| Case |
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|---|---|---|
| Geometry | ||
| No dimensions needed; Kt depends only on the stress ratio. | ||
| D | ||
|---|---|---|
| d | ||
| di | ||
| h | ||
| r | ||
| t | ||
| a | ||
| b | ||
| Loading & Material | ||
| Axial Force P | ||
|---|---|---|
| Bending Moment M | ||
| Torque T | ||
| Remote Stress σ1 | ||
| Remote Stress σ2 Stress perpendicular to σ₁ (positive = tension). Leave 0 or blank for uniaxial. | ||
| Notch Sensitivity q 0 to 1. Kf = 1 + q(Kt − 1). Use 1 (default) for brittle materials or when unsure; ductile metals with large radii approach 1, small radii and soft materials are lower. See Peterson/Neuber charts. | ||
| Material | ||
| Grade | ||
| Yield Strength Sy Filled from the material library; edit freely (pick Custom to keep your own values when switching units). For plastics without a listed yield, tensile strength is used. | ||
| Ultimate Strength Su | ||
| Endurance Limit Se' Uncorrected rotating-beam endurance limit (steels: 0.5·Su; aluminums: fatigue strength at 5×10⁸ cycles). Blank = no fatigue check. | ||
| Marin Factor k Product of endurance-limit modifying factors ka·kb·kc·kd·ke (surface, size, load, temperature, reliability). Se = k·Se'. Typical machined steel shaft ≈ 0.6–0.8. Default 1. | ||
| Stress Concentration Kt | ||
|---|---|---|
| Fatigue Factor Kf | ||
| Nominal Stress | ||
| Peak Stress | ||
| Fatigue Peak | ||
| Yield FOS Sy / peak (Kt) stress. Conservative for ductile metals under static load, which yield locally and redistribute; for those, compare Sy to the nominal stress too. | ||
| Ultimate FOS Su / peak (Kt) stress. Most relevant for brittle materials (cast iron, many plastics), where Kt applies fully to static loads. | ||
| Fatigue FOS k·Se' / (Kf·nominal) for a fully reversed load of the entered amplitude. For mean + alternating loads use Goodman with these numbers. |