Estimation of Fracture Toughness by Testing Notched Fracture Specimens and Applying the Theory of Critical Distances

Abstract

This paper applies a methodology that allows the fracture toughness of a given material to be estimated by testing notched fracture toughness specimens and applying the Theory of Critical Distances, which requires the elastic stress field at the notch tip to be determined by finite elements simulation. This methodology, which is not intended to substitute any standardised fracture characterisation procedure, constitutes an alternative in those situations where pre-cracking processes may be too time-consuming, too expensive or, simply, cannot be performed. It comprises testing two notched specimens with different notch radii, defining the corresponding stress fields at fracture by using finite elements analysis, and applying the Theory of Critical Distances in order to calibrate the material's critical distance and to apply the corresponding apparent fracture toughness formulation. The methodology has been applied to two different materials, PMMA and Al7075-T651, and the results have proven that, as long as the Theory of Critical Distances has been applied within its validity range, the fracture toughness estimations are highly accurate.

Investigation of production parameters in fracture behavior of hot‐pressed Al2O3–SiC/graphite fibrous monolithic ceramics: Fibers orientation and cell boundary fraction

“…As regards in laminated structures, radial‐median cracks may not form under a Knoop indent or precracking process may be too time‐consuming or, simply, cannot be performed, in this work for estimating fracture toughness, SENB method was applied. Results containing different fibers orientations, except the direction of 90°, and cell to cell boundary volume ratios were presented in Table .…”

Investigation of Fracture Toughness of Bidirectional Jute / Epoxy Composite and Analysis by using FEA

“…The three-dimensional computational results show a good agreement with the experiments, except for the load region where the global deformations were dominated by the Lueders zone in the material stress-strain curve. S. Cicero [11] study applies a methodology that allows the fracture toughness of a given material to be estimated by testing notched fracture toughness specimens and applying the Theory of Critical Distances, which requires the elastic stress field at the notch tip to be determined by finite element simulation. This methodology, which is not intended to substitute any standardized fracture characterization procedure, constitutes an alternative in those situations where pre-cracking processes.…”