Ograniczanie wyników
Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 149

Liczba wyników na stronie
first rewind previous Strona / 8 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  wibracje
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 8 next fast forward last
EN
The aim of the current paper is to investigate a small airplane model propeller of class F2D according to requirements of Fédération Aéronautique Internationale (FAI, or World Air Sports Federation). In some cases, practical tests show that F2D models with flexible propellers produce specific extra noise and increase flight speed in comparison with “rigid” propellers. Therefore, the following hypothesis could be proposed: flexible characteristics of the increased noise are related to the resonant eigenfrequencies of the propeller. The operating range of the F2D class propeller (28,000-35,000 rpm) is close to or equal to the eigenfrequency resonance. The current investigation addresses dynamic/flexible vibrations of elastic propeller during engine run and researches dynamic parameters of the propeller as well as the contribution of these parameters to the model flight characteristics. To resolve this type of a problem, a stand, which allows completing a physical investigation of flexible propeller vibration modes and dynamic characteristics was created.
PL
Celem artykułu jest przedstawienie wyników badań śmigła małego modelu samolotu zaliczanego do klasy F2D (według klasyfikacji Fédération Aéronautique Internationale, FAI). W niektórych przypadkach testy wykazały, że modele F2 z giętkimi śmigłami, w porównaniu do śmigieł sztywnych, wydają dodatkowy hałas i zwiększają prędkość samolotu. Dlatego wysunięto hipotezę, że elastyczne charakterystyki zwiększonego hałasu są powiązane z rezonansem częstotliwości własnych śmigła. Zakres pracy śmigła klasy F2D (28 000-35 000 obr/min) jest zbliżony do jego częstotliwości własnych. Badania dotyczą elastycznych wibracji dynamicznych śmigła giętkiego w czasie rozruchu silnika i są nakierowane na wyznaczanie parametrów dynamicznych i ich wpływu na charakterystyki lotu modelu. Wykonano i opisano stanowisko, na którym przeprowadzono testy modalne drgań giętkiego śmigła. Na tej podstawie uzyskano charakterystyki dynamiczne.
EN
In industrial field, there is an increasing demand for monitoring systems enabling predictive maintenance programs. In this context, the present work concerns the monitoring of distributed wear (pitting) in planetary gearboxes. For this purpose, some metrics of the synchronous average of the vibration signal, based on the statistical moment of the fourth order, are present in literature; in this paper, a new indicator is proposed, namely NA4mod. The effectiveness of this metric in identifying the early stage of pitting has been evaluated by conducting an accelerated life test of about 700 hours on a test bench using a back-to-back configuration. The paper introduces the proposed metric, describes the test, presents and dis-cusses the results. Metric NA4mod exhibits satisfactory capability to detect pitting with better reliability than other metrics in literature. In addition, the metric is shown to be sensitive to both early stage damage and pitting severity in the final stage. Results are verified by means of wavelet-transform analysis.
EN
This work presents the results of the numerical analyses pertaining to the influence of resonance vibration amplitude on the fatigue life of a compressor blade with a defect made by a collision with a hard object (FOD). The research object was the first stage compressor blade of the PZL-10W engine. The numerical simulation of the notch formation was performed for the tested blade. The material fatigue models (for e-N analysis), three cyclic hardening models, and two mean stress correction models were used in the numerical analyses. As a result of the numerical analysis, the information on the distribution of principal stress was obtained. The values of the principal stresses were used for numerical e-N fatigue analysis using the aforementioned models of fatigue, hardening, and mean stress correction. Obtained results were compared to previously published experimental research, where a notch was created at the leading edge in 8 blades. The blades damaged under laboratory conditions were subjected to experimental fatigue tests during which the effect of resonance amplitude on the number of damage cycles was determined. As a result of the comparison work carried out, the impact of the vibration amplitude on the durability of the element with plastic deformation was determined.
EN
This paper presents the impact of selecting the fatigue material model on the numerically determined fatigue life of a compressor blade. In the work, the first stage compressor blade of the PZL‑10W turbine engine was used. The research object contained a geometric notch with a known location and shape. In numerical studies, 8 fatigue estimation methods were used in the ε ‑N analysis (based on the Manson‑Coffin‑Basquin model). At the same time, three methods for estimating material constants associated with the cyclic hardening were employed. On the basis of the selected models, 24 sets of fatigue parameters were obtained, which were used in numerical studies. The numerical tests were carried out under resonant conditions with amplitudes of 1.5 and 1.8 mm. The numerical tests were confirmed by the experimental fatigue tests. As a result of the above‑mentioned tests, the impact of selecting the material fatigue model and hardening model on the obtained results was determined and they were referred to the initiation of the crack with the length a = 0.2 mm (achieved during experimental studies). The obtained results will constitute the basis for further fatigue tests.
5
Content available remote Drgania samowzbudne w maszynach pozadrogowych
PL
Drgania samowzbudne generują wibracje oraz hałas, które oddziałują bezpośrednio na operatorów maszyn pozadrogowych. Minimalizacja wartości tych parametrów jest korzystna z wielu powodów, przede wszystkim zdrowotnych, ekologicznych, a także ekonomicznych.
EN
Self-excited vibrations are a generator of vibrations and noise that directly affect operators of off-road machines. Minimizing the values of these parameters is beneficial for a number of reasons, among which the health and ecological as well as economic ones should be considered the most important.
EN
The article is aimed at the development of the analytical approach for evaluating the parameters of the Basset force acting on a particle in two-dimensional fluid flow induced by the oscillating wall. By applying regression analysis, analytical expressions to determine complementary functions were established for evaluating the Basset force. The obtained dependencies were generalized using the infinite power series. As a result of studying the hydrodynamics of a two-phase flow, analytical dependencies to determine the Basset force were proposed for assessing its impact on particles of the dispersed phase in a plane channel with the oscillating wall. It was discovered that the Basset force affects larger particles. However, in the case of relatively large wavelengths, its averaged value for the vibration period is neglected. Additionally, the value of the Basset force was determined analytically for the case of relatively small wavelengths. Moreover, it was discovered that its impact can be increased by reducing the wavelength of the oscillating wall.
EN
As part of an ongoing study into hydropower runner failure, a submerged, vibrating blade is investigated both experimentally and numerically. The numerical simulations performed are fully coupled acoustic-structural simulations in ANSYS Mechanical. In order to speed up the simulations, a model order reduction technique based on Krylov subspaces is implemented. This paper presents a comparison between the full ANSYS harmonic response and the reduced order model, and shows excellent agreement. The speedup factor obtained by using the reduced order model is shown to be between one and two orders of magnitude. The number of dimensions in the reduced subspace needed for accurate results is investigated, and confirms what is found in other studies on similar model order reduction applications. In addition, experimental results are available for validation, and show good match when not too far from the resonance peak.
EN
The paper presents results of preliminary research of vibroarthrography signals recorded from one healthy volunteer. The tests were carried out for the open and closed kinematic chain in the range of motion 90° – 0° – 90°. Analysis included initial signal filtration using the EMD algorithm. The aim was to investigate the occurrence of differences in the values of selected energy and statistical parameters for the cases studied.
9
Content available remote Przegląd rozwiązań aktywnej kontroli drgań dla narzędzi skrawających
PL
W artykule przedstawiono problematykę drgań występujących w trakcie obróbki skrawaniem, negatywne konsekwencje, jakie za sobą niosą, a także to, w jaki sposób wpływają na proces obróbki skrawaniem. Omówiono również nowoczesne materiały wykorzystywane w aplikacjach tłumiących drgania, niemniej jednak zasadniczą część publikacji stanowi przegląd opublikowanych rozwiązań konstrukcyjnych wspomagających walkę ze zjawiskiem drgań towarzyszącym procesowi skrawania.
EN
The paper presents the issue of vibrations during the machining process, negative consequences caused by them and how they influence the machining process. Moreover, smart materials used in vibration damping have been discussed. The main part of the paper describes a review of published solutions which support the fight with the vibration phenomenon during machining.
EN
The influence of vibration and stirring of 90% and 98% hydrogen peroxide (high test peroxide – HTP) of two different purity levels in accordance with MIL-PRF-16005F, was determined. Testing was conducted in order to evaluate safety of use of highly concentrated solutions of hydrogen peroxide. The influence of vibration on HTP was tested at different frequencies up to 100 Hz. Further testing investigated the influence of stirring HTP, at three different speed values: 2000 rpm, 4000 rpm and 6000 rpm. During both tests, decomposition was determined by measuring concentration loss using density assay. Liquid during the tests was visually inspected for visible signs of decomposition such as: foaming, gas emission, turbidity.
PL
Określono wpływ wibracji i mieszania na 90% i 98% nadtlenek wodoru klasy HTP o dwóch poziomach czystości zdefiniowanych w normie MIL-PRF-16005F. Badanie przeprowadzono w celu oceny bezpieczeństwa stosowania roztworów nadtlenku wodoru o wysokim stężeniu. Został zmierzony wpływ wibracji o częstotliwości do 100 Hz na HTP. W ramach kolejnego badania sprawdzono wpływ mieszania na HTP, gdzie zastosowano trzy różne prędkości mieszania: 2000 rpm, 4000 rpm i 6000 rpm. Rozkład nadtlenku wodoru mierzony był poprzez pomiar stężenia roztworu przy zastosowaniu metody densymetrycznej. Dokonano wizualnych obserwacji roztworu podczas badań pod kątem występowania widocznych oznak rozkładu, jak: pienienie, emisja gazów, zmętnienie.
EN
Tapered beams are more efficient compared to uniform beams as they provide a better distribution of mass and strength and also meet special functional requirements in many engineering applications. In this paper, the linear and non-linear fundamental frequency parameter values of the tapered Timoshenko beams are evaluated by using the coupled displacement field (CDF) method and closed form expressions are derived in terms of frequency ratio as a function of slenderness ratio, taper ratio and maximum amplitude ratio for hinged-hinged and clamped-clamped beam boundary conditions. The effectiveness of the CDF method is brought out through the solution of the large amplitude free vibrations, in terms of fundamental frequency of tapered Timoshenko beams with axially immovable ends. The results obtained by the present CDF method are validated with the existing literature wherever possible.
EN
Effects of structural parameters on the vibration of a tapered non-homogeneous rectangular plate with different combinations of boundary conditions are discussed. Tapering in the plate is assumed to be sinusoidal in the x-direction. Here, temperature variation and non-homogeneity in the plate material are also considered sinusoidal in the x-direction. The Rayleigh-Ritz method is used to calculate the frequency parameter for the first two modes of vibration for different values of the structural parameters, i.e. the taper parameter, thermal gradient, aspect ratio and non-homogeneity constant. Results are obtained for three boundary conditions, i.e. clamped boundary (C-C-C-C), simply supported boundary (SS-SS-SS-SS) and clamped-simply supported boundary (CSS-C-SS). Numerical values of the frequency parameter are given in a compact tabular form.
EN
The boom of BWE is a very complex structure, dictated by its functions in operation of the excavator. In the simplest approach, it can be considered as an arm of an R-R robotic manipulator, having at distal extremity the working element, i.e. the bucket wheel, being fixed at proximal extremity by a joint to the turret, which, at its turn is articulated to the infrastructure which includes the undercarriage (travelling mechanism). In order to reduce the weight/stiffness ratio and to include the on board conveyer, the boom is generally embodied as a lattice – truss structure. The constitutive elements i.e. the members and joints are subject to severe loads, which due to their cyclical variable character with a high random component, lead to failures which are caused by overloading and/or fatigue. The actual paper deals with the field measurements performed in past years on several BWEs from CEO open pits, including acceleration measurements and stress measurements using strain gauges. Both kind of sensors-accelerometers and strain gauges were mounted on several critical points of the boom, and the measurements were performed both in normal operation and in some loading-operating scenarios. The recorded data were postprocessed in order to obtain spectral graphs in order to obtain information about the influence of different excitation sources on the boom elements behaviour.
PL
Wysięgnik wielonaczyniowej koparki kołowej jest złożoną strukturą definiowaną przez technologię pracy koparki. W celu zmniejszenia stosunku waga/sztywność oraz występowania przenośnika taśmowego wysięgnik jest zaprojektowany jako konstrukcja kratownicowa. Jej elementy są poddawane silnym obciążeniom, które ze względu na ich cykliczny charakter z wysoką składową losową prowadzą do awarii spowodowanych przeciążeniem lub zmęczeniem konstrukcji. Niniejszy artykuł przedstawia pomiary terenowe wykonane w ostatnich latach na wielonaczyniowych koparkach kołowych pracujących w kopalniach CEO za pomocą tensometrów oraz akcelerometrów. Pomiary te zostały zamontowane w krytycznych punktach wysięgnika, a pomiary zostały wykonane zarówno podczas normalnej pracy koparki jak i podczas realizacji scenariuszy obciążenia. Zarejestrowane dane zostały poddane obróbce w celu uzyskania wykresów widmowych.
EN
The Department of Geotechnical Equipment is involved since two decades in research and development of teeth, buckets and other active parts of different kinds of mining excavators. The actual study is devoted to reveal new difficulties arising when excavating in the sandstone as overburden rock, mainly regarding the buckets of bucket wheel excavators. As a consequence of the increased cutting forces, the buckets suffer deformations. In case of the change of cutting geometry, as a result of renewal (strengthening) of buckets, the winning becomes no-optimal and there will be more breakdowns. The investigations made and reported in the actual paper led to provide guidelines for a better renewal method of buckets.
PL
Department of Geotechnical Equipment od dwóch dekad zajmuje się badaniami i rozwojem zębów, czerpaków oraz innych aktywnych elementów różnych maszyn podstawowych. Aktualne badania służą rozwiązaniu problemów związanych z pracą koparek wielonaczyniowych kołowych w nadkładzie zawierającym piaskowce. W wyniku pracy w takim środowisku, a co za tym idzie, zwiększonych sił skrawania, czerpaki koparek ulegają odkształceniom. Zmiana geometrii procesu cięcia skały, która jest rezultatem renowacji czerpaków prowadzi do nieoptymalnego urabiania skutkującego zwiększoną ilością awarii. Przeprowadzone badania, przedstawione w niniejszym artykule, doprowadziły do opracowania wytycznych nowej, lepszej metody renowacji czerpaków.
EN
In this study, a new damage detection method is developed which directly uses input–output data of a forced vibration of a structure. For this, the dynamic vibration formulation of an FE model has been integrated within the time domain of the vibration of the structure. Also, the static condensation scheme is used to reduce required measured degrees of freedom (DOF's). Hence, the main characteristic of the proposed method is that it just uses translational time history response of a structure at specified nodes corresponding to the finite element model of that structure. Also, the only required data from the original FE model of the structure is its stiffness matrix. To assess the capability of the proposed method in damage detection in beam type structures a cantilever beam is studied. Not only can the method locate damaged elements, but also the quantity of damage in every damaged element is computed successfully. Also, it has been shown that as the frequency of the applied load in simulated experiment approaches to the first natural frequency of the beam, the accuracy dwindles significantly. Hence, for obtaining more reliable results, the frequency of the applied load shall be far enough from the first natural frequency of the free vibration of the beam. The results demonstrate that the integrated displacements in specified nodes through the time of vibration carry enough information about damages in elements and the proposed method can be successfully used for damage detection in beam type structures.
16
Content available Wibroizolatory sprężynowe w nawierzchni torowej
PL
Niniejszy artykuł poświęcony jest niestosowanym dotychczas w Polsce rozwiązaniu konstrukcyjnym jakim jest nawierzchnia kolejowa, która wyposażona jest w wibroizolatory sprężynowe. Nawierzchnia z wibroizolacją sprężynową stosowana jest od 30 lat w krajach europejskich i azjatyckich. W artykule przedstawiono różne typu wibroizolatorów sprężynowych stosowanych w nawierzchni podsypkowej i bezpodsypkowej oraz wyniki badań wpływu zastosowania wibroizolacji sprężynowej w nawierzchni bezpodsypkowej.
EN
The paper presents tuned track bed vibration isolation systems used for the railway and tramway lines. The presented solution based on mass spring systems and is effective especially at lower frequencies. The tuning frequency of such systems is mostly in the range 5 to 8 Hz. With measures based on spring elements elaborated the significant vibration and noise reduction coming from the railways and tramways can be achieved. This new technology in Poland can be used during the track structure modernization as well as in the new projects, in which the track bed vibration isolation is required.
PL
W pracy zaprezentowano sprzężony model obliczeniowy do analizy dynamiki elektromagnetycznego stołu wibracyjnego. Model zawiera opis pola magnetycznego oraz obwodu elektrycznego z uwzględnieniem ruchu liniowego. Badany układ składa się ze stalowej podstawy, na której umieszczono elektromagnes zasilany prądem przemiennym oraz płyty aluminiowej zamontowanej na sprężynach z umieszczonymi na jej spodzie magnesami trwałymi. Do opisu obwodu magnetycznego wykorzystano dwuwymiarową metodę elementów skończonych. Wielkością sprzęgającą pomiędzy modelami obwodu elektrycznego i magnetycznego jest prąd płynący w uzwojeniu elektromagnesu, natomiast sprzężenie pomiędzy modelem obwodu magnetycznego a modelem mechanicznym jest realizowane poprzez siłę magnetyczną wyznaczoną z tensora naprężeń Maxwell’a. Ruch liniowy jest modelowany metodą odkształcania elementów. Zbadano wpływ nasycenia obwodu magnetycznego na wyniki obliczeń przebiegów dynamicznych siły elektromagnetycznej oraz przemieszczeń.
EN
This paper presents a coupled computational model for dynamic analysis of the electromagnetic vibrating table. The model contains description of the magnetic field and the electrical circuit taking account of the linear motion. Studied system consists of an electromagnet fixed on the steel slab and an aluminum plate suspended on springs with permanent magnets mounted underneath. In order to describe the magnetic circuit a two–dimensional finite element method is used. Coupling between the electrical and magnetic circuits is realized by current that flows through the winding of the electromagnet, whereas the coupling between the magnetic circuit and the mechanical model is accomplished by a magnetic force determined from the Maxwell's stress tensor. A linear movement is modeled using distorted elements. The influence of saturation of the magnetic circuit on the calculation results is examined showing small impact on the system performance.
PL
Służba na okręcie podwodnym jest najbardziej stresującą i wymagającą psychologicznie formą służby wojskowej. Posiada swoiste, odmienne od typowych warunki bytowe oraz sanitarno-epidemiologiczne. Praca została przygotowana w oparciu o analizy raportów badań laboratorium środowiska pracy i protokołów kontroli zespołu nadzoru i kontroli sanitarnej WOMP Gdynia, w roku 2014 i 2015 okrętów podwodnych typu Kobben. Wojskowe Ośrodki Medycyny Prewencyjnej kontrolują Jednostki Wojskowe na podstawie przepisów obowiązujących powszechnie w środowisku cywilnym oraz wystandaryzowanych norm NATO. Pomiary dotyczą poziomu hałasu, drgań mechanicznych, czynników chemicznych, promieniowania elektromagnetycznego, fizykochemicznych i biologicznych badań wody oraz przedmiotów kuchennych. Celem tego badania jest ocena warunków służby na okręcie podwodnym pod kątem sanitarno-epidemiologicznym, jako narażenie na choroby zakaźne i zawodowe. Odnotowuje się zwiększony na wybranych stanowiskach poziom hałasu, promieniowania elektromagnetycznego, nadmierną ilość kolonii bakterii na przyrządach kuchennych.
EN
Service on a submarine is the most stressful and psychologically challenging form of military service. It is characterised by specific living and sanitaryepidemiological conditions which are far from typical. This work is based on the analyses of reports formulated from research conducted by a working environment laboratory, and on the control protocols of the sanitary supervision and control team (WOMP) Gdynia, from the Kobben submersible vessels in the years 2014 and 2015. Military Centres of Preventive Medicine hold supervision over Military Units pursuant to generally applicable regulations in the civil environment and standardised NATO norms. Measurements concern the level of noise, mechanical vibrations, chemical agents, electromagnetic radiation, physiochemical and biological water and kitchenware tests. The objective of the research is to evaluate the service conditions on a submersible vessel with regard to sanitary-epidemiological aspects such as exposure to infectious and occupational diseases. In selected stations, the conducted measurements indicate an increased level of noise, electromagnetic radiation and excess quantities of bacteria colonies on kitchenware.
19
PL
Przedstawiono metodę automatycznej oceny stanu wibracyjnego i technicznego stojana turbogeneratora. W metodzie wykorzystano kryteria wibracyjne wraz z ich wartościami granicznymi wyznaczonymi na podstawie własnych badań pomiarowo-analitycznych i wizualizacyjnych turbogeneratorów o mocach 50 MW ÷ 560 MW. Dla istotnych części stojana i ich elementów programy komputerowe podają na wykresie dopuszczalnych obciążeń turbogeneratora ocenę stanu wibracyjnego (dla bieżącego nadzoru) zaś w zestawieniu tabelarycznym w postaci raportu − ocenę stanu technicznego w zadanym okresie pracy turbogeneratora (dla planowania remontów). Opracowana metoda rozszerza możliwości diagnostyczne systemu monitoringu wibracji turbogeneratora opracowanego w Instytucie Energetyki i wdrożonego w energetyce polskiej.
EN
This paper describes a method for an automatic evaluation of a vibrating and technical condition of turbogenerator's stator. Vibration criteria and their threshold values have been used in the method. The criteria have been created on the basis of measurement, analytical and visualization research in 50 MW ÷ 560 MW turbogenerators. Software applications show an evaluation of the vibration condition of crucial turbogenerator stator elements on the permissible load plot (for on-line monitoring) and an evaluation of the technical condition in a given time span in a tabular form (for a scheduled preventive maintenance). The presented method extends capabilities of the vibration monitoring system that has been implemented in Polish power engineering and developed by the Institute of Power Engineering.
EN
The issues related to the use of test dummies for experimental research in the field of automotive engineering have been addressed. The article discusses the historical introduction and development of the dummies in the biomechanical tests, which have contributed to the replacement of, previously conducted tests on corpses or volunteers. The evolution of dummies development Evolution of the dummies construction development to the present times has been presented. Question was raised: what is the “similarity” between the dummy living human being. Contemporary dummies reflect very well features of the human body are made of good quality materials and can be equipped with numerous sensors performing various measurements. Comparative empirical tests carried out with an adult dummy and a living adult of similar parameters such as: size (weight and height) body proportions have been presented. The impact of vibrations on the human occupant riding a motor vehicle was examined, with road tests being carried out of realized driving on various road surfaces within that work and with the data recorded being analysed in the time domain and frequency domain. In the time domain, time histories of the accelerations recorded were analysed and the root-mean-square (RMS) acceleration values were calculated. In the frequency domain, the power spectral density (PSD) values and the absolute transmittance (amplification) values were determined for the acceleration signals recorded. The analysis of the measurement results for the ability to absorb vibration by living human being and the dummy has been done. The differences and similarities between the living human subject and the test dummy have been presented from the point of view of utilizing such subjects for experimental tests.
first rewind previous Strona / 8 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.