Stress Ratio
Based on B31.3 Paragraph 323.2.2.b1-3, the software defines the stress ratio as the maximum of:
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The circumferential pressure stress (hoop stress) divided by the allowable stress.
CAESAR II uses the generic mechanical stress equation because B31.3 does not provide an equation for the hoop stress. Define how the software calculates the Base Hoop Stress On parameter in the Configuration Editor.
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The combined stress defined for an operating condition (sustained plus displacement strains) divided by the allowable stress.
The software calculates the combined stress using Paragraph 323.2.2.b1-3, equations 23a through 23d, the load primitives in the load case, and SIFs of 1.0. Corrosion and mechanical tolerances are deducted.
The software uses Shx, which is the hot allowable corresponding to Tx, because Paragraph 323.2.2.b1-3 does not define the allowable stress. If temperature is not included in the load case, the software uses the ambient Sh value.
Reduction
The software bases the reduction in lowest exemption temperature on the calculated stress ratios and B31.3 Figure 323.2.2B or Table 323.2.2B. The table provides reduction values for stress ratios from 0.30 to 1.0.
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For a stress ratio £ 0.30, the software sets the reduction to 217°F.
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For a stress ratio > 1.0, no reduction is used.
Final MDMT
The final MDMT calculation depends on the stress ratio value.
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For a stress ratio > 0.30, Final MDMT = MAX[Base MDMT – Reduction, -55°F]
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For a stress ratio £ 0.30, Final MDMT = MAX[Base MDMT – Reduction, -155°F]
Status
OK
Specifies Final MDMT £ Tmin.
Impact
Specifies Final MDMT > Tmin.
The report displays the rows for the node in red.
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Specifies an OK status from Error Check 
. The software did not calculate stress ratio or reduction as part of the full analysis.
The software copies Base MDMT from the error check in the Final MDMT column of the report. See elements 30-40 and 50-60 in the full analysis example report.
Unknown
Specifies an unknown status carried over from Error Check . The report displays no values in the Stress Ratio, Reduction, and Final MDMT columns
of the report. See element 70-80 in the full analysis example report.
The report displays the rows for the node in red.
Examples
See the example MDMT Report.
Node 10
Stress Ratio = 0.32
Final MDMT = MAX[49°F – 172.4°F, -55°F] = -55°F
Tmin = 30°F
Status is OK because -55°F < 30°F
Node 28
Stress Ratio = 0.29
Final MDMT = MAX[49°F – 217°F, -155°F] = -155°F
Tmin = 30°F
Status is OK because Stress Ratio < 0.30 and Tmin > -155F
Node 120
Stress Ratio = 0.48
Final MDMT = MAX[49°F – 66.8°F, -55°F] = -17.8°F
Tmin = -25°F
Status is Impact because Final MDMT > Tmin