Spricktmekanik

Spricktmekanik, or fracture mechanics, is the branch of mechanics focused on understanding how and why cracks form and propagate in materials subjected to stresses. It combines fracture theory, material properties, and stress analysis to predict crack growth and failure.

Key concepts include the stress intensity factor K, the critical fracture toughness K_IC, and energy-based measures such as the energy release rate G and the J-integral. Linear elastic fracture mechanics (LEFM) assumes small-scale yielding and is used for brittle materials and high-strength steels; elastic-plastic fracture mechanics (EPFM) accounts for plastic deformation near the crack tip.

Crack growth can occur under static loading or cyclic loading (fatigue). The fatigue behavior is often described by the crack growth rate da/dN versus the stress intensity range Delta K, with thresholds and Paris-type relations describing the rate of growth at different loading levels. Experimental determination uses standard specimens such as compact tension (CT) and three-point bending to measure K_IC and to characterize crack growth. Numerical methods, notably finite element analysis, are used to compute K, G, or J for complex geometries.

Applications and design practices in spricktmekanik aim to ensure structural integrity by predicting crack initiation and propagation to prevent catastrophic failure. The field is essential in aerospace, automotive, civil engineering, energy systems, and materials research, guiding material selection, inspections, and maintenance schedules.

Historical development began with Griffith's energy criterion in the 1920s and Irwin's formalization of fracture mechanics concepts in the 1950s. The discipline continues to address environmental effects, such as corrosion and hydrogen embrittlement, and to extend to microstructural phenomena and small-scale yielding.