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National Repository of Grey Literature 3 records found  Search took 0.00 seconds. 
Modelling approaches to the stress wave propagation in a cracked specimen
 Kruisová, Alena ; Kopačka, Ján ; Kober, Jan
One of the essential tasks of non-destructive testing is to detect a crack in a specimen. It is well known that a component with a crack exposed to a harmonic excitation of a given frequency\nhas a nonlinear response as a function of the excitation amplitude. The focus of this paper is the numerical modelling of this phenomenon using the finite element method with the consideration\nof the contact constraint at the crack interface. In addition to the nonlinear transient dynamic problem solved by explicit time integration, a more efficient procedure based on the harmonic\nbalance method is developed. The results of numerical simulations are also compared with experimentally obtained data.
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Dispersion errors for wave propagation in thin plate due to the finite element method
 Kruisová, Alena ; Kolman, Radek ; Mračko, Michal
In modelling of wave propagation by finite element method, both the spatial and temporal discretization lead to dispersion errors. For 2D plane strain elements these errors can be stated analytically. These analytical relations derived for harmonical waves in the infinite continuum can be used for error estimation on an example of simulation of Lamb's wave in plate using the implicit time integration method. So the analytical relations for dispersion errors can serve for determination of element size and time step size in wave propagation.
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Bi-penalty stabilized explicit finite element algorithm for one-dimensional contact-impact problems
 Kolman, Radek ; Kopačka, Ján ; Tkachuk, A. ; Gabriel, Dušan ; Gonzáles, J.A.
In this contribution, a stabilization technique for finite element modelling of contact-impact problems based on the bipenalty method and the explicit predictor-corrector time integration is presented. The penalty method is a standard method for enforced contact constrains in dynamic problems. This method is easily implemented but the solution depends on numerical value of the stiffness penalty parameter and also the stability limit for explicit time integration is effected by a choice of this parameter. The bipenalty method is based on penalized not only stiffness term but also mass term concurrently. By this technique with a special ratio of mass and stiffness penalty parameters, the stability limit of contact-free problem is preserved. In this contribution, we also present a modification of the explicit time scheme based on predictor-corrector form. By meaning of this approach, spurious contact oscillations are eliminated and the results do not depend on numerical parameters.
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