Methods of determining natural frequencies of the D76D88, B76D88, A86E93, C86G90, C86L90 and C125L89 turbine wheel designs for various environmental conditions were investigated by application of Finite Element Analysis and beam theory. Modelling and simulation methods were developed ; the first method composed of 15 finite element simulations ; the second composed of 15 finite element simulations and a set of experimental frequency survey results; the third composed of 5 simulations , an incorporated mathematical model and a set of experimental frequency survey results. Each of these methods was designed to allow prediction of resonant frequency changes across a range of exhaust gas temperature and shaft rotational speed. For the new modelling and simulation methods, an analysis template and a plotting tool were developed using Microsoft Excel and MATLAB software. A graph showing a frequency-temperature-speed variations and a Campbell Diagram that incorporates material stiffening and softening effects across a range of rotational speeds was designed, and applied to the D76D88, B76D88, A86E93, C86G90, C86L90 and C125L89 turbine wheel designs. New design methodologies for turbine wheels were formulated and validated, showing a good agreement with a range of data points from frequency survey, strain-gauge telemetry and laser tip-timing test results. The results from the new design method were compared with existing single compensation factor methodology, and showed a great improvement in accuracy of prediction of modal vibration. A new nomenclature for the mode shapes of a turbocharger’s blade was proposed, designed and demonstrated to allow direct identification of associated mode shape. It is concluded that Finite Element Analysis combined with the frequency survey is capable of predicting changes in turbine natural frequencies and, when incorporated into the existing turbine design methodology, resulted in a major improvement in the accuracy of the predictions of vibration frequency.

The stability of the high-walls is one of the major concerns for open pit mines. Among the various factors affecting the stability of high-walls, blast vibrations can be an important one. In general, worldwide the established respective government regulations and industry standards are used as guidance to determine the maximum recommended levels of the peak particle velocity and frequency from the blast to avoid any effects on the structures around the mining project. However, most of the regulations are meant for buildings or houses and do not concern high-walls. This thesis investigates the response of high-walls under the effects of vibrations from mine blasting. In this research, the relationship between the high-wall response, the geometry of the slope, the frequency and the amplitude, of the ground vibration produced by blasting, is explored using numerical models in 3DEC. The numerical models were calibrated initially with data collected using seismographs installed in a surface mine operation and recording vibrations produced by an underground mine drill and blast operation. Once the calibration was accomplished, a parametric study was developed to explore the relationships between various parameters under study and its impact on the stability of high-walls.

Abstract The purpose of this study is to determine the exact natural frequencies and mode shapes of multi-span uniform and multi-step Euler-Bernoulli beams with various concentrated elements (such as point masses, rotary inertias, linear springs, rotational springs, spring-mass systems, etc.) by using the matrix assembly method (MAM). To this end, the coefficient matrices for an intermediate pinned support, an intermediate concentrated elements, left-end support and right-end support of a beam are derived, first. Next, the overall coefficient matrix for the whole structural system is obtained by using the assembly technique of the finite element method. Finally, the natural frequencies and the associated mode shapes of the vibrating system are determined by equating the determinant of the last overall coefficient matrix to zero and substituting the corresponding values of integration constants into the associated eigenfunctions respectively. The effects of in-span pinned supports and various concentrated elements on the free vibration characteristics of the beam are also studied.

<p>Today’s bridge design work in many cases demands a trustworthy dynamic analysis instead of using the traditional dynamic amplification factors. In this thesis a reliable 3D Bernoulli-Euler beam finite element model of the New Årsta Railway Bridge was prepared for thorough dynamic analysis using in situ bridge monitoring for correlation. The bridge is of the concrete box girder type with a heavily reinforced and prestressed bridge deck. The monitoring system was designed for long term monitoring with strain transducers embedded in the concrete and accelerometers mounted inside the edge beams and at the lower edge of the track slab.</p><p>The global finite element model used the exact bridge geometry but was simplified regarding prestressing cables and the two railway tracks. The prestressing cables and the tracks were consequently not included and an equivalent pure concrete model was identified.</p><p>A static macadam train load was eccentrically placed on one of the bridge’s two tracks. By using Vlasov’s torsional theory and thereby including constrained warping a realistic modulus of elasticity for the concrete without prestressing cables and stiffness contribution from the railway tracks was found. This was allowed by comparing measured strain from strain transducers with the linear elastic finite element model’s axial stresses. Mainly three monitoring bridge sections were used, each of which was modelled with plane strain finite elements subjected to sectional forces/moments from a static macadam train load and a separately calculated torsional curvature.</p><p>From the identified modulus of elasticity the global finite element model was updated for Poisson’s ratio and material density (mass) to correspond with natural frequencies from the performed signal analysis of accelerometer signals. The influence of warping on the natural frequencies of the global finite element model was assumed small and the bridge’s torsional behaviour was modelled to follow Saint-Venant’s torsional theory.</p><p>A first preliminary estimation of modal damping ratios was included. The results indicated that natural frequencies were in accordance between modelling and signal analysis results, especially concerning high energy modes. Estimated damping ratios for the first vibration modes far exceeded the lower limit value specified in bridge design codes and railway bridge dynamic analysis recommendations.</p>

Vibration generated from various sources (engine, road surface, tires, exhaust, etc.) should be considered in the design of a car body. These vibrations travel through transfer systems (drivetrain, suspension, body, etc.) to the steering wheel, seats and other areas where it is detected by the passengers of the vehicle. Transmission routes must be studied and efforts made to keep transfer systems from amplifying vibration and to absorb it instead. Since the superior vibration transfer system is the car body, finite element analysis and experimental vibration analysis are performed on car body-in-white. Body vibration analysis entails understanding and improving the body&rsquo / s dynamic characteristics that act as vibration transfer channels. In the previous study, a finite element model has been created for a car body-in-white available in Automotive Laboratory (Mechanical Engineering Department, Middle East Technical University, Ankara) and its natural frequencies and mode shapes have been determined using finite element analysis software. In this study, vibration tests have been performed on actual car body-in-white. Frequency response functions between 34 response locations and force application point have been measured. Using these frequency response functions, natural frequencies and mode shapes of the body-in-white have been determined. Finite element analysis and experimental results have been compared to evaluate the finite element model reliability.

Orientador: Prof. Dr. Reyolando M. L. R. F. Brasil / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Mecânica, 2017. / Neste trabalho realiza-se um estudo do efeito causado pela alteracao da rigidez geometrica, por meio de forcas axiais, na frequencia natural de bases de maquinas rotativas, na forma de viga e portico plano, todos metalicos, no intuito de tira-las na ressonancia ou proximo dessa regiao. Essa regiao proxima da ressonancia e chamada de regiao fora de seguranca e compreende o intervalo que comeca em 20% abaixo da frequencia da maquina ate 25% acima dela. Duas ferramentas foram utilizadas para realizar o estudo, Metodo de Rayleigh e Metodo dos Elementos Finitos (MEF). Na viga estuda-se um perfil estrutural de um tubo retangular em aco estrutural, utilizando o Metodo de Rayleigh e o MEF. Ja o portico e estudado somente pelo MEF, so que mais perfis foram analisados desse mesmo tubo. No caso da base como viga, sem carregamento algum, ela se mostrou dentro na zona perigosa, tanto por Rayleigh como por MEF. Uma intervencao com forcas axiais foi realizada para estabilizar as bases. No portico tanto portico, o perfil 60x60 nao ficou dentro da zona perigosa, ja os demais, 80x80 e perfil ¿§, ficaram dentro da regiao { 0,8¿¶, 1,25¿¶ }. O estudo mostrou que a rigidez geometrica / In this work a study of the effect caused by the alteration of the geometric stiffness, by means of axial forces, in the natural frequency of bases of rotating machines, in the form of beam and plan portico, all metallic, in order to take them out in the resonance or near this region. This region near the resonance is called unsafe region, and comprises the range starting at 20% below the frequency of the machine and to 25% above it. Two tools were used to carry out the study, Rayleigh Method and Finite Element Method (FEM). In the beam, a structural profile of a rectangular tube in structural steel is studied, using the Rayleigh Method and MEF. Already the portico is studied only by MEF, except that more profiles were analyze in this same tube. In the case of the base as beam, without any loading, it showed itself inside the dangerous zone, by both Rayleigh and MEF. An axial force intervention was performed to stabilize the bases. In the planar portal frame, the 60x60 profile was not inside the dangerous zone, while the others, 80x80 and profile É, were within the region {0.8Ù, 1.25Ù}. The study showed that the geometric stiffness has a close relation with the natural frequencies in solid structures.

A content of this diploma thesis is construction design of torsional vibration rubber damper of four-stroke diesel supercharged engine. It` s realized evaluation of crankshaft from aspect of torsional vibrations and checked mechanical stress of crankshaft without using rubber damper. Consequently basic parameters of rubber damper are specified, then checked mechanical stress of crankshaft and designed own construction design of damper.

This thesis is focused on building a replacement torsion system of drivetrain of 8x8 and 8x4 trucks and subsequent computational analyses of built systems. There were made two analyses. The first one is a computational analysis of the shapes of vibration and The second one is a sensitivity analysis. The sensitivity analysis is studying effect on the size of the natural frequencies under the effect of gear ratio.

This work deals with virtual designing of ball screw drives of CNC machine by modern software tools to approximate evaluation of dynamic behavior of real system. Realized multi body system of thrust axes actuated by synchronous motor is analyzed and after that are designed elements of control used for accuracy positioning of table.

This master thesis deals with VUT~081~Kondor aircraft flutter analysis. This aircraft is being designed at the Institute of Aerospace Engineering, Faculty of Mechanical Engineering, Brno University of Technology. The thesis contains detailed aircraft description, natural frequency and normal modes computation as well as aircraft structure flutter analysis and critical flutter velocity determination. Some structure improvement recommendations have been given in order to increase the critical flutter velocity and to fulfil the CS-VLA regulation requirements.