Understanding Metal Fatigue: Causes, Consequences, and Prevention

Metal fatigue can cause sudden, catastrophic failures—such as a fan blade detaching from a jet engine—without any obvious warning. To prevent these incidents, engineers must first grasp how repeated stresses interact with a metal’s microstructure.

How Stresses Lead to Fatigue

When a metal component is bent, the outer surface experiences tension while the inner surface is compressed. Reversing the bend swaps these stresses. Repeatedly cycling these forces creates microscopic cracks that grow silently until a failure occurs.

Additional Factors That Accelerate Fatigue

Beyond bending, manufacturing defects, corrosion, temperature swings, wear, and vibrational loads also lower a part’s fatigue life. Stress concentrators—such as the edges of holes—can further reduce durability. Engineers evaluate a material’s fatigue strength by testing multiple specimens under cyclic loading and plotting the results on an S–N curve, as recommended by ASTM E466 and ISO 6892.

Common Forms of Fatigue Failure

• Thermal fatigue – caused by rapid temperature changes in the environment or from intermittent operation.
• Corrosion fatigue – corrosive media initiate microcracks that are then enlarged by cyclic stress.
• Vibration fatigue – excessive vibration generates high cyclic stresses beyond design limits.
• Mechanical fatigue – general repeated loading, often combined with environmental degradation.

Design Strategies to Mitigate Fatigue

By knowing a material’s fatigue limit, engineers can conduct finite‑element fatigue analyses, redesign geometries to smooth stress risers, or select alloys with higher endurance limits. Applications that routinely face cyclic stresses include:

• Jet engine turbofans and rotating compressors
• Aircraft fuselage and wing skins
• Off‑road vehicle suspensions
• Bridge decks subjected to traffic and wind loads
• Automotive drivetrain components
• Manufacturing presses and robotic arms
• Any part exposed to sustained vibration

Material Selection Matters

Choosing alloys with inherent corrosion resistance and high thermal conductivity—such as 7075‑Al, 316‑SS, or duplex stainless steels—significantly reduces fatigue susceptibility. We provide comprehensive material test reports for all aluminum, stainless steel, and carbon steel sheets, plates, and long products.

Aviation‑Specific Considerations

Aircraft components endure cyclic pressure, temperature, and atmospheric exposure, leading to gradual crack growth in aluminum, carbon steel, and stainless steel. Critical zones include:

• External skin panels under aerodynamic load
• Internal structural members carrying high stresses

Routine inspections and surface polishing—often performed under FAA or EASA guidelines—extend fatigue life.

Preventing Fatigue with High‑Performance Materials

Optimal design, careful material selection, and proactive maintenance together minimize fatigue risks. Industrial Metal Supply offers a broad inventory of metals and accessories; visit any of our six California or Arizona locations for expert advice and detailed material test reports.