Crack assessment with fracture mechanics methods

Crack Lossy welding details can be assessed with fracture mechanics methods. Using the example of both sides welded butt weld is to show how advances a technical crack initiation at the fatigue critical weld toe until it comes to rest break. The overall life ultimately emerges from the number of cycles to crack initiation (determined with the notch strain concept KDK) and the number of cycles to failure (determined using the crack propagation concept RFK).

The following figures show single Crack stages of 1 mm to 10 mm are shown. In the diagram, the stress intensity factor (SIF) KI on the number of cycles N is evaluated. This means that statements about the remaining service life for steel structures (in this case welding detail) possible. Such inspections can be determined using the crack propagation concept.

Fatigue life as a function of crack propagation
Stress intensity factor as a function of crack propagation

Individual stages of crack growth in a butt weld

Initial crack a = 1mm
Initial crack a = 3mm
Initial crack a = 7mm
Initial crack a = 10mm