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Study of crack growing through an interface of two different materials based on analysis of crack profile in the vicinity of crack tip
Bareš, Pavel
Paper describes a numerical study of a crack penetrating the interface between two different elastic materials. The stability conditions of a crack terminating at the interface are formulated. The method introduces herein for these purposes is based on the assumption that the crack will start to propagate through the interface into the second material M2 when the shape of the crack face in the immediate vicinity of the crack tip will correspond to that in the same sample but made of purely homogeneous material M2. The numerical calculations are performed on the sample with surface protective layer under the small scale yielding conditions. The resulting critical stresses are compared with those obtained by other approaches. All results are in qualitative agreement. This method should be applicable in cases of larger crack-tip plastic deformations as well, where so far known methods are not able. All numerical calculations are performed by finite element method (system ANSYS).
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Crack stability analysis of the crack in surface protective layers based on crack mouth opening displacement
Bareš, Pavel
Paper deals with stability analysis of a crack in a coating on a substrate. It is considered that the crack is perpendicularly oriented to the interface between the coating and the substrate and the crack tip lies directly on the material interface. The simple method based on crack mouth opening displacement parameter CMOD is proposed here for a critical stress calculation in the case of through coating crack in very thin coatings. The method is then applied herein on the model example and the critical stresses for different material combinations of the coating and the substrate are calculated. Note that under these stresses the crack will start propagate across the interface to the substrate. All calculations are performed by a finite element method FEM in the system ANSYS.
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Determination of elastic moduli by the resonant ultrasound spectroscopy method
Kolman, Radek ; Plešek, Jiří ; Landa, Michal
An optimization method for the determination of elastic moduli by resonant ultrasound spectrocopy (RUS) was proposed. All components of the fourth-order tensor of elastic moduli for a general anisotropic material is determined from the knowledge of the resonance responce(spectrum) of the mechanical system. This spectrum is obtained from experimental measurements, using the RUS method on the prismatic specimen. For the iterative computation of elastic moduli an identification algorithm based on the direct iteration method is used. Spatial discretisation is performed by the finite element method.
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Numerical solution of problems of finite hyperelasticity
Poživilová, Alena
Hyperelastic material model based on the logarithmic description is implemented in the finite element code. Procedure for the calculation of all the necessery quantities at the Gaussintegration points is described in details. The second-rank update BFGS solver is used to process the governing equilibrium equations. The solution algorithm is then combined with the prediscretization contact search method in order to include contact boundary conditions. As an example, numerical simulation of the compression test of a rubber cylindrical specimen is presented.
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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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