Linear-elastic fracture mechanics (LEFM)

This chapter presents a concise description of linear-elastic fracture mechanics, starting with the 1 / r crack-tip stress singularity and the definition of the stress-intensity factor K to define the crack-tip stress distribution in a linear-elastic solid. Solutions for the crack-tip stress and displacement fields in mode I, II, and III are tabulated together with K-solutions for a variety of crack configurations and test geometries. The criterion for the measurement of the plane-strain fracture toughness, K Ic, is described, together with the test methods, in light of the size of the local plastic zone which defines the specimen size requirements for small-scale yielding and plane strain. The corresponding energy approach, based on the strain-energy release rate is also presented, together with the measurement of toughness under non-plane-strain conditions using crack-resistance curves. Finally, a description of mixed-mode fracture mechanics is presented, for inclined cracks, deflected cracks, cracks in dissimilar interfaces, and cracks subjected to multi-axial loading.