Fundamentals of Strength by Paul S. Follansbee

Author:Paul S. Follansbee
Language: eng
Format: epub
Publisher: Wiley
Published: 2013-12-16T16:00:00+00:00

Figure 9.30 Computed variation of with strain using Equation (9.7) for the adiabatic test at 148 K and a strain rate of 1.0 s−1 along with the dashed-line fit to the evolution equation (Eq. 6.28).

Figure 9.31 Computed variation of with strain using Equation (9.7) for the adiabatic test at 148 K and a strain rate of 0.01 s−1 along with the dashed-line fit to the evolution equation (Eq. 6.28).

Figure 9.30 shows the fit of Equation (6.28) to the test at 148 K and a strain rate of 1.0 s−1. Even though there is a yield phenomenon in this test, note that Equation (6.28) can be made to agree with the data closely with the selected parameters. Also evident in this figure, when compared with Figure 9.23, is that a single smooth curve through both loading steps is achieved, which gives confidence in the model parameters in Equation (9.7).

Figure 9.31 shows the result for the test at 148 K and a strain rate of 0.01 s−1. Since this is an isothermal test, the slight difference between the stress levels in the two loading steps represents experimental uncertainty. It is also apparent that Equation (6.28) with the noted parameters fits well with the measurements, although a translation of the curve along the strain axis by a strain of ∼1% would force even better agreement with the first loading step—without affecting the choice of model parameters.

Figure 9.30 and Figure 9.31 show application of the guidelines summarized earlier in analyzing plots of versus strain. Table 9.10 lists the values of θII and for all of the conditions listed in Table 9.9. In all cases, κ = 2. It is worth highlighting the two dynamic tests at 653 and 673 K, where the values of range from 420 MPa at the lower temperature to 510 MPa at the higher temperature. This difference represents experimental scatter since these two test conditions were so similar. It is also apparent in Table 9.10 that the tests at 873 and 973 K do not yield ranges of θII and that are consistent with the lower temperature tests.

Table 9.10 Parameters to Equation (6.28) for Each of the Tested Conditions for Annealed AISI 1018 Steel

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