The fatigue performance of S355J0WP weathering steel is generally comparable to conventional S355 structural steel, but with some unique considerations due to its weathering properties. Here's a concise yet comprehensive analysis:
1. Fatigue Strength Basics
Endurance Limit:
Like most carbon steels, S355J0WP exhibits a fatigue limit (stress below which failure won't occur, typically ~50–60% of its tensile strength). For S355J0WP (Rm = 470–630 MPa), this translates to ~200–250 MPa at 10⁷ cycles (varies with stress ratio R and surface conditions).
SN Curve Behavior:
Follows standard ferritic-pearlitic steel trends, with fatigue life decreasing under higher stress amplitudes.
2. Key Influencing Factors
Surface Condition:
The protective patina layer itself has minimal impact on fatigue.
However, initial pitting (before patina forms) or corrosion fatigue (in aggressive, wet environments) can reduce fatigue life by up to 20–30% versus inert conditions.
Welding & Notches:
Weld toes and fabrication defects (e.g., slag inclusions) act as stress concentrators, significantly lowering fatigue resistance.
Post-weld treatments (e.g., grinding, peening) improve performance.
3. Comparison to Ordinary Carbon Steel
Uncorroded State: Similar fatigue strength to S355JR (non-weathering).
Long-Term Exposure:
In dry/stable environments, the patina's self-limiting corrosion preserves fatigue life.
In cyclic wet/dry or salt-laden conditions (e.g., coastal bridges), fatigue resistance may degrade faster than painted carbon steel unless maintained.
4. Design Recommendations
Eurocode 3 (EN 1993-1-9): Use Fatigue Detail Category 71–112 (depending on joint type, similar to S355).
Critical Applications:
Monitor for pitting in high-stress areas.
Consider protective coatings if corrosion fatigue is a risk (e.g., splash zones).
5. Testing & Real-World Data
Laboratory tests show ~10–15% lower fatigue limits in simulated industrial/marine atmospheres versus controlled dry air.
Field data from weathering steel bridges (e.g., UK/Europe) indicate satisfactory performance when designed per standards.
