The FatigueLab Material Library provides reference fatigue properties for commonly used engineering materials. These values help engineers estimate fatigue life, select appropriate materials, and perform fatigue damage analysis using the FatigueLab Calculators.
1. Introduction
Fatigue failure occurs when materials experience repeated stress cycles over time.
Even when stresses remain below the yield strength, cyclic loading can initiate
micro-cracks that gradually propagate until final fracture occurs.
Material fatigue properties are therefore essential for predicting fatigue life and
designing reliable engineering components such as shafts, aircraft structures,
automotive parts, and rotating machinery.
All stress values listed in this library are approximate reference values expressed
in MPa (megapascals). Actual fatigue performance depends on heat treatment,
surface finish, temperature, and loading environment.
2. Common Engineering Materials
| Material | Yield Strength (MPa) | Ultimate Strength (MPa) | Endurance Limit (MPa) | Notes |
|---|---|---|---|---|
| AISI 1020 Steel | 350 | 420 | 210 | Low carbon steel |
| AISI 1045 Steel | 530 | 570 | 290 | Common shaft material |
| AISI 4140 Alloy Steel | 655 | 850 | 305-420 | High strength alloy steel |
| Aluminum 6061-T6 | 275 | 310 | ~96 (10⁷ cycles) | No true endurance limit |
| Aluminum 7075-T6 | 503 | 540 | ~160 (10⁷ cycles) | Aerospace applications |
| Stainless Steel 304 | 215 | 505 | No clear limit | Corrosion resistant |
| Titanium Ti-6Al-4V | 880 | 950 | 510-600 | High strength-to-weight |
3. S-N Curve Parameters (Basquin Equation)
In high-cycle fatigue analysis, the stress-life relationship is often represented
using Basquin’s equation:
σₐ = A · N−b
Where A and b are material fatigue constants obtained from experimental testing.
| Material | A (MPa) | b |
|---|---|---|
| 1045 Steel | 1500 | 0.085 |
| Aluminum 6061-T6 | 850 | 0.10 |
| Ti-6Al-4V | 1800 | 0.06 |
4. Surface Finish Effects on Fatigue Strength
Surface condition significantly influences fatigue life because fatigue cracks
usually initiate at the surface of a component.
| Surface Condition | Fatigue Strength Effect |
|---|---|
| Polished | Highest fatigue strength |
| Machined | Moderate fatigue strength |
| Hot-Rolled | Reduced fatigue strength |
| Forged | Depends on finishing |
5. Fatigue Design Correction Factors
Actual fatigue strength in engineering design is often adjusted using correction factors.
- Surface finish factor
- Size factor
- Temperature factor
- Reliability factor
- Loading factor
These factors allow engineers to estimate realistic fatigue strength values for
actual operating conditions.
6. Using Material Data in Fatigue Calculations
Material fatigue properties can be used together with stress history data to estimate
fatigue damage and remaining life of engineering components.
You can perform fatigue calculations using the FatigueLab Damage Calculator
Simply upload stress history data in CSV format, apply rainflow cycle counting,
and evaluate fatigue damage using S-N curves and Miner’s Rule.