|
|
Application of contour integrals to assessment of notch stability in linear elasticity
Gröger, Roman ; Knésl, Zdeněk
The article yields a teoretical background of a well- sophisticated numerical method for calculation of GSIF and T stress, especially for case when the integration across the nonhomogeneous material interface is unavoidable. The main advantage of the integral approach over the well-known direct methods is its accuracy induced by monotonous convergence of the solution. This work contributes to more accurate description of the instability state of V-notches in composite structures.
|
|
|
THE INFLUENCE OF T-STRESS FOR RELATIONSHIP BETWEEN CTOD AND J
Hutař, Pavel ; Knésl, Zdeněk
Relations between crack opening displacement (CTOD) and other fracture mechanics parameters are of a great importance in fracture mechanics. The basic aim of this paper is to describe an influence of T-stress on the plastic eta factors, plastic rotation factor and proporcional factor, i.e. the factors correlating J-integral and CTOD. Specimens with different values of T-stress (compact tension,three point bend and single edge cracked tension) are analysed by finite element method, the factors are calculated as functions of corresponding crack length and results obtained are discussed from the point of view of two-parameter fracture mechanics.
|
|
|
Integral methods for the determination of fracture characteristics of general stress concentrators
Gröger, Roman
The integral appoaches for calculation of generalized stress intensity factors (GSIF) are presented. Integral identities are derived using the Betti reciprocal theorem as a superposition of two independent solutions satisfying the sam boundary conditions. The complementary solution for computation of GSIF is assembled using the negative eigenvalues lambda. This algorithm yields a set of integral identities that allow to estimate GSIF separately for mode I and II. A quantitative comparsion of the integral approach with recently used extrapolation method is proposed in conclusion.
|
|
|
Analysis of crack propagation in vicinity of bi-material interface in framework two parameter fracture mechanics
Seitl, Stanislav ; Knésl, Zdeněk
Existence of the interface between regions with different elastic properties have a pronounced influence on the behaviour of cracks The aim of the present contribution is an analysis of a crack growing in a vicinity of the interface between two different elastic materials.. The basic assumption of the contribution corresponds to two-parameter linear elastic fracture mechanics. The values of stress intensity factor KI and KII corresponding to normal and shear mode of loading and the value of T-stress are calculated for a generally oriented crack approaching to the interface. The calculations are performed by finite element method for short and long cracks. The dependence of KI, KII and T values on the distance and the orientation of a crack with respect to the interface is studied. It is shown that short cracks are influenced by the presence of the interface more significantly in comparison with long cracks. The results contribute to better understanding of short cracks behaviour in relation to microstructure of material.
|
|
|
Influence of bi-materials interface on crack interaction
Seitl, Stanislav
Existence of the interface between regions with different elastic properties has a pronounced influence on the behaviour of cracks. The aim of the present contribution are a modelling and analysis of two perpendiculars cracks growing in a vicinity of the interface between two different elastic materials. The dependence of stress intensity factor for mod I (KI) on the distance of a crack with respect to the interface is studied. The results contribute to better understanding of crack's behaviour in relation to microstructure of material.
|
|
|
Estimation of the Critical Stress for Failure of a Protective Layer
Náhlík, Luboš ; Knésl, Zdeněk
This contribution describes a study of the behaviour of a crack growing in a protective layer and penetrating through an interface into a substrate. Special attention is devoted to a crack touching the interface. Conditions for the stability of a crack terminating at the interface between two materials are analyzed. The problem is studied under the assumptions of linear-elastic fracture mechanics. A new tentative criterion of stability based on application of the strain energy density concept is formulated and applied to the problem. The suggested criterion is used to estimate the critical applied stress for the failure of a substrate caused by a crack growing through the protective layer. It is shown that the critical stress may strongly depend on the fracture toughness of the substrate and on the bi-material parameters.
|
|
|
Crack propagation analysis in multilayered pipes
Bareš, Pavel
The fracture behavior of multilayered pipes applied for water and gas distribution is analyzed in this paper. The attention is focused on numerical modeling of crack propagation through twolayered pipe. Special attention is paid to the influence of interface between the layers on fatigue crack growth. The analysis is performed under the assumption of validity of linear-elastic fracture mechanic. Numerical calculations are performed by finite element method (system ANSYS).
|
|
| |
|
|
Interaction of crack and aggregate in concrete
Keršner, Z. ; Náhlík, Luboš ; Knésl, Zdeněk
Concrete is represented as a two-phase material in this paper. Behaviour of a single macrocrack approaching to the interface between hardened cement paste (matrix) and aggregate (particle) is modelled. It is shown that in the case of where Young modulus of cement paste is greater then those of aggregates, the effective fracture toughness of concrete is predominantly given by fracture properties of aggregates.
|
|
| |
guest ::
