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Fracture toughness — Charpy DBTT

Ductile-to-brittle transition curve (tanh fit)

Plots the Charpy energy CVN(T) tanh fit and overlays the service temperature against the code-required minimum. Drives MDMT (UCS-66) and B31.3 §323.2.2 impact-test exemption decisions.

Inputs

°C
50 % of upper-shelf energy; from Charpy testing or master-curve fit
°C
Sharper steels = lower C (10-20); ferrite-pearlite = wider (30-40)
J
J
°C
Design minimum metal temperature (MDMT). Refining default −29 °C.
J
ASME B31.3 §323.2.2 typical 27 J / 20 ft-lb single value · UCS-66.
pressure vessel plate, ~0.20 C, normalized

Results

DBTT — Charpy ductile-to-brittle transition
min req 27 JT₀ = -10 °CT_svc -29 °C → 53 J-100-50050100055110165220Test temperature (°C)Charpy energy CVN (J)ASTM E23 / E1921 Master Curve · ASME III NB-2330 fracture toughness · brittle | transition | ductile zones
tanh fit · T₀=-10 °C · USE=220 J · LSE=6 J · transition width C=30 °C
CVN at service T53.0J
Margin above code minimum26.0J
Service zonetransition region
VerdictPASS
The tanh model is the ASTM E1921-style master-curve fit. For RPV irradiation embrittlement use the Eason-Wright-Odette (EWO) formulation; austenitic steels do not exhibit a DBTT.
Download all inputs + calculations + outputs as a single PDF.