Wyniki wyszukiwania - BazTech

1

Numerical modeling of the solidification process with consideration of shrinkage cavities formation and the influence of solid phase content on the feeding of the casting

Węgrzyn-Skrzypczak Ewa, Skrzypczak Tomasz

Journal of Applied Mathematics and Computational Mechanics

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2023

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Vol. 22, nr 2

75--86

EN

The paper focuses on the numerical modeling of the three-dimensional solidification process of steel using the finite element method (FEM). The model includes and discusses the formation of shrinkage cavities and the influence of the solid phase content on the feeding of the casting through the riser. The analysis assumed a critical value of the solid phase content, at which the transport of liquid phase from the riser to the casting is interrupted. The results of numerical simulation are presented to investigate the influence of this factor on the final quality of the casting. The model neglects the fluid motion in the liquid and solid-liquid regions and replaces the influence of the mold with appropriate boundary conditions.

2

Impact of input parameters on numerical calculations optimized by swarming algorithms during computer simulations of the heat conduction phenomenon

Zych Maria, Gawrońska Elżbieta, Dyja Robert, Krawiec Piotr

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 4

107--118

EN

The article presents the application of swarming algorithms in heat conduction, taking into account the continuity of the boundary condition (type IV). The influence of the input parameters of the bee and ant algorithm and tessellation on the selection of the heat conduction coefficient between the casting mold and the casting in computer simulations was presented. The results were compared for two different finite element grids, a different number of individuals, and a different number of iterations. The study also considered the magnitude of the reference temperature disturbance as the input temperature for numerical calculations. The analysis showed that the relative error of reproducing the value of the thermal conductivity coefficient in the continuity condition did not exceed 1.5% of the reference value of this coefficient.

3

Diagnosis of vortex induced vibration of a gravity damper

Scappaticci L., Castellani F., Astolfi D., Garinei A.

Diagnostyka

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2018

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Vol. 19, No. 2

31--39

EN

A gravity damper is a one-way valve, employed for regulating the airflow rate in ducts, generally constituted by a series of rectangular panels (closure sections), connected to an articulated quadrilateral synchronizing the movements. If the device needs to process large masses of high speed air, as common in the case of energy conversion systems, disadvantageous dynamic effects can occur. In this study, vortexinduced vibration (VIV), occurring on a gravity damper for high values of the Reynolds number, is investigated. The analysis of this work couples numerical methods (Computational Fluid Dynamics with Large-Eddy Simulation turbulence model and Finite Element Method) to experiments: a full-scale accelerometric measurement campaign is actually performed at the wind tunnel facilities of the University of Perugia. VIVs are diagnosed and quantified through the experimental vibration analysis, which is interpreted through numerical simulations. The large amplitude of VIV is interpreted as due to a tendency towards lockin because of the approaching of the vortex shedding frequency to a natural vibration mode of the system. The integrated numerical and experimental framework finally inspires two different design solutions for mitigating the amplitude of VIV: these strategies are tested at the wind tunnel and they are indeed shown to be effective.

4

Peridynamics for damage modelling and propagation via numerical simulations

Martowicz A.

Diagnostyka

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2017

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Vol. 18, No. 1

73--78

EN

The present work provides an overview on the selected applications of peridynamics to damage modelling and simulations of its propagation in mechanical structures. The theoretical fundamentals of the method are briefly described to highlight its advantages and the scope of practical use in the field of computational mechanics. Selected results of numerical analyses are provided to illustrate demanded capabilities. The perspectives of nonlocal and integral based problem formulations for dynamics are discussed.

PL

Artykuł stanowi przegląd wybranych zastosowań perydynamiki w modelowaniu uszkodzeń i symulacji zjawisk ich propagacji w konstrukcjach mechanicznych. Przedstawiono podstawy teoretyczne metody ze szczególnym uwzględnieniem specyfiki zalet perydynamiki w zastosowaniach w mechanice komputerowej. Opisywane zalety metody są zilustrowane wybranymi przykładami analiz numerycznych. Artykuł przedstawia możliwości obliczeniowe nielokalnych sformułowań dla dynamiki bazujących na całkowych równaniach ruchu.

5

Zastosowanie metod modelowania komputerowego i symulacji do weryfikacji systemu montażu dodatkowego opancerzenia

Morka A., Stanisławek S., Niezgoda T., Rudnik D.

Szybkobieżne Pojazdy Gąsienicowe

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2016

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nr 1 (39)

77--85

PL

Artykuł omawia zagadnienie weryfikacji systemu montażu dodatkowego opancerzenia z zastosowaniem metod modelowania komputerowego i symulacji. Dla realizacji tego celu opracowano modele numeryczne istotnych elementów konstrukcji systemu mocowania oraz panelu i reprezentatywnej części płyty kadłuba. Dokonano selekcjię odpowiednich modeli konstytutywnych wykorzystywanych materiałów oraz doboru właściwych parametrów materiałowych. Badane panele poddano obciążeniom normatywnym wg Normy Obronnej NO-06-A 103/2005 dla grupy N11 oraz uderzeniu pocisku AP 14,5x114 mm B32 zgodnie z wytycznymi zawartymi w STANAG 4569. Rezultaty uzyskane na drodze analiz numerycznych w szczególności rozpatrywano pod względem możliwości wystąpienia trwałych odkształceń plastycznych w elementach systemu mocowania opancerzenia dodatkowego. Stwierdzono, że w badanych przypadkach uderzenie pocisku powoduje powstanie trwałych (plastycznych) odkształceń w elementach mocowania (tulejki, spoiny spawu), ale ilościowo są one dalekie od wartości niszczących. W śrubach, podkładkach oraz dla połączeń gwintowych nie zidentyfikowano niepokojących wartości naprężenia i odkształceń. Jedyną sytuacją wymagającą uwagi są trwałe odkształcenia w obszarze zagniecenia nitonakrętek zaobserwowane dla obciążeń udarem jednokrotnym i wielokrotnym. Analiza wariantów uderzenia pocisku AP 14,5 centralnie w osi śruby układu mocowania wykazuje brak zdolności ochronnej w tym obszarze. Pocisk perforuje elementy systemu mocowania bez istotnego oporu tracąc nieznaczną część swojej energii, tym samym stanowi nadal zagrożenie dla perforacji kadłuba.

EN

The paper discusses the problem of verifying systems of additional armour installation with the use of computer modelling and simulation methods. To achieve this purpose, numerical models of essential structural elements of the fastening arrangement, of the panel and of the representative portion of hull plate have been developed. Suitable constitutive models of the materials used and proper parameters thereof have been selected. Tested panels were subjected to group N11 standard loads in accordance with the Defence Standard NO-06-A 103/2005 and AP 14.5x114 mm B32 projectile impact in accordance with the guidelines included in STANAG 4569. The results obtained by means of numerical analyses were studied in particular in terms of establishing the probability of permanent plastic deformations in the elements of the additional armour fastening system. It was found that in the cases studied the impact of a projectile results in permanent (plastic) deformations in the fastening arrangement elements (bushings, welds), but in quantitative terms these were far from destructive. No disturbing stresses or strains have been identified in bolts, washers and threaded connections. The only situation that needs to be looked into are permanent strains in the crush area of blind rivet nuts observed for loads from single and repeated impacts. Analysis of the impact of an AP 14.5 projectile centrally along the axis of the bolt of the fastening arrangement showed lack of protective capacity in this area. The projectile perforates elements of the fastening arrangement with no significant resistance, while its energy decreases only slightly and thereby the threat of hull penetration is still retained.

6

Wpływ uproszczeń w badaniach symulacyjnych zderzeń pocisków z tarczą na dokładność wyników

Stanisławek S., Morka A., Niezgoda T.

Biuletyn Wojskowej Akademii Technicznej

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2013

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Vol. 62, nr 3

137-143

PL

Artykuł omawia zagadnienie możliwości stosowania określonych uproszczeń w symulacji komputerowej. Stanowi on niezbędny warsztat dla każdego badacza stosującego opisane sposoby modelowania. Weryfikacja uproszczeń numerycznych polegała na przeprowadzeniu trzech testów zderzeniowych dla rdzenia pocisku 7,62 × 51 WC oraz czwartej symulacji polegającej na porównaniu efektów uderzenia pełnego modelu pocisku oraz jedynie jego rdzenia. Opracowane modele tarczy symulowały materiał stalowy z wprowadzonymi typowymi parametrami, natomiast pocisk był opisany modelem Johnsona-Cooka. Prędkość początkowa pocisku wynosiła 854 m/s, zaś tarcza pozostawała nieruchoma i zamocowana w płaszczyźnie prostopadłej do kierunku lotu. Opisane badania potwierdzają możliwość stosowania modelu materiału nieodkształcalnego oraz sprężystego do uproszczonego opisu ciał materialnych. Pozwala to na uproszczenie i przyspieszenie obliczeń numerycznych w sytuacjach, gdzie materiały zderzających się ciał mają znacznie różne właściwości mechaniczne. Z dużą ostrożnością powinno się odnosić do odczytywania sił rejestrowanych na ściance nieodkształcalnej. Analiza sił oraz energii pokazuje natomiast, że sabot i płaszcz pocisku nie odgrywają zasadniczej roli przy uderzeniu w nieruchomą tarczę. Doznaje ona większego popędu, jednak nie jest to różnica zasadnicza.

EN

The paper presents the possibility of applying certain simplifications for computer simulations. It is the essential knowledge for each scientist employing the described methods of modelling. Verification of numerical simplifications consisted in conducting three impact tests for a 7.62 × 51 WC projectile core and a forth one which referred to a comparison of a full model of the penetrator with its core only. The target was described with a simple steel material while the projectile with an advanced Johnson-Cook model. Projectile initial speed was 854 m/s while a target remained motionless and fixed in a plane perpendicular to the motion direction. The performed tests confirm the possibility of using rigid and elastic materials for a simplified material body description. It allows simplification and shortening of computational time when materials are characterized by very different strength. However, a user should be very careful when analyzing the forces recorded on a rigid wall. Furthermore, analysis of the forces and energies shows that both a sabot and a jacket do not play a significant role during the impact into a motionless target. It register a bigger force impulse but it is not a substantial difference.

7

Analiza przestrzennych ścianowych konstrukcji usztywniających budynki wysokie z dodatkowymi sztywnymi belkami

Wdowicki J., Wdowicka E.

Biuletyn Wojskowej Akademii Technicznej

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2013

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Vol. 62, nr 1

215-233

PL

Praca przedstawia analizę przestrzennych niesymetrycznych ścianowych konstrukcji usztywniających budynki wysokie z dodatkowymi sztywnymi belkami. Sztywne, wysokie belki zastosowane nawet na niewielu poziomach ścianowej konstrukcji z nadprożami znacznie zwiększają sztywność układu konstrukcyjnego. W analizie wykorzystano pewien wariant metody ciągłych połączeń, opracowany dla przestrzennych ścianowych konstrukcji usztywniających, mających skokowe zmiany sztywności wzdłuż wysokości. W podejściu ciągłym nadproża są zastępowane równoważnymi pionowymi pasmami ciągłych połączeń. Równania zgodności przemieszczeń są zapisane w punktach znajdujących się w środkach rozpiętości nadproży i sztywnych belek. Układy równań różniczkowych dla stref układów usztywniających o stałym przekroju poprzecznym są rozdzielane przy wykorzystaniu ortogonalnych wektorów własnych. Wyniki obliczeń dla proponowanej metody zostały porównane z wynikami uzyskanymi przy wykorzystaniu różnych metod obliczeniowych, zarówno analitycznych jak i numerycznych, oraz z opublikowanymi wynikami badań doświadczalnych. Stwierdzono dobrą zgodność wyników.

EN

The paper presents the analysis of non-planar asymmetric shear wall structures with stiffening beams. The stiff deep beams incorporated at various levels of coupled shear walls improve the stiffness of the structural system of a tall building. The analysis is based on a variant of the continuous connection method for three-dimensional shear wall structures having stepwise changes in a crosssection. In the continuous approach, the connecting beams are replaced by equivalent continuous connections. The compatibility equations have been written at the midpoints of connecting and stiffening beams. The differential equation systems for shear wall structure segments of the constant cross-section are uncoupled by orthogonal eigenvectors. The results obtained by the presented method have been compared with those obtained experimentally and analytically, given in literature, and a good match has been observed.

8

Znaczenie dyskretyzacji przestrzennej na przykładzie numerycznej analizy problemu perforacji płyt

Morka A.

Biuletyn Wojskowej Akademii Technicznej

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2012

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Vol. 61, nr 4

123-131

PL

Wiele zagadnień mechaniki analizowanych metodami numerycznymi, szczególnie z obszaru procesów szybkozmiennych, wykazuje dużą wrażliwość na gęstość dyskretyzacji przestrzennej. Fakt ten związany jest z występowaniem szeregu złożonych zjawisk fizycznych oraz czynników o charakterze numerycznym, jak np. erozja, czyli usuwanie z obliczeń zniszczonych elementów. Prezentowana praca, posługując się przykładem numerycznej analizy zagadnienia perforacji płyty przez wybrany pocisk, dostarcza narzędzia (metodyki) do oceny zbieżności rozwiązania numerycznego ze względu na zmiany dyskretyzacji przestrzennej problemu. Zadanie to zostało zrealizowane poprzez adaptację metody stosowanej przez NASA w analizach CFD (ang. Computational Fluid Dynamics) do problemu z zakresu mechaniki ciała stałego. W rezultacie możliwe jest uzyskanie ilościowego wyniku obarczonego określonym błędem niezależnego od siatki numerycznej. Ponadto dostępna jest informacja określająca rząd zbieżności rozwiązania, który może stanowić dodatkowy wskaźnik poprawności rezultatu.

EN

Many of mechanic issues analyzed by numerical methods, especially in the area of fast-changing processes, are highly sensitive to the density of spatial discretization. This fact is related to the presence of a number of complex physical phenomena and factors such as numerical erosion that is removal of damaged parts of material from the calculation. The present work using the example of a numerical analysis of the plate perforation by the selected projectile provides the tools (methodology) to assess the convergence of numerical solution due to changes in the spatial discretization of the problem. This task was carried out by adapting the method used by NASA in the CFD (Computational Fluid Dynamics) analysis to the problem of solid mechanics. Consequently, it is possible to obtain a quantitative mesh size independent result carrying the particular error. In addition, there is information indicating the convergence order of solutions, which can be an additional indicator of the result correctness.

9

Process description of piercing when using degenerated model

Jamroziak K.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 26, nr 1

57-64

EN

Purpose: The material piercing process is an extremely complex phenomenon for the theoretical analysis. This is connected with the fact that the materials used mainly for ballistic shields may not be treated as isotropic media. The description of piercing of ballistic shields made of light weight composite materials, on the basis of the Hooke's model and the Young's module reflects the too low result effectiveness for practical applications. The purpose of this article is the mathematical description of the impact phenomenon of a bullet of the speed ca. 400 m/s, with the use of a degenerated model. Design/methodology/approach: In the study, an attempt has been made to apply an untypical model for the piercing phenomenon analysis. Basing on the model, the theoretical analysis of the piercing phenomenon in quasistatic and dynamic load conditions, in the impact load form, has been carried out. Findings: This analysis enabled derivation of significant conclusions useful in the design process of effective ballistic shields. Research limitations/implications: In the study, the concept has been assumed that a dynamic model simple as possible, that may be analyzed not only by numerical methods but also (at least approximately) with the mathematical analysis methods, may provide significant directions concerning material piercing. Practical implications: The use of so called degenerated model allows to describe the phenomenon in more detail at various piercing speeds what extends the possibilities in the sphere of designing the optimum ballistic shields and of identification of the properties of materials applied for construction of shields. Originality/value: The proposed method of identification of material properties in the piercing process, within the relation: force – deformation, is a novel one since the essence of the identification is the standard rheological model in an adequate plastic component describing the viscous attenuation with dry friction.

10

Modelling of dynamical systems in transportation using the modyfit application

Żółkiewski S.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 1

71-74

EN

Purpose: of this paper is to present a numerical application for analysis and modelling dynamical flexible systems in transportation. This application enables controlling and regulation of rotating systems with the interaction between the working motion and local vibrations of elements. Design/methodology/approach: Numerical calculations are based onto mathematical models derived in other publications. The objectives of making this application were connected with emerging wants of analyzing and modelling rotating systems with taking into consideration relation between main and local motions. Theoretical considerations were made by classical methods and by the Galerkin's method. Findings: In way of increasing the value of angular velocity we can observe creating additional poles in the characteristic of dynamical flexibility and after increasing it is evident that created modes are symmetrically propagated from the original mode. It is evident, instead of modes there are created zeros. Research limitations/implications: Analyzed systems were limited to simple linear type beams and rods. Main motion is plane motion. Future research should consider complex systems and nonlinearity. Practical implications: of the application are possibilities of numerical analysis of beam and rod systems both the free-free ones and fixed ones. Engineers thank to this application can derived the stability zones of analyzed systems and can observe eigenfrequencies and zeros in the way of changing the value of angular velocity. In practice we should implement more adequate models such as those presented in this paper. Originality/value: This paper consist the description of the application called the Modyfit. The Modyfit is an implementation of derived models in a numerical environment. Those models are rotating flexible systems with consideration the transportation effect.

11

Identification of composite materials at high speed deformation with the use of degenerated model

Jamroziak K., Bocian M.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 2

171-174

EN

Purpose: Composite materials on account of some their characteristics have application in a construction of ballistic shield. An example of the ballistic shield is laminate with the mix-structure materials such as layer pressed of aramid cloths on matrix polymer. Because of the shield’s assignment the aramid cloths are exposed to impact loads caused by an energy made by impact force of cumulated mass (bullet). Previous analyses of the effect are based on linear-elastic reaction of resisting forces between the materials of a bullet and a shield. The article exemplifies the procedure of mechanical properties analysis in the punch effect of the ballistic shield with the use of some of the non-elastic models. Design/methodology/approach: In the article the theoretical analysis of punch effect in the quasi-static load condition based on some of the degenerated models is also presented. Findings: The results of the analysis make aware of demand for designing safety ballistic shields. Research limitations/implications: The main conception was optimum material selection (composite) that has to be done according to the theoretical analysis, which is based on non-elastic models selected in the context of velocity and mass of punching bullet. Practical implications: Application of the complex degenerated model allows to define more characteristics of the punching process of the ballistic shield. Determination of the effect of energy impact dissipation causes material damage of the ballistic shield is enabled to do because of implementation of boundary conditions. Originality/value: Based on the boundary conditions of energy in the way of changing parameters of model we are able to describe non-destructive deformation process.

12

Finite element simulation of wheel impact test

Chang C. L., Yang S. H.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 2

167-170

EN

Purpose: In order to achieve better performance and quality, the wheel design and manufacturing use a number of wheel tests (rotating bending test, radial fatigue test, and impact test) to insure that the wheel meets the safety requirements. The test is very time consuming and expensive. Computer simulation of these tests can significantly reduce the time and cost required to perform a wheel design. In this study, nonlinear dynamic finite element is used to simulate the SAE wheel impact test. Design/methodology/approach: The test fixture used for the impact test consists of a striker with specified weight. The test is intended to simulate actual vehicle impact conditions. The tire-wheel assembly is mounted at 13° angle to the vertical plane with the edge of the weight in line with outer radius of the rim. The striker is dropped from a specified height above the highest point of the tire-wheel assembly and contacts the outboard flange of the wheel. Because of the irregular geometry of the wheel, the finite element model of an aluminium wheel is constructed by tetrahedral element. A mesh convergence study is carried out to ensure the convergence of the mesh model. The striker is assumed to be rigid elements. Initially, the striker contacts the highest area of the wheel, and the initial velocity of the striker is calculated from the impact height. The simulated strains at two locations on the disc are verified by experimental measurements by strain gages. The damage parameter of a wheel during the impact test is a strain energy density from the calculated result. Findings: The prediction of a wheel failure at impact is based on the condition that fracture will occur if the maximum strain energy density of the wheel during the impact test exceeds the total plastic work of the wheel material from tensile test. The simulated results in this work show that the total plastic work can be effectively employed as a fracture criterion to predict a wheel fracture of forged aluminum wheel during impact test. Research limitations/implications: A standard impact load is used to carry out the test. For future study, a heavier striker or higher impact can be used to perform the test in order to produce the rupture at impact. Originality/value: In this study, the nonlinear dynamic finite element analysis is performed to simulate a forged aluminium wheel during SAE impact test. The structural damage parameter of the wheel is estimated by the strain energy density, and the fracture criterion is based on the total plastic work of the wheel material. Computer simulation of wheel impact test can significantly reduce the time and cost required to finalize a wheel design.

13

Criteria of material selection for ballistic shields in the context of chosen degenerated models

Kulisiewicz M., Bocian M., Jamroziak K.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 2

505-509

EN

Purpose: The models come from complex rheological models that static and quasi-static loading analysis was presented in the following publications. The main conception of the research is determination of the mechanical properties of ballistic shield materials with the use of the complex constitutive compounds. Design/methodology/approach: In the paper criteria of material selection for ballistic shields in the context of chosen degenerated models are described. Findings: Based on the research in direction of the first phase analysis of the punching process the final result gives designing criteria for the new effective ballistic shields. The results of the presenting analysis give specific technical solution in the context of material selection for the ballistic shields. Practical implications: The article exemplifies the importance of material selection that is responsible for the first punching phase. That data is necessary to design the optimal ballistic shields. Originality/value: The new conception based on degenerated model finds application in analysis of punching process. Nevertheless application of the technical solution will be possible after the new material testing methods are curried out (identification methodology in the dynamic conditions). This is the main goal in the next step of the research.

14

Analysis and modelling of rotational systems with the Modyfit application

Żółkiewski S.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 30, nr 1

59-66

EN

Purpose: of this article is to present an application to analysis and modelling of rotational systems. Independent modules of application enables controlling and regulation of characteristics of systems in transportation. The base problem of analyzing systems in transportation is expressing the interaction between the main motion and local vibrations of subsystems. Design/methodology/approach: Mathematical models derived in previous articles were used to implement the mathematical models in numerical calculations. The objectives of creating the Modyfit application were connected with analyzing and modelling rotating systems with taking into account relations between major and local motions. Considerations were done by the Galerkin's method. Findings: There are many effects of analyzing systems with rotation consideration. Main of them are connected with analyzing systems in function of increasing the value of angular velocity. In such way of analyzing we can observe creating additional poles in the dynamical characteristics and we can also observe that instead of modes there are created zeros. Research limitations/implications: Analyzed systems are simple linear homogeneous beams and rods. Working motion is limited to plane motion. Future research would consider complex systems, damping and nonlinearity. Practical implications: of the application are numerical analysis of beams and rods in rotational transportation and designing such systems. Thank to the Modyfit we can derived the stability zones of analyzed beams and rods and we can observe eigenfrequencies and zeros in function of angular velocity. Originality/value: The Modyfit is a forerunner implementation of derived models in a numerical environment of dynamical flexibility. Analyzing models are rotating flexible systems with consideration the rotational transportation effect.

15

Numerical analysis of beams on unilateral elastic foundation

Torbacki W.

Archives of Materials Science and Engineering

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2008

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Vol. 29, nr 2

109-112

EN

Purpose: The main issue of this paper is to present results of finite element analysis of beams elements on unilateral elastic foundation received with a use of special finite elements of zero thickness designated for foundation modelling. Design/methodology/approach: Computer strength analysis with a use of Finite Element Method (FEM) was carried out. Findings: The paper presents possibilities of special finite elements of zero thickness which enable taking into consideration unilateral contact in construction-foundation interaction as well as an impact of surrounding construction environment to its behaviour. Research limitations/implications: Further researches should concentrate on taking into consideration a multi-layer aspects as well as elasto-plasticity of foundation. Practical implications: Modern engineering construction on elastic foundation analyze require not only standard analysis on Winkler (one parameter) foundation but also calculation of construction on two-parameter foundation which will take into consideration a possibility of loosing contact between construction and foundation (unilateral contact). Originality/value: The paper can be useful for person who performs strength analysis of beams on elastic foundation with a use of finite element method.

16

Research activities of computer-aided materials processing laboratory

Im Y. T., Lee H. W., Lee H. C., Awais M., Jin Y. G., Jung K. H., Jung K. H.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 1

219-229

EN

Purpose: of this paper is to review the research works carried out at the national research laboratory for computer-aided materials processing at the department of mechanical engineering at KAIST. Design/methodology/approach: The research papers published so far from the laboratory were carefully reviewed and highlights for developing simulation tools for mesh generation, 2D or 3D finite element analyses for forging, shape rolling, solidification, semi-solid forging, compression molding of thermoset composites, injection molding without or with short fibers, and expert system for multi-stage axi-symmetric cold forging, extrusion, and multi-pass shape rolling are recaptured. Findings: According to this survey, the important issues involved with program developments and their industrial applications were revisited. Research limitations/implications: Understanding of material behaviour at various processing conditions and characterization of proper boundary conditions in terms of friction and temperature should be carefully made. Handling of complex geometry and computational efficiency for such geometry should be improved as well. Further development of three dimensional design systems should be necessary. Practical implications: Proper usage of the simulation tools and interface such tools with the automatic design system with the help of artificial intelligence will be very useful at the design stage of new manufacturing products and processes. In addition, proper understanding of deformation mechanics is of importance to properly utilize such numerical tools. Originality/value: Various aspects of limitations involved with program developments and their usage are identified and some important industrial applications demonstrated.

17

Numerical strength and fatigue analysis in application to hydraulic cylinders

Torbacki W.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 25, nr 2

65-68

EN

Purpose: The main issue of this paper is to present results of strength and fatigue limit analysis applied to piston type hydraulic cylinders. It will also shows advantages of application of the up-to-date digital chain of engineering analysis within which CAD tools are being used as well as strength and fatigue limit analysis. Design/methodology/approach: Computer analysis of the strength analysis by using Finite Element Method (FEM) and fatigue life analysis by using Fatigue Life Prediction Method (FLP) were carried out. Findings: The most strenuous and at the same time opened to a damage risk cylinder zones were localized. Two construction solution possibilities of fixing the tongue stub with a hydraulic cylinder jacket were analysed. Finally Wöhler fatigue graphs for a different values of operating average pressure and stress concentration factor were presented. Research limitations/implications: Further researches should concentrate on modifications and analysis which will help to recognize the best possible zones of fixing a tongue stub with a hydraulic cylinder jacket in order to find the best configuration of construction kinematic pair. Practical implications: Modern engineering construction analyze require not only standard strength analysis but also calculation of fatigue life. Originality/value: The paper can be useful for person who performs strength analysis with a use of finite element method but has never used digital fatigue life analysis method. It might be also useful for a person interested in recognizing of both methods.

18

Modified design for the poppet in check valves

Lee S. W., Shin D. Y., Byun C. W., Yang H. J., Paek I. C.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 23, nr 1

67-70

EN

Purpose: of this paper: The check valve, which is composed of sleeve, connector and poppet, is the one direction valve that blocks fluid flow. The sleeve and connector are constrained and fixed. But the position of the poppet is swiftly moved by the direction of the fluid pressure. In this check valve, water hammer is applied to the poppet by rapid pressure change. Impact of the water is a reason why the fracture of the poppet is occurred. Using computational fluid dynamics (CFD) and finite element method (FEM), the design of the poppet was verified and modified to avoid the fracture. The diameter of the flow path in the poppet decreased from 6.0 mm to 5.0 mm. By CFD, differential pressure of the modified design was compared with differential pressure of the initial design. So, safety for the structure of the poppet was analyzed and verified using available commercial software MSC.MARC. Based on the numerical results, differential pressure increased about 8.7 %. However, Von Mises stress of the old poppet with 6.0 mm was two times that of the new poppet. It is verified and disclosed from the experiment results that the newly modified poppet had no problem being used in a practical product. Design/methodology/approach: In this paper, pressure loss was calculated by CFD. As such, safety for the structure of the poppet was analyzed and verified using available commercial software MSC.MARC. Findings: Safety and pressure loss of the modified design are obtained from CFD and FEM. Research limitations/implications: CFD is very complicated in regards to boundary and surface condition of the wall such as surface roughness. Therefore, calculated results using CFD are definitely verified by practical experimentation. Practical implications: When the design is modified, the number and expense of the experiment is reduced. Originality/value: The new design for the poppet was analyzed and modified by CFD and FEM. So the modified poppet was verified through the real experiment and is available in a practical product.

19

Materials science virtual laboratory as an example of the computer aid in materials engineering

Dobrzański L. A., Honysz R.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

219-222

EN

Purpose: The purpose of the presented article is to describe the material science virtual laboratory, which is an open scientific, investigative, simulating and didactic medium for the realization of the didactic and educational tasks performed by traditional and e-learning methods. Design/methodology/approach: The laboratory is an aggregate of testers and training simulators, placed in the virtual reality and created in various languages and the programming techniques, which represents the properties, functionality and manual principles of real equipment installed and accessible in the real laboratories of scientific universities. Findings: Application of the equipment, that is practically imperishable, cheap in exploitation and easy in the use certainty will encourage students and scientific workers to independent audits and experiments in situations, where the possibilities of their execution in the true investigative laboratory will be limited because of the high material costs, difficult access to real equipment or the possible risk of his damage. Practical implications: The use possibilities of the virtual laboratory are practically unrestricted; it can be a base for any studies, course or training programme. It is assumed, that the project of the laboratory as fully multimedial. The participants of this laboratory can e.g. investigate training experiments from the definite field of material engineering, give questions, pass tests, contact with lecturers and the different users of the laboratory and obviously on participate in his design and content. Originality/value: The project of the virtual laboratory corresponds with the global tendency for expand the investigative and academical centers about the possibilities of training and experiments performance with use of the virtual reality. This enriches the education programme of the new abilities reserved so far exclusively for effecting only on real equipment.

20

Analysis of a degenerated standard model in the piercing process

Jamroziak K.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 22, nr 1

49-52

EN

Purpose: The purpose of this paper is the mathematical description of the impact phenomenon of a bullet of the speed ca. 400 m/s, with the use of a degenerated model. Design/methodology/approach: In the study, an attempt has been made to apply an untypical model for the piercing phenomenon analysis. Basing on the model, the theoretical analysis of the piercing phenomenon in quasistatic and dynamic load conditions, in the impact load form, has been carried out. Findings: This analysis enabled derivation of significant conclusions useful in the design process of effective ballistic shields. Research limitations/implications: In the study, the concept has been assumed that a dynamic model, simple as possible, that may be analyzed not only by numerical methods but also (at least approximately) with the mathematical analysis methods, may provide significant directions concerning material piercing. Practical implications: The use of so called degenerated model allows to describe the phenomenon in more detail at various piercing speeds what extends the possibilities in the sphere of designing the optimum ballistic shields and of identification of the properties of materials applied for construction of shields. Originality/value: The proposed method of identification of material properties in the piercing process, within the relation: force - deforamtion, is a novel one since the essence of the identification is the standard rheological model in an adequate plastic component describing the viscous attenuation with dry friction.