Rod seals are one of the most critical components of hydraulic systems. However, the fundamental physics of seal behavior is still poorly understood and the seal designers have virtually no analytical tools with which to predict the behavior of potential seal designs. In pursuit of a comprehensive physics based seal analysis/ design tool, in this work, a multi-scale multi-physics (MSMP) seal model is developed. The model solves the transient problem involving macro-scale viscoelastic deformation mechanics, macro-scale contact, micro-scale two phase fluid mechanics in the sealing zone, micro-scale asperity contact mechanics and micro-scale deformation mechanics of the sealing edge in a strongly coupled manner. The model takes into account surface roughness, mixed lubrication, cavitation and two phase flow, transient squeeze film effects and the dynamic operation as well as the effect of macro/micro/nano scale viscoelasticity. A hybrid finite element-finite volume-statistical computational framework is developed to solve the highly coupled multi-physics interactions of the MSMP model simultaneously. Surface characterization experiments are performed to extract the parameters like RMS roughness, asperity density, autocorrelation length and asperity radius needed by MSMP. To remove the high frequency noise without removing the high frequency real surface features, a wavelet transform based adaptive surface extraction method is implemented. Dynamic mechanical analysis (DMA) is performed to extract the macro-scale viscoelastic parameters of the seal. Through atomic force microscopy (AFM) experiments, the local micro/nano scale elastic moduli were found to be varying within two orders of magnitude higher than the bulk of the polymer. Significant differences in local stiffness, adhesion and the relaxation time scales of individual surface asperities were also observed. With the MSMP model, dynamic seal performance was analyzed. The results confirmed the mixed lubrication and the effect of surface roughness. Thicker fluid films during instroke and cavitation during the outstroke were found to be important for non-leakage. Seal behavior was a function of the complex dual dependence on the time varying sealed pressure and hydrodynamic effects. Viscoelasticity is seen to critically affect the leakage and friction characteristics. It produces thicker fluid films and produces a significant increase in Poiseuille component of flow during instroke. Ignoring viscoelasticity leads to under-prediction of the time required to reach the zero leakage state. Several high pressure - high frequency sealing applications were analyzed. In such applications, a new phenomenon of "secondary contact" was observed. Viscoelastic creep was seen to critically affect the contact pressure and hence the friction characteristics. In high frequency applications, viscoelasticity induced significant differences in Poiseuille flow and friction force from cycle to cycle. Cycle frequency was seen to play an important role in governing visco-elastohydrodynamics and the leakage of such seals. The seals need to be designed by considering the relationship between relaxation time scales of the polymer and the cycle frequencies. Study also revealed the presence of characteristics like "critical temperature" and "critical frequency". Using the multi-physics modeling capability of MSMP framework, several novel seal designs using smart materials like piezo-ceramic embedded polymers are proposed and analyzed. The MSMP computational framework developed here has a great potential to be used as a stand-alone seal design and analysis software in academic and industrial research.

Fluid power technology has been widely used in industrial practice; however, its energy efficiency became a big concern in the recent years. Much progress has been made to improve fluid power energy efficiency from many aspects. Among these approaches, using a valve-less system to replace a traditional valve-controlled system showed eminent energy reduction. This thesis studies the valve-less solution-pump displacement controlled actuators- from the view of controls background. Singular perturbations have been applied to the fluid power to account for fluid stiffness; and a novel hydraulic circuit for single rod cylinder has been presented to increase the hydraulic circuit stabilities. Recursive Least Squares has been applied to account for measurement noise thus the parameters have fast convergence rate, square root algorithm has further applied to increase the controller's numerical stability and efficiency. It was showed that this technique is consistent with other techniques to increase controller's robustness. The developed algorithm is further extended to a hybrid adaptive control scheme to achieve desired trajectory tracking for general cases. A hardware test-bed using the invented hydraulic circuit was built up. The experimental results are presents and validated the proposed algorithms and the circuit itself. The end goal of this project is to develop control algorithms and hydraulic circuit suitable for industrial practice.

Within the framework of risk assessment and risk management, determination of the failure probability of dams plays an important role. In this paper, the probabilistic approach to hydraulic failure elaborated by the author in the nineties will be developed further and refined. Furthermore, it is shown how the random event “gate failure” can be taken into account when calculating the overtopping probability of barrages. / Im Rahmen von Risikobetrachtungen spielt die Bestimmung der Überflutungswahrscheinlichkeit eine wichtige Rolle. Im vorliegenden Beitrag wird der probabilistische Ansatz, welcher in den neunziger Jahren vom Autor erarbeitet worden ist, weiterentwickelt und modifiziert. Außerdem wird gezeigt, wie das zufällige Ereignis „Versagen von Verschlüssen“ in die Berechnung der Überflutungswahrscheinlichkeit von Stauanlagen einbezogen werden kann.

Up-to-date methods of numerical modelling of random fields were applied to investigate some features of solute transport in saturated porous media with stochastic hydraulic conductivity. The paper describes numerical experiments which were performed and presents the first results.

<p>This master thesis consists of the creation of shock absorber models for percussive rock drills. A model of the rock was also developed. These models were connected to existing models of the rock drill to create a complete simulation of the rock drilling process.</p><p>When the models had been created the rock model was evaluated by comparison with measured values from lab tests. The verified rock model was then used to evaluate the shock absorber models.</p><p>Four new shock absorber concepts have been developed. Three of these have been modelled, while the fourth have only been sketched and described.</p><p>The evaluation of the models showed the following:</p><p>• Simulations of the single shock absorber don’t correlate to reality very well. The movement is too rapid and poorly damped.</p><p>• The simulated behaviour of the tandem shock absorber corresponds to reality, but the simulated hydraulic pressures aren’t reliable and neither is the damping.</p><p>• Simulation of the double shock absorber reflects reality fairly well, although the model of the check valve can be improved.</p><p>• There are problems with fluttering damper pressures in simulation whenever an accumulator is connected directly to the damper volume. The problem doesn’t exist if there is a line or an orifice with enough losses between the volume and the accumulator.</p><p>• The feeder system needs to be modelled.</p> / <p>Examensarbetet gick ut på att ta fram simuleringsmodeller av olika dämpare i en bergborrmaskin. Dessutom behövdes en bergmodell som gav korrekta reflexer från berget vid simulering. Dessa modeller kopplades samman med befintliga modeller för att skapa en simulering av hela bergborrningsprocessen.</p><p>Efter att modeller skapats utvärderades bergmodellen mot mätvärden som uppmätts under prov. Efter att bergmodellen verifierats användes den för att verifiera dämparmodellerna.</p><p>Fyra dämparkoncept har tagits fram. Tre av dessa har modellerats, medan det fjärde endast har skissats och förklarats.</p><p>Verifieringen av modellerna visade följande:</p><p>• Simulering av enkeldämpare stämmer dåligt med verkligheten utan ger för snabba och odämpade rörelser.</p><p>• Simulering av dubbeldämparen stämmer bra med verkligheten men modellen över backventilen behöver ses över något.</p><p>• Simulering av tandemdämpare stämmer beteendemässigt men de simulerade trycken är inte tillförlitliga och inte heller dämpningen.</p><p>• Det finns problem med trycksvängningar vid simulering av modeller där dämpvolymen är direkt ansluten till en ackumulator. Om en strypning eller en ledning med tillräckliga förluster ansluter ackumulator och dämpvolym med varandra märks inte detta problem.</p><p>• Modell över matningen behöver tas fram.</p>

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2009. / Härtill 4 uppsatser.

Thesis (M.S.) in Mechanical Engineering--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 46-49).

This product presents the design of a useful multi-functional adjustable table. It will bring great convenience to people with disability who spend most of time in bed, so as to meet their daily needs. Since there are already many similar products on the market, we focused on updating the functions on table, which can help people reading books or using tablet PC on beds in a comfortable way. It can also support people to stand up and walk around. There is a C-clamp fixing the product consolidated to bed. Besides, the hydraulic and micro-computer systems are used to adjust the table into a proper height automatically. The whole structure was designed in Autodesk Inventor 2015, and the simulation, test, analysis experiments were made in Abaqus 6.1.2 to ensure its safety and stability. In addition, this design can be an incentive for the improvement of the auxiliary equipment, highlighting the importance of the development of mechanisms for the healthcare.

All life depends upon water. For man, however, water can supply the power necessary to relieve him from the drudgeries of life and give the time and means to enrich his existence beyond the bounds set by the mere need to survive. Large scale hydropower makes a significant contribution to the total generated power of the developed world. The means of harnessing water power for large flows and heads above three metres are efficient and well established. There remains however, the fact that many people, especially in developing countries live adjacent to water courses and tidal estuaries where heads of 2 metres or less exist but are not exploited. The reasons for this are often that practical machines do not exist or are insufficiently well developed to be used. Much effort has been made in recent years to develop equipment suitable for small, low-head sites in remote places. The writer has worked on three such devices in both the laboratory and on site - these are the Salford Transverse Oscillator, the AUR Water Engine and the Underwater Motor. This thesis describes these machines in detail together with other contemporary devices. The initial chapter contains an assessment of machines used in the past to exploit low head sites. There is little doubt that some of these older machines, suitably brought up to date in design and materials, would be more suited to the needs of developing peoples than many of the esoteric devices described in later chapters. The thesis is concerned mainly with the need to provide a means of generating power rather than the assessment or suitability of a site for power generation. The writer draws on experience gained in the laboratory, and as a Mechanical Engineering Consultant for small installations in the United Kingdom and overseas.

Appraisal and design of small-scale hydro power plants requires a knowledge of hydraulics, hydrology, civil, mechanical, and electrical engineering, and basic economics. Further, small hydro is site specific in nature and marginal from an economic view point. Methods of appraisal and design are required therefore that will keep engineering fees to a minimum and yet still achieve a reliable evaluation of scheme potential and economics. In this context it should be appreciated that small hydro is not large hydro scaled down, and that small hydro needs its own experts (Ref. 1). This thesis considers techniques for appraisal of small hydropower schemes, the selection and specification of scheme components, their costing and economic evaluation. These appraisal techniques are subsequently applied to regional assessment of small-scale hydro-electric potential in the U. K, and to the development and application of a new type of ultra low-head hydropower generator called the Salford Transverse oscillator (STO). Although this work is predominately concerned with assessment of scheme potential in the U.K., it also draws on experience gained by the writer during short visits to India and Nepal, and during a six month design appraisal for rehabilitation of mini-hydro schemes in Sri Lanka (Ref. 2).