On “lower bound crack resistance curves” as material law for the safety assessment of components

Abstract Experimental fracture-mechanics investigations were carried out on large scale specimens. The specimen geometries and the crack depth ratio, a / W , in a parameter field were varied. Three materials of different toughness were chosen for the specimens. Their load—deformation behaviour, crack resistance curves, stretched zones Δa ; and crack inititiation values J i were determined and compared with the results from CT25 specimens. Numerical finite-element calculations were made to determine the state of stress in the specimens and the size of the plastic zones.