S-N Curve Fatigue Calculator

Calculate fatigue life using industry-standard S-N curves from DNV, API, BS 7608, and more. Interactive visualization with instant results.

DNV-RP-C203 API RP 2A BS 7608 Eurocode 3

Input Parameters

Typical range: 10 - 300 MPa
Leave blank to calculate allowable cycles only
Default: 1.0 (no concentration)

S-N Curve Visualization

About DNV-RP-C203 S-N Curves

DNV-RP-C203 provides S-N curves for fatigue analysis of offshore steel structures. The curves account for different weld details, environments, and thickness effects. This is the most widely used standard for offshore fatigue assessment.

S-N Curve Equation

Basic S-N Relationship:

N = a / (Sm)

Where:
N = Number of cycles to failure
S = Stress range (MPa)
a = S-N curve intercept (log scale)
m = Negative inverse slope

Fatigue Damage (Miner's Rule):

D = n / N

Where:
D = Cumulative fatigue damage
n = Applied number of cycles
N = Allowable cycles from S-N curve
Failure when D >= 1.0

Engineering Disclaimer This calculator is provided for educational and preliminary estimation purposes only. Actual fatigue assessments must consider load spectra, thickness effects, mean stress corrections, weld quality, inspection intervals, and other factors. Always consult the full standard documentation and qualified engineers for critical applications.

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