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Vliv singularity způsobené volným povrchem na chování tenkých těles s v-vrubem
Majer, Zdeněk ; Hutař, Pavel ; Náhlík, Luboš
The influence of the singularity induced by the free surface on the behaviour of a body with a V-notch is investigated in this paper. Attention is focused mainly on the change of the singularity and the stress state through the thickness of a three-dimensional specimen. Numerical finite-element analysis of the tension loaded specimens with a V-notch were performed. The displacements and the stresses from the analysis were used to estimate the power of singularities using a log-log regression analysis along the crack front. It was found that in the middle of the specimen singularity of the V-notch is dominant this can be found using analytic equations describing two-dimensional stress distribution around the sharp V-notch. The thickness of boundary layer (region influenced by corner singularity) depends only on the Poisson's ratio of the material. The presented results can be used for a more reliable estimation of the free-surface effect on singular concentrator behaviour.
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Crack tip opening determination for a crack terminating at the bimaterial interface
Bareš, Pavel ; Knésl, Zdeněk
In the paper the method suggested by Irwin for the crack tip opening displacement (CTOD) determination in homogeneous materials is generalized and the analytical expression for the CTOD in the case of a crack with its tip at the interface of two different materials is presented. The obtained results are used to formulate the condition of stability of a crack terminating at the interface. The suggested method is applied herein on the critical stress calculation in a case of the through-cracked protective coating. The numerical calculations are performed by finite element method (system ANSYS)
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Estimation of generalized stress intensity factors by means of mean value of strain energy density factor
Klusák, Jan
The contribution deals with bi-material wedges whose stress field is characterized by two stress singular terms. The exponents of stress singularity are generally in the interval (0; 1). For these cases each of the singularities covers both normal and shear mode of loading. Because of the inherently combined loading mode, it is advantageous to utilize the strain energy density concept. A mean value of the strain energy density factor taken from a numerical solution of particular materials junction is compared to its analytical representation to ascertain values H1 and H2. These values enter to stability criterion to indicate if crack is initiated in the wedge tip.
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