On the Line Method apparent fracture toughness evaluations: Experimental overview, validation and some consequences on fracture assessments

Abstract

This paper analyses the capacity of the Line Method to provide evaluations of the apparent fracture toughness, which is the fracture resistance exhibited by materials in notched conditions. With this aim, the experimental results obtained in 555 fracture tests are homogeneously presented and compared to the Line Method evaluations. It is remarked that the Line Method provides adequate estimates of the apparent fracture toughness, and also that it conveniently addresses the physics of the notch effect. All this makes the Line Method a valuable scientific and engineering tool for the fracture assessment of materials containing notches.

On the assessment of U-shaped notches using Failure Assessment Diagrams and the Line Method: Experimental overview and validation

“…With the aim of reducing the number of unsafe predictions when applying the notch correction in the FAD, the lower bound expression of the LM proposed in [41] will be used here. Equations (16) and (17) gather the notch correction and the corresponding K r correction, respectively.…”

“…Equations (16) and (17) gather the notch correction and the corresponding K r correction, respectively. The "0.73" factor intends to capture the scatter observed in the fracture toughness results obtained in cracked conditions [41], intending to provide a 95% confidence level of the whole population of tests. This factor, together with the "20" factor inside the square root provide a lower estimate of the apparent fracture toughness results of the 555 tests used here.…”

“…The authors have recently provided [41] a wide validation of the LM, demonstrating the accuracy of its apparent fracture toughness predictions through its homogenous application to 555 experimental results. From an engineering (and scientific) point of view, the next step consists in using such apparent fracture toughness predictions to perform structural integrity assessments, given that fracture is not the only failure mechanism and, thus, equation (12) would not be sufficient in many practical situations (those where plastic collapse is the main failure mechanism and those where the failure is a consequence of the interaction between fracture and plastic collapse).…”

Estimation of Fracture Loads in AL7075-T651 Notched Specimens Using the Equivalent Material Concept Combined with the Strain Energy Density Criterion and with the Theory of Critical Distances

“…These two criteria are the Theory of Critical Distances (TCD) [1][2][3][4][5][6][7][8] and the Strain Energy Density (SED) criterion [9][10][11][12][13][14][15][16][17]. The TCD has been successfully applied to polymers (e.g., [1,2]), metals (e.g., [2][3][4]), composites (e.g., [5]) and rocks (e.g., [6]), and has also been combined with Failure Assessment Diagrams in order to provide structural integrity assessment methodologies for structural components containing notches [7]. A comprehensive review of the TCD may be found in [8].…”

“…Both of them (TCD and SED) have a linear-elastic nature and provide accurate predictions when analyzing fracture conditions in brittle materials. When applied in more ductile situations, the TCD may still be applied after a calibration process (e.g., [1,2,5]), while the SED criterion loses accuracy (e.g., [13,15,16]). …”