Creep — Robinson life-fraction rule

Cumulative creep damage

Sum t/t_rupture across each operating period; D ≥ 1 means design creep life is consumed.

T (°C)σ (MPa)Hours at conditiont_rupture (h) at (T,σ)t/t_r
0.1000
0.0625
0.0333
Creep damage accumulation · Robinson Σ(t/tr)
code limit Σ = 1.0123Σ 0.196cumulative damage →0.000.250.500.751.00period · T / σ / t · Σ damage contribution#1540 °C · 100 MPa · 25,000 h0.1000#2580 °C · 100 MPa · 5,000 h0.0625#3600 °C · 90 MPa · 1,000 h0.0333
3 periods · total Σ 0.196 · remaining 0.804 · PASS.
Total Σ(t/t_r)0.1958
Remaining life-fraction0.8042
VerdictPASS
Robinson's rule (1952). t_rupture comes from a Larson-Miller parameter fit to material-specific stress-rupture data — see ASME II-D Section II Part D Tables U / Y.
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