Principal materials engineer, TRW Aeronautical Systems, Shaftmoor Lane, Birmingham,
Senior lecturer, The University of Wolverhampton, Wolverhampton,
(Received 19 April 2000; accepted 14 December 2000)
The single-edge precracked-beam (SEPB) fracture toughness method has been investigated using finite element methods to analyze the stress intensity (KI) resulting from variations in bridge span, punch length, and virtual crack length. A two-dimensional half-plane, semi-infinite model was used to approximate the stress intensity from a fit of the nodal displacements of a crack face under SEPB loading conditions. The finite element method models the crack in situ, using six-node triangular elements specified around a singular point that simulates the crack tip.
The analysis reveals that for increasing virtual crack length (a), the stress intensity increases to a maximum where ΔKI/Δa = 0. With further increasing virtual crack length, the stress intensity decreases. The inflection point ai, KIi differs for varying span and fixed punch length, and for varying punch lengths with fixed span.
The resulting stress intensities per new ton force loading are presented in tabular and graphical form. The presented series of graphs can be used to explore variations in precracking parameters. This finite element analysis provides useful data for those developing or adopting the SEPB fracture toughness measurement technique.
Paper ID: JTE12257J