his diploma work themed: Five-cylinder in-line Diesel engine with balancing unit is dealing with analysis of balancing possible alternatives of arranging crankshaft, analysis of arranging counterweight, concept of balancing shaft, engineering design of crank-shaft, calculation of frequency, computational control of crank-shaft in light of torsional oscillations and proposal of dynamic pendulum damper.

The point of the dissertation is to describe the design of powertrain of four-cylinder diesel engine equipped with vibration damper. After estimating the discreet model of powertrain, forced vibration calculation is performed to design appropriate vibration damper. The following part describes the safety factor solution of crankshaft fatigue using FEM. The dissertation provides a useful comparison for versions with and without damper. Crankshaft and viscous type vibration damper drawings are also included as appendices.

This diploma thesis studies the use of air springs for race car, precisely Formula Student race car. Research part of the thesis deals with choosing suitable air spring for given application. In practical part, there is computation of parameters for appropriate setting of air spring, so it will comply with the rules of Formula Student. There is also simulation of air spring functionality in real use.

The thesis deals with design magnetorheological strut of vibration isolation adapter for cosmonautics. For its optimization is necessary to create several virtual models. The dynamic model of the mechanism - the Stewart platform, rheological model for determining the damping force of MR damper and model of the magnetic circuit to guarantee the required intensity in the gap. These models, along with controls models that are primarily concerned with strength calculations, will help with design. Designing using virtual models requires constant monitoring and verification. It is a rather broad topic including eliminate vibration also kinematics, dynamics, hydraulics, pneumatics and last but not least electronics and magnetism. It is necessary to communicate with experts in their field and use their knowledge and experience to create, but also to control of the individual models. The thesis was created in cooperation with Honeywell Aerospace Division (ESA).

The aim of this thesis is to find out the influence of eccentricity of crank mechanism on the duration of the force between the piston and the cylinder liner. At the same time I wanted to find out its influence on the balance of the whole system. It is important to design the balance for the selected value of the eccentricity and subsequently put through the crank shaft to stress analysis with torsional vibrations. I got so interested in this problem that in addition to the whole topic I designed a torsional vibration damper.

In this master thesis the performance of external viscous dampers attached to cables in cable-stayed bridges have been studied. A comparison has been performed between a linear and a non-linear cable model. The comparison was carried out for two bridge cables, one from the Dubrovnik Bridge and the other from the Normandie Bridge. The performance of the dampers have been measured in terms of maximum achieved damping ratio and minimum amplitude of vibration. The analysis was performed using the finite element method. The damping ratio was measured using both the half-power bandwidth method and by calculating the loss factor. The half-power bandwidth method can only be applied to a linear system. Therefore, the loss factor was evaluated for the linear model and compared to the results obtained using the half-power bandwidth method. From the comparison, it was concluded that the damping ratio evaluated using the loss factor was similar to the results obtained when using the half-power bandwidth method. However, when calculating the loss factor, it was of great importance that the resonance frequency of the system was accurately determined. The loss factor was then calculated for the non-linear model and compared to the results obtained for the linear model. Since the loss factor measures the energy dissipated in a system, it could be utilised for the non-linear model. When computing the strain energy for the non-linear model an approximate method was used to take into consideration the strain energy caused by the static deformation of the cable. From the comparison between the linear and non-linear cable models, it was concluded that the optimal damper coefficients obtained by both models are not significantly different. However, there is an uncertainty in the results due to the fact that an approximate method was used when calculating the strain energy for the nonlinear model. It was also observed that a very accurate evaluation of the system’s resonance frequency was needed to calculate the loss factor. It was also observed that the variation in amplitude of vibration for varying damper coefficient was small for all modes of vibration for the Dubrovnik Bridge Cable as well as for the first mode of vibration for the Normandie Bridge Cable. The difference in the results between the two bridge cables needs to be investigated further in order to get a better understanding of the results.

This work deals with the research of degradation of magnetorheological (MR) fluid during long-term loading under conditions that correspond to the real load in the linear MR devices such as dampers. The behaviour of MR fluid is described by a Bingham model of viscoplastic fluid. The parameters of this model are the yield stress and viscosity. Their values are determined by the shear rate from 1 to 2,8104 s-1. Results of durability tests show a significant decrease in viscosity of MR fluid, a gradual increase in yield stress in the off-state and a significant decrease in MR effect. The paper also described the effect of temperature on these parameters and there is also designed a method of non-assembly diagnostic of the MR fluid state in the damper using the "rate of pulsation."

Doctoral thesis deals with combustion engine cranktrain vibrations and vibration analysis methods. The work applies new computational models aimed at powertrain vibration decrease. The computational models can be used in the first stages of powertrain development. Temperature dependences of the rubber shear modulus and loss factor characteristic are found by response analysis of the free damped vibrations in the first part of the thesis. Viscoelastic model parameters of two dampers with different rubber hardness are calculated using optimization methods. Temperature distribution inside the rubber part during the harmonic oscillation is calculated with the knowledge of previous values. Computational models together with a user interface are assembled in Matlab/Simulink software tool. Computational model results of the viscoelastic rubber damper are verified by measurements on a prototype diesel engine in the whole operating engine speed range. Torsional vibrations of the crankshaft with torsional damper are measured by POLYTEC laser rotational tools. The temperature distribution on the damper surface is obtained by Infratec VarioCAM thermographic system. Combustion pressures in the cylinder are measured by SMETEC Combi indication tools. Both the temperature distributions and combustion pressures are used for computational purposes. All the measurement procedures are described also in the thesis.

<p> A numerical algorithm has been developed to solve the sloshing motion of liquid in a Tuned Liquid Damper (TLD) outfitted by slat screens under large and random amplitude of excitation. It is based on the finite-difference method. The free surface has been reconstructed using volume of fluid method. Donor-acceptor technique has been used for tracking the volume fraction field. The effect of slat screen has been included and modeled using the partial cell treatment method. </p> <p> The algorithm is an integrated fluid-structure model where the response of the structure is determined considering the effects of TLD. The structure is assumed as a single degree of freedom system (SDOF) and its response is calculated using the Duhamel integral method. </p> <p> The algorithm has been validated against experimental data for the cases with and without screens. An excellent agreement was obtained between numerical and experimental results. </p> <p> An extensive parametric study has been carried out investigating the effect of slat screens and screen pattern on the TLD performance and on the structure response. A new parameter termed as slat ratio was introduced to characterize the slat screens based on their pattern. Results indicated that screen pattern has a significant effect on the TLD performance and it could lead up to 33 % reduction in structure response. It was found that decreasing the slat ratio will increase the damping effect of a TLD outfitted by slat screen. </p> <p> The validity of the most commonly used approach, Baines and Peterson model, to calculate pressure drop of slat screens has been investigated. A conelation factor as a function of Reynolds number and solidity ratio of screen has been proposed to improve the results of this model. A new concept termed as effective solidity ratio has been proposed to account for the physical significant of screen pattern on TLD performance. </p> / Thesis / Doctor of Philosophy (PhD)

<p> Tuned Liquid Dampers (TLDs) are increasingly being used to suppress the dynamic vibration of tall buildings. An equivalent mechanical model is essential for rapid analysis and design of a TLD. The most common TLD tank geometries are circular, annular and rectangular. Rectangular tanks are utilized for 1-D and 2-D TLDs, whereas circular and annular are usually applied to axisymmetric structures. The amount of fluid that participates in the sloshing motion is directly influenced by the tank geometry. Although not commonly used, a TLD having a curved-bottom tank is expected to perform more effectively due to its relatively large value of effective mass. The main objective of this study is to develop mechanical models for seven TLDs with different tank geometries including the curved-bottom case, and to theoretically investigate the performance of rectangular, vertical-cylindrical and horizontal-cylindrical TLDs.</p> <p> Potential flow theory, linear long wave theory, Lagrange's equations and virtual work method are employed to develop the equivalent mechanical model parameters of TLDs with rectangular, vertical-cylindrical, horizontal-cylindrical, hyperboloid, triangular, sloped-bottom, and parabolic tank geometries. A rectangular, vertical-cylindrical and horizontal-cylindrical TLD are selected for further study using a single-degree-of-freedom (SDOF) model and a two degree of freedom structure-TLD system model applying the derived equivalent mechanical parameters.</p> <p> The dynamic characteristics of the TLDs as a SDOF system are investigated. The mechanical model is verified by comparing calculated values with experimental results for a rectangular TLD. The free surface motion, sloshing force and energy dissipation are found to be dependent upon the excitation amplitude. Analytical results also indicate that the horizontal-cylindrical TLD possesses the greatest normalized sloshing force and energy dissipation among the TLDs considered.</p> <p> The performances of various TLDs installed in a structure are studied in terms of effective damping, efficiency and robustness. Tuning ratio, structural response amplitude, mass ratio and liquid depth are adjusted to investigate their affect on the performance of the studied TLDs. Performance charts are developed and subsequently used to present the results. It is found that small liquid depth ratio and large mass ratio can lead to a robust structure-TLD system with small relative motion ratio between the structure and the vibration absorber. Comparisons of performance between the three TLDs are made and it can be concluded that the horizontal-cylindrical TLD is the most robust and effective device with the smallest relative motion ratio.</p> / Thesis / Master of Applied Science (MASc)