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The main purpose of this report was to test several common viscoelastic polymers and identify key attributes of their applicability to a small aircraft landing gear system for improved damping performance. The applied viscoelastic damping treatment to the gear was of a constrained layer type, promoting increased shear deformation over free surface treatments, and therefore enhanced energy dissipation within the viscoelastic layer. A total of eight materials were tested and analyzed using cyclic loading equipment to establish approximate storage modulus and loss factor data at varying loading frequencies. The three viscoelastic polymers having the highest loss factor to shear modulus ratio were chosen and tested using a cantilever beam system. A Ross, Kerwin, and Ungar analysis was used to predict the loss factor of the cantilever beam system with applied treatment and the predictions were compared to experimental data. Customer requirements often govern the scope and intensity of design in many engineering applications. Limitations and constraints, such as cost, weight, serviceability, landing gear geometry, environmental factors, and manufacturability in regards to the addition of a viscoelastic damping treatment to a landing gear system are discussed. Based on results found from theoretical and experimental testing, application of a damping treatment to a small aircraft landing gear system is very promising. Relatively high loss factors were seen in a cantilever beam for simple single layer constrained treatments for very low strain amplitudes relative to strains seen during loading of the landing gear. With future design iterations, damping levels several times those seen in this document will be seen with a constrained treatment applied to a landing gear system. / Master of Science

<p>In the industry, all passenger vehicles are treated with damping materials to reduce structure-borne sound. Though these damping materials are effective to attenuate structure-borne sound, they have little or no effect on the air-borne sound transmission.The lack of effective predictive methods for assessing the acoustic effects due to added damping on complex industrial structures leads to excessive use of damping materials.Examples are found in the railway industry where sometimes the damping material applied per carriage is more than one ton. The objective of this thesis is to provide a better understanding of the application of these damping materials in particular when applied to lightweight sandwich panels.</p><p>As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist in the design process. Sound transmission loss of sandwich plates with isotropic core materials can be accurately predicted by calculating the wave propagation in the structure. A modified wave propagation approach is used to predict the sound transmission loss of sandwich panels with honeycomb cores. The honeycomb panels are treated as being orthotropic and the wave numbers are calculated for the two principle directions. The orthotropic panel theory is used to predict the sound transmission loss of panels. Visco-elastic damping with a constraining layer is applied to these structures and the effect of these damping treatment on the sound transmission loss is studied. Measurements are performed to validate these predictions.</p><p>Sound radiated from vibrating structures is of great practical importance.The radiation loss factor represents damping associated with the radiation of sound as a result of the vibrating structure and can be a significant contribution for structures around the critical frequency and for composite structures that are very lightly damped. The influence of the radiation loss factor on the sound reduction index of such structures is also studied.</p> / QC 20100519 / ECO2-Multifunctional body Panels

The aerospace industry is utilizing low cost miniature inertial measurement units (IMUs) that employ Micro Electro-Mechanical Systems (MEMS) technology in an effort to reduce size, weight, and cost of systems. A drawback of these MEMS devices is they are sensitive to vibration, shock and acoustic environments, which limits the usefulness of such devices in the severe environments imposed by many aerospace applications. In an effort to reduce the vibration, shock and acoustic environments experienced by these MEMS devices, the desire to develop passive damping treatments to structural components used to mount these devices. The damping treatments can be applied at the printed circuit board (PCB) level, the component level, the component interface, or at the airframe level. The purpose is to reduce the overall environment and improve the usefulness and performance of the MEMS based sensors. The primary technique to introduce damping into metallic parts and PCBs is to provide a viscoelastic coating or layer. The ability to analyze structures with this configuration requires a thorough understanding of the dynamic properties. Hooke’s law of elasticity is one of the most fundamental relationships governing dynamic properties. Metals typically have a low damping coefficient, and Hooke’s law of elasticity represents a linear relationship between the ratio of stress and strain, known as the modulus of elasticity. But for viscous materials the modulus of elasticity becomes a complex value since the stress and strain are not in phase. The complex modulus of elasticity is a complex function of frequency. The complex modulus can be established via frequency response function measurements of compliance, mobility, and accelerance, and the dimensions of the block of material under test. At low frequencies (less than resonance of the block) the results are relatively straight forward, but at higher frequencies where resonances of the block occur the inertial forces begin to influence the FRF results. This thesis effort establishes techniques for measuring the complex moduli associated with viscoelastic materials, and presents methods and results from modulus tests conducted for this thesis.

In the industry, all passenger vehicles are treated with damping materials to reduce structure-borne sound. Though these damping materials are effective to attenuate structure-borne sound, they have little or no effect on the air-borne sound transmission.The lack of effective predictive methods for assessing the acoustic effects due to added damping on complex industrial structures leads to excessive use of damping materials.Examples are found in the railway industry where sometimes the damping material applied per carriage is more than one ton. The objective of this thesis is to provide a better understanding of the application of these damping materials in particular when applied to lightweight sandwich panels. As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist in the design process. Sound transmission loss of sandwich plates with isotropic core materials can be accurately predicted by calculating the wave propagation in the structure. A modified wave propagation approach is used to predict the sound transmission loss of sandwich panels with honeycomb cores. The honeycomb panels are treated as being orthotropic and the wave numbers are calculated for the two principle directions. The orthotropic panel theory is used to predict the sound transmission loss of panels. Visco-elastic damping with a constraining layer is applied to these structures and the effect of these damping treatment on the sound transmission loss is studied. Measurements are performed to validate these predictions. Sound radiated from vibrating structures is of great practical importance.The radiation loss factor represents damping associated with the radiation of sound as a result of the vibrating structure and can be a significant contribution for structures around the critical frequency and for composite structures that are very lightly damped. The influence of the radiation loss factor on the sound reduction index of such structures is also studied. / QC 20100519 / ECO2-Multifunctional body Panels

Este trabalho baseia-se no estudo e aplicação da Análise Estatística de Energia (SEA). Tal técnica é amplamente empregada nos estudos de vibrações em altas freqüências, dominadas por altas densidades modais e oferecendo toda a solução para o modelo em termos de parâmetros estatísticos. Aplica-se SEA tanto a modelos teóricos e numéricos quanto a modelos experimentais. Qualquer uma das duas abordagens descrita anteriormente tem como objetivo a obtenção dos parâmetros SEA, conhecidos por fator de perda por dissipação interna, fator de perda por acoplamento e densidade modal. Para o estudo e aplicação experimental da técnica SEA utiliza-se o Método de Injeção de Potência, sendo este aplicado a estruturas acopladas do tipo viga, numa configuração em T e estruturas acopladas do tipo placa que formam uma caixa. O estudo numérico e analítico também faz parte deste trabalho, tendo como base o desenvolvimento de uma formulação para vigas relativamente espessas, mostrando a influência geométrica na transmissão da vibração entre subsistemas. Comparações também são feitas entre os resultados obtidos experimentalmente na caixa e na viga T com os obtidos analiticamente e computacionalmente e em ambos os casos estes apresentaram uma boa correlação. Por fim, uma estrutura composta por uma cavidade acústica é estudada e um aparato o para injeção de potência é construído com base no estudo em altas freqüências. / This work is based in the study and application of the Statistical Energy Analysis (SEA), which is applied to high frequencies vibrations characterized by high modal densities and the solution, is given in statistical terms. This analysis is used in numerical, analytical and experimental models and the principal objective is the estimative of the SEA parameters, known by damping loss factors, coupling loss factors and modal densities. The experimental model is based on the Power Injection Method (PIM), and this was applied in coupled structures, like beam type, that was coupled in a T-beam configuration and the other type of coupling was studied in a box type structure. An analytical model was developed in this thesis, it was based on the Timoshenko beam formulation and the possible geometrical effects were studied. The results obtained as experimentally as numerically or analytically were compared and showed a good agreement. Finally, an acoustic cavity was studied and a new display was constructed to inject power in the cavity and a high frequency study was performed.

Este trabalho baseia-se no estudo e aplicação da Análise Estatística de Energia (SEA). Tal técnica é amplamente empregada nos estudos de vibrações em altas freqüências, dominadas por altas densidades modais e oferecendo toda a solução para o modelo em termos de parâmetros estatísticos. Aplica-se SEA tanto a modelos teóricos e numéricos quanto a modelos experimentais. Qualquer uma das duas abordagens descrita anteriormente tem como objetivo a obtenção dos parâmetros SEA, conhecidos por fator de perda por dissipação interna, fator de perda por acoplamento e densidade modal. Para o estudo e aplicação experimental da técnica SEA utiliza-se o Método de Injeção de Potência, sendo este aplicado a estruturas acopladas do tipo viga, numa configuração em T e estruturas acopladas do tipo placa que formam uma caixa. O estudo numérico e analítico também faz parte deste trabalho, tendo como base o desenvolvimento de uma formulação para vigas relativamente espessas, mostrando a influência geométrica na transmissão da vibração entre subsistemas. Comparações também são feitas entre os resultados obtidos experimentalmente na caixa e na viga T com os obtidos analiticamente e computacionalmente e em ambos os casos estes apresentaram uma boa correlação. Por fim, uma estrutura composta por uma cavidade acústica é estudada e um aparato o para injeção de potência é construído com base no estudo em altas freqüências. / This work is based in the study and application of the Statistical Energy Analysis (SEA), which is applied to high frequencies vibrations characterized by high modal densities and the solution, is given in statistical terms. This analysis is used in numerical, analytical and experimental models and the principal objective is the estimative of the SEA parameters, known by damping loss factors, coupling loss factors and modal densities. The experimental model is based on the Power Injection Method (PIM), and this was applied in coupled structures, like beam type, that was coupled in a T-beam configuration and the other type of coupling was studied in a box type structure. An analytical model was developed in this thesis, it was based on the Timoshenko beam formulation and the possible geometrical effects were studied. The results obtained as experimentally as numerically or analytically were compared and showed a good agreement. Finally, an acoustic cavity was studied and a new display was constructed to inject power in the cavity and a high frequency study was performed.

Master of Science / Department of Architectural Engineering and Construction Science / Raphael A. Yunk / Sustainable design and green engineering practices have become a priority in the architectural design industry over the past few years. Energy codes and standards have become more stringent as energy costs rise and buildings become larger, consuming more energy and having a larger impact on the environment. One major area for improvement to meet these new requirements is in the lighting area. Kansas State University (KSU) in Manhattan, KS has had the same campus walkway lighting system for over 50 years and it does not meet the current energy codes and standards. This paper will perform a case study of the current walkway lighting system on the KSU campus, specifically focusing on the Quad area and applying the same principles to the entire campus. The illumination and fixture distribution characteristics will first be established and analyzed to determine an accurate baseline for later comparison. Issues regarding the illumination, efficiency, aesthetics, maintenance, and landscaping will be addressed once the current conditions are established. Lighting technology has changed dramatically in the past year with the development of high efficiency fluorescent, induction, and light emitting diode (LED) lighting. New LED technology has proven to be the most efficient and has been adapted to create outdoor LED fixtures that could help KSU surpass the current energy standards and improve the overall quality of light to correct some of the current issues the existing lighting creates. A full analysis of the illumination, efficiency, aesthetics, and economic feasibility will be performed. The economic analysis will compare existing maintenance and energy costs to that of the first-cost with maintenance, and energy costs to determine an estimated payback. Once the analysis is complete, future options for KSU to implement new lighting technology will be discussed. By creating a more environmentally conscious campus, using high efficiency lighting, KSU could set an example for other universities to pursue sustainable technology and design.

Gas bearings in oil-free micro-turbomachinery for process gas applications and for power generation (< 400 kW) must offer adequate load capacity and thermal stability, reliable rotordynamic performance at high speeds and temperatures, low power losses and minimal maintenance costs. The metal mesh foil bearing (MMFB) is a promising foil bearing technology offering inexpensive manufacturing cost, large inherent material energy dissipation mechanism, and custom-tailored stiffness and damping properties. This dissertation presents predictions and measurements of the dynamic forced performance of various high speed and high temperature MMFBs. MMFB forced performance depends mainly on its elastic support structure, consisting of arcuate metal mesh pads and a smooth top foil. The analysis models the top foil as a 2D finite element (FE) shell supported uniformly by a metal mesh under-layer. The solution of the structural FE model coupled with a gas film model, governed by the Reynolds equation, delivers the pressure distribution over the top foil and thus the load reaction. A perturbation analysis further renders the dynamic stiffness and damping coefficients for the bearing. The static and dynamic performance predictions are validated against limited published experimental data. A one-to-one comparison of the static and dynamic forced performance characteristics of a MMFB against a Generation I bump foil bearing (BFB) of similar size, with a slenderness ratio L/D=1.04, showcases the comparative performance of MMFB against a commercially available gas foil bearing design. The measurements of rotor lift-off speed and drag friction at start-up and airborne conditions are conducted for rotor speeds up to 70 krpm and under identical specific loads (W/LD =0.06 to 0.26 bar). The dynamic force coefficients of the bearings are estimated, in a ‘floating bearing’ type test rig, while floating atop a journal spinning to speeds as high as 50 krpm and with controlled static loads (22 N) applied in the vertical direction. The parameter identification is conducted in the frequency range of 200-400 Hz first, and then up to 600 Hz using higher load capacity shakers. A finite element rotordynamic program (XLTRC2) models a hollow rotor and two MMFBs supporting it and predict the synchronous rotor response for known imbalances. The predictions agree well with the ambient temperature rotor response measurements. Extensive rotor response measurements and rotor and bearing temperature measurements, with a coil heater warming up to 200 ºC and placed inside the hollow rotor, reveal the importance of adequate thermal management. The database of high speed high temperature performance measurements and the development of a predictive tool will aid in the design and deployment of MMFBs in commercial high-speed turbomachinery. The work presented in the dissertation is a cornerstone for future analytical developments and further testing of practical MMFBs.

Statistical Energy Analysis (SEA) is one of the methods in literature to estimate high frequency vibrations. The inputs required for the SEA power balance equations are damping and coupling loss factors, input powers to the subsystems. In this study, the coupling loss factors are derived for two and three plates joined with a stiffener system. Simple formulas given in the literature for coupling loss factors of basic junctions are not used and the factors are calculated from the expressions derived in this study. The stiffener is modelled as line mass, Euler beam, and open section channel having double and triple coupling. Plate is modelled as Kirchoff plate. In the classical SEA approach the joint beam is modelled as another subsystem. In this study, the beam is not a separate subsystem but is used as the characteristics of the joint and to calculate the coupling loss factor between coupled plates. Sensitivity of coupling loss factors to system parameters is studied for different beam approaches. The derived coupling loss factors and input powers are used to calculate the subsystem energies by SEA. The last plate is joined to the first one to simulate the fuselage structure. A plate representing floor structure and acoustic volume are also added. The different modelling types are assessed by applying pressure wave excitation. It is shown that deriving the parameters as given in this study increases the efficiency of the SEA method.