M.Phil. / This study identifies and evaluates dynamic models used to characterise the dynamic stiffness and phase angle of hydraulic elastomeric mounts that are primarily used as engine and operator cab isolators in vehicular applications. Linear models developed for hydraulic elastomeric mounts are analysed for their suitability to be used to characterise the dynamic stiffness and its phase angle in the low and high frequency range. A sensitivity analysis provides insight into the parameters with a high level of sensitivity to changes in model parameters. The models selected from the linear analysis are enhanced and updated by performing a quasi-linear analysis to compensate for the dynamic behaviour of certain parameters. Non-linear dynamic behaviour of the decoupler is also investigated. These models are then verified experimentally. To set-up an analytical model that can be used to predict the dynamic characteristics of the hydraulic elastomeric mount it is necessary to develop a physical model from which the system differential equations are extracted. From the physical model flow continuity equations and fluid momentum equations are developed to obtain an expression that describe the fluid response in the inertia track and decoupler respectively. Lumped parameter mechanical models are developed next from which equivalent differential equations are derived to describe the internal dynamics of the hydraulic mount. These differential equations along with the transmitted force equation directly derived from the physical model are used to develop the dynamic stiffness transfer function. Time domain input displacement and output transmitted force data are taken at a specific frequency and amplitude, and are used to generate hysteresis loops to extract the dynamic stiffness and phase angles. For most of the computational effort, both analytical and experimental, MATLAB programs are written to perform curve fitting, FFT calculation, numerical integration and dynamical simulation. Emphasis is placed on the dynamic considerations of hydraulic mount design in the automotive industry and where machines are subjected to shock and vibration. The results and techniques used to model and the mounts are useful to designers in the field of shock and vibration isolation. Finally, the aim of the work is to keep the dynamic models as simple as possible, to be used effectively in the identification of the structural dynamic characteristics of hydraulic elastomeric mounts. To avoid complexity two models are used to describe the dynamics of the mount, one model for the low frequency, large amplitude conditions and one for the high frequency, small amplitude conditions. The information is then used to determine how the mount will respond under certain dynamical conditions.

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Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 28, 2007). Vita. Includes bibliographical references.

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M.S.

This thesis describes an investigation into the effect of fluid and flow parameters on cavitation dynamics and cavitation erosion. A rotating disc test apparatus was developed fo: dow-type cavitation studies. A vibratory test device was also developed to study the role of cathodic and anodic potentials applied to cavitating bodies. Some major results are given below. Erosion "peaksat about 50°C in water, but under certain conditions material degradation caused by increased corrosion rate cancels out thermodynamic effects at higher temperatures. An erosion peak is also observed as a function of static pressure. Damage increases with velocity until cavitation is fully developed, at which stage the influence of velocity becomes negligible. The changes in erosion zone geometry and mass loss caused by temperature, velocity and pressure variations may be correlated with the effect these parameters have on the cavitation pressure profile. Efforts are described to develop a system for measuring this profile in the rotating disc device. Water quality including dissolved ions, as well as solid and gas impurities, influences both cavitation inception and the amount of cavitation damage caused. The synergism between cavitation erosion and corrosion causes high damage rates in corrosive, cavitating liquids. Solid impurities at medium concentrations may enhance or retard cavitation damage substantially, depending on the physical properties of the solid. Below the saturation level, increasing concentration of dissolved air in water results in a slight decrease in damage, but damage can be almost completely eliminated by the release of air bubbles into the cavitation region. Another important result is that the gas developed by the application of external potentials to a cavitating body provides protection against cavitation erosion through a gas cushioning mechanism. Cathodic protection of cavitating bodies will thus serve to decrease damage rates even in the case of corrosion-resistant materials like stainless / GR 2016

The aim of this study is to perform the dynamic force analysis of a 3-degrees-of-freedom excavator during digging the soil and to simulate the motion on computer screen. Standard load calculations are done statically, therefore the effects of forces changing with time on the system cannot be observed. The dynamic analysis method used in the thesis is Recursive Newton &ndash / Euler Method and the numerical analysis method for simulation is 4th Order Runge &ndash / Kutta Method. After this study, the effects of sudden velocity changes / i.e, accelerational movements on construction machines, positions of bodies and dynamic forces on joints will be appointed and it will be possible to plan and control the motion.

The aim of this study is to develop a dynamic model of the loader system of a backhoe-loader. Rigid bodies and joints in the loader mechanism and loader hydraulic system components are modelled and analyzed in the same environment using the physical modelling toolboxes inside the commercially available simulation software, MATLAB/Simulink. Interaction between the bodies and response of the hydraulic system are obtained by co-operating the mechanical and hydraulic analyses. System variables such as pressure, flow and displacement are measured on a physical machine and then compared with the simulation results. Simulation results are consistent with the measurement results. The main result of this work is the ability to determine the dynamic loads on the joints and attachments of the backhoe-loader. In addition to that, prototyping time and costs can be highly reduced by implementing this model in the design process.

Reciprocating rod seals are widely used in hydraulic systems to prevent the hydraulic fluid from leaking into and polluting the environment. In this research an elastohydrodynamic model of a generalized reciprocating hydraulic rod seal, including mixed lubrication and surface roughness, has been successfully developed. This model consists of coupled fluid mechanics, contact mechanics, thermal analysis and deformation analyses. Such model is capable of predicting the key seal performance characteristics, especially net leakage and friction force. This allows evaluation of potential seal designs and serves as design tools. Also as this model has been developed, the basic physics of seal operation has been clarified, which stimulates the development of innovative seal concepts, such as seals with engineered sealing surfaces. The results of this study indicate that in general, hydraulic rod seals operate in the mixed lubrication regime, although under certain conditions full film lubrication may occur over a portion of the sealing zone. The roughness of the seal surface and the rod speeds play important roles in determining whether or not a seal will leak. Cavitation during the outstroke and partial full film lubrication during the instroke tend to prevent net leakage. The behavior of a reciprocating hydraulic rod seal with a double lip or two seals in tandem arrangement can be very different from that of a similar seal with a single lip. For the double lip seal, the secondary lip can strongly affect the behavior of the primary lip by producing an elevated pressure in the interlip region. The same seal characteristics that promote effective sealing in a single lip seal and, in addition structural decoupling of multiple lips, are found to promote effective sealing in a multiple lip seal. The model is validated through comparisons of model predictions with experimental measurements and observations by industry partners. The results have shown the predicted leakage and friction force for various seal and operation conditions are consistent with the measurements. A seal with micro-pattern on the sealing surface also has been investigated. The results indicate that an elaborately designed pattern can improve the sealing characteristics of the seal, without significantly affecting the friction force. In the end, the selection of the rod seal for a specific application using this analytical model is demonstrated. The best design can be picked up before a prototype being built.