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1

2D FE Micromechanics Modelling of Honeycomb Core Sandwich Panels

Betts Ch., Lin J., Balint D., Atkins A.

Engineering Transactions

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2012

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Vol. 60, iss. 3

187-187

EN

A repeating unit cell 2D ?nite element modelling procedure has been established to model the mechanical behaviour of honeycomb core sandwich panels (e.g. Young’s modulus, energy absorbed, etc.). Periodic boundary conditions have been implemented within the model to simulate an in?nitely long sandwich panel. An analytical solution using Timoshenko beam theory has been developed to predict the Young’s modulus of the honeycomb core, and this has been compared with the FE model results; it is found that there is good agreement between the two values. The FE model can shed light on the mechanics of more complex 3D metal foams.

2

Influence of chosen microstructure features on residual stress distribution in FGM surface coating system with the use of FEM micromechanical random models

Szymczyk W., Włodarczyk J.

Journal of KONES

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2007

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Vol. 14, No. 2

485-492

EN

Multilayered coatings established on parts of internal combustion as well as jet engines may be used as TBC systems providing their better thermal-mechanical efficiency, tribological properties, wear resistance and ability to withstand the influence of aggressive media. The example coating system was established on a beryllium copper substrate and consisted of the NiCr midsurface and TiN external layers. The system was analyzed as a functionally gradient material (FGM) with an assumed linear gradient function of material properties in transition zones between volumes of the pure materials of the substrate, midsurface and the external coating. The influence of the chosen microstructure features onto distribution of residual stresses was investigated. . These features were: transition zones, porosity and roughness of the external surface of the coating. Transition zones are the areas at the borders between particular layers of different materials where they are mutually interpenetrated. Different types of porosity were taken into comparisons: evenly dispersed and forming clusters. The 5, 10, 15 and 20% porosities of both of the types were investigated. At last roughness of the coating surface was introduced into the models. All the features were automatically generated with the use of random procedures.

3

FEM micromechanical modelling of a porous surface coating system

Włodarczyk J., Szymczyk W.

Journal of KONES

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2006

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Vol. 13, No. 4

429-436

PL

Pokrycia wielowarstwowe wykonywane na częściach silników zarówno wewnętrznego spalania jak i odrzutowych, mogą być używane jako bariera cieplna, która będzie zapewniać ich większą sprawność cieplną i mechaniczną, lepsze własności tribologiczne, odporność na zużycie i na oddziaływanie agresywnych mediów. Prezentowane są mikromechaniczne modele MES wybranego systemu warstwy powierzchniowej, które uwzględniają wpływ porowatości na rozkład naprężeń resztkowych. Przykładowe pokrycie powierzchniowe było wykonane na podłożu z brązu berylowego i składało się z międzywarstwy NiCr i zewnętrznej warstwy TiN. Pokrycie było analizowane jako materiał funkcjonalnie gradientowy, z założoną liniową funkcją gradientu własności materiałowych w strefach przejściowych pomiędzy warstwami czystych materiałów podłoża, międzywarstwy i warstwy zewnętrznej. Badano wpływ porowatości na rozkład naprężeń resztkowych, a w szczególności wpływ efektu skupiania się i łączenia porów. Mikromechaniczne modele do wyznaczania efektywnych własności materiałów porowatych z efektem łączenia się porów i bez łączenia się porów, efektywne wartości modułu Younga wyznaczone z modeli mikromechanicznych, z efektem i bez efektu skupiania łączenia się porów, modele warstwy powierzchniowej, z mikromechaniczną symulacją mikrostruktury, naprężenia resztkowe w funkcji porowatości, przykład wyników obliczeń naprężeń resztkowych oraz przykład wyników obliczeń naprężeń resztkowych są prezentowane w artykule.

EN

Multilayered coatings established on parts of internal combustion as well as jet engines may be used as TBC systems providing their better thermal-mechanical efficiency, tribological properties, wear resistance and ability to withstand the influence of aggressive media. FEM micromechanical models of a chosen surface coating system are presented which take into consideration the influence of porosity onto distribution of residual stresses. The example coating system was established on a beryllium copper substrate and consisted of the NiCr midsurface and TiN external layers. The system was analyzed as a functionally gradient material (FGM) with an assumed linear gradient function of material properties in transition zones between volumes of the pure materials of the substrate, midsurface and the external layer. The porosity influence on the distribution of residual stresses was investigated, and the clustering effect influence in particular. Micromechanical models for appointing of effective properties of porous materials with the effect convergence pores and without convergence pores, effective values of Young's modulus appointed from micromechanical models with the effect and without the effect concentrating convergence pores, models surface layer, with the micromechanical simulation of the microstructure, residual stresses in the function of the porosity, the example of results of calculations of residual strains and the example of results of calculations of residual strains are presented in the paper.

4

Comparative study of a few fem models of a surface coating system

Szymczyk W.

Journal of KONES

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2006

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Vol. 13, No. 4

41-49

EN

Multilayered coatings established on parts of internal combustion as well as jet engines may be used as TBC systems providing their better thermal-mechanical efficiency, tribological properties, wear resistance and an ability to withstand the influence of aggressive media. A comparative review of a few different FEM models of a surface coating system is presented which can be used for the needs of designing improved parts of engines. The coating system was established on a beryllium copper substrate and consisted of the NiCr midsurface and TiN external layers. The system was analyzed as a graded as well as functionally gradient material (FGM) with an assumed gradient function of material properties. The more advanced models use a micromechanical technique of modeling which enables consideration of microstructure influence on the residual stress distribution. They contain transition zones between the pure material volumes where the material properties change accordingly to the linear gradient function. Simulations of microstructural effects in the area of surface coating are strongly recommended. The results of micromechanical calculations are affected locally too strong to be excluded from considerations.