ASME STP-PT-080:2016 pdf free download.DEVELOPMENT OF AVERAGE ISOCHRONOUS STRESS-STRAIN CURVES AND EQUATIONS AND EXTERNAL PRESSURE CHARTS AND EQUATIONS FOR 9Cr-1Mo-V STEEL.

The ASME FFS-1 tertiary creep equation is of the same form as the Ellis equation and the parameters. initial creep rate and omega, have nearly consistent meaning as the initial creep rate and alpha in this study. l3oth parameters in ASME FFS-l are related to time and Stress using Larson-Miller type expressions. though the Larson-Miller expressions are presented in logarithmic form. On this basis, we can compare the initial creep rate and alpha parameter determined from the regressions of the digitized NIMS data for “virgin” material to the published curves in ASME FFS- I recommended for service aged material. In order to make the comparison, we must use the same Larson-Miller Constants for the data set as the ASME FFS-I tables, which differ slightLy from the constants we found, optimized the current data set. The resultant parametric lit determined for the initial creep rate in this study is similar to the curve developed br ASMF. FFS-l curve (see Figure 1.9). This was not expected since the ASME FFS-l curves were bused on service aged materials. The Larson-Miller constants in the parametric fits are remarkably close. The sensitivity of the R value to the constant is very low within the range of 30-40 and so either a value of 35.5 (current study) or 34 produce nearly the same results. The ASME FFS- I expression appears to be better suited for extrapolation, but is less accurate a description of this data set.

The values for Omega in ASME FFS-l and the a-parameter in the current study have also been compared.

Using a Larson-Miller Constant of 2 for u-parameter results in a poor fit for the NIMS and Ellis data(Figure 1.10) and the predicted Omega parameter at the test data conditions is, on average, about 40% of the a-parameter.

2.4 Average Isochronous Curves

Section NH of the Nuclear Code and the newly developed Code Case 284383 for Section VIll-2 show isochronous curves with average values. Also, the design methodologies in NH and the newly developed Code Case are based on the average isochronous curves. Accordingly, in this part average isochronous stress-strain charts for 9Cr- I Mo-V (Grade 91) steel in increments of 50°F from 800°F to 1200°F are developed as shown in Appendix B. These charts and tables were developed by Mike Swindenian and Robert Swindeman from the equations and data shown above.

• Figure B, I. Average isochronous curves at 800°F

• Table 3.1. Tabular values for average isochronous curves at 800°F

• Figure 3.2. Average isochronous curves at 850°F

• Table 3.2. Tabular values for average isochronous curves at 850°F

• Figure 11.3. Average isochronous curves at 900°F

• Table 3.3. Tabular values for average isochronous curves at 900°F

• Figure B.4. Average isochronous curves at 950°F

• Table B.4. Tabular values for average isochronous curves at 950°F

• Figure B.5. Average isochronous curves at 1000°F

• Table B.5. Tabular values for average isochronous curves at 1000°F

• Figure 3.6. Average isoehronous curves at 1050°F

• Table B.6. Tabular values fbr average isochronous curves at 1050°F

• Figure 11.7. Average isochronous curves at 1100°F

• Table 3.7. Tabular values for average isochronous curves at 1100°F

• Figure 3.8. Average isochronous curves at 1150°F

• Table B.8. Tabular values for average isochronous curves at 1150°F

• Figure B.9. Average isochronous curves at 1200°F

• Table B.9. Tabular values for average isochronous curves at 1200°F

The external pressure chart in ASME BPVC Section ll-D is constructed by plotting Eq. (3.23) versus the value of S12. This reduction factor takes into account the reduction of buckling stress in an actual cylinder due to imperfections compared to the values obtained from theoretical buckling equations which are based on perfectly round cylinders. In the ASME I3PVC Section VIll-2 code the reduction factor is embedded in the design equation for buckling since Vlll-2 does not use external pressure chart.

Example 3.2

Plot the external pressure curve for Grade 91 at 37,000 hours and lO650F using Actual stress, S

One-half the stress, S/2. This is the curve adopted by Vlll-l for external pressure calculations.

# ASME STP-PT-080:2016 pdf free download

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