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1

Modelling of blood thrombosis at microscopicand mesoscopic scales

Kopernik M.

Computer Assisted Methods in Engineering and Science

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2018

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Vol. 25, no. 1

21--45

EN

Blood coagulation at the place of the complete severing of a vessel or puncturing of a vessel sidewall is usually a beneficial reaction, as it protects the body from bleeding and maintains hemostasis, while the formation of a blood clot inside the blood vessel is a pathological phenomenon, which is highly dangerous, and sometimes leads to serious complications. In this paper, two scales of modelling blood thrombosis will be introduced using numerical methods and fluid dynamics. The meso-scale model of the flow is described by Navier-Stokes equations and the blood thrombosis model is based on equations of transport and diffusion. The equations describing levels of concentrations of factors responsible for blood coagulation can be implemented into a solver solving Navier-Stokes equations, what will enable simulation of blood flow and estimation of the risk of thrombus formation related to flow conditions. The proposed micro-scale model is using molecular dynamics to simulate interactions between blood cells and vascular walls. An effective combination of both models is possible thanks to the introduction of the multiple-time stepping algorithm, which enables a full visualization of blood flow, coupling molecular interaction with the fluid mechanics equation. The goal of the paper is to present the latest literature review on the possibilities of blood coagulation modelling in two scales and the main achievements in blood thrombosis research: the key role of transport and experimental background.

2

The key problems of local approach to cleavage fracture

Kotrechko S.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 1

75--89

EN

Based on the suggested multi-scale model of Local Approach (LA) to fracture, four main problems of LA are considered, namely: (i) the effect of micro-stress fluctuations on the crack nuclei instability; (ii) intensity of micro-crack nucleation and its influence on fracture probability; (iii) theoretical and experimental assessment of the value of threshold stress; (iv) stochastic analysis of “multi-barrier” effect at micro-crack growth in polycrystalline metal.

PL

W oparciu o zaproponowany wieloskalowy model lokalnego sformułowania procesu pękania (Local Approach – LA) wyróżniono cztery podstawowe problemy do rozważenia: (i) efekt fluktuacji makronaprężeń na niestabilność jądra pęknięcia, (ii) intensywność zawiązywania się mikropęknięcia i jego wpływ na prawdopodobieństwo powstania przełomu, (iii) teoretyczne i eksperymentalne oszacowanie wartości naprężenia krytycznego, (iv) stochastyczna analiza efektu „wieloprogowego” na wzrost mikropęknięcia w metalu polikrystalicznym.

3

Modelowanie procesów obróbki plastycznej metali - od problemów w skali makro do nowoczesnych rozwiązań wieloskalowych

Pietrzyk M., Madej Ł.

Mechanik

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2009

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R. 82, nr 7

605-609

PL

Przedstawiono rozwój zastosowań metod numerycznych do symulacji procesów obróbki plastycznej, przy czym szczególny nacisk położono na metodologię uwzględniania w modelowaniu fizycznych aspektów procesów. W pierwszej części omówiono przykłady wybranych symulacji, przeprowadzonych głównie w skali makro z wykorzystaniem programów opartych na MES oraz przedstawiono pierwsze próby tworzenia modeli wieloskalowych, które bazowały na rozwiązaniu równań różniczkowych opisujących zjawiska w skali mikro. W drugiej części zaprezentowano dynamiczny rozwój metod modelowania wieloskalowego, który nastąpił w ostatnim dziesięcioleciu. Omówiono także klasyfikację metod wieloskalowych oraz zaprezentowano opracowane przez Autorów próby analizy wieloskalowej, umożliwiające skuteczną symulację zjawisk związanych z lokalizacją odkształcenia.

EN

A history of numeric methods applications for simulation of metal plastic working processes. Discussion on selected simulation examples generally carried out in the macro scale using the MES based software. Also presented is dynamic development of the multiple scale modelling methods as observed during the current decade.

4

Multi-scale modelling of surface topography in single-point diamond turning

Lee W. B., Cheung C. F., To S.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 1

260-266

EN

Purpose: A multi-scale model is proposed to explain the effect of material induced vibration and the quantitative relation between cutting force and the surface quality from dislocations, grain orientations, cutting tools, machine tools used in the simulation of the nano-3D surface topology in single-point diamond turning. Design/methodology/approach: The model-based simulation system composes of several model elements which include a microplasticity model, a dynamic model and an enhanced surface topography model. Findings: This research is the first attempt in which the microplasticity theory, theory of system dynamics and machining theory are integrated to address the materials problems encountered in ultra-precision machining. Indeed, this is a new attempt to link up the microplasticity theory to macro-mechanisms in metal cutting. The successful development of the model-based system allows the prediction of the magnitude and the effect of periodic fluctuation of micro-cutting force and its effect on the nano-surface generation in ultra-precision diamond turning of crystalline materials. It also helps to explain quantitatively the additional roughness caused by the variation of the crystallographic properties of the workpiece, and leads us to a better understanding of the further improvement of the performance of ultra-precision machines. Research limitations/implications: The multi-scale model brings together knowledge from various disciplines to link up physical phenomenon occurring at different length scales to explain successfully the surface generation in single-point diamond turning of crystalline materials. Originality/value: This model offers a new direction of research in ultra-precision machining.