Die Kenntnis der dynamischen Eigenschaften von Turbomaschinenrotoren sind bei magnetgelagerten Maschinen von entscheidender Bedeutung für den sicheren Betrieb und die Regelung. Besonders der Temperatureinfluss auf die Materialien und die Eigenformen müssen dabei berücksichtigt werden. In diesem Beitrag wird ein MATLAB-Tool vorgestellt mit dem es möglich ist, die Eigenfrequenzen und -formen für magnetgelagerte Turbomaschinen zu berechnen und das Rotormodell für dynamische Simulationen zu erstellen. Es wird auf die zu Grunde liegende Mathematik eingegangen und die Implementierung vorgestellt. Die bisher erreichten Ergebnisse und die Implementierung in ein Simulationsmodell für eine magnetgelagerte Maschine werden gezeigt. / Knowledge of the dynamic properties of turbomachinery rotors is of crucial importance for safe operation and control in machines with magnetic bearings. Especially the temperature influence on the materials and the eigenmodes have to be considered. In this paper, a MATLAB tool is presented with which it is possible to calculate the natural frequencies and shapes for magnetically levitated turbomachinery and to create the rotor model for dynamic simulations. The underlying mathematics is discussed and the implementation is presented. The results achieved so far and the implementation in a simulation model for a machine with magnetic bearings are shown.

<p>Lubrication and friction of modern rolling element bearings were investigated to develop a physics-based bearing friction model. A test rig was designed and developed to measure the frictional torque of radially loaded rolling element bearings with oil bath lubrication. Deep groove ball bearings and radial needle roller bearings were studied at various loads, speeds and lubrication conditions. Experimental results indicate that bearing friction models currently used in industry can be inaccurate, especially when predicting bearing fluid drag losses. A separate test rig was designed and developed to investigate the lubrication and friction of rolling element bearing cage pockets, as new cage pocket designs could improve bearing efficiency. Cage pocket oil starvation was observed for certain operating conditions, and the starvation was found to correlate strongly with cage pocket friction. In order to better understand friction and lubrication characteristics of bearings, computational fluid dynamics (CFD) models were developed to compare with the experimental results. Fluid motion inside the rolling element bearings was investigated using CFD to determine fluid drag torque of bearing components. Fluid drag torque obtained from CFD and experimental measurements are in good agreement. Results from the CFD models also included pressure distributions over bearing surfaces and fluid velocity near rolling elements, but were limited to global length scales. At the micro-scale, rolling element bearing lubrication and friction is dictated by elastohydrodynamic lubrication (EHL). The radial needle roller bearings and deep groove ball bearings used in this investigation are characterized by line and elliptical contacts, respectively. EHL modeling was therefore developed for line contacts with a strongly coupled fluid solid interaction (FSI) solver. Solid bodies were modeled with finite element (FE) software to incorporate inhomogeneities such as inclusions and surface features which affect EHL pressure, film thickness and friction. Results were used to investigate lubricant film thickness at lubricated line contacts under various operating conditions. This work was further extended to model EHL circular contacts with an FSI approach, combining CFD and FE software. The newly developed FSI EHL model provided critical insights regarding fluid behavior in and around EHL point contacts and fluid properties within the lubricant film. Given the modeling results at the micro and macro scale within the rolling element bearings, a better understanding of bearing friction and lubrication is developed, and supported by experimental data.</p>

No description available.

No description available.

No description available.

No description available.

I de flesta maskiner används lager för att ta upp krafter från roterande komponenter. I en växellåda används lager för att ge axlarna möjlighet att rotera fritt och att begränsa deras rörlighet i axiell och radiell led. För att öka växellådors prestanda är det viktigt att minimera effektförluster och att ha en hög tillförlitliglitlighet. Effektförluster orsakade av lager kan vara betydande i växellådor. Att kunnaprediktera effektförlusterna i lager mera exakt kan ge en bättre översikt av fördelningen av effektförluster i växellådor och för att förbättra deras prestanda. rullager. Huvudsyftet med det här projektet är att ta fram en friktionsmodell för NJ 406 cylindriska rullager. Experiment utfördes i en omgjord kugghjulsrigg, där parametrar som varvtal, last och oljenivåer varierades. Baserat på resultat från de utförda experimenten, jämfördes de med tre redan framtagna lagermodeller från Palmgren, Harris och SKF. Den huvudsakliga forskningsfrågan separerades i fyra delfrågor där analys och jämförelse gjordes mellan de existerande modellerna och utförda experiment. De fyra delfrågorna som undersöktes var; lastoberoende friktionsförluster, lastberoende friktionsförluster, mätosäkerhet och modellering. Oljenivåns, oljetypens, oljetemperaturens, varvtalets och lastens inverkan på lagrens friktionsrespons undersöktes också. Resultaten från mätosäkerhetsanalysen visar att experimenten i det här projektet är repeterbara och att det är möjligt att utveckla nya lagermodeller genom att använda resultaten från de utförda experimenten. Baserat på mätresultaten, passar de lastoberoende friktionsförlusterna från Harris modell bäst. En ny modell för lastberoende förluster utvecklades eftersom ingen av de tre existerande modellerande passar mätresultaten. Därför utvecklades en ny modell som kombinerar Harris modell för lastoberoende lagerförluster och en ny modell lastberoende friktionsförluster. / In most of machines, rotating parts are supported by many types of bearings which may have different requirements. In a gearbox, bearings are normally used to support gear shafts which allow the shafts to rotate freely and limit the axial and radial motion of the shafts. For improving of gearbox performance, it is important to minimize power losses and have high reliability. Power losses caused by bearings can be significant in gearbox system. To be able to predict bearing power losses accurately can give a better overview of the distribution of power losses in the system and is helpful for improving of gearbox performance. The main purpose of this project is to develop an accurate NJ 406 cylindrical roller bearing friction torque model. Numerous experiments were performed on a bearing test rig modified from a back-to-back gear test rig under different conditions, such as different rotating speeds, different loads, different oil level, etc. Based on the results from the experiments, analysis of three existing models, Palmgren, Harris and SKF, were performed. By separating the main research question into four sub research questions, the analysis and comparing between existing models and experimental data were also separated into load independent friction torque analysis, load dependent friction torque analysis, precision analysis and modeling. The influences of oil level, oil type, oil temperature, rotating speed and load on bearing friction torque were also studied. The results of precision analysis show the results of experiments in this project are repeatable and it is able to develop new bearing models by using these experimental results. Based on the experimental data, after modified, the load independent friction torque from Harris model fits the experimental data well. A new model of load dependent bearing friction torque was developed since none of the three existing models fit the experimental data. Therefore, a new NJ 406 cylindrical roller bearing friction torque model was developed which is modified Harris model for load independent friction torque and the new model for load dependent friction torque.

Wave energy and wave energy converters is a fast rapidly developing field of research and energy harvesting. In recent years, more and more designs have seen operational success, and more and more are in development. Wave energy converters face a challenge not properly explored until recently, high loaded, oscillating motion in a highly hostile environment. Which poses a multitude of challenges ranging from contact fatigue to corrosion wear. However, this field is still in early development, seeing little to no research published about it. This work intends to inform about the challenges these wave energy designs pose in tribology and more specifically to bearings, through a literature study and review. The review establishes a rating for different bearing designs based on how applicable a certain bearing selection would be based on available research. Reaching the conclusion that whilst currently inappropriate to employ, seawater lubricated bearings could reach commercial viability in the future for wave energy devices. Additionally, with the help of excellent sealing solutions and well conducted lubrication regimes, both sliding bearings and rolling element bearings have their advantages and disadvantages and can make use of a multitude of different materials. / Vågkraft och vågkraftsgeneratorer är ett område som växer snabbt i intresse för både forskning och produktutveckling. På senare år har fler och fler vågkraftsgeneratorer och designer för dessa sett framgång i prototyptester och flera är på fortsatt utveckling. Vågkraftsgeneratorer står inför flera utmaningar, med de sammansatta faktorerna av en väldigt korrosiv miljö, höga krafter och oscillerande rörelse. Vilket stället flera krav på designers på allt ifrån korrosionsskydd till materialkunskap krig utmattning av maskinkomponenter. Dessvärre finns ytterst lite noga dokumenterad forskning kring området då det är en väldigt ung bransch. Denna rapport söker att utforska och informera kring de utmaningar som kan ställas på vågkraftsgeneratorer inom specifikt tribologi och specifikt för lager och lagerval. Arbetet fokuserar på en litteraturstudie över de möjliga utmaningarna området skapar. Grundat på relevant forskning inom liknande områden betygsattes ett urval av lagerval för vågkraftsgeneratorer. Där slutsatserna pekar på att då det möjligtvis är olämpligt i nuvarande läge att nytta saltvatten som smörjningsmedel, i framtiden kan detta bli en kommersiell verklighet. Där både glidlager och rullningslager har sina fördelar och nackdelar inom applikationen, med noga valda materialkombinationer, smörjningsmedel och tätningar.

Bridge bearing is an essential component with the function of connecting the superstructure and substructure of the bridge, transmitting load and providing movability to the superstructure. Under dynamic conditions, the internal friction of bridge bearing dissipates the vibration energy and therefore reduces the dynamic response of the bridge. Meanwhile, bearing friction is considered to have possible contribution to some nonlinear dynamic behaviour of the bridge structure, which requires further investigation.However, bearing friction, in most cases, are ignored or considered roughly and implicitly as part of structural damping in current bridge designing codes and methods. Most previous research was also focusing on bearing friction’s effect under high-amplitude vibration conditions, such as earthquake or heavy wind load. Bearing friction’s effect under common low-amplitude vibration in SLS such as train-induced vibration and vehicle-induced vibration is less attended. Although the effect of such low-amplitude vibration is less significant to structural safety, it plays an essential role to the bridge’s traffic safety and comfort. Meanwhile, the cumulative effect of such vibration can significantly influence the life and durability of bridge bearings due to its high occurring frequency. Hence, a clearer understanding of bearing dynamic behaviour is required to improve the understanding of bridge and bearing dynamics.In this thesis, an advanced numerical tool is developed for dynamic analysis of bearing friction. A 3D pot bearing finite element that can be implemented in commercial FE software ABAQUS, is programmed based on the mathematical friction models developed in previous research and the Bouc-Wen hysteretic model. Numerical results that accord with the results of relevant friction tests are produced by the calibrated and validated bearing finite element, giving proof that the element is capable to reflect the dynamic friction response of bridge pot bearing in reality.The 3D shell numerical model of Banafjäl bridge located on the Bothnia Line in Norrland, Sweden, is built as a study case of bridge dynamic analysis in this thesis, with implementation of the newly developed bearing element. The feasibility of implementing the bearing element in bridge dynamic analysis is proven by the numerical results. The nonlinear influence of bearing friction on the dynamic response of bridge structure, especially the influence on structural damping properties, is discussed preliminarily. The analysis results show that with the consideration of bearing friction, the damping presents a clear amplitude-dependency, which accords the phenomenon reported in previous research.

Unexpected bearing failures in agricultural equipment can result in considerable inconvenience, potential hazard, and monetary loss. Continuous bearing condition monitoring using vibration and audio spectrum analysis can detect imminent bearing failures before dangerous situations develop. Current application of bearing condition monitoring using vibration signature analysis has focused on fixed industrial applications involving high cost equipment and high shaft speeds. The feasible application of current technology on mobile agricultural equipment requires a lower-cost method of signal sensing and processing. Lower shaft speeds and the use of neural-net based pattern recognition techniques can allow the use of lower-cost transducers necessary for practical adoption on mobile equipment. A test apparatus was developed and constructed to test the feasibility of using a electret microphone as a sensor for monitoring bearing condition through vibration signature analysis. Laboratory experiments designed to evaluate the sensors with test bearings at both an advanced and an early stage of wear were developed. A field-worn bearing that had been removed from a unit of farm machinery was obtained and examined. Twelve new bearings identical in type to the field worn bearing were also examined, altered to simulate an early stage of wear, and re-examined. Identical experiments were conducted on both the field-worn and altered bearings. The signal acquired from a field-worn bearing was compared with the signal acquired from a new bearing using a two-sample, paired t-test for means at an alpha level of 0.05 and a graphical defect frequency analysis. The signals acquired from the altered bearings were compared with the signals acquired from the new bearings using the same statistical and graphical test performed on the field-worn bearings. The goal of the analysis was to evaluate the performance of the microphone by attempting to identify significant frequency patterns that could be used to determine the condition of the test bearing while in operation. Duplicate experiments conducted using the accelerometer provided a comparison of sensor performance. The microphone performed well for bearings at an advanced stage of wear. The sensitivity of the accelerometer resulted in better performance when used with bearings at an early stage of wear. / Master of Science