Some recent criteria for brittle fracture assessment under mode II loading

Abstract

Different criteria are available in the literature to assess the fracture behaviour of sharp Vnotches. A typical and well-known criterion is based on the application of the notch stress intensity factors (NSIFs), which are able to quantify the intensity of the stress fields ahead of the notch tip. This work considers two recent energy-based criteria applied here to sharp Vnotches. The first criterion is based on the averaged value of the strain energy density (SED), while the second one called Finite Fracture Mechanics (FFM) criterion is available under two different formulations: that by Leguillon et al. and that by Carpinteri et al. Considering the averaged SED criterion, a new expression for estimating the control radius Rc under pure Mode II loading is proposed and compared with the sound expression valid under pure Mode I loading. With reference to pure Mode II loading the critical NSIF at failure can be expressed as a function of the V-notch opening angle. By adopting the three criteria considered here the expressions for the NSIFs are derived and compared. After all, the approaches are employed considering sharp V-notched brittle components under in-plane shear loading, in order to investigate the capability of each approach for the fracture assessment. With this aim a bulk of experimental data taken from the literature is used for the comparison.

An experimental and theoretical comparison of CCNBD and CCNSCB specimens for determining mode I fracture toughness of rocks

“…The rock specimen for K Ic measurements usually has either a straight‐through notch or a chevron notch. The straight‐through notch is often regarded as the critical crack whose length is directly correlated to the fracture toughness calculation, so the notch tip must be machined to be very sharp, as the local stresses/strains/energies ahead of a blunt notch tip are quite different from those ahead of a crack tip . Otherwise, costly precracking procedures are needed for the straight‐notch specimens to generate a crack.…”

Aging effect on combined mode fracture resistance of bitumen

“…However some other researchers have demonstrated that by considering more precise description for the crack tip stress/strain field, more accurate theoretical predictions can be obtained for combined mode fracture of brittle materials . For instance, taking into account the influence of first nonsingular stress term (often called T ‐stress) in addition to K I and K II via the generalized MTS criterion proposed first by Smith et al can reduce significantly the difference between the test data and theoretical predictions of combined mode I + II fracture in several engineering brittle materials . The practical ability of such theoretical frameworks has rarely been investigated till now for crack growth behaviour of aged and unaged bitumen and binder.…”

“…[65][66][67][68] For instance, taking into account the influence of first nonsingular stress term (often called T-stress) in addition to K I and K II via the generalized MTS criterion proposed first by Smith et al 65 can reduce significantly the difference between the test data and theoretical predictions of combined mode I + II fracture in several engineering brittle materials. [69][70][71][72][73][74][75] The practical ability of such theoretical frameworks has rarely been investigated till now for crack growth behaviour of aged and unaged bitumen and binder. Hence in the following, the ability of conventional and generalized MTS criteria are examined for predicting the combined mode I + II fracture toughness data obtained for the aged and unaged 30/40 bitumen.…”

Fatigue surface crack propagation and intersecting cracks in connection with welding residual stresses

“…In spite of significant progress in the study of the effect of welding residual stress on the fatigue crack growth rate, the interpretation of most results is given in terms of the stress intensity factor in the framework of the validity of linear elastic fracture mechanics. It should be noted that other failure theories such strain‐based criteria can also be used to predict the fatigue life of welded structures …”