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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.
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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.
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The Influence of T-stress on Mixed Mode Fracture Criterion
Seitl, Stanislav
In this paper, two-parameter constraint based linear elastic fracture mechanics is used to modify brittle fracture criterions under combination of normal and shear loading (Mode I and II). The value of constraint is characterized by T-stress. The results contribute to better description of influence of the geometry of a body on its fracture behaviour.
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Two-Parameter Approach for Short Cracks at Notches
Seitl, Stanislav ; Hutař, Pavel ; Knésl, Zdeněk
A two parameter constraint-based fracture mechanics method is applied to the behavior of microstructurally and mechanically short fatigue cracks. A short crack in the vicinity of a grain boundary and a crack which is engulfed by the plastic strain field of a notch are studied as examples. The different levels of stress constraint are quantified by using the T-stress and the Q parameter. The corresponding calculations are performed by using a finite element method (ANSYS system). The influence of the T values on the propagation of short fatigue cracks is analyzed. The size of the plastic zone and the crack closure are significantly affected by the level of constraint. The influence of constraint on small fatigue crack growth kinetic is studied under the assumption that the controlling variable for the rate of propagation of the fatigue crack is the size of the plastic zone.
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Quantitative Assessment of the T-stress in Short Fatigue Crack Propagation
Seitl, Stanislav ; Knésl, Zdeněk
Two parameter constrained based fracture mechanics is applied to quantitative assessment of microstructurally short fatigue cracks propagation. The different levels of a stress constraint are quantified by T-stress. Corresponding calculations are performed by finite element method (ANSYS system). The values of the T-stress are numerically estimated as a function of material properties, location and orientation of the short crack with respect to the grain boundary. The influence of constraint on small fatigue crack growth kinetic is discussed. It is shown that the level of constraint of the near-tip fields for microstructurally short fatigue cracks may influence the fatigue crack rate substantially.
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Evalution of Q-parameter in the case of microstructurally short fatigue cracks
Seitl, Stanislav
The paper presents evaluation of the elastic-plastic Q-parameter in the case of microstructurally short fatigue cracks, i.e. for cracks for which the crack size is comparable to the scale of the characteristic microstructural dimension such as the grain size. The microstructurally short crack is modelled as a crack with its tip in the vicinity of an interface between two different materials (elastic one and steel 12060), see Fig.1. Q-parameter is calculated by means of direct use of finite element results, namely the difference from the T = 0 reference solution, see Eq.5. Q-parameter is determined as a function of the crack orientation with respect to the interface, the crack length and the ratio of Young's modulus of both materials, see. Fig.1.
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Problems of calculation T-stress in solid bodies
Seitl, Stanislav
Contribution is about problems of calculation T-stress in solid bodies. The calculation is performed by using finite element method. The problem was solved on center cracked plate tension specimen (CCT). The constraint distribution is investigated along the crack front.
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