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PL
Przedstawiono zagadnienia związane z dynamiką pracy wałów przegubowych z przegubem homokinetycznym. Główny nacisk położono na ocenę wpływu przegubu w wale poddawanym obciążeniom dynamicznym na drgania poprzeczne centralnej podpory wału.
EN
The article discusses analyze issues of drive shafts incorporating constant velocity joints dynamics. It focuses mainly on an impact of a joint on a shaft center support lateral vibrations caused by dynamic loads.
EN
A mathematical model of dynamic processes in pumping unit of a drilling rig with friction clutch, taking into account variable moment of inertia of slider-crank mechanism links and random number of pistons of the pump, was developed. Joint integration of differential equations of motion of pumping unit parts was carried out with numerical methods. The calculations performed considered the torque moment of friction in the clutch and equations of electromagnetic processes in asynchronous motor. The results of research of run-up processes of pumping unit were presented. The influence of parameters of friction clutch on the performance of pumping unit was established.
EN
The wearing degradation of the structure is accompanied by the increase of non-linear disturbances of the observed dynamic processes. The first of the mentioned effect can become the basis of the technical diagnostics as well as of the prognosis of the machine state change during its maintenance, if only it is possible to describe and measure such effect. In the further part of this study, it is shown that modern methods of signal analysis allow one to achieve such aims. The example of a gearbox diagnosis is considered.
PL
Zużyciu eksploatacyjnemu maszyny towarzyszy zwykle nieliniowe zaburzenie obserwowanych procesów dynamicznych. To zjawisko może stanowić podstawę diagnostyki technicznej oraz prognozy pozwalającej na przewidywanie stanu maszyny w trakcie eksploatacji, jeżeli tylko potrafimy taki efekt zmierzyć i opisać. W artykule pokazano, że nowoczesne metody analizy sygnałów pozwalają na rozwiązanie tego zadania. Rozpatrzono przykład diagnostyki przekładni zębatej.
EN
The study relates to the phenomenon of power distribution in mechanical systems equipped with a dynamic vibration absorber. It is one of the methods of eliminating vibrations in a mechanical system, which stabilises its operation. This solution helps to reduce dynamic stress in subsystems of a vehicle's suspension or stabilise the motion of flying machines, such as helicopters. The article describes the phenomenon of power distribution of structural forces, which has not been described so far. The phenomenon reveals the power distribution in a dynamic structure of a system of interest and can be used to determine the rate of energy flow as a function of the dynamic state resulting from the selection of dynamic parameters of the vibration absorber. The energy analysis applied in the study is based on an energy-based optimization method of adjusting the dynamic vibration absorber to the main mechanical system without changing its dynamic parameters, as is the case, for example, in turbine rotor balancing.
5
Content available remote Modelling friction phenomena in the dynamics analysis of forest cranes
EN
A dynamics analysis of a forest crane, with a special consideration of friction in joints, is considered. The LuGre friction model is applied in all revolute and prismatic joints of the crane. A load handling simulation is performed for a typical operation. Various friction factors and loading conditions are examined. As shown, friction phenomena plays a significant role when defining loads acting on crane elements.
PL
Maszyny elektryczne, zwłaszcza asynchroniczne, są szeroko wykorzystywane w przemyśle. Do grona tego można dopisać maszyny wzbudzane magnesami trwałymi, które zyskują coraz szersze zastosowanie. Jednym z przykładowych zastosowań tego typu maszyn są elektromechaniczne przetwornice częstotliwości. Przetwornice te są wykorzystywane do zasilania stanowisk pomiarowych i testowych przekładników napięciowych lub prądowych. W przetwornicach tych najczęściej maszyną napędzającą jest silnik indukcyjny sprzęgnięty na stałe z generatorem np. wzbudzanym magnesami trwałymi. Generatory te – w porównaniu do innych maszyn – charakteryzują się najwyższą sprawnością oraz największą gęstością mocy uzyskiwanej z jednostki objętości [1]. Maszyny te są powszechnie stosowane do specyficznych warunków pracy [2]. Jednym z takich zastosowań może być trójfazowy generator synchroniczny przeznaczony do pracy jednofazowej, który został przedstawiony w niniejszym artykule. W pracy zaprezentowano model obliczeniowy, wyniki symulacji oraz wyniki badań laboratoryjnych wykonanego generatora.
EN
The article presents the concept of an electromagnetic circuit generator with permanent magnets mounted on the surface rotor core designed for single phase work. Computation field-circuit model was shown. The spectrum of time course of voltages in the idle work was presented. The cross section with graphically presentation of magnetic induction in particular parts of electromagnetic circuits was presented. Distribution of magnetic induction at the rated load point for each phase were shown. The time course of voltages and currents for rated power were displayed. An analysis of laboratory results and measurement of load characteristics of the generator was discussed. The work deals with three electromagnetic circuits of generators with permanent magnet where output voltage characteristics versus rated power were expressed.
EN
Vibration tests of marine gas turbine engines are performed as researches online and off-line types. Systems on-line type generally monitored one or two vibration symptoms, which asses the limited and/or the critical values of parameters and they potentially can warn and/or shutdown engines. Systems off-line types are usually used for vibration analyzing during non-steady state of work. The paper presents comparison of different methods of analyzing vibration symptoms measured under run-up and shut-down processes of marine gas turbine engines. Results of tests were received on two gas turbine engines types of the COGAG type propulsion system simultaneously. Both types of engines were not fitted with vibration monitoring system. Main goal of researches was qualified of helpfulness and unequivocally results received by methods of synchronous measurement, order tracking and auto tracking.
PL
Badania drganiowe silników turbinowych realizowane są w według procedur online i off-line. Systemy typu on -line zwykle nadzorują jeden lub dwa symptomy drganiowe, których przekroczenie tolerowanych wartości wyzwala alarm lub zatrzymuje maszynę. Systemy off- lne są zwykle stosowane przy analizie w stanach nieustalonych. Referat przedstawi a porównanie dwóch metod diagnostycznych stosowanych w trakcie procesów rozruchu i zatrzymania silników turbinowych tj. pomiaru synchronicznego i śledzenia rzędów. Rezultaty badań przedstawiają wyniki uzyskane w badaniach realizowanych równocześnie na silnikach typu DR w układzie napędowym typu COGAG. Badane silniki nie posiadały własnego systemu monitoringu drgań. Głównym celem badań było uzyskanie odpowiedzi na pytanie, która z prezentowanych metod badawczych jest bardziej wrażliwa na zmiany stanu technicznego układu wirnikowego.
PL
W referacie przedstawiono symulacyjne badania stateczności dynamicznej ładowarki Ł34. Symulacje przeprowadzono dla dwóch przeszkód z prędkością biegu pierwszego. Określono również wpływ zmian niektórych parametrów konstrukcyjnych na poprawę stateczności dynamicznej badanej ładowarki.
EN
In this article are presented simulation studies of loader Ł34 dynamic stability. Simulations were carried out for two obstacles with first gear velocity. In this paper are also defined effects of parameters modification to improvement loader dynamic stability.
PL
Przedmiotem modelowania i symulacji jest oryginalny młot udarowy sprężynowy o nazwie RG -1, zaprojektowany i wykonany w Katedrze Mechaniki i Informatyki Stosowanej Wydziału Mechanicznego Wojskowej Akademii Technicznej w Warszawie [1]. Opracowano nieliniowy dyskretny model dynamiczny układu młot-badany element energochłonny-wibroizolacja-fundament-podłoże i wyznaczono wartości parametrów tego modelu. Sformułowano nieliniowe równania ruchu układu w niejawnej postaci i opracowano algorytm numerycznego całkowania tych równań. Opracowano program komputerowy KESHA v2 do symulacji numerycznej drgań układu. Przeprowadzono wstępne badania numeryczne energochłonności elementów kompozytowych cylindrycznych. W celu redukcji drgań wywołanych pracą młota, urządzenie posadowiono na żelbetowym fundamencie blokowym za pośrednictwem wibroizolacji GERB, którą stanowi układ czterech wibroizolatorów sprężynowych z tłumikami wiskotycznymi, typu KV-452-247 03. Badany młot udarowy należy do klasy młotów o średnich prędkościach uderzenia i średniej energii uderzenia (vu = 2,5-11 m/s; Eu = 0,1-6,0 kJ).
EN
The study presents modelling and numerical simulation of the RG -1 spring stroke hammer, using the multi-body dynamics approach. The device has been designed and erected at the Laboratory of Strength of Materials of the Department of Mechanics and Applied Computer Science of Military University of Technology, Poland. The study develops a nonlinear discrete dynamic model of the hammer-examined specimen-vibroisolation-foundation-subsoil system as well as determines the values of the system parameters. A nonlinear matrix equation of motion of the system has been formulated partly in the implicit form, taking into consideration subsequent/simultaneous stages of the dynamic process, i.e., rapid release of the ram catch, expansion of the mainsprings, impact of the ram onto the examined specimen, shock absorption by the elastomeric pads, reduction of the forced vibrations by GERB vibroisolators, propagation of the vibrations in the subsoil, free damped vibrations of the system. An implicit algorithm for numerical integration of equations of motion, based on Newmark's average acceleration method, has been formulated. The problem has been reflected by a computer programme written in Pascal. The study presents numerical simulations reflecting dynamic tests of energy-absorbing composite cylindrical specimens. The ram fixed to the moving traverse is able to induce progressive failure up to the specimen length minus 15 mm. A distance of 15 mm is reserved for gathering the material of the destroyed part of the specimen. If this distance is achieved, the moving traverse strikes onto the elastomeric pads fixed to the cantilevers. All possible breakings away are taken into consideration in the matrix equation of motion. In order to reduce vibrations, induced by rapid releasing of the ram catch and by the main impact, the device has been connected to RC block foundation with four viscoelastic KV-452-247 03 GERB vibroisolation units. The fundamental natural frequency of the system is close to f1 = 3.4 Hz. The exemplary time histories of vibrations of select subsystems, corresponding to the initial shortening of the mainsprings equal to s = 75 mm and 150 mm, number of bobs n = 0, and the carbon/epoxy specimen CE-1, are shown in Figs. 10 and 11. The multi-body dynamic model of the device, the dynamic equation of motion, the computer algorithms and the computer programme constitute an effective tool for predicting energy absorption of composite specimens and for assessment of vibration isolation effectiveness. The GERB vibroisolation has appeared to be very effective. The investigated device belongs to the hammers class of the medium impact velocities (vu = 2.5-11 m/s) and the medium impact energy (Eu = 0.1-6.0 kJ).
11
Content available remote Kinematic Analysis of Parallel 3-RPS Manipulator
EN
There was solved a problem of inverse kinematics of parallel manipulator - tripod type (3RPS). Above relationships allow to calculate the length l of kinematic pairs with variable length - P type. Solving above system of equations one can solve a problem of inverse kinematics of similar parallel structures to presented ones in this work. Relationships can be used to create control algorithm of parallel mechanism. Simulations of equations (5), (6) and (7) were performed in LabVIEW software. Verification of equations will be conducted after development of physical model of manipulator and control algorithm with usage of these equations.
PL
Pokazano wyniki badań symulacyjnych wpływu czterech różnych obwodowych położeń pęknięcia wału turbiny średnioprężnej na stan dynamiczny turbozespołu dużej mocy. Przedstawiono pokrótce narzędzia numeryczne do analizy dynamiki wirników łożyskowanych ślizgowo z pęknięciem oraz model maszyny. W wyniku obliczeń okazało się, iż pęknięcie znacznie silniej wpływa na drgania bezwzględne panwi łożyskowych niż na drgania względne czopów.
EN
The paper is being focused on lateral vibrations caused by the crack in one section of 200 MW turbo-set shaft. The research was made in a way of computer simulation. The computer code that we use to simulate the rotating machinery dynamic state is called NLDW. A diathermic model of heat transfer in slide bearings is it's base. The rotor line is modeled with FEM using typical Timoshenko beam elements with 6 DOF's per node. Crack is modeled by a simple "on-off" model introduced by Knott. Crack depth is described by the crack coefficient Wp. It can be also called a "relative crack depth" which is absolute crack depth divided by the shaft diameter (both in the length units). The object of the research is a 200 MW turbo-set. The model was identified and tuned on the parameters related to the particular real machine working in one of the Polish power plants. Crack was placed in one section of IP turbine. Four different angular crack locations alpha p were taken into account to compare their influence on dynamics of the machine. Rotor is forced by the system of time-varying forces and moments, thus the resultant force is time-varying too. It causes different (and probably also time-varying) phase between crack and resultant force. Calculations were carried on with constant Wp=0.45 and rotational speed 3000 rpm. The results confirmed that crack angular position may have influence on dynamics of the machine. V RMS of absolute vibration of bearing bushes rises even to twelve times (bearing No 1, alpha p=0 to the 0), usually 3-4 times. The amplitudes of relative vibrations of journals don't rise so much (about 25-30%). The growth of vibration levels is observed only in bearings No 1, 2 and 3. Trajectories of bushes became chaotic and higher harmonics of significant levels were observed. Bearings demonstrate the presence of subharmonics 1/2X caused by oil whirls. Higher harmonics are also observed, but their values are not significant.
EN
The article presents the problem of structural friction appearing in a screw joint with frictional effects between its elements. In the article are analysed two mathematical models of screw joint. In the first model is assumed the influence of screw with foundation of large stiffness the nut. In the second model is assumed influence both of cooperating elements (the screw and nut).
EN
Tank trucks are the particular group of vehicle to transport fuel and other dangerous materials. Because of their specific role on the roads they have to be safe, reliable and economic. Designing these type of construction one concentrates on the economic factors. In consequence these type of constructions tends to minimize its masses and maximise load-carrying ability. To gain these goals most of modern tank trucks have self-load-carrying ability construction. To design proper construction of cistern the mechanics of deformable structures, membrane theory, stability and optimisation have to be known. The complexity of the matters has been taking into consideration in many references so far. One of the publication worth to look through is "Strength end optimisation of sheet metal tanks" (Magnucki, 1998). It is only polish version. The author assumes the science achievements in this field until 1998. The examples enhanced in the book show the scale of complication of this subject. Strict mathematic solution could be used only for really simplified cases of tanks. The article describes the new method of modelling influences of liquid on tank truck's elements in dynamic condition with FEM. The method makes allowance for modelling viscosity and compressibility of liquid and filling the chambers up to different levels. Most of the cisterns for fuel are designed to transport a few types of liquid (fuel, oil etc.). To enable the modelling of this kind of situation every chambers could be filled by different liquid's models. The results of investigations could develop up-to-date method of cistern's analysing. It'll be change into dynamic direction. It is a subject of doctor' thesis which has been written in Institute of Machine Design Fundamentals (Warsaw University of Technology). The hyperelastic material has been used to define properties of liquid. The models of tanks are modelled as typical shell construction (shell elements 3 or 4 nodes). The liquid's volume was modelled as 8 or 6 nodes solid elements with properties of hyperelastic material.
15
EN
The article discusses methods of modelling reactions in systems of rotor-bearings-supporting structure type. Author's attention was focused most of all on modelling reactions between the supporting structure and the rotor supported on slide bearings. In the article an overview of well known and presently used methods for determining dynamic characteristics of the rotor supporting structure is given. Significant part of the article is devoted to the presentation and discussion of the proposed method of determining supporting structure characteristics in cases when subtle changes of these characteristics, for instance those caused by the presence of certain defects, are to be taken into account. The proposed method of dynamic characteristics determination allows various changes taking place in the structures supporting the rotating machines to be analysed both at the design stage and during their operation. These changes have frequently noticeable influence on the rotor dynamics.
16
Content available remote Applying Principle of Compatibility for Determining Reaction Forces of Constraints
EN
The determination of constraint forces is one of the interesting problems in dynamics of machinery. For this problem only the method of Lagrange multiplier method is applied. However the use of the mentioned method will increase the complex of the problem due to the additional multipliers. In this paper the authors use directly the Principle of Compatibility to get away from this difficulty.
17
Content available remote Prototype magnetorheological fluid damper for active vibration control system
EN
Purpose: The paper presents a concept of a system for isolation from external vibration sources with use of a magnetorheological (MR) dampers. Design/methodology/approach: Results of experimental studies of a prototype magnetorheological damper at various magnitudes of control current and the manner of modelling electromagnetic phenomena occuring in the damper are presented in this paper. The effect of magnetic field on magnetorheological fluid is modelled by the finite element method. The mathematical model of the system as well as the damper model are outlined along with the relevant control facilities. Numerical simulations were carried out for an exemplary excitation. Findings: The elaborated damper and applied control algorithms substantially infuences the values for velocities and accelerations. Incorporation of a controllable damper into the stabilization system significantly decreases displacements of the mass to be stabilized being the results of shocks and bumps caused by excitations w(t) as a compared to similar displacement of the same mass when only a passive damper was used. Research limitations/implications: For the future research it is necessary to improve characteristics of elaborated damper in order to improve its efficiency. Practical implications: Many mechanical systems should separate from sources of vibrations. The active or semiactive vibration control systems offer a number of advantages as compared with passive systems so that better efficiency of vibration damping is assured. Originality/value: The paper presents new concept of vibration damper with magnetorheological fluids and way of its application in industrial practice.
PL
W pracy autor dyskutuje tezę, że prosty model dynamiczny może być użyteczny w diagnostyce wibroakustycznej maszyn, jeżeli jest dobrze zdefiniowany, nieliniowy i dobrze zidentyfikowany.
EN
The main thesis of this paper is that simple dynamic model could be useful in vibroacoustic diagnostics only if is properly defined, nonlinear and correctly identified.
PL
W pracy omówiono proces identyfikacji modelu konstrukcji podpierającej wirnik na przykładzie wybranej maszyny wirnikowej. Obiektem badań była konstrukcja podpierająca wirnik wielkogabarytowego Stanowiska Badawczego Dynamiki Wirników i Łożysk, znajdującego się w Laboratorium Wibrodiagnostyki Instytutu Maszyn Przepływowych PAN w Gdańsku. W kolejnych punktach omówiono wszystkie etapy procesu identyfikacji, tzn.: eksperyment, modelowanie, estymację parametrów oraz weryfikację modelu. W wyniku identyfikacji otrzymano model dobrze odzwierciedlający zachowanie rzeczywistego obiektu oraz umożliwiający jego dalszą, wszechstronną analizę.
EN
The paper discusses an identification process of the rotor support structure model in relation to selected example of rotor machine. The object of investigation was the rotor support structure of the large-size Dynamics of Rotors and Bearings Test Rig, located in Vibro-diagnostics Laboratory of Institute of Fluid Flow Machinery PAS, Gdansk. All stages of identification process have been talked over: experiment, modeling, estimation of parameters and model verification. As the result of identification, the structure model has been built, which well reflects the actual object and enables its subsequent diverse analysis.
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