Analysis of Crack Arrest Toughness.

Abstract : The objective of the research was to provide theoretical and experimental backing for three concepts that will facilitate the design of structures capable of arresting cracks. The first concept is that the conventional static toughness measures, JIc or the JR curve, are bona fide measures of the fracture arrest capability of tough ductile steels. The second is that the J-values represent the crack driving force when a crack arrests in a tough material, provided the bulk of the propagation just prior to arrest occurs in a relatively brittle material. The work includes (1) Verification of J-intergal evaluation of arrest properties: (a) Analysis of the crack velocity dependence of toughness for the fibrous mode of crack extension; (b) A new test method for studying fast fracture and arrest in tough steels; (c) Measurements of fast fracture and crack arrest; (d) Fractographic studies; (2) Application of J-resistance curve concept to crack arrest: (a) Development of a finite element model for analysis of a rapidly loaded stationary crack of a compact specimen of a tough, rate dependent steel; (b) Development of a general method for quantifying temperature and rate-sensitive constitutive relations for steel; (c) Development of crack extension capability using 'local control' in the finite element program; (d) Finite element modeling of rapid crack extension in ductile viscoplastic materials.