Workflow for fatigue and durability analysis - cycle counting, damage accumulation, and fatigue life prediction.
Predict fatigue life from FEA stress results using S-N curves and damage accumulation.
Route here when user mentions:
Route elsewhere:
/abaqus-static-analysis/abaqus-static-analysisAbaqus has limited native fatigue capabilities. The typical workflow is:
For full fatigue analysis, consider external tools: fe-safe, nCode, FEMFAT.
Before fatigue analysis:
Use /abaqus-static-analysis for constant loads or /abaqus-dynamic-analysis for time-varying.
Ensure output requests include:
S - Stress components (principal, Mises)E - Strain componentsPEEQ - Equivalent plastic strain (for low-cycle)Find the maximum stress location:
/abaqus-odb to extract peak stressFor constant amplitude: single max/min stress values. For variable amplitude: full stress-time history for rainflow counting.
Use appropriate method based on loading and life regime.
Apply Basquin equation for life, Miner's rule for cumulative damage.
| Approach | When to Use | Data Needed |
|---|---|---|
| Stress-life (S-N) | High-cycle (N > 10^4) | S-N curve |
| Strain-life (e-N) | Low-cycle (N < 10^4) | Coffin-Manson params |
| Fracture mechanics | Crack growth | da/dN curve |
| Loading | Analysis Method |
|---|---|
| Constant amplitude | Single static analysis |
| Variable amplitude | Multiple loads + rainflow |
| Proportional | Single load case |
| Non-proportional | Critical plane method |
| Method | Use Case |
|---|---|
| Goodman | Conservative, tensile mean |
| Gerber | Less conservative |
| Soderberg | Very conservative |
| SWT | Strain-life with mean stress |
If unclear, ask:
| Parameter | Typical Values | Notes |
|---|---|---|
| S-N slope (b) | 0.08-0.15 | Lower = longer life |
| Endurance limit | 40-50% UTS (steel) | Stress below which infinite life |
| Fatigue notch factor (Kf) | 1.0-3.0 | Kf = 1 + q(Kt-1) |
| Notch sensitivity (q) | 0.7-0.95 | Higher for stronger steels |
| Problem | Cause | Solution |
|---|---|---|
| Unrealistically short life | Stress singularity | Use Kf correction, refine mesh away from singularity |
| Wrong units | MPa vs Pa mismatch | Verify stress units match S-N data |
| Unconservative prediction | Missing mean stress | Apply Goodman/Gerber correction |
| Very long calculated life | Stress below endurance limit | Check if stress > endurance limit |
/abaqus-static-analysis - Base stress analysis/abaqus-dynamic-analysis - Time-varying loading/abaqus-amplitude - Cyclic loading definition/abaqus-odb - Extract stress history from resultsFor API syntax, equations, and code examples, see: