Source: https://guthlabs.ai/docs/instruments/stress-concentration-factor-lookup/mechanism/

instrument mechanism / verified-clean

# Stress Concentration Factor Lookup mechanism

The inspectable method record for Stress Concentration Factor Lookup, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The core formula is standard, but the instrument needs the exact Peterson chart edition or digitized dataset, geometry definitions, interpolation policy, extrapolation policy, ratio validity ranges, and nominal-stress convention before it can be marked PASS. The four vectors use explicit reference fragments so their outputs are independently computable.

- The relationship σmax = Kt·σnom is correct for linear-elastic elastic stress concentration, provided Kt and σnom use the same load case and nominal-stress convention.

- Kt is geometry- and loading-specific; the specification does not define the exact Peterson geometry, boundary conditions, or nominal section used for each feature.

- The lookup/curve-fit validity ranges for r/d, D/d, d/W, plate thickness, and 2D versus 3D geometry are unspecified.

- Kt is an elastic stress-concentration factor and must not be presented as a fatigue notch factor Kf or as an elastic-plastic peak-stress prediction.

- The actual digitized Peterson table or polynomial coefficients are not supplied, so the implementation cannot be fully verified against its claimed source.

## Units and conventions

- Stress inputs and σmax use the same units, here MPa.

- All geometric ratios are dimensionless and must be formed from lengths in consistent units.

- For finite-width plates, σnom is the nominal far-field tensile stress based on the gross section unless explicitly stated otherwise.

- The calculations assume homogeneous, isotropic, linear-elastic material, small deformation, and the plane-stress chart convention unless the source chart specifies another condition.

- For the elliptical-hole case, a is the major semi-axis and b is the minor semi-axis; the Inglis result applies to an effectively infinite plate under uniaxial tension.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "feature_type": "circular hole in effectively infinite plate",
    "load_type": "uniaxial tension",
    "hole_diameter_mm": 20,
    "plate_width_mm": "infinite",
    "sigma_nom_MPa": 100
  },
  "expected_outputs": {
    "Kt": 3,
    "sigma_max_MPa": 300
  },
  "reference_data": {
    "geometry": "circular hole, d/W -> 0",
    "Kt": 3,
    "source_convention": "Peterson's Stress Concentration Factors, standard circular-hole infinite-plate tension entry; widely tabulated standard value"
  },
  "working": "1. Boundary ratio: d/W -> 0, so use the infinite-plate row. 2. Kt = 3. 3. σmax = Kt·σnom = 3·100 MPa = 300 MPa."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The stated instrument depends on Peterson chart data or curve-fit coefficients that are not provided. Consequently, valid finite geometries such as r/d = 0.1 and D/d = 2 cannot produce numerical Kt values from this specification alone. The instrument also has explicit failure points at r/d = 0 and d = 0 that require rejection or an unbounded/undefined result.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/stress-concentration-factor-lookup/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/stress-concentration-factor-lookup/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/stress-concentration-factor-lookup/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`