4,781 research outputs found
Corner point singularities under in-plane and out-of-plane loading: A review of recent results
No full textThe linear elastic analysis of homogeneous, isotropic cracked bodies started in the 1900s. The existence of three dimensional corner point effects in the vicinity of a corner point where a crack front intersects a free surface was investigated in the late 1970s. An approximate solution by Bažant and Estenssoro explained some features of corner point effects but there were various paradoxes and inconsistencies. Results derived from finite element models showed that the analysis is incomplete. The stress field in the vicinity of a corner point appears to be the sum of two different singularities (i.e. stress intensity factors and corner point singularities). In this paper some recent results for the corner point singularities under in and out of plane loadings is reviewed and discussed
Fatigue Crack Paths. Special Issue of the International Journal Fatigue and Fracture of Engineering Materials and Structures
No full text
Coupled fracture modes under anti-plane loading
Full text linkThe linear elastic analysis of homogeneous, isotropic cracked bodies is a Twentieth Century
development. It was recognised that the crack tip stress field is a singularity, but it was not until the introduction
of the essentially two dimensional stress intensity factor concept in 1957 that widespread application to practical
engineering problems became possible. The existence of three dimensional corner point effects in the vicinity of
a corner point where a crack front intersects a free surface was investigated in the late 1970s: it was found that
modes II and III cannot exist in isolation. The existence of one of these modes always induces the other. An
approximate solution for corner point singularities by Bažant and Estenssoro explained some features of corner
point effects but there were various paradoxes and inconsistencies. In an attempt to explain these a study was
carried out on the coupled in-plane fracture mode induced by a nominal anti-plane (mode III) loading applied
to plates and discs weakened by a straight crack. The results derived from a large bulk of finite element models
showed clearly that Bažant and Estenssoro’s analysis is incomplete. Some of the results of the study are
summarised, together with some recent results for a disc under in-plane shear loading. On the basis of these
results, and a mathematical argument, the results suggest that the stress field in the vicinity of a corner point is
the sum of two singularities: one due to stress intensity factors and the other due to an as yet undetermined
corner point singularity
Coupled fracture mode of a cracked plate under anti-plane loading
No full textThe existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Despite increased understanding, three-dimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study a coupled fracture mode generated by a nominal anti-plane (Mode III) loading applied to linear elastic plates weakened by a straight through-the-thickness crack. With this aim accurate 3D finite element (FE) analyses have been performed. The results obtained from the highly accurate finite element models have improved understanding of the behaviour of through cracked plates under anti-plane loading. The influence of plate bending is increasingly important as plate thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the plate surfaces. Discussion on whether KIII tends to zero or infinity as a corner point is approached is futile because KIII is meaningless at a corner point. Calculation of the strain energy density (SED) in a control volume at the crack tip allows us to predict the most critical point through the plate thicknes
Coupled fracture mode of a cracked disc under anti-plane loading
No full textThe existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Understanding improved when the existence of corner point singularities and their implications became known. Despite increased understanding, three-dimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study by means of accurate 3D finite element (FE) models a coupled fracture mode generated by anti-plane loading of a straight through-the-thickness crack in linear elastic discs. The results obtained from the highly accurate finite element analyses have improved understanding of the behaviour of through cracked discs under anti-plane loading. The influence of plate bending is increasingly important as disc thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the disc surfaces. Calculation of the strain energy density (SED) in a control volume at the crack tip shows that the position of the maximum SED is a function of disc thickness
Coupled fracture mode of a cracked disc under anti-plane loading
Full text linkThe existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Understanding improved when the existence of corner point singularities and their implications became known. Increasingly powerful computers made it possible to investigate three-dimensional effects numerically in detail. Despite increased understanding, three-dimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study by means of accurate 3D finite element (FE) models a coupled fracture mode generated by anti-plane loading of a straight through-the-thickness crack in linear elastic discs. The results obtained from the highly accurate finite element analyses have improved understanding of the behaviour of through cracked discs under anti-plane loading. The influence of plate bending is increasingly important as disc thickness decreases. Bazant and Estenssoro's analysis works well for the symmetric mode (mode I), but it is incomplete for the asymmetric mode (a combination of modes II and III). It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the disc surfaces. Discussion on whether K-III tends to zero or infinity as a corner point is approached is futile because K-III is meaningless at a corner point. Calculation of the strain energy density (SED) in a control volume at the crack tip shows that the position of the maximum SED is a function of disc thickness
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