Fatigue Crack Initiation
Fatigue crack initiation is the start of a microscopic crack at locations with uneven stresses or inhomogeneities due to repeated loading. It leads to fatigue fracture.
Physicochemical Mechanism of Action
Fatigue crack initiation occurs when microscopic cracks form at geometric notches or structural inhomogeneities. These cracks are enlarged by local slip band formation during cyclic loading and can lead to fatigue fracture.
Metallurgical Relevance & Risks in Welding
Fatigue phenomena can lead to microscopic cracks that propagate under repeated loading. This can cause macroscopic cracks and deterioration of the material's mechanical properties. One example is fatigue phenomena in weld metal areas under high stress cycles.
Workshop Practice & Action Guidelines
To avoid fatigue crack initiation, the following measures should be taken:
• Use high-quality materials with low stress concentration.
• Reduce loading through optimized design and geometry.
• Choose appropriate welding processes to minimize stress cycles.
• Regularly inspect the mechanical properties of the material under cyclic loading.