Turn nominal stresses into realistic peak estimates fast. Choose detail type, then refine with factors. Download results in seconds for safer field decisions always.
This tool estimates stress intensification (peak-to-nominal amplification) using geometric concentration (Kt) and optional notch sensitivity (q) for fatigue-style amplification (Kf).
Sample scenario for quick validation of inputs and outputs. Your actual project factors may differ.
| Scenario | Nominal σeq | Detail | Geometry | Kt | q | Kf | Design factor | σpeak |
|---|---|---|---|---|---|---|---|---|
| Plate hole tension | 85 MPa | Hole | d=22 mm, W=120 mm | ~2.52 | 0.70 | ~2.06 | 1.10 | ~192 MPa |
Example values are rounded and intended for demonstration.
1) Nominal equivalent stress (combined loading)
For loads mode, the calculator estimates axial stress (σa), bending stress (σb), and torsional shear (τ), then combines them using a common equivalent-stress form:
2) Theoretical stress concentration (Kt)
3) Notch sensitivity and fatigue amplification
4) Peak design stress
For critical components, validate inputs and factors with a qualified engineer and governing standards.
Construction components often include holes, weld toes, notches, or cutouts that disturb stress flow. Even when nominal stresses look acceptable, local peaks can govern cracking, distortion, or premature fatigue. A practical intensification workflow converts nominal stress into a peak estimate so details can be revised early.
For common steel details, geometric concentration factors (Kt) frequently fall between 1.5 and 3.5. A wide plate with a small hole approaches Kt near 3.0, while large radii and smooth transitions reduce Kt. Notch sensitivity (q) ranges from 0 to 1 and is often 0.5–0.9 for many metals, depending on microstructure and radius.
This calculator provides Kt for geometry and converts it to a fatigue concentration factor Kf using Kf = 1 + q(Kt − 1). If q is low, the detail behaves less notch-sensitive and Kf stays closer to 1. If q is high, Kf approaches Kt and peak stresses increase sharply.
Consider a nominal equivalent stress of 85 MPa with a plate-hole detail using d/W = 22/120. The estimated Kt is about 2.52. With q = 0.70, Kf becomes roughly 2.06. Applying a 1.10 design factor gives σpeak ≈ 85 × 2.06 × 1.10 ≈ 192 MPa, matching the example table trend.
Use the CSV/PDF exports to document assumptions, compare alternatives, and support QA reviews. If σpeak approaches allowable limits, consider increasing radii, adding reinforcement, improving weld profile, reducing discontinuities, or rechecking loads. Always confirm final factors against project standards and inspection practices.
Kt is the geometric stress concentration factor. Kf is the fatigue stress concentration factor that accounts for notch sensitivity using Kf = 1 + q(Kt − 1).
Use Kt when you want a purely geometric amplification for a static-style check or when your procedure specifies Kt directly. For fatigue-sensitive evaluations, Kf is usually more representative.
q is notch sensitivity, from 0 to 1. Lower values mean the material is less affected by notches, reducing fatigue amplification. Higher values mean the detail’s fatigue response closely follows Kt.
Combined loading is common in frames, brackets, and supports. The calculator forms an equivalent nominal stress using axial, bending, and torsional shear so the intensification applies to a consistent baseline.
This is a general estimator for stress concentration and fatigue intensification. For piping components that require tabulated SIFs, follow the applicable piping standard and verified manufacturer or code tables.
Select it to reflect dynamics, uncertainty, and project guidance. For example, higher factors may be used for vibration-prone supports or uncertain load paths. Keep it consistent with your overall design approach.
A utilization above 1.0 indicates σpeak exceeds the allowable stress you entered. Recheck inputs, confirm load combinations, and consider reducing discontinuities, increasing radii, strengthening the section, or revising the detail.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.