korroosioväsymys

korroosioväsymys, known in English as corrosion fatigue, is a material failure process that occurs when a metal is simultaneously subjected to cyclic mechanical loading and corrosive environmental conditions. The combination of stress and corrosion accelerates crack initiation and propagation much faster than either stress or corrosion alone. This mechanism is especially relevant in high‑strength steels, aluminum alloys, and other engineering materials used in automotive, aerospace, marine, and civil infrastructure where both dynamic loads and aggressive media such as saltwater, acid, or chlorides are present.

The initiation of corrosion‑fatigue cracks typically begins at sites of surface roughness, inclusions, or corrosion pits. During the compressive portion of a loading cycle, the crack may be sub‑critical and not propagate, but during the tensile phase, the stress intensity at the crack tip exceeds the material’s resistance. Corrosion products can act as a conduit for further oxygen diffusion, increasing the local solubility and facilitating crack growth. The crack growth rate follows a Paris‐type law modified by a corrosion‑enhancement factor, which depends on the specific environment, temperature, and stress range.

Detection of korroosioväsymys is performed through non‑destructive evaluation methods such as acoustic emission, eddy current testing, magnetic flux leakage, and periodic visual inspection, often augmented by accelerated corrosion‑fatigue testing in laboratories. Design mitigation strategies include the use of corrosion‑resistant alloys or protective coatings, stress relief treatments, fatigue pre‑loading (residual compressive stress), and environmental controls such as de‑humidification or sacrificial anodes. Life‑prediction models incorporate both mechanical fatigue data and corrosion rate measurements to estimate service life under realistic operating conditions. By acknowledging that corrosion and fatigue are synergistic, engineers can avoid premature failure and enhance the durability and safety of critical structural components.