16 Internal Heat Generation in Tension Tests of AISI 316 Using Full-Field Temperature and Strain Measurements 101 Fig. 16.5 Strain and temperature along the specimen at various times Fig. 16.6 Calculated beta along the specimen at various times In Fig. 16.5, the rise in temperature is characterized with the rise in axial strain across the length of the specimen. The strain and temperature measurements along the gage are almost uniform along the gage section up until 356 ms into the test. The large increase in the localization temperature and strain are also evident in these graphs, reaching their peak levels at the point before failure (426 ms) and directly after (446 ms). The measured strains and temperatures in Fig. 16.5 were then used in concert with the estimated stresses in the specimen to calculate the partition of plastic work (ß) converted to heat over the gage length of the material. It is evident that during the early stages of deformation the strain energy is mostly being transferred to the mechanical work in the material, resulting in a beta lose to 0.6 over the length of the gage section. However, as the deformation increases the beta to 0.8–0.9 across the specimen as the temperature of the material rises and more energy is released as heat (Fig. 16.6). Figure 16.7 shows the calculated beta at the maximum point of strain from Fig. 16.4 as well as the estimated temperature based on the measured stress and strain data coupled with a constant beta value. As was displayed in the waterfall plots, the beta value is highly dependent on the level of strain in the material as the beta ranges from 0.6 to 0.9 throughout the test. The average beta for this point was calculated as 0.786. Figure 16.8 shows the large amount of data that is generated in a single test as 24,000 separate points have measurements of strain, interpolated temperatures, and calculated betas.
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