Content of this master thesis is analysis of torsional vibration of the three cylinder engine with balancing shaft. In theoretical part of the thesis the kinematic and dynamic description of the cranktrain mechanism is included. The formation of unbalancing of the engine and methods of balancing are described in the theoretical part as well. In practical part of the thesis the analytical calculation of torsional vibration is provided. Simulation of the engine model in multibody software Adams/Engine was used as the other way of torsional vibration analysis. In the result part of the thesis the comparison of the both way of analysis were discussed. Last step of the thesis was design proposal of the torsional vibration damper done by the analytical calculation.

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.

The study of the shear behavior of particulate (soil) – continuum (man-made material) interfaces has received significant attention during the last three decades. The historical belief that the particulate – continuum interface represents the weak link in most geotechnical systems has been shown to be incorrect for many situations. Namely, prescribing properties of the continuum material, such as its surface roughness and hardness, can result in interface strengths that are equal to the contacting soil mass internal shear strength. This research expands the engineering implications of these findings by studying the response of interface systems in different loading conditions. Specifically, the axial and torsional shear modes are studied in detail. Throughout this thesis it is shown that taking an engineering approach to design the loading conditions induced to the interface system can result in interface strengths that exceed the previously considered limiting shear strength of the contacting soil. Fundamental experimental and numerical studies on specimens of different types of sand subjected to torsional and axial interface shear highlighted the inherent differences of these processes. Specifically, micro-scale soil deformation measurements showed that torsional shear induces larger soil deformations as compared to axial shear, as well as complex volume-change tendencies consisting of dilation and contraction in the primary and secondary shear zones. Studies on the global response of torsional and axial shear tests showed that they are affected differently by soil properties such as particle angularity and roughness. This difference in global behavior highlights the benefits of making systems that transfer load to the contacting soil in different manners available for use in geotechnical engineering. Discrete Element Modeling (DEM) simulations allowed for internal information of the specimens to be studied, such as their fabric and shear-induced loading conditions. These findings allowed for the development of links between the measured micro-scale behavior and the observed global-scale response. The understanding of the behavior of torsional and axial interfaces has allowed provides a framework for the development of enhanced geotechnical systems and applications. The global response of torsional shear found to induce larger cyclic contractive tendencies within the contacting soil mass. Therefore, this shear mode is more desirable than the conventional axial shear for the study of phenomena that depend on soil contractive behavior, such as liquefaction. A study on the influence of surface roughness form revealed that surfaces with periodic profiles of protruding elements that prevent clogging are capable of mobilizing interface friction angles that are 20 to 60% larger than the soil friction angle. These findings have direct implications in engineering design since their implementation can result in more resilient and sustainable geotechnical systems.

The dynamic properties of several rectangular and V-shaped microcantilevers were investigated. Particular attention was paid to the higher flexural eigenmodes of oscillation. The potential of the higher flexural modes was demonstrated through the use of cantilevers as standalone sensors for adsorbed mass. The mass adsorbed on the surface of a cantilever was in the form of a homogeneous water layer measured as a function of relative humidity. The minimum detectable water layer thicknesses were 13.7 Å, 3.2 Å, 1.1 Å, and 0.7 Å for the first four modes of a rectangular cantilever, clearly demonstrating enhanced accuracy for the higher eigenmodes of oscillation. These thicknesses correspond to minimum detectable masses of 33.5 pg, 7.8 pg, 2.7 pg and 1.7 pg for the first four modes. For quantitative applications the spring constants of each cantilever must be determined. Many methods exist but only a small number can calibrate the higher flexural eigenmodes. A method was developed to simultaneously calibrate all flexural modes of microcantilever sensors. The method was demonstrated for the first four eigenmodes of several rectangular and V-shaped cantilevers with nominal fundamental spring constants in the range of 0.03 to 1.75 N/m. The spring constants were determined with accuracies of 5-10 %. Spring constants of the fundamental mode were generally in agreement with those determined using the Sader method. The method is compatible with existing AFM systems. It relies on a flow of gas from a microchannel and as such poses no risk of damage to the cantilever beam, its tip, or any coating. A related method was developed for the torsional modes of oscillation. Preliminary results are shown for the fundamental mode of a rectangular cantilever. The method can be easily extended to the higher torsional modes, V-shaped cantilevers, and potentially, the flapping modes of the legs of V-shaped microcantilevers.

Rotary endodontic instruments have different cross sectional designs that may effect their resistance to torsional stress. The purpose of this study is to evaluate the static torsional properties of two nickel titanium files that have recently been introduced for use in endodontics and compare them to the same size Profile instruments. Ten new files of each brand and size were tested. The files tested were: RaCe 25 tip 0.02, 0.04, 0.06 taper, K3 and Profile 25 and 40 tip in 0.02, 0.04 and 0.06 taper. The diameter of each file was measured at 3mm from tip. The last three millimeters of the working area of the file was grasped with a non-rotating stainless steel chuck and the handle was held in freely rotating chuck. Torque was applied with the Instron Universal Tester in a counter-clockwise direction to simulate the direction of torque encountered clinically. The crosshead speed was set to produce 2 rotations per minute until fracture occurred. The maximum torque achieved and the rotations to fracture were recorded. A multi-way ANOVA of rotations revealed that RaCe 25-0.02 exhibited significantly less rotations to fracture than Profile and K3 of the same size (p<0.0001). RaCe 25 tip exhibited lower maximum torque in all tapers than corresponding K3 and Profile instruments. The mean diameter was significantly smaller for the RaCe files. In this study the RaCe file series exhibited lower values for maximum torque and rotations to fracture. These results should be taken into account while using these files clinically, however further testing is indicated.

Doctor of Philosophy / Department of Civil Engineering / Hayder A. Rasheed / Thin-walled structures are major components in many engineering applications. When a thin-walled slender beam is subjected to lateral loads, causing moments, the beam may buckle by a combined lateral bending and twisting of cross-section, which is called lateral-torsional buckling. A generalized analytical approach for lateral-torsional buckling of anisotropic laminated, thin-walled, rectangular cross-section composite beams under various loading conditions (namely, pure bending and concentrated load) and boundary conditions (namely, simply supported and cantilever) was developed using the classical laminated plate theory (CLPT), with all considered assumptions, as a basis for the constitutive equations. Buckling of such type of members has not been addressed in the literature. Closed form buckling expressions were derived in terms of the lateral, torsional and coupling stiffness coefficients of the overall composite. These coefficients were obtained through dimensional reduction by static condensation of the 6x6 constitutive matrix mapped into an effective 2x2 coupled weak axis bending-twisting relationship. The stability of the beam under different geometric and material parameters, like length/height ratio, ply thickness, and ply orientation, was investigated. The analytical formulas were verified against finite element buckling solutions using ABAQUS for different lamination orientations showing excellent accuracy.

One of the central tasks for biomolecular modeling is to develop accurate and computationally cheap methods. In this dissertation, we present the development of a brand new polarizable force field—Polarizable Simulations with Second order Interaction Model (POSSIM) involving electrostatic polarization. The POSSIM framework combines accuracy of a polarizable force field and computational efficiency of the second-order approximation of the full-scale induced point dipole polarization formalism. POSSIM force field has been extended to include parameters for small molecules serving as models for peptide and protein side-chains. Parameters have been fitted to permit reproducing many-body energies, gas-phase dimerization energies and geometries and liquid-phase heats of vaporization and densities. Quantum mechanical and experimental data have been used as the target for the fitting. The resulting parameters can be used for simulations of the parameterized molecules themselves or their analogues. In addition to this, these force field parameters have been employed in further development of the POSSIM fast polarizable force field for proteins. The POSSIM framework has been expanded to include a complete polarizable force field for proteins. Most of the parameter fitting was done to high-level quantum mechanical data. Conformational geometries and energies for dipeptides have been reproduced within average errors of ca. 0.5 kcal/mol for energies of the conformers (for the electrostatically neutral residues) and 9.7º for key dihedral angles. We have also validated this force field by simulating an elastin-like polypeptide GVG(VPGVG)3 in aqueous solution. Elastin-like peptides with the (VPGVG)n motif are known to exhibit anomalous behavior of their radius of gyration that increases when temperature is lowered (the so called inverse temperature transition). We have simulated the system with the OPLS-AA and POSSIM force fields and demonstrated that our newly developed polarizable POSSIM parameters permit to capture the experimentally observed decrease of the radius of gyration with increasing temperature, while the fixed-charges OPLS-AA ones do not. Furthermore, our fitting of the force field parameters for the peptides and proteins has been streamlined compared with the previous generation of the complete polarizable force field and relied more on transferability of parameters for non-bonded interactions (including the electrostatic component). The resulting deviations from the quantum mechanical data are similar to those achieved with the previous generation, thus the technique is robust and the parameters are transferable. At the same time, the number of parameters used in this work was noticeably smaller than that of the previous generation of our complete polarizable force field for proteins, thus the transferability of this set can be expected to be greater and the danger of force field fitting artifacts is lower. Therefore, we believe that this force field can be successfully applied in a wide variety of applications to proteins and protein-ligand complexes.

Drill String dynamic behaviour during the oil drilling operation, was a major source for the failure of the Bottom Hole Assembly (BHA). The behaviour produced torsional vibration, which underpins the stick slip phenomena. Besides threatening the safety of the oil drilling process, such failure cause interruptions in the drilling operations and incurred high maintenance cost to the oil drilling company. This issue can be resolved with the implementation of the optimum control mechanism while operating the drill string. In this research, an optimum control mechanism was proposed to suppress the torsional vibration as well as mitigate the risk of stick slip phenomenon from occurring. The mechanism was proposed through a series of rigorous research strategies i.e. updated-mathematical equation modelling, experimentation and simulation. As the first step, a mathematical equation model describing system dynamics was derived to set the parameter of investigation. Representing the freedom torsional of the two degrees - conventional vertical drill string, the model was used to predict the frictional Torque On Bit (TOB) through non-linear friction force, denoting the ground-formation behaviour during drilling activity. Using a velocity feedback system, the drill-string oscillation was reduced while gradually increasing its velocity via gain scheduling method - allowing fast response to load disturbance. To avoid the motor torque from exceeding the maximum threshold, a Weight On Bit (WOB) was introduced. This approach remarks the novel contribution of this research. Next, an experiment on the preliminary test rig within a controlled laboratory set up was conducted. The rotary drill rig was assembled to identify the dynamics (i.e. parameters) of an individual part of the drill string. The results obtained were then applied in the drill string operation experiment, to identify the optimum control mechanism that can avoid the torsional vibration. To enable triangulation of results, a simulation was conducted by applying the same parameters obtained from the test rig experiment in the model- which is the optimum control mechanism that was proposed in this research to minimise torsional vibration, as well as reducing the chance of drill-string failure due to stick-slip phenomenon.

The aim of this study was to evaluate the cyclic and torsional fatigue resistance of Nickel-Titanium rotary instruments manufactured by different thermal treatments. Were tested a total of 140 rotary instruments (n=20): Genius (GN size 25, .04 taper), Trushape (TS size 25, .06 taper), Logic (LOG size 25, .06 taper), Vortex Blue (VB size 25, .06 taper), ProTaper Gold (PTG size 25, .08 taper), Hyflex CM (HCM size 25, .06 taper) and Hyflex EDM (EDM size 25, .08 taper). Cyclic fatigue resistance testing was performed using an artificial stainless steel canal with a curvature (60° angle and 5- mm radius) located at 5 mm from the tip. The files (n=10) rotated until fracture and time was recorded in seconds. The torsional test evaluated the angular deflection and torque at failure of the instruments (n=10) at 3 mm from the tip according to ISO 3630- 1. The fractured surface of five instruments of each brand was observed by using scanning electron microscopy (SEM). Data were analysed using one-way ANOVA and Tukey tests, and the level of significance was set at 5%. The cyclic fatigue resistance value of EDM size 25, .08 taper was significantly higher than those of all instruments tested (P<0.05). The LOG size 25, .06 taper showed a higher cyclic fatigue resistance than those of GN size 25, .04 taper; TS size 25, .06 taper (P<0.05). There was no difference among the others groups. The torsional test showed that PTG size 25, .08 taper had the highest torsional strength value of all instruments tested followed by VB size 25, .06 taper and EDM size 25, .06 taper (P<0.05). The LOG size 25, .06 taper showed significant difference only with GN size 25, .04 taper (P<0.05). No difference was found among the others groups (P>0.05). In relation to angular deflection, the GN size 25, .04 taper; TS size 25, .06 taper; HCM size 25, .06 taper, and EDM size 25, .08 taper showed significantly higher values until fracture than the others groups (P<0.05). No difference was found among PTG size 25, .08 taper, LOG size 25, .06 taper, and VB size 25, .06 taper (P<0.05). The EDM size 25, .08 taper presented the highest cyclic fatigue resistance among all the tested instruments. For the torsional test, the PTG size 25, .08 taper showed highest torsional strength and lowest angular deflection values. / O objetivo deste estudo foi avaliar a resistência às fadigas cíclica e torsional de instrumentos rotatórios de Níquel - Titânio fabricados por diferentes tratamentos térmicos. Foram testados o total de 140 instrumentos (n=20): Genius (GN diâmetro 25, conicidade .04), Trushape (TS diâmetro 25, conicidade .06), Logic (LOG diâmetro 25, conicidade .06), Vortex Blue (VB diâmetro 25, conicidade .06), ProTaper Gold (PTG diâmetro 25, conicidade .08), Hyflex CM (HCM diâmetro 25, conicidade .06) e Hyflex EDM (EDM diâmetro 25, conicidade .08). O teste de resistência à fadiga cíclica foi realizado utilizando um canal artificial de aço inoxidável com curvatura (ângulo de 60° e raio de 5mm) localizada a 5 mm da ponta. Os instrumentos (n=10) foram rotacionados até a fratura e tempo foi registrado em segundos. O teste torsional avaliou a deflexão angular e torque até a falha dos instrumentos (n=10) a 3 mm da ponta de acordo com a ISO 3630-1. A superfície da fratura de 5 instrumentos de cada fabricante foi observado utilizando o microscópio eletrônico de varredura (MEV). A análise-estatística foi realizada utilizando o teste de análise de variância com um fator ANOVA e teste de Tukey, o nível de significância foi de 5%. O valor de resistência a fadiga cíclica do EDM diâmetro 25, conicidade .08 foi significantemente maior que todos os instrumentos testados (P<0.05). A LOG diâmetro 25, conicidade .06 mostrou maior resistência à fadiga cíclica que o GN diâmetro 25, conicidade .04; TS diâmetro 25, conicidade .06 (P<0.05). Não houve diferença significante entre os outros grupos. O teste torsional mostrou que PTG diâmetro 25, conicidade .08 obteve o maior valor de torque até a fratura de todos os instrumentos testados seguido por VB diâmetro 25, conicidade .06 e EDM diâmetro 25, conicidade .06 (P<0.05). O LOG diâmetro 25, conicidade .06 mostrou diferença significativa apenas com com GN diâmetro 25, conicidade .04 (P<0.05). Não houve diferença significativa entre os outros grupos (P>0.05). Em relação a deflexão angula, o GN diâmetro 25, conicidade .04; TS diâmetro 25, conicidade .06; HCM diâmetro 25, conicidade .06 e EDM diâmetro 25, conicidade .08 apresentou significantimente o maior valor até a fratura que os outros grupos (P<0.05). Nao foi encontrado diferença significativa entre PTG diâmetro 25, conicidade .08, LOG diâmetro 25, conicidade .06, e VB diâmetro 25, conicidade .06 (P<0.05). O EDM diâmetro 25, conicidade .08 apresentou a maior resistência a fadiga cíclica entre todos os instrumentos testados. Para o teste torsional, o PTG diâmetro 25, conicidade .08 apresentou o maior valor de torque e menor deflexão angular.

Structural steel design standards recognize lateral torsional buckling as a failure mode governing the capacity of long span unsupported beams with wide flange cross-sections. Standard solutions start with the closed form solution of the Vlasov thin-walled beam theory for the case of a simply supported beam under uniform moments, and modify the solution to accommodate various moment distributions through moment gradient expressions. The Vlasov theory solution is based on the assumption that cross-sectional distortional effects have a negligible effect on the predicted elastic critical moment. The present study systematically examines the validity of the Vlasov assumption related to cross-section distortion through a parametric study. A series of elastic shell finite element eigen-value buckling analyses is conducted on simply supported beams subject to uniform moments, linear moments and mid span point loads as well as cantilevers subject to top flange loading acting at the tip. Cross-sectional dimensions are selected to represent structural steel cross-section geometries used in practice. Particular attention is paid to model end connection details commonly used in practice involving moment connections with two pairs of stiffeners, simply supported ends with a pair of transverse stiffeners, simply supported ends with cleat angle details, and built in fixation at cantilever roots. The critical moments obtained from the FEA are compared to those based on conventional critical moment equations in various Standards and published solutions. The effects of web slenderness, flange slenderness, web height to flange width ratio, and span to height ratios on the critical moment ratio are systematically quantified. For some combinations of section geometries and connection details, it is shown that present solutions derived from the Vlasov theory can overestimate the lateral torsional buckling resistance for beams.