Isochronous behavior

Isochronous graphs are particularly valuable when obtained experimentally, because they are less time consuming and require less specimen preparation than creep curves. Such graphs at several time intervals can also be used to build up creep curves and indicate areas where the main experimental creep program could be most profitable. They are also popular as means of evaluating de-formational behavior, because their method of data presentation is similar to the conventional tensile test data. 

A method is described for fitting the Cole-Cole phenomenological equation to isochronal mechanical relaxation scans. The basic parameters in the equation are the unrelaxed and relaxed moduli, a width parameter and the central relaxation time. The first three are given linear temperature coefficients and the latter can have WLF or Arrhenius behavior. A set of these parameters is determined for each relaxation in the specimen by means of nonlinear least squares optimization of the fit of the equation to the data. An interactive front-end is present in the fitting routine to aid in initial parameter estimation for the iterative fitting process. The use of the determined parameters in assisting in the interpretation of relaxation processes is discussed. 

Fig. 13. Isochronal annealing behavior of the major Si—H bands in Si that has received an H+ implantation at room temperature. [From Stein (1975). Reprinted with permission from Journal of Electronic Materials, Vol. 4, p. 159 (1975), a publication of The Metallurgical Society, Warrendale, Pennsylvania.]...

The Type A melilite data also reinforce earlier arguments about the absence of any connection between mineralogical alteration and Mg isotopic behavior. Melilites in 3529-45 are extensively altered, mainly to grossular and Na-rich plagioclase, yet show much less evidence for a disturbed Mg isotopic composition than relatively pristine melilites from B1 inclusions. B1 melilites exhibit much larger deviations from the standard isochron than anorthites (see also [1]). 

In order to study the annealing behavior of the hydrogen-related defects, infrared absorbance spectra were recorded at 10 K after each step in a series of isochronal heat treatments (annealings) at temperatures in the range 400-1200 °C. The annealings were performed in a furnace purged with argon gas and the duration of each treatment was 30 min. 

The isochronous cyclotrons can accelerate different particles from protons to the ions of the heaviest elements. The energy of the particles is determined by the setting of the cyclotron, and that can be changed in a wide range. The relativistic behavior of the particles can be neglected for the sake of these considerations. The heavy-ion cyclotron can be specified by the so-called factor determining the maximum kinetic energy of the ions by the relation... 

In Figure 2, the data in Table I have been replotted as isochrones of log true stress versus log strain. The isochrones cover four decades in time. The behavior is highly nonlinear over nearly the entire range of strains examined. 

For the quenched polypropylene, the stress-strain behavior becomes linear only in the region of strain below 1%. Observe that at a strain of 7.6% the isochrones are flattening to a zero slope, and the modulus has been reduced by a factor of at least 3.2 from what it would have been if the behavior were linear. Also, at strains above about 2% the nonlinearity becomes essentially independent of time, i.e. the isochrones form a set of nearly parallel curves. 

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