DNV-RP-C203 S-N and Miner fatigue screening

DnvRpC203FatigueDesignKernel provides a reusable, immutable calculation path for an explicit DNV-RP-C203 2024-10+AMD:2025-10 basis. It applies a caller-supplied S-N curve to a verified stress-range spectrum and performs Palmgren-Miner summation. The result is always a screening result that requires engineering approval.

NeqSim does not reproduce or select DNV’s licensed S-N tables. The curve identifier and numeric parameters must come from the project’s controlled copy of the standard and must match the detail category, environment, fabrication, thickness, weld, and inspection basis. Setting curveDefinitionVerified(true) records an attestation; it does not create that evidence.

The publisher page was checked on 2026-08-02 and identifies the current basis as edition 2024-10, amended 2025-10: DNV-RP-C203.

Calculation contract

For each spectrum bin, the supplied factors are applied to the nominal stress range:

\[\Delta\sigma_{eff,i}=\Delta\sigma_{nom,i}\,SCF\,f_{th}\,f_{other}\]

For each active S-N branch, the kernel evaluates:

\[\log_{10}N_i=\log_{10}A-m\log_{10}(\Delta\sigma_{eff,i})\]

It then reports raw and design damage, utilization, and a linear life extrapolation:

\[D_{raw}=\sum_i\frac{n_i}{N_i},\qquad D_{design}=DFF\,D_{raw},\qquad U=\frac{D_{design}}{D_{limit}},\qquad L_{est}=\frac{t_{spectrum}}{U}\]

Single-slope and continuous bi-linear curve definitions are supported. A bi-linear definition is blocked when its branches differ by more than one percent at the supplied transition cycle count. Zero-cycle bins are retained in the result, but at least one positive cycle count is required.

Java example

The numeric curve below is deliberately named as project-controlled demonstration data; it is not a DNV curve-table transcription.

StandardEdition edition = StandardEdition.defaultEdition(StandardType.DNV_RP_C203);
DnvRpC203FatigueDesignKernel.Input input = DnvRpC203FatigueDesignKernel.Input
    .builder(edition, "Pipeline")
    .snCurve(DnvRpC203FatigueDesignKernel.SnCurve
        .singleSlope("PROJECT-CONTROLLED-DEMO", 12.0, 3.0))
    .addStressBin("high range", 100.0, 1.0e5)
    .addStressBin("moderate range", 50.0, 2.0e5)
    .stressConcentrationFactor(1.0)
    .thicknessCorrectionFactor(1.0)
    .otherStressRangeFactor(1.0)
    .designFatigueFactor(3.0)
    .minerDamageLimit(1.0)
    .assessedExposureYears(20.0)
    .curveDefinitionVerified(true)
    .stressSpectrumVerified(true)
    .build();

EngineeringCalculationResult<DnvRpC203FatigueAssessment> result =
    new DnvRpC203FatigueDesignKernel().calculate(input, null);
DnvRpC203FatigueAssessment assessment = result.getValue();
Map<String, Object> report = assessment.toMap();

DnvRpC203FatigueDesignKernelTest.documentedExampleIsRunnable executes the public API used in this snippet. The executed notebook shows the bin contributions and a deliberately blocked unverified input.

Fail-closed readiness

Calculation is blocked for:

• an edition other than 2024-10+AMD:2025-10, or additional project amendments;
• equipment outside Pipeline, AdiabaticPipe, Pipe, Riser, or OffshoreStructure;
• a missing, invalid, or discontinuous S-N curve;
• missing curve verification or stress-spectrum verification;
• missing bins, invalid stress ranges or cycle counts, or no positive cycles;
• non-positive stress factors, a design fatigue factor below one, or a damage limit outside (0, 1];
• an invalid assessed exposure or a non-finite numerical result.

Engineering boundary

The kernel does not derive structural stress, select a fatigue detail or S-N curve, perform rainflow counting, calculate stress concentration or thickness/environmental factors, combine simultaneous loads, determine fabrication tolerances, plan inspection, or perform a conformity assessment. Those inputs and decisions remain external controlled evidence.

The older PipeMechanicalDesignCalculator and RiserMechanicalDesignCalculator fatigue methods remain for compatibility. They use embedded simplified parameters that differ between classes and must not be presented as current-edition DNV-RP-C203 evidence. New explicit C203 studies should pass their approved stress spectra and curve parameters through this kernel.