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1
Content available Fatigue damage and reliability assessment of cemented hip prosthesis
100%
Doliński K.
Journal of Theoretical and Applied Mechanics
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1999
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tom nr 3
505-518
EN
Continuum damage mechanics model is used in the finite element calculation of fatigue process in a cemented hip prosthesis. The cement mantle is assumed to be subjected to the fatigue damage resulting in evolution of the damage-induced material anisotropy and leading, eventually, to loosening of the prosthesis. Fatigue parameters and loads are assumed to be random variables. The reliability analysis is carried out for a linear appriximation of the limit state function and, eventually, some corrections are presented to improve the fatigue lifetime probability distribution assessment.
PL
Do modelowania procesu zniszczenia zmęczeniowego cementowanej protezy biodrowej zastosowano metodę elementów skończonych oraz kontynualny model mechaniki zniszzenia. Otoczka cementowa tworząca zamocowanie protezy narażona jest na uszkodzenia zmęczeniowe, kyóre powodują powstanie i ewolucję anizotropii materiału oraz prowadzą do obluzowania protezy. Parametry materiałowe charakteryzujące proces zmęczenia oraz obcążenia przyjęto jako zmienne losowe. W analizie niezawodności przyjęto liniową aproksymację warunku granicznego określającego przydatność protezy i zaproponowano pewne modyfikacje pozwalające efektywnie szacować rozkład prawdopodobieństwa czasu życia protezy.
2
Content available remote Localisation effect during wave pulse propagation in randomly stratified elastic medium
63%
Doliński K. , Kotulski Z.
Archives of Mechanics
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1999
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tom Vol. 51, nr 3-4
311-334
EN
In this paper the propagation of the planar wave pulses in a two-dimensional randomly stratified elastic medium is considered. The waves propagate in the plane (x1,x2) and are independent of the third variable z. The problem is described by means of the transition matrix method. The transition matrix and the wave equation for a homogeneous layer is presented. The equations for the wave fields reflected from and transmitted through the randomly stratified elastic slab are derived. The theoretical results are illustrated by graphically presented numerical calculations. A possibility of application of the wave analysis to modelling of the fatigue crack propagation initiated at the interfaces and continued due to sequences of the reflected and transmitted stress waves is discussed.
3
Content available remote Reliability-based structural optimization accouting for manufacturing and material quality
63%
Doliński K. , Stocki R.
Engineering Transactions
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2001
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tom Vol.49, iss.4
624-636
EN
The reliability-based optimization problem in which the structural material and manufacturing quality is assumed to be uncertain is considered. Moreover, the quality cost is appropriately taken into consideration in the formula determining the total cost of the structure. Some parameters describing the quality, namely the means and variances of the material properties and the variances of the precision of assembling of the structure are considered as the design parameters in the optimization procedure, in which the required structural reliability level determines some constrains to be satisfied in searching for the minimum structural cost.
4
Content available Damage modeling in graded layer system
51%
Petaś M. , Mróz K. , Doliński K.
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tom Vol. 7, no. 2
99--106
EN
The simplified approach to the modelling of low cycle fatigue (LCF) of functionally graded materials (FGM) based on the continuum mechanics is presented. The fatigue damage model takes into account the mechanical part of the load and a constant service temperature. The concept of FGM as a particle-reinforced metal-matrix composite with gradual change of the reinforcement fraction is used. The FGM is considered as a material consisting of homogeneous layers containing different volume fractions of the reinforcement. The variation of the reinforcement fraction changes the material properties for each layer. The different material properties are obtained according to modified rule of mixture. Since the fatigue damage of metal matrix composites is strongly influenced by the inelastic deformation of the metallic matrix, the constitutive equations of LCF damage model are taken into consideration. The combined isotropic/kinematic hardening model with linear behaviour of isotropic and kinematic parts of hardening is adopted. The damage scalar parameter is associated with the plastic energy dissipation which is used to update the material properties. The fatigue damage model presented in this paper is applied to the fatigue damage analysis of the cooling channel of thruster used in space shuttles and rockets.
5
Content available Failure modes of coatings on steel substrate
38%
Mróz K. P. , Kucharski S. , Doliński K. , Bigos A. , Mikułowski G. , Beltowska-Lehman E. , Nolbrzak P.
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tom Vol. 64, nr 1
249--256
EN
The critical monotonic strain of Ni-W and MoS2(Ti,W) coatings on steel substrates was studied. The idea of axisymmetric bending test (called here as coin bending test) limited to monitoring of the coating failure was used. Experiments revealed mechanism of the coating failure, as cracking initiated from coating surface defects and/or substrate was demonstrated using indentation technique. By pushing the center of the uncoated side of a circular plate, the axisymmetric stress state was generated in the coating. The stress components varied gradually from the greatest value in the center to the smallest value at the edge of the specimen. The changes of the sample surface as a result of loading were monitored step by step via optical microscopy.
6
Content available Failure modes of coatings on steel substrate
32%
Mróz K. P. , Bigos A. , Kucharski S. , Doliński K. , Mikułowski G. , Bełtowska-Lehman E. , Nolbrzak P.
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nr 1
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