. Ref [16].

Figure 45b (upper part) shows the residual stress contribution of the strained filler clusters for the different pre-strains, obtained by subtracting the polymer contributions (solid lines) from the experimental stress-strain data (symbols) of Fig. 45a. The resulting data (symbols) are fitted to the second addend of Eq. (47) (solid lines), whereby the size distribution of filler clusters Eq. (37), shown in the lower part of Fig. 45b, has been used. The size distribution (x ) is determined by the adapted mean cluster size =< ifd>=26 and the pre-chosen distribution width Q=-0.5, which allows for an analytical solution of the integral in Eq. (47). The tensile strength of filler-filler bonds is found as Q b/d3=24 MPa. The different fit lines result from the different stress-strain curves ctR1( ) that enter the upper boundary of the integral in Eq. (47). Note that this integral, representing the contribution of the strained filler clusters to the total stress, becomes zero at = max for every pre-strain.

Similar well fitting simulation curves for the experimental stress-strain data as those shown in Fig. 46b can also be obtained for higher filler concentrations and silica instead of carbon black. In most cases, the log-normal distribution Eq. (55) gives a better prediction for the first stretching cycle of the virgin samples than the distribution function Eq. (37). Nevertheless, adaptations of stress-strain curves of the pre-strained samples are excellent for both types of cluster size distributions, similar to Fig. 45c and Fig. 46b. The obtained material parameters of four variously filled S-SBR composites used for testing the model are summarized in Table 4, whereby both cluster... 

Equations proposed by Struik (1977,1978) that are able to describe experimental stress relaxation below Tg are for short-time experiments... 

There is overwhelming evidence that the aramide fibres possess a radially oriented system of crystalline supramolecular structure (see Fig. 19.1). The background of the properties, the filament structure, has been studied by Northolt et al. (1974-2005), Baltussen et al. (1996-2001), Picken et al. (2001), Sikkema et al. (2001, 2003), Dobb (1977-1985) and others. The aramid fibres (and the "rigid" extended chain fibres in general) are exceptional insofar as they were - with the rubbers - the first polymer fibres whose experimental stress-strain curve can very well be described by a consistent theory. 

J.W. Dally and W.F. Riley, Experimental Stress Analysis, 2nd edn, McGraw-Hill, 1978. 

FIGURE 13-17 Experimental stress/strain plot for single crystals of polydiacetylene [redrawn from the data of C. Galiotis and R. J. Young, Polymer, 24, 1023 (1983)]. 

The relative stress is calculated as experimental stress by using the following Equation (1). 

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