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INFLUENCE OF MATERIAL PARAMETERS ON POLZNOM USED FOR MODIFICATION PARIS LAW
Seitl, Stanislav
In this paper sensitivity analysis of the effect of material properties (particularly a yield stress and hardening exponent) on the polynomial function used at modification of the Paris-Erdogan law was performed. The modification, which is based on the two-parameter fracture mechanics, describes fatigue crack propagation using a size of the plastic zone. The stress field around a crack tip is described by two parameters – stress intensity factor K and T-stress. Dependency of the plastic zone size and the parameters K, T is then formulated by using the polynomial function, which is found out in the contribution. The finite element method together with the method of modified boundary layer for the numerical simulations was used. The results should lead to safer transmission of the data from laboratory specimens to real structures and their components.
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Influence of the T-stress on Plastic zone shape and size for different form of specimens
Seitl, Stanislav
In framework of two-parameter fracture mechanics the shape and size of the plastic zone at the tip of a crack were studied. Analytical estimate of the size and shape of the plastic zone was made by substituting Mises yield criterion. For three different specimens (namely CCT-center cracked plate tension specimen, CT-compact tension specimen and 3PB-single edge cracked three point bending specimen) the numerical solution is calculated by using ANSYS. Numerical results are presented to show the influences of the T-stress on the plastic zone. Both solutions are compared and the effect of constraint on the plastic zone was discussed
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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.
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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.
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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.
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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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