Wyniki wyszukiwania - BazTech

1

Characteristic Features of Hybrid Bridge Structure Models

Machelski Czesław

Civil and Environmental Engineering Reports

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2021

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Vol. 31, no. 1

44--53

EN

This work discusses the classification of bridge structures and their models. Examples of hybrid models are also indicated in the case of homogeneous and mixed structures. Where hybrid design and model cases are presented, an algorithm for the analysis of contact interactions between subsystems is provided. The soil and shell structure is adopted as an example of analyses, where in its characteristic feature, differentiating it from classic bridges, is the large influence of both the soil backfill and the road surface as load-bearing elements of the structure. There are two structural subsystems present in the model of the soil-shell structure: a corrugated sheet coating and a soil backfill with a surface. The interaction between them is modeled as a contact interaction, i.e. forces with a direction normal and tangent to the line of the circumferential band of the shell. The paper presents an algorithm of their analysis, resulting from the outcomes of tests with the use of strain gauges, with the load being a vehicle changing its position. The advantage of the algorithm is that it takes into account the actual physical properties of the soil in the backfill layers and the contact layer of the coating with the soil. Direct contact force measurements along the entire length of the circumferential strip are very difficult. In practice, pressure gauges are used to determine normal interactions.

2

Modelowanie numeryczne geometrii wzorców wad powierzchniowych szyn kolejowych

Lesiak Piotr, Podsiadło Rafał

Przegląd Komunikacyjny

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2019

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R. 74, nr 6

14--18

PL

W pracy przedstawiono wybrane modele geometryczne wzorców wad powierzchniowych szyn kolejowych. Wykorzystano do tego celu aplikację grafiki komputerowej opartą o krzywe Béziera, zaimplementowaną w programie symulacyjnym UM Loco. Pozwoliło to na zamodelowanie profili szyn z wzorcowymi wadami. Tak utworzone wady, posłużyły do badań symulacyjnych dynamiki układu tor - pojazd, przy przejeździe wagonu towarowego z różnymi prędkościami. Przeanalizowano wpływ wymiarów wybranych wzorców wad, na wartość sił kontaktowych, pod kątem zagrożeń eksploatacyjnych.

EN

The paper presents selected models of geometric patterns of surface flaws in railway rails. The simulation based on Bezier's splines has been carried out using UM Loco simulation software. It allows for the simulation of the rail profile with pattern flaws. These flaws have been used to simulate dynamic interaction between the vehicle and the track for the freight carriage moving with different speeds. The impact of the flaw dimensions on the contact forces have been analyzed.

3

Badania symulacyjne wpływu sprężystych deformacji promieniowych obrotowego pierścienia na siły kontaktowe w łożysku skośnym

Muszyński Mateusz

Modelowanie Inżynierskie

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2019

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T. 40, nr 71

63--68

PL

W pracy przedstawiono wyniki badań symulacyjnych sił kontaktowych łożyska skośnego. Badania przeprowadzone zostały przy użyciu metody elementów skończonych. Dzięki zastosowaniu dwóch różnych sposobów podparcia wirującego pierścienia możliwe było określenie wpływu jego przemieszczeń na kierunku promieniowym na siły kontaktowe. Przemieszczenia te, których wartości są bardzo niewielkie - rzędu kilku μm, są efektem działania dużych sił odśrodkowych i istotnie wpływają na siły oddziaływania między kulką a bieżnią. Na podstawie wyników symulacji można stwierdzić, że pominięcie deformacji pierścienia skutkuje zaniżeniem wartości sił kontaktowych przy dużych prędkościach obrotowych, co może doprowadzić do zaniżenia wielkości modelowanych oporów mchu.

EN

The paper presents results of simulation tests of contact forces in angular bearing. Research was carried out using the finite element method. Using two different ways to support the rotating ring it was possible to determine the impact of its displacements on the radial direction on contact forces. These displacements, whose values are small - a few μm, are the effect of a large centrifugal forces and have an important impact on the forces between the ball and raceway. Based on the results of the simulation, it can be concluded that the omission of the deformation of the ring results in the undervaluation of the contact forces at high rotational speeds, which may lead to underestimation of the modeled motion resistance.

4

Regression model change of normal contact forces in hexagonal idler housing for pipe conveyor loaded with transported material

Molnár Vieroslav, Stehlíková Beáta

Advances in Science and Technology. Research Journal

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2018

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Vol. 12, no 2

244--251

EN

Pipe conveyors make up important elements of ecological transport systems. They ensure the material is transported in the conveyor belt coiled to the shape of a pipe. Various stresses impact their most important component - the conveyor belt - straining it in both, the longitudinal and the transverse direction. This phenomenon arises in connection with the shape of the conveyor route of the pipe conveyor, the width and thickness of the conveyor belt, the volume of the material conveyed, and the like. In recent years, more and more authors have been researching contact dependencies of the normal forces acting on the idler rolls located in idler housings. Their task is to design such structure of a conveyor belt that will put the least strain on the idler rolls, thus significantly reducing the power required to ensure the movement of the pipe conveyor. In this way, greater efficiency of eco-friendly transport will be achieved. Following experimental research, the paper describes a regression model of dependencies of normal contact forces on tension forces required, as per individual idler rolls in idler housing.

5

Design of a calculation fem model of the test static set-up of pipe conveyor for analysis of contact forces

Fedorko G., Molnár V.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 2

220--225

EN

Experimental research in the field of pipe conveyors is a difficult matter and yet necessary in order to answer the questions regarding the motion resistances and contact resistances of pipe conveyors, loading of the conveyor belts etc. These research activities can be performed not only during the actual operation of pipe conveyors, but also by means of the special laboratory test set-ups combined with the application of the computational simulation models. The main task of this paper is to assess the creation of a suitable simulation model of the test set-up for a specified pipe conveyor developed with regard to realisation of the FEM analyses, using the software product Abaqus, as well as presentation of its application possibilities.

6

A tension equalizer in lift carrying ropes

Hrabovský L., Michalik P.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 4

326--332

EN

In many high-rise residential buildings or multi-storey warehouses, machinery, so called lifts, are used for the vertical transportation of people or weights between attitudinally distant places. Carriers used for lifts are steel ropes or sprocket chains, on which a cage or a counterbalance is hinged. Apparatus of all carriers, attached to the hinge of the cage or counterbalance, should be even. This can be hundred percently made only by hammer hinge. Fixed or springe hinge cannot be a perfect equalizing apparatus. This article describes an apparatus, which allows an even distribution of the strain into lift carriers, which use springe hinge of carrier ropes.

7

Estimation of the contact forces between the hexapod legs and the ground during walking in the tripod gait

Grzelczyk D., Stańczyk B., Awrejcewicz J.

Vibrations in Physical Systems

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2016

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Vol. 27

107--114

EN

The paper is devoted to the dynamical modelling of the hexapod robot walking on a flat and hard ground. The main goal is to determine time series of reaction forces acting on individual legs of the robot during tripod gait often used both by the six-legged insects as well as mobile walking robots found in engineering applications. The movement of the considered robot is realized by the kinematic excitation of its legs using the so-called Central Pattern Generator (CPG) method. The paper demonstrates that there are different contact forces and overload acting on the robot, resulting from different models working as a CPG. The mentioned forces belong to the important issues that should be taken into account when the robot locomotion on the unknown terrain is planned.

8

Dynamical analysis of a constrained flexible extensible link with rigid support and clearance

Dupac M

Journal of Theoretical and Applied Mechanics

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2014

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Vol. 52 nr 3

665--676

EN

Dynamic response of robotic systems is affected by deformation of their flexible components, velocity and mass of the systems, as well as by the presence of clearance or impact between the components. Since accurate simulations of such robotic systems are increasingly important, the modelling and dynamical behaviour of an extensible mechanism with a rigid crank and a flexible link is investigated in this paper. The equations of motion of the extensible flexible link, constrained to a circular, Cartesian, elliptical, Cassinian, Lame or pear-shaped quartic path, are presented. A dynamical analysis is carried out in order to compare the dynamical response of the flexible link vs. a rigid link under the combined effect of different parameters such as flexibility and clearance. The simulation result shows clear trajectories divergence due to the impact effect of the flexible link on the rigid crank.

9

Simulation of contact forces and contact characteristics during meshing of elastic beveloid gears

Do T. P., Ziegler P., Eberhard P.

Computer Assisted Methods in Engineering and Science

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2014

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Vol. 21, no. 2

91--111

EN

Beveloid gears, also known as conical involute gears with very complex tooth shapes, gain more and more importance in industrial practice due to their ability to realize gear stages with crossed axes. This is why they are frequently found in power transmissions. The most familiar application of beveloid gears is the reduction gear used in marine transmissions, but in the last few years they have also been used increasingly often in the automotive industry. In the last decade many studies on beveloid gears were published, however, the meshing between teeth and the contact characteristics during meshing of beveloid gears still have not been studied in detail using fully elastic models. In this work, the fully elastic multibody approach will be applied to study contact forces and contact characteristics including contact patterns during meshing of straight beveloid gears. To validate the fully elastic approach, simulation results of a beveloid gear pair by finite element method and by the fully elastic multibody system are compared. The comparison shows very good agreement.

10

Simulation of elastic gears with non-standard flank profiles

Do T. P., Siegler P., Eberhard P.

Archive of Mechanical Engineering

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2013

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Vol. LX, nr 1

55--73

EN

There exist cases where precise simulations of contact forces do not allow modeling the gears as rigid bodies but a fully elastic description is needed. In this paper, a modally reduced elastic multibody system including gear contact based on a floating frame of reference formulation is proposed that allows very precise simulations of fully elastic gears with appropriately meshed gears in reasonable time even for many rotations. One advantage of this approach is that there is no assumption about the geometry of the gears and, therefore, it allows precise investigations of contacts between gears with almost arbitrary non-standard tooth geometries including flank profile corrections. This study presents simulation results that show how this modal approach can be used to efficiently investigate the interaction between elastic deformations and flank profile corrections as well as their influence on the contact forces. It is shown that the elastic approach is able to describe important phenomena like early addendum contact for insufficiently corrected profiles in dependence of the transmitted load. Furthermore, it is shown how this approach can be used for precise and efficient simulations of beveloid gears.

PL

Istnieją przypadki, gdy dla dokładnej symulacji sił kontaktowych nie można modelować kół zębatych jako ciał sztywnych, lecz jest potrzebny opis w pełni sprężysty. W artykule zaproponowano model systemu wielu ciał uwzględniajacy styki między zębami, modalnie zredukowany i z zastosowaniem układu odniesienia o płynnych ramach, umożliwiający bardzo dokładną symulację w pełni sprężystych kół zębatych o różnych rodzajach zazębienia. Symulacja jest możliwa dla znacznej liczby obrotów, przy czym wymagany czas obliczeń jest stosunkowo krótki. Zaletą tego podejścia jest, że nie wymaga ono założeń co to geometrii zębów, dzięki czemu można dokładnie badać zjawiska na stykach między zębami dla dowolnych, niestandardowych geometrii zębów, w tym również o skorygowanym profilu powierzchni bocznej. W artykule przedstawiono wyniki symulacji, które pokazują, że takie modalne podejście może być użyteczne przy badaniu zależności między odkształceniami sprężystymi a korekcją profili zębów, a także ich wpływu na siły kontaktowe. Pokazano, ze stosując model sprężysty można opisywać ważne zjawiska, takie jak wczesny kontakt głowy zęba w przypadku niedostatecznej korekcji profilu w zależności od przenoszonego obciążenia. Co więcej, pokazano że opisany sposób podejścia może być wykorzystany przy precyzyjnej i wydajnej symulacji przekładni stożkowych.

11

Analiza sił kontaktowych w warunkach asymetrii struktury koła oraz nieliniowej charakterystyki sprężyny Hertza

Dżuła S.

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

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2006

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z. 1/60

31-40

PL

Praca zawiera wyniki obliczeń numerycznych sił stykowych i niektórych współrzędnych wektora stanu układu dynamicznego jakim jest sprężyste koło kolejowe poruszające się prostoliniowym ruchem tocznym bez poślizgu ze stałą prędkością. Zmienność sił stykowych wywołana jest wymuszeniami dynamicznymi jako odpowiedź układu na dynamiczną asymetrię struktury koła. Dynamiczna asymetria struktury, która może powstać w procesie wytwarzania kół lub ich nierównomiemego zużycia w procesie eksploatacji rozumiana jest jako niewyważone masy tarczy i wieńca koła. Niewyważenia modelowane są jako lokalna ciągła zmiana gęstości materiału koła.

EN

The results of numerical calculations of contact forces and some coordinates of stale vector of dynamic system represented by elastic railway wheel in straight linear rotating motion with constant speed are included in the work. Variations of contact forces are caused by dynamical excitations as the system response to dynamical non-symmetry of wheel structure. The dynamical non-symmetry of structure which can come up in the manufacturing process of wheels or their non-equal wear under operation is understood as unbalanced mass of wheel disc or wheel tire. The non-balances are modeled as local continuous change of wheel material density.