KEVOS® MAKEOS · Springs
Compression Spring Fatigue Check (Working Stroke, Goodman Factor)
Will this compression spring survive millions of cycles between its preload and working lengths, by the Goodman criterion and against first-cycle yield?
Fatigue check of a helical compression spring cycling between two lengths: rate, loads and corrected shear stresses at the preload and working lengths and the solid length (as the compression spring tool), the alternating and mean shear stresses, and the Goodman, Soderberg and Gerber factors with first-cycle yield (as the Goodman fatigue tool, using the torsional endurance limit, ultimate and yield of the wire), against your required factor.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Wire diameter | mm | Wire diameter. |
| Mean coil diameter | mm | Mean coil diameter. |
| Active coils | coils | Active coils. |
| End type | choice | End type of the spring. |
| Shear modulus | GPa | Shear modulus of the wire. |
| Unloaded length | mm | Length with no load. |
| Preload (longest working) length | mm | Length at the smallest working load (preload). |
| Working (shortest) length | mm | Length at the largest working load. |
| Wire strength (torsional) | ||
| Torsional endurance limit (corrected) | MPa | Torsional endurance limit of the wire, corrected for surface finish and shot peening (from your spring data). |
| Torsional ultimate strength | MPa | Torsional ultimate strength of the wire (often about 0.67 × tensile). |
| Torsional yield strength | MPa | Torsional yield strength of the wire. |
| Required fatigue safety factor | Safety factor you need against fatigue. | |
Method and formulas
- k = G d⁴ ÷ 8 D³ N_a; F = k (L₀ − L); τ = K 8 F D ÷ π d³ with the Wahl factor (as the compression spring tool).
- τ_a = (τ₂ − τ₁) ÷ 2; τ_m = (τ₂ + τ₁) ÷ 2.
- Goodman n = 1 ÷ (τ_a ÷ S_es + τ_m ÷ S_us); yield n = S_sy ÷ (τ_a + τ_m) (as the Goodman fatigue tool).
- Example: the spring cycles between 233.49 and 437.8 MPa; Goodman factor 1.5757.
Limitations
- Wahl factor applied to both mean and alternating stress (conservative).
- Infinite-life criteria; surge and resonance at high speed need a separate check.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a valve, clutch or die spring for fatigue life
- Choose a working stroke that gives infinite life
- Compare spring wire grades
Who it is for
- Design engineers
- Spring designers
- Machine designers
What you get
- Loads and stresses at both lengths
- Alternating and mean stresses
- Goodman, Soderberg, Gerber and yield factors
Interpreting the result
- Shot peening raises the endurance limit far more than a stronger wire does.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 304–324, 200–211. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Compression Spring Fatigue Check (Working Stroke, Goodman Factor) calculator
