Wyniki wyszukiwania - Biblioteka Nauki

1

Design modifications of pressure boilers with flat endplates with stress relief groove

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Szybiński B. , Wygoda M.

Journal of KONES

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2017

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tom Vol. 24, No. 3

309--316

EN

Stress concentration is still present in the vicinities of structural notches in engineering structures. Zones with higher level of stress are particularly dangerous for structures subjected to fatigue or dynamic loads. The vessels with flat endplates with stress relief grooves are the common examples of such structures. Unfortunately, no clear evidence is given in existing codes how optimally to choose the circular groove radius and the optimal value of that radius depends on the dimensions of the boiler, operating conditions and the material used in manufacturing. Additionally, commonly used grooves with circular shapes are not optimal. Series of experimental tests, numerical or analytical studies presented in numerous articles confirmed these facts. In the presented article, the Authors proposed two-stage modification of the investigated vessel. The first step relies on change of the shape of the groove in the endplate, which provides certain reduction of stress concentration but still plastic deformations in the groove vicinity are not eliminated. The second step of the design modification is proposed for the boiler with the optimal elliptic groove configuration. In this step, some material is added around the top of the outer edge of the endplate. Two simple shapes are proposed for these parts - the short cylindrical ring or alternatively the circular ring welded on the top the endplate is used. For both concepts, the search of optimal dimension/parameters is performed. The numerical results of that study clearly show that the full elimination of plastic deformations near the groove is possible. The numerical analysis and optimizations were made with the well- established finite element software ANSYS, which is accepted by commonly used codes for designing of pressure vessels.

2

Obliczenia sejsmiczne budynku hali handlowej

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Jurkowski K.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2013

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tom z. 102

57-58

EN

This paper presents the results of FEM analysis of dynamic trading hall to the influence of shock mining using Eurocode 8, on LGOM area. Seismic calculations were done in package Autodesk Robot Structural Analysis with the built-in module for seismic calculations.

3

Influence of mesh refinement on results of elastic-plastic FEM analysis

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Szabracki P. , Lipiński T.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2014

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tom nr 17(2)

149--163

EN

To improve fitting of numerical results to experimental data, in the past, distances between nodes were decreased for whole mesh. A typical mesh generator for Finite Element Method (FEM) analysis ensures possibility to decrease distances between nodes for edges or surfaces of described geometries. Influence of local mesh refinement for a flat and round tensile specimen on fitting of numerical tensile simulation results to experimental data was presented in the paper. Local mesh refinement was performed for areas with the error values higher than threshold value. First iteration of flat and round mesh refinement has to improved correlation of numerical and experimental data with acceptable increase of mesh file size. Similar observations have been made for the second iteration of the flat specimen mesh. On the basis of analysis, shown that second iteration of round mesh refinement caused crucial increase of mesh file size and computation time with negligible fitting improvement.

4

Identification of thermo-mechanical properties of natural polymers with a hybrid method

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Malujda I. , Talaśka K.

Engineering Transactions

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2016

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tom Vol. 64, iss. 4

635--641

EN

This article presents the results of experimental research into beech wood shearing. The applied research methodology has made it possible to obtain average values of basic strength parameters of wood: ultimate strength, yield point and the Kirchhoff’s shear modulus. In order to investigate the phenomenon of wood damage resulting from shearing forces, the attempt has been made to use the hybrid method. It combines the advantages of experimental research with a detailed investigation of the phenomenon by means of FEM analysis. The wood shearing tests have been recreated in Abaqus software in order to identify the areas in wood specimens where damage stresses appear first. The article contains sample results of experimental and numerical research with their comparative evaluation.

5

Theoretical and numerical study of the flexural behaviour of BFRP RC beams

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Pawłowski D. , Szumigała M.

Engineering Transactions

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2016

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tom Vol. 64, iss. 2

213--223

EN

Fiber-reinforced polymer (FRP) bars are a relatively new reinforcement material used in civil engineering. This type of reinforcement has low modulus of elasticity and high tensile strength. Hence, the behaviour of FRP reinforced concrete (RC) members is significantly different to that of traditional steel RC. This paper presents the results of numerical and theoretical studies of the flexural behaviour of simply supported basalt fiber-reinforced polymer (BFRP) RC beams under short-term static loads. The numerical analysis was performed using the finite element method (FEM). The main goal of this paper was to investigate deflections and failure mechanisms of BFRP RC members depending on the reinforcement ratio. The results of the numerical analysis were examined and compared with code formulations.

6

Comparative analysis and modelling of newly developed and unconventional processes of plastic forming of toothed gear elements

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Michalczyk J. , Wiewiórowska S. , Muskalski Z.

Archives of Metallurgy and Materials

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2019

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tom Vol. 64, iss. 1

87--94

EN

The article reports the results of a comparative analysis made for three novel unconventional gear wheel forging processes based on the authors’ patented [5,6,21] plastic forming methods developed chiefly for the purposes of extruding hollow products as well as valves and pins. These processes are distinguished by the fact that part of the tooling elements which are normally fixed during conventional forging are purposefully set in motion. This is intended to change the conditions of friction at the metal-tool contact surface and to induce additional thermal effects due to the transformation of the plastic deformation energy into thermal energy and, as a consequence, to improve the plastic flow of metal and to reduce the force parameters of the process.

7

Badanie symulacyjne wpływu geometrii tarczy hamulcowej na efektywność jej chłodzenia

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Antczak K. , Sosnowski M.

International Journal of Engineering and Safety Sciences

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2020

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tom Vol. 1

39–52

PL

W artykule poruszono problem chłodzenia tarcz hamulcowych oraz ich wpływ na bezpieczeństwo. Wykonano trzy warianty chłodzenia tarcz hamulcowych, które następnie zostały wykorzystane w analizie obciążenia termicznego z użyciem MES.

EN

The article discusses the problem of brake disc cooling and its impact on safety. Three variants of brake disc cooling were made, which were then used in the thermal load analysis with the use of FEM.

8

Numerical analysis of contact plastic bodies made by aluminium alloy with taking account of micro-roughness surfaces

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Sidun P. , Piwnik J.

Journal of Theoretical and Applied Mechanics

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2019

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tom Vol. 57 nr 1

73--84

EN

The following article describes selected aspects of numerical modeling of the process of bonding metal alloys with consideration for micro-roughness. Plastic contact between two deformable bodies is studied within a DEFROM FEM environment. The paper presents selected numerical analysis results for an aluminum alloy. The mathematical model of surface roughness has been created on the basis of the surface real profile. The dependence between the tool lathe angle and the feed has been used to build a numerical model of roughness after completion of the turning process. The article investigates the impact of wave roughness in respect to the size effect and the possibility of cold welding as well as the simplification process of real surface roughness.

9

Influence of Modifications on Fatigue Strength of AlSi17Cu5Mg(Fe) Alloy Used for Pistons for Internal Combustion Engines

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Piątkowski J. , Wieszała R.

Archives of Metallurgy and Materials

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2018

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tom Vol. 63, iss. 1

135--141

EN

Technological progress in construction of automotive vehicles, particularly in construction of engines, enforces simultaneous changes in foundry properties of aluminum alloys used in automotive industry. Until recently, abrasion resistance was the main usability criterion of a material used for pistons for internal combustion engines. At present however, because of the complexity of the process of the fuel mixture combustion, more restrictive standards of limited hydrocarbon emission, and the pursuit of reduction of the vehicle’s mass, fatigue strength of silumins enjoys a continuously increasing interest. The paper presents results of a computer simulation using the finite element method (FEM) and a real fatigue test of AlSi17Cu5Mg(0.5Fe) (A390.0) alloy with unilateral variable bending. The tests aimed to simulate a deflection of a combustion engine piston in a cylinder barrel were carried out in two variants: for a non-modified alloy and an alloy modified with CuP10 master alloy. Based on the distribution of stresses according to the Huber-Mises-Hencky theory (for a given range of the deflection from 0.1 to 0.3 mm), Wöhler curve was determined for the studied alloy. Based on on microstructural investigations, cracks of primary Si crystals were found, caused by fatigue changes resulting from unilateral pulsating vibrations.

10

FEM analysis of critical loads plate with cut-out

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Falkowicz K. , Ferdynus M. , Wysmulski P.

Applied Computer Science

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2015

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tom Vol. 11, no 2

43--49

EN

The work presents the original conception of thin-walled plate element with the cut-out of irregular shape for use as a elastic or bearer element. The influence of geometrical parameters and the shape of the cut-out on the value of the critical load of the structure was researched. To discrete model and to perform numerical calculations used commercial program ABAQUS. Numerical calculations constitued own solution problem of compression structure and are the initial stage of research on work construction in elastic postcritical field with forced torsional-bending form of loss of stability was performed.

11

Verification of ram-press pipe bending process using elasto-plastic fem model

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Sidun J. , Łukaszewicz A.

Acta Mechanica et Automatica

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2017

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tom Vol. 11, no. 1

47--52

EN

In this paper selected aspects of numerical modelling of bending pipes process are described. Elasto-plastic material model was used in COMSOL FEM environment. The results of numerical analyses of two kinds of steel were presented. The correctness of the proposed model was verified based on comparison shapes of deformed pipe profile obtained at the ending step of bending both from numerical simulations and experiment.

12

FEM approach to estimate the behaviour of biocomposite metal-surface coating systems

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Sobieszczyk S. , Wojnicz W. , Nowak B.

Advances in Materials Science

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2008

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tom Vol. 8, nr 1(15)

153-158

EN

A three dimensional (3D) model of biocomposite metal-surface coating system, which is influenced by known external forces, is proposed. This model consists of the metallic substrate (Ti6AI4V) and the hydroxyapatite (HA) coating. Using FEM (finite element method), strain-stress maps of model were generated for investigating rela-tions between the extreme stress of HA coating and the magnitude of external force and the thickness of the coat-ing. The analysis of numerical simulations results confirms that the system with the greatest coating thickness (i.e. 10-3 m) has the least extreme stress in this surface coating.

13

Short review and 3-D FEM analysis of basic types of foundation for offshore wind turbines

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Iwicki P. , Przewłócki J.

Polish Maritime Research

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2020

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tom nr 3

31--39

EN

Some problems of the foundations of offshore wind turbines are considered in this paper. A short review is presented on the two basic types of foundations, i.e. monopiles and gravity foundations, including their basic features and applications as well as general design considerations. Also, some issues regarding analysis are discussed, including geotechnical problems and modelling techniques. A numerical model of offshores turbine and some preliminary computations are presented. Finite element analysis was carried out for wind turbines supported on both gravity and monopile foundations. The wind turbine tower, blades (simplified model), gravity foundation and part of the surrounding soil are included in the model. The turbine was loaded by wind and loads induced by waves, inertia and gravity. Both non-linear static and dynamic analysis of the wind turbine was performed. The displacements and stresses under the tower foundations were calculated and a comparison analysis carried out.

14

Development and Modelling of a Novel Process of Manufacturing Cylindrical Products with a Variable Longitudinal-Section Stub Pipe

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Michalczyk J. , Wiewiórowska S. , Muskalski Z.

Archives of Metallurgy and Materials

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2019

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tom Vol. 64, iss. 3

1187--1193

EN

The publication presents a novel concept of the process of plastic forming of variable longitudinal-section cylindrical products, being the subject of Patent Application P.427426 [1]. Additionally, these products are provided with a connection stub pipe. The plastic forming method proposed in the article combines many advantages and utilitarian benefits associated with the manufacturing technology itself, as well as with its further implementation. Using stock in the form of normalized bar commonly available in the metal product market as a finished product obviously reduces the process costs involved with stock preparation, i.e. casting, rolling, machining, etc. It also results in obtaining a much smaller surface area of stock contact with the tool and, as a consequence, a smaller surface of stock friction against the tool, which contributes to a reduction of force needed for the plastic forming of the product. The smaller contact surface area and the shorter time of stock contact with the cooler tool cause, above all, less intensive heat exchange and stock chilling. This has a significant effect on the plasticity of the cast material and, as a consequence, the plastic forming force. The proposed method enables also manufacturing cylinders with either a closed or open stub pipe with a regulatedlength and a varying section. In addition, unlike the method known from Polish Patent Specification PL 212062 [2], the proposedmethod does not require using a multi-tool press. The upper punch is furnished with a flange, whose job is to start the stock extrud-ing sleeve at the next process stage.

15

The Development and Modeling of an Innovative Process of Forming the Internal Toothing of Flange Coupling Spline Sleeves

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Michalczyk J. , Wiewiórowska S. , Muskalski Z.

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16

Impulse Excitation in a Watertight Steel Circular Cylindrical Shell and Influence of Structural Configuration on Underwater Radiated Noise

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Wu C.-I. , Too G.-P. , Wu B.-H.

Archives of Acoustics

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2023

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tom Vol. 48, No. 4

509--521

EN

This study used experimental measurements and the finite-element method (FEM) simulations to investigate transient underwater radiated noise induced by the impulse excitation of water surrounding a watertight steel-structured circular cylindrical shell submerged in the 176 × 8 × 4 m towing tank. The excitation was caused by dropping an iron block onto a structural bracket in the shell to generate structural vibration. The experimental results were found to be consistent with the FEM results, with the difference between the experimental and simulated sound pressure levels being less than 3 dB. Moreover, it was determined that the structural vibration also generated airborne noise in the cylindrical shell, but this contributed much less than the impulse excitation to the induction of underwater radiated noise. Finally, analysis of the sound field of the underwater noise radiation showed that it was influenced by the wall thickness of the watertight steel cylindrical shell and that of the reinforced bracket seat structure. In particular, the structural reinforcement position proved to be the diffusion breakpoint of the underwater sound radiation. This demonstrates that compared with the studied structure, a thicker and more complex reinforced structure will transmit less or incomplete sound radiation into water.

17

Statistical and Probabilistic Techniques in Modeling of Epoxy Cracking Phenomena

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Nowak T. , Ambroziński M.

Computer Methods in Materials Science

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2013

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tom Vol. 13, No. 1

49--55

EN

Epoxy resins filled with mineral particles, such as silica and alumina, are well known and extensively used as insulating materials in power product applications. They are relatively cheap and easy to process, and their dielectric, thermal and mechanical properties are appropriate to maintain their functionality in different electrical devices. However, the mechanical performance of particle filled epoxy systems can be often influenced by limited resistance to cracking. It is frequently experienced during the lifetime of the epoxy cast products that some members of the production lot will crack during verification tests, while the others will remain healthy, even if the test loads are seriously increased. It is especially seen during low-temperature tests, when the thermal conditions are changed from +120°C to -60°C, when a few products can crack at +10°C, while others may easily survive till end of the tests. This phenomenon prohibits of using the classical material strength as a failure criterion. For this reason, some statistical and probabilistic approaches to describe the cracking resistance of the epoxy-based material have to be considered. This work is focused on a study of process-induced residual stresses in epoxy components and their effect on material cracking likelihood. The proposed failure probability model incorporates Weibull distribution. The paper provides the experimental procedure for estimation of the Weibull model parameters (α,β), as well as implementation remarks. In addition, the Design of Experiment (DoE) method was used to support FEM calculations, and to find out the correlation between product design parameters and the failure likelihood. Finally, the article outlines some recommendations for applying statistical and probabilistic methods into numerical procedures of FEM analysis.

PL

Żywice epoksydowe zawierające napełniacze mineralne, takie jak tlenek glinu czy krzemionka, są chętnie stosowane jako materiały izolacyjne w produktach przemysłu energetycznego. Materiały te oferują dobre właściwości dielektryczne, termiczne oraz mechaniczne, są stosunkowo łatwe w obróbce, a jednocześnie ekonomiczne. Jednak żywice epoksydowe z napełniaczami mineralnymi wykazują także pewne wady, wśród który najbardziej kłopotliwą jest niska odporność na pękanie. Cecha ta, jest tym bardziej uciążliwa, iż ma charakter silnie stochastyczny. Często zdarza się bowiem, że realizacja cyklicznych testów zmienno-temperaturowych w zakresie roboczym od -60°C do +120°C skutkuje zniszczeniem części próbek już przy pierwszym cyklu przy temperaturze +10°C, podczas gdy inne produkty zachowują swoją integralność przez cały zakres testu. Taki charakter materiału w znaczniej mierze utrudnia zastosowanie klasycznie rozumianej wytrzymałości materiału, jako kryterium zniszczenia. Zachęca natomiast do zastosowania metod statystycznych, dzięki którym zjawisko pękania żywicy epoksydowej można opisać w sposób probabilistyczny - bliższy rzeczywistości. W artykule przedstawiono analizę naprężeń mechanicznych wywołanych procesem produkcyjnym elementu z żywicy epoksydowej z napełniaczem mineralnym, zawierającego metalowe elementy. Z uwagi na stochastyczny charakter zjawiska pękania takich wyrobów, zastosowano model zniszczenia w oparciu o rozkład Weibulla. Zaproponowano doświadczalną procedurę dla wyznaczenia parametrów modelu Weibulla (α,β), jak również wskazano algorytm uzupełnienia deterministycznych metod obliczeniowych MES o model prawdopodobieństwa. Wykorzystano statystyczną metodę projektowania eksperymentu (DoE) by przeprowadzić analizy numeryczne MES w taki sposób, by uzyskać liczbową korelacją pomiędzy parametrami geometrycznymi projektowanego wyrobu a jego prawdopodobieństwem zniszczenia. Artykuł przedstawia także kilka zaleceń praktycznych zarówno dla wykorzystania metod statystycznych i probabilistycznych w obliczeniach numerycznych, oraz sposobów obniżenia naprężeń rezydualnych w wyrobach z żywicy epoksydowej.

18

Identification of strains in a multilayer composite pipe

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Krysiak P. , Kaleta J. , Gąsior P. , Błachut A. , Rybczyński R.

Zeszyty Naukowe / Wyższa Szkoła Oficerska Wojsk Lądowych im. gen. T. Kościuszki

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2017

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tom Nr 4

272--282

EN

The paper presents the measurements and the analysis of deformations between layers and the outside surface of a multilayer filament wound composite pipe. The pipe was made through the hoop wrap of roving stripes hence ring-shaped samples were prepared for test purposes. Carbon fibers and glass fibers were used for winding. In the course of their manufacturing, strain gauges and fiber optic sensors were placed between the composite layers. Then, the strength tests were performed. The samples were subjected to the internal pressure of 30 MPa. During the tests peripheral deformations were measured on outside surfaces of individual layers of the structure.

19

The analysis of stresses and displacements beneath strip foundations in terms of FEM

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Sternik K.

Foundations of Civil and Environmental Engineering

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2010

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tom No. 13

73--89

EN

Soil is a material dependent on the load history. The load history has a significant influence on stress distribution in the ground beneath the footing and the settlement of a foundation. In the paper the load history has been considered as the sequence of loading the ground with two strip footings. Differences in the distributions of stresses in the ground as well as the settlements of footings have been shown. Nonlinear load-settlement relationship does not allow the application of the principle of superposition.

20

Finite element analysis of the pillar - guide tool setup of the machine for microforming processes

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Zimniak Z. , Marciniak M. , Polak S.

Computer Methods in Materials Science

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2013

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tom Vol. 13, No. 3

402--406

EN

In contrast to traditional manufacturing applications, small-scale manufacturing processes usually require sophisticated equipment which is generally associated with high costs and low productivity. Current trends suggest manufacturing metallic parts by ‘microforming’. Microforming is a well suited technology, in particular in case of mass production, of very small metallic parts required in many industrial products and resulting from widespread application of micro technology. Fundamental issues and problems in the micro world are connected with processes, forming tools, construction of the machines, handling of micro parts, equipment and also with material. The dimensions of micro machines are much smaller than those of conventional large-scale presses. The development of such machines has attracted a lot of interest from researchers for many years. The purpose of this study was to optimize a tool system concept and to investigate its stiffness. FEM analysis was carried out to receive the theoretical stiffness. For receiving experimental stiffness laser interferometer was used. Based on experimental and FEM results it can be concluded that the designed tool system is useful for microforming processes.

PL

Ciągły wzrost popytu na miniaturowe części, takie jak na przykład: mikrośruby, mikronarzędzia, czy mikroimplanty - stosowane w inżynierii biomedycznej, powoduje szybki rozwój metod mikroformowania z zastosowaniem obróbki plastycznej. W przeciwieństwie do tradycyjnych zastosowań produkcyjnych, procesy produkcyjne elementów w małej skali wymagają przeważnie skomplikowanego sprzętu, co wiąże się z wysokimi kosztami i niską wydajnością. Mikroformowanie jest odpowiednią technologią do produkcji bardzo małych metalicznych elementów, zwłaszcza w przypadku produkcji masowej. Podstawowe zagadnienia i problemy w „mikroświecie” są głównie zawiązane z samym procesem technologicznym, narzędziami, konstrukcją, sprzętem, a także z samym materiałem. Mikromaszyny mają znacznie mniejsze wymiary niż konwencjonalne maszyny. Zainteresowanie nimi znacznie wzrosło w ciągu ostatnich lat. Celem pracy jest optymalizacja koncepcji przyrządu wchodzącego w skład urządzenia do mikroformowania w oparciu o symulacje numeryczne oraz wyznaczenie jego sztywności. Sztywność teoretyczna została wyznaczona przy zastosowaniu analizy MES. Przy użyciu interferometru laserowego na specjalnie zaprojektowanym stanowisku badawczym możliwe było wyznaczenie eksperymentalnej sztywności. Badanie sztywności nowego urządzenia ma duże znaczenie, ponieważ w głównej mierze to od niej zależy prawidłowy przebieg procesów formowania, a także jakość wykonanych elementów. Na podstawie wyników doświadczalnych i numerycznych potwierdzono przydatność zaprojektowanego i wyprodukowanego przyrządu do zastosowań mikroformowania.