Structural Integrity Assessment of Componets with Low Constraint

When performing Structural Integrity assessments using Failure Assessment Diagrams, a point with coordinates K

r

and L

r

is representative of the component situation. The first one represents its situation against fracture and the second one against plastic collapse:

(1)

$$ K_r = \frac{{K_I }} {{K_{IC} }},{\text{ }}L_r = \frac{P} {{P_L }} $$

The fracture toughness value, K

IC

, is obtained in tests under high constraint conditions in such a way that the obtained value is a lower bound of the material resistance to fracture. This working scheme often leads to overconservative results when the component being assessed has lower constraint conditions, as shown in Fig.1, where point A represents the component at failure. The point should lead over the Failure Assessment Line (point B) but actually it is far away from it, leading to a safety factor bigger than two (defined as OA/OB).