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Steel is widely used because of its unique properties. It’s a material known for its high strength, resistance to mechanical damage, and tolerance to harsh environmental conditions. A key factor in its performance is fatigue strength. Depending on the type of iron alloy, the fatigue resistance will vary for bending, tension, and torsion.
Material fatigue refers to the reduction of mechanical strength due to repeated or variable loading. Damage does not occur immediately—it happens only after a certain number of load cycles.

When Can We Talk About Material Fatigue?

Although steel is a very strong and durable material, it eventually deteriorates under repetitive stress. Steel is often used as a structural material, and problems arise when long-term cyclic loads occur—something unavoidable in many applications.Material Fatigue Continuous stress gradually alters the mechanical properties of steel, reducing its service life and durability.
Interestingly, the magnitude of stress doesn’t have to be high. This can be compared to a drop of water that, over time, carves a hole in solid rock. Similarly, cyclic stresses—even at lower values than the metal’s yield strength—can lead to fatigue failure.
Thus, material fatigue occurs when small cracks form and propagate in the material due to cyclic loading.

What Should You Know About Material Fatigue?

Material fatigue is one of the most significant challenges in steel construction, as it accelerates structural degradation. Each material can withstand a specific number of load cycles before failure. The type, sequence, and duration of loads influence fatigue behavior.
When designing steel structures, engineers always consider fatigue strength. Various methods are used to determine it, most notably the Wöhler curve test. Fatigue life can also be estimated using damage accumulation laws and stress amplitude ranges.
In some cases, materials exhibit infinite fatigue life, meaning no fatigue fracture occurs within the tested range. The fatigue limit depends on the type of stress — tension, compression, or bending.
Modern fatigue testing is performed with advanced hydraulic testing machines, enabling precise evaluation of steel endurance.