National Repository of Grey Literature 83 records found  beginprevious66 - 75next  jump to record: Search took 0.01 seconds. 
Assessment of T-stress values using finite element method
Seitl, Stanislav ; Hutař, Pavel ; Knésl, Zdeněk
The common used procedures for calculation values of T-stress are presented by using finite element method in this contribution. Such calculational procedures, that make possible to estimate T-stress by using comparison of analytical and numerical solution stress and strain near crack tip, are presented. The aim of contribution is provide survey these procedures and points to their advantages and disadvantage and in this way we intend to possible users the endeavourer orientation in this realm. Contribution is appended with practical examples of calculation of T-stress values.
Computation of the Q-parameter for a crack in the vicinity of an elastic-plastic material interface
Seitl, Stanislav
The different levels of a stress constraint are quantified by Q-parameter. The values of the Q-parameter are numerically estimated as a function of length of crack, material properties and with respect to bi-material interface. Corresponding calculations are performed by finite element method (ANSYS system).
TWO-PARAMETER DESCRIPTION OF CRACKS IN THE VICINITY OF INHOMOGENEITY
Seitl, Stanislav ; Knésl, Zdeněk
In case of two-parameter linear fracture mechanics a study of inhomogeneity influence on behaviour of short cracks is performed. The values of stress intensity factor (KI), T-stress and strain energy density (SED) are shown as a function of material constants of both components. The calculation of numerical values of mechanical parameters is accomplished by using finite element method ANSYS.
Assessments of the fatigue crack growth direction in threshold region by two parameter fracture mechanics
Seitl, Stanislav
In framework two-parameter fracture mechanics there is analysis of influence a parameter r0 on fatigue crack growth direction. Cracks are loaded by normal a shear mode. The maximum tangential stress and minimum stress energy density criterions are used for studying. The cracks are characterizing by stress intensity factors for normal and shear mode and a T-stress. The T-stress determines the level of a constraint.
Comparison of fracture behaviour of a crack and general singular stress concentrators
Klusák, Jan ; Seitl, Stanislav ; Hutař, Pavel ; Náhlík, Luboš ; Knésl, Zdeněk
Under the assumptions of linear elastic fracture mechanics the behaviour of cracks and general singular stress concentrators is studied and compared. The stress distribution in the vicinity of singular stress concentrators is analysed and a general fracture mechanics procedure based on stress method is suggested which makes it possible to formulate fracture behaviour of such concentrators. Examples illustrating the suggested approach are added. The results generally contribute to a better understanding of the failure and increase reliability of life estimations of structures.
STUDY OF PLASTIC ZONE IN FRAMEWORK OF TWO-PARAMETER FRACTURE MECHANICS
Seitl, Stanislav
The size of the plastic zone geometry ahead of cracks is presented in this article. The plastic zone is studied in framework two-parameter fracture mechanics. Compact tension and center cracked plate tension specimens are selected for analysis, because they have different sign of T-stress. Size and shape of the plastic zone are studied on dependence T-stress. The results two and three-dimensional solution are compared with analytical solution.
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.
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.
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.

National Repository of Grey Literature : 83 records found   beginprevious66 - 75next  jump to record:
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3 Seitl, S.
40 Seitl, Stanislav
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