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As the industry is being reshaped concentrically around sustainability, the consumption of fossil fuels is targeted to decrease day by day. As a consequence of that, a righteous rise of electricity as energy source prevails in different branches of industry. It results for electric vehicle components to increase in size and weight which in fact were relatively smaller on conventional fossil fuel driven vehicles e.g. trucks. Every component weighing more than two kilograms is classified as a large component by Scania and these large electric components uncovers the need of evaluation of established testing methods in terms of their validity. This thesis project was carried out at Scania, Södertälje, and deals with the investigation on vibration testing methods that are currently used in different fields of engineering and identification of potentially applicable ones at Scania in testing large components. A case study on the stiffness of an individual component is performed to assess its impact on alteration of eigenfrequencies. Few case studies based on empirical tests as well as finite element method simulations on certain large components, i.e. high voltage junction box and battery packs, are performed with respect to their vibration behaviours while undergoing Scania’s established vibration testing spectra. Investigation into the vibration behaviour on dependence on measurement locations were performed. Additionally, rudimentary case studies are conducted on thermal loads during vibration testing, thermal dwell time, and required energy to oscillate large components at certain levels. How thermal features of the component are affected due to its size is noted., Den senaste tekniska paradigmen inom fordonsindustrin är fokus på minskning av beroende på fossila bränslen, högre energisnålhet och en ökad hållbarhet och effektivitet i produktionsprocessens alla delar. Detta och de stora genombrotten i batteritekniken hade som påföljd att utvecklingen av fordon riktades mot elektrifiering av alla fordon. Elmotorer har sedan tidigare funnit sin tillämpning på mindre maskiner i inomhusmiljöer som t.ex. palldragare och lasttruckar. För tyngre applikationer som t.ex. personbilar och lastbilar ställs det helt nya krav på komponenternas storlek och prestanda, vilket leder till de elektriska komponenternas högre vikt. Scania, som vill vara ledande inom denna omställning, klassificerar alla komponenter med större vikt än 2 kg som stora komponenter. De stora elektriska komponenterna skapar ett behov att utvärdera de aktuella testmetoderna och verifiera deras validitet. Det här magisterexamensarbetet har genomförts på Scania i Södertälje och handlar om undersökning av vibrationstestningsmetoderna som nuförtiden används i olika teknikområden samt identifiering av de eventuellt applicerbara metoderna för provning av stora elektriska komponenter. En fallstudie genomfördes gällande en individuell komponent och påverkan på dess egenfrekvenser med varierande styvhetskonstanter. Dessutom genomfördes några andra fallstudier utgående från empiriska tester samt simuleringar med hjälp av finita elementmetoden på vissa stora komponenter såsom högspänningsförgreningsdosa och batteripacken. Vibrationsprov genomfördes genom att utsätta komponenterna för Scanias nuvarande vibrationstestningsspektrum. Även vibrationsbeteendet beroende på positionen av mättningspunkterna har undersökts. Utöver det utfördes fallstudier angående termiska belastningar under vibrationstestning, tid för värmeöverföring samt energibehovet för att oscillera stora komponenter på förbestämda accelerationsnivåer. Inverkan av komponenternas storlek på deras värmeöverföringsegenskaper

Non-stationary non-Gaussian random vibration problems of structures are challenging and drawing increasing attention. In the present study, firstly, an explicit time-domain method (ETDM) is proposed to determine the higher-order response statistics of linear systems subjected to non-stationary non-Gaussian random excitations, in which the first four orders of cumulants of dynamic responses are directly formulated through the cumulant operation rule based on the explicit expressions of responses. Secondly, an equivalent linearization – explicit time-domain method (EL-ETDM) is further developed to solve the non-stationary non-Gaussian random vibration problems of Duffing systems, in which the equivalent linear system is derived discarding the assumption of Gaussian response, and the corresponding higher-order cumulant analyses of the linearized system are accomplished by the efficient ETDM. The present approach can account for non-Gaussian random excitations with arbitrary forms, and two specific applications to the Poisson white noise and the square form of Gaussian random process are investigated. Four numerical examples are presented to demonstrate the effectiveness of the proposed methods.

In this thesis, novel analytical and computational approaches are proposed for addressing several topics in the field of random vibration. The first topic pertains to the stochastic response determination of systems with singular parameter matrices. Such systems appear, indicatively, when a redundant coordinate modeling scheme is adopted. This is often associated with computational cost-efficient solution frameworks and modeling flexibility for treating complex systems. Further, structures are subject to environmental excitations, such as ground motions, that typically exhibit non-stationary characteristics. In this regard, aiming at a joint time-frequency analysis of the system response a recently developed generalized harmonic wavelet (GHW)-based solution framework is employed in conjunction with tools originated form the generalized matrix inverse theory. This leads to a generalization of earlier excitation-response relationships of random vibration theory to account for systems with singular matrices. Harmonic wavelet-based statistical linearization techniques are also extended to nonlinear multi-degree-of-freedom (MDOF) systems with singular matrices. The accuracy of the herein proposed framework is further improved by circumventing previous “local stationarity” assumptions about the response. Furthermore, the applicability of the method is extended beyond redundant coordinate modeling applications. This is achieved by a formulation which accounts for generally constrained equations of motion pertaining to diverse engineering applications. These include, indicatively, energy harvesters with coupled electromechanical equations and oscillators subject to non-white excitations modeled via auxiliary filter equations. The second topic relates to the probabilistic modeling of excitation processes in the presence of missing data. In this regard, a compressive sampling methodology is developed for incomplete wind time-histories reconstruction and extrapolation in a sin

This research is concerned with the impact of onboard passengers’ seating arrangement on the carbody flexural vibrations of a high-speed railway vehicle. In this regard, the previously developed passenger body-seat models are used to consider the dynamic influence of the passengers. The carbody is modeled using the Euler–Bernoulli beam model to evaluate its flexural deformation. The frequency-domain analysis demonstrates that the carbody behaves almost like a rigid body when the vehicle is full of passengers. It is established that the passengers' presence causes a 31% enhancement of the ride quality determined based on EN 12299 standard for a fully occupied vehicle compared with an empty car. A scaled model of a ratio of 1:24.5 of the Shinkansen vehicle is constructed for validation purposes. The experimental results exhibit a similar trend as found by the simulations in terms of the impact of the passengers’ distribution on the carbody flexural vibrations, Postprint (author's final draft)

A finite element model of the CubeSat MIST was created, in order to assess the stresses that occur in the satellite in response to loads during its launch. Due to size limits of thesoftware used, simplifications had to be made to the geometry of the model. The loads assessed were quasi-static accelerations, random vibrations, shock loads, as well as a combined quasi-static acceleration and random vibration case. The study assumed the worst possible loads from a list of different potential launch vehicles for the satellite. Non-linear boundary conditions could not be modelled, and instead different linear boundary condition combinations were assessed. The results showed that the satellite showed positive margins of safety for the quasi-static loads. The lowest natural frequency for the satellite was above 130 Hz. For the random vibration loads, positive margins of safety could be shown if adverse stresses attributed to the boundary conditions inthe worst case were ignored. The model proved too conservative to qualify the satellite for the shock loads. Shock testing is therefore recommended for future work, unless requirements for waiving the shock testing can be met. The random vibration and combined loads analysis showed that the −X shear panel experienced high stresses in the corners of its windows, and the part should be inspected once environmental tests are conducted. The −X shear panel only showed adverse stresses in the most extreme boundary condition case, where its deformation was deemed unrealistic., En finit elementmodell av nanosatelliten MIST skapades for att undersöka dess respons till lasterna under uppskjutning. På grund av storleksbegränsningar i programvaran behövde modellens geometri förenklas. Lasterna som undersöktes var kvasistatiska accelerationer, stokastiska vibrationer, chocklaster samt ett kombinerat kvasistatiskt accelerations- och stokastiskt vibrationsfall. Studien använde de värsta tänkbara lasterna från en lista över olika potentiella bärraketer för satelliten. Icke-linjära gränsvillkor kunde inte modelleras och istället utvärderades olika kombinationer av linjära gränsvillkor. Resultaten visade positiva säkerhetsmarginaler för kvasistatiska belastningar. Den lägsta naturliga frekvensen för satelliten var över 130 Hz. För de stokastiska vibrationsbelastningarna kunde positiva säkerhetsmarginaler motiveras om hänsyn togs till oegentligheter orsakade av gränsvillkoren i det extremaste fallet. Chocklastanalysen visade på begränsningar i modellen. Mekaniska chocktester kommer därmed behövas för att undersöka chocklasterna, om inte kraven for att hoppa över chocktestning uppfylls. Analyserna av de stokastiska vibrationerna och det kombinerade lastfallet visade att skjuvpanelen på −X-sidan upplever höga spänningar i hörnen på sina fönster, och bör inspekteras när experimentella tester genomförs. Skjuvpanelen på −X-sidan upplevde enbart för höga spänningar i fallet med mest extrema gröäsvillkor, där deformationerna bedömdes vara orealistiska.

The vibro-acoustic analysis of complex structures over a broadband frequency range is an extremely challenging problem that may often require the use of a hybrid deterministic-statistical approach. Due to manufacturing imperfections, the frequency response functions (FRFs) of an ensemble of nominally identical systems can be considered to be random. These FRFs, however, have statistical properties that can be potentially used in vibro-acoustic models. This work explores some of these fundamental properties by using measured FRFs from an ensemble of nominally identical structures, obtained by randomising a thin rectangular plate using point masses. It is first shown that the measured ensemble of FRFs satisfies the analyticity-ergodicity condition, experimentally verifying this recently demonstrated fundamental property. Then, the ensemble is used to explore whether the direct field dynamic stiffness, a key parameter in a well-established hybrid deterministic-statistical formulation, can be obtained experimentally. The results are compared against those computed using numerical techniques, showing that measured data may be a suitable alternative provided that an ensemble of systems can be measured. Finally, an alternative method, based on the use of virtual point masses, opposed to physical ones, is proposed for those cases where experimental randomisation is particularly challenging. It has been found, however, that the method may be extremely sensitive to measurement imprecisions, specially when applied to lightly damped structures. It is concluded that the statistical properties of random causal FRFs are not only interesting in themselves, but can enhance and extend vibro-acoustic prediction models, The authors gratefully acknowledge the financial support provided by the Engineering and Physical Sciences Research Council under grant number Engineering and Physical Sciences Research Council EP/P005489/1, Design by Science, with industrial partners Bentley Motors Ltd, Brüel & Kjær, Dyson Ltd and Wave six LLC. The authors would also like to express their gratitude to Dr David Hawes for his contribution to the near edge point calculations presented in this work, Postprint (author's final draft)

In this research, the effect of rail vehicle carbody’s flexural modes on the ride comfort of an example high-speed railway vehicle is investigated. The vehicle is modeled as a rigid multi-body system, where the rigid body vertical, longitudinal, pitch, and roll degrees of freedom of the carbody and bogie frames and the rigid body vertical and roll degrees of freedom of the wheelsets are considered. An Euler–Bernoulli beam theory is used to account for the flexural motion of the carbody. The longitudinal interaction between carbody and bogie through the traction rod is modeled as a nonlinear spring element. The corresponding equations of motion of the system in the frequency domain are obtained by using the equivalent linearization method. The effect of the traction rod is explored by using this model. Also, the optimal stiffness of the traction rod element that minimizes the flexural vibrations of the carbody is obtained through a genetic algorithm. With the optimal stiffness for the traction rod, the ride quality index at the center of the carbody floor is improved by 41% at a speed of 300 km/h. For the validation of numerical results, a scaled model of the vehicle with a scale factor of 24.5 was constructed, and its associated results are presented. The model was excited by random input signals, which were generated based on the power spectral density of the track irregularity function. The agreement between the simulation results and the scaled experimental outcome when compared with the measured data from other sources is found to be satisfactory. In the framework of the physical scaled model, the filtering effect due to the vehicle bogie base is also examined, Postprint (author's final draft)

The remaining useful life (RUL) of electronic modules under the influence of rugged random-vibration and operational conditions is investigated in this paper. The effects of storage conditions and soft failures, caused by the vibrations to solder joints of a printed circuit board (PCB) are analyzed. The RUL is estimated with the help of vibration testing and finite element analysis techniques. Keeping in view the standard and working environmental conditions, the PCB of a power distribution module is subjected to random and sine vibrations. Besides the significance of fatigue damage and RUL estimation of solder joints, caused by storage or operation for a period of five years has not been addressed in existing literature so far. The current study performs the modal analysis to find the natural frequencies, mode shapes, and participation factor ratios of a PCB and its components. These natural frequencies are subsequently verified via comparison with experimental sine sweep results. A random vibration test over the frequency range from 10 Hz to 2000 Hz is also applied for recording the time-to-failure ratio of the PCB. Moreover, the spectrum analysis is performed using the commercial ANSYS software, to assess the acceleration response and the stress power spectral density (PSD) of the critical solder joints. The stress PSD is then used to estimate the random vibration fatigue damage of the solder joint. The calculated fatigue life, based on the modified Miner's rule and the Basquin power-law conform to the actual random vibration testing results., QC 20200630

This paper deals with a random vibration generation on vibration shakers using a FIR filter. Every shaker has its resonances and anti-resonances which causes troubles in random vibration generation, for instance in presented shaker the difference between maximum and minimum in frequency characteristic is nearly 50 dB. Therefore, we decided to create a FIR filter with inverse characteristic with respect to the shaker to minimize those differences. To design such a filter a freqeuncy characteristic of the shaker has to be measured, then the characteristic is simplified using Ramer–Douglas–Peucker algorithm. Finally, the characteristic is inverted and FIR filter is designed using Remez algorithm. Using this FIR filter the difference in frequency characteristic drops from 50 dB to less 2 dB.

This paper deals with a random vibration generation on vibration shakers using a FIR filter. Every shaker has its resonances and anti-resonances which causes troubles in random vibration generation, for instance in presented shaker the difference between maximum and minimum in frequency characteristic is nearly 50 dB. Therefore, we decided to create a FIR filter with inverse characteristic with respect to the shaker to minimize those differences. To design such a filter a freqeuncy characteristic of the shaker has to be measured, then the characteristic is simplified using Ramer–Douglas–Peucker algorithm. Finally, the characteristic is inverted and FIR filter is designed using Remez algorithm. Using this FIR filter the difference in frequency characteristic drops from 50 dB to less 2 dB.

This paper deals with a random vibration generation on vibration shakers using a FIR filter. Every shaker has its resonances and anti-resonances which causes troubles in random vibration generation, for instance in presented shaker the difference between maximum and minimum in frequency characteristic is nearly 50 dB. Therefore, we decided to create a FIR filter with inverse characteristic with respect to the shaker to minimize those differences. To design such a filter a freqeuncy characteristic of the shaker has to be measured, then the characteristic is simplified using Ramer–Douglas–Peucker algorithm. Finally, the characteristic is inverted and FIR filter is designed using Remez algorithm. Using this FIR filter the difference in frequency characteristic drops from 50 dB to less 2 dB.

In this paper, we evaluate the performance of the so-called parametric t-distributed stochastic neighbor embedding (P-t-SNE), comparing it to the performance of the t-SNE, the non-parametric version. The methodology used in this study is introduced for the detection and classification of structural changes in the field of structural health monitoring. This method is based on the combination of principal component analysis (PCA) and P-t-SNE, and it is applied to an experimental case study of an aluminum plate with four piezoelectric transducers. The basic steps of the detection and classification process are: (i) the raw data are scaled using mean-centered group scaling and then PCA is applied to reduce its dimensionality; (ii) P-t-SNE is applied to represent the scaled and reduced data as 2-dimensional points, defining a cluster for each structural state; and (iii) the current structure to be diagnosed is associated with a cluster employing two strategies: (a) majority voting; and (b) the sum of the inverse distances. The results in the frequency domain manifest the strong performance of P-t-SNE, which is comparable to the performance of t-SNE but outperforms t-SNE in terms of computational cost and runtime. When the method is based on P-t-SNE, the overall accuracy fluctuates between 99.5% and 99.75%., Peer Reviewed, Postprint (published version)

This paper deals with a random vibration generation on vibration shakers using a FIR filter. Every shaker has its resonances and anti-resonances which causes troubles in random vibration generation, for instance in presented shaker the difference between maximum and minimum in frequency characteristic is nearly 50 dB. Therefore, we decided to create a FIR filter with inverse characteristic with respect to the shaker to minimize those differences. To design such a filter a freqeuncy characteristic of the shaker has to be measured, then the characteristic is simplified using Ramer–Douglas–Peucker algorithm. Finally, the characteristic is inverted and FIR filter is designed using Remez algorithm. Using this FIR filter the difference in frequency characteristic drops from 50 dB to less 2 dB.

When performing operational modal analysis, the mechanical system being investigated is assumed to be linear. If this assumption is not true, errors could be made when estimating the modal parameters of the system. There are no generally accepted robust analysis procedures available that can verify or validate the assumption of linearity in an output-only setting. In the present study, a method of detecting nonlinear behavior from a random response signal is proposed. The method is based on the random decrement (RD) technique, which involves identifying triggering points (TPs) in a measured response signal. The proposed procedure is to identify a set of TPs, where each member of the set represents a unique initial condition. A RD signature is then calculated for each set member of TPs. For the response of a linear system, all RD signatures are equal regardless of the initial conditions. For a nonlinear system, not all RD signatures will be equal for different initial conditions. Detection of nonlinear behavior is then possible by using principal component analysis and a parameterization of RD signatures to analyze the sameness of all the RD signatures in the set. The proposed analysis procedure is investigated with numerical and experimental test cases of a single-degree-of-freedom stick-slip system. Results show that it is possible to distinguish between linear and nonlinear behavior using this method. It is also possible to characterize which aspect of the system the nonlinear behavior relates to.

An adequate estimation of wave load to offshore structure is essential to evaluate its stability in its future usage. Despite uncertainty relevant to its extreme valure, static wave load based on Morison's equation is conventionally used in design process because of its usefulness. Though random vibration analysis provides accurate estimation of structural response corroborated reliability, it is obviously inefficient to analyze dynamic response in each design step. In this study, a design wave load in static analysis is examined to ensure efficiency of design process and reliability of structure simultaneously. It is suggested that the maximum value of the dynamic response of the offshore structure can be evaluated with the approximate maximum wave force based on static analysis.

Test Pods are the test fixtures used to conduct vibration testing of the cubesats. A test-pod acts as an interface between the shaker and the test specimen, while simulating the same interface as the one between Launch Vehicle (LV). FHWN developed one such test-pod for the PEGASUS cubesat, which was launched in 2017. The test-pod (2U) was successfully used for vibration testing of PEGASUS, however, the results indicated that during the horizontal operation of the shaker, the amplification factor for the loads experienced at the top was 1.5 times higher than that at the bottom. This could result in an over-test at the top, and could potentially damaged the test object.The follow up mission to the PEGASUS would be a 3U cubesat. Utilizing the learnings from the design of previous 2U test-pod, a new test-pod would be developed that could be used for 2U as well as 3U cubesats. The new design would avoid the need of horizontal shaker configuration, to avoid the similar over-test situation as experienced with the old test-pod. The test-pod would be designed and analyzed using FEM simulations, manufactured and experimentally validated on the shaker.The new Test-POD was developed, manufactured and tested on vibration shaker table. The results obtained from simulations were compared to experimental results to draw important conclusions regarding simulation settings, which can be used in future to enhance the accuracy and reduce computational effort and time. A methodology was developed to use random vibration test to determine damping, which helps calculate the Quality Factor (Q), to determine if structure is sufficiently damped or not. Finally, the issues faced during design & manufacturing were summarized, to help shape up the design of future hardware of similar nature. *****Test Pods are the test fixtures used to conduct vibration testing of the cubesats. A test-pod acts as an interface between the shaker and the test specimen, while simulating the same interface as the o

The investment of space commerce is skyrocketing and it is predicted to be a nascent business in the future. The spacecraft demand has been growing not only for NASA and other space agency’s mission but also collaboration business between small space industries, academia, and scientific community. This glimpse brought an interest to a new investor, government, military, and manufacturing company to deliver their objectives efficiently. Nowadays, many startups compete embracing innovation and pioneering the novelty of space project beyond prodigious vision in an unprecedented way. Many players foresee that decreasing size of the rocket is an important key to survive and succeed in the space business. One of the efficient acts is lowering the launch cost. This can be achieved by designing a small size, lightweight and affordable spacecraft. Within this context, a Beyond Atlas Spacecraft which will be sent to Asteroid 2016-HO3, has achieved a wet mass of 20.85 kg with the size of 24.7 x 42.2 x 40.8 cm in stowed mode and 84 x 399 x 40.8 cm in unstowed mode. However, the drawback being light and small may lead to catastrophic failure due to resonance frequency events. According to past experience, the gyro of the Swedish national satellite was damaged during ground testing and it was suspected due to high amplification when the natural frequency coincides to the main structure resonance. Therefore, this work is focusing on a spacecraft development and a non-destructive structural analysis. The coupled-load analysis of a preliminary spacecraft design including sinusoidal, random vibration and shock analysis are calculated using FEM. This effort can reduce the risk of component destruction before laboratory testing as well as understand better the dynamic behavior of the spacecraft. The critical frequency in each orthogonal axis with base input from launch environment of the LM-3A Launch Vehicle was devised. The maximum stress, amplitude, and acceleration in accordance of, Investeringen av rymdhandeln är skyrocketing och det förväntas bli en växande verksamhet i framtiden. Efterfrågan på rymdfarkoster har ökat inte bara för NASA och andra rymdorganisationens uppdrag utan även samarbete mellan små rymdindustrier, akademin och det vetenskapliga samfundet. Denna glimt väckte intresse för en ny investerare, regering, militär och tillverkningsföretag för att effektivt kunna leverera sina mål. Idag konkurrerar många startups om att omfatta innovation och banbrytande rymdprojektets nyhet bortom en fördärvad vision på ett aldrig tidigare skådat sätt. Många spelare förutser att minskad storlek på raketen är en viktig nyckel för att överleva och lyckas i rymdverksamheten. En av de effektiva handlingarna sänker lanseringskostnaden. Detta kan uppnås genom att utforma en liten storlek, lätt och prisvärd rymdfarkost. Inom detta sammanhang har en Beyond Atlas Spacecraft som skickas till Asteroid 2016-HO3, uppnått en våt massa på 20,85 kg med storleken 24,7 x 42,2 x 40,8 cm i stuvningsläge och 84 x 399 x 40,8 cm i ostoppat läge. Nackdelen som är ljus och liten kan emellertid leda till katastrofalt fel på grund av resonansfrekvenshändelser. Enligt tidigare erfarenhet skadades gyroen i den svenska nationella satelliten under marktestning och det misstänktes på grund av hög förstärkning när den naturliga frekvensen sammanföll med huvudstrukturen resonans. Därför fokuserar detta arbete på rymdskeppsutveckling och en icke-destruktiv strukturanalys. Den kombinerade belastningsanalysen av en preliminär rymdfarkostkonstruktion inklusive sinusformad, slumpvibration och chockanalys beräknas med användning av FEM. Denna insats kan minska risken för komponent förstörelse före laboratorietestning samt förstå bättre rymdskeppets dynamiska beteende. Den kritiska frekvensen i varje ortogonal axel med basinmatning från startmiljön för LM-3A-startkärlet utformades. Den maximala spänningen, amplituden och accelerationen i enlighet med kvalifikationstestkriterierna utvä

The purpose of this thesis is to show the process of designing, simulating, and prototyping a tool used to adapt the features of a conventional vibration test equipment in order to qualify space components. Due to cost reduction reasons and time limitations, AST&Science decides to manufacture an amplifier fixture which will be used for the testing campaign of the first space mission, planned on September 2019. The fixture will be able to increase the acceleration values of a common shaker reaching the desired ones established by the company. Most times, it will be used to test small electronic components, up to eighty millimeters length. An iterative process of designing and simulating is carried out with Solidworks and Ansys Simulation software. Frequency response and random vibration analysis are studied in order to know the behaviour of the amplifier fixture in operational conditions. Previously to the design phase, the main parameters of design that influence the natural frequency result and the value of overall energy amplification, are exhaustively analyzed to be more efficient and do not spent more time than necessary. Once the tendency of each parameter is known, the document is focused on the final solution, showing a more detailed model and including the basic parts for the installation. The fixture is designed taking into account safety margins and margins of error which ensure the structural commitment of the tool and a tolerance of the analysis results. Two different solutions are achieved after the iterative process. First, a circular geometry is proposed and later, rectangular shape geometry is proposed trying to improve the obtained results of the previous one. Due to company procedure, a prototyping process is an optional prerequisite to the manufacturing phase, so it is also included in the annexes of this document. Both solutions guarantee the fulfillment of aerospace testing and mechanical standards., El propósito de este proyecto es mostrar el proceso de diseño, simulación y prototipado de un utillaje usado para adaptar las características de un sistema de testeado de vibración convencional, con el objetivo final de evaluar componentes aeroespaciales. Debido a una reducción de costes y limitaciones de tiempo, AST&Science decide fabricar un utillaje amplificador que va a ser utilizado en las campañas de testeado de la primera misión espacial, planeada para Septiembre de 2019. El utillaje será capaz de incrementar los valores de aceleración de un shaker común, alcanzando los valores deseados establecidos por la compañía. La mayoría de las veces se usará para testear equipos electrónicos pequeños, de hasta ochenta milímetros de longitud. Se lleva a cabo un proceso iterativo de diseño y simulación con ayuda de programas como Solidworks y Ansys Simulation. Se estudia la respuesta frecuencial y el análisis de vibración aleatoria para saber el comportamiento del utillaje en condiciones operativas. Previo a la fase de diseño, se realiza un estudio exhaustivo de los parámetros principales de diseñoo que tienen un impacto en el valor de la frecuencia natural del sistema y de la amplificación de la energia global, medida en Grms. Dicho análisis se realiza con el propósito de ser más eficiente y optimizar tiempos. Una vez se conoce la tendencia de cada parámetro, el documento se centra en la solución final, mostrando un diseño más detallado e indicando el material necesario para su instalación. El utillaje se ha diseñaado teniendo en cuenta los márgenes de seguridad y de error que aseguran el compromiso estructural del mismo y una tolerancia de los resultados obtenidos. Se alcanzan dos soluciones distintas tras el proceso iterativo, primero se propone una solución con geometría circular y seguidamente, una solución rectangular en la que se pretende mejorar los resultados de la primera propuesta. Debido a procedimientos de empresa, un proceso de prototipado es pre-requisito

To efficiently select track irregularity random samples for satisfying the ergodicity requirements of excitation sources in stochastic dynamics and reliability analysis in vehicle-track system, the weak-stationarity and similarity spectral of track irregularities were introduced to propose a track irregularity probabilistic model. Using the discrete probability integration and statistical approaches, the massively measured track irregularity time histories were divided into multiple time-domain sequences. The statistical power spectral density distribution of each sequence was calculated by the spectral analysis method. Then, using the matrix-based method, the set representation of the power spectral density function of track irregularities was obtained. It was assumed that the power spectral densities could be linearly accumulated at different frequencies, allowing the probabilities of entire spectra line to be obtained using the power spectral density probability distribution of a single frequency. The representative track irregularity spectra were selected through the commonly random simulation methods, and the track random irregularities were inversely simulated. The height and direction track irregularities of high-speed railway about 269 km were measured. Based on the vehicle-track coupled dynamics theory, the calculation results between the track irregularity probabilistic model and track irregularity stochastic model was compared from the aspects of the simulated amplitude of track irregularity and the probability density distribution for dynamic response in the vehicle-track system to verify the validity and high efficacy of the track irregularity probabilistic model. Calculation result shows that when taking the track random irregularities caused by the two models as excitation sources, the difference of the obtained probability entropies of vehicle-track system dynamic response between the two models is less than 2%. Both models can accurately express, Railway Engineering

The capability of using a linear kinetic energy harvester — A cantilever structured piezoelectric energy harvester — to harvest human motions in the real-life activities is investigated. The whole loop of the design, simulation, fabrication and test of the energy harvester is presented. With the smart wristband/watch sized energy harvester, a root mean square of the output power of 50 μW is obtained from the real-life hand-arm motion in human’s daily life. Such a power is enough to make some low power consumption sensors to be self-powered. This paper provides a good and reliable comparison to those with nonlinear structures. It also helps the designers to consider whether to choose a nonlinear structure or not in a particular energy harvester based on different application scenarios.

The thesis work deals with the study and determination of static and dynamic stresses acting on windscreen structures during transportation from the manufacturing site to the production plant. To simulate the stress distribution affected by the transportation, a finite element model of the windscreen is development of the structure and tested. The evaluated results from the stress analysis are then verified against results from literature and by own experimental results. The constructed FE model is simulated for modal response, and the response is validated against data from the experimental modal analysis. The data from the experiment is also used to calibrate the material card in an effort to get the most realistic dynamic response. The dynamic stress experiment was carried out at RISE Borås in accordance to ASTM D4169-16 DC3. Strain gauges were mounted at areas of interest. The readings obtained from the strain gauges used in the analytical calculation of stress, which were used to verify the finite element stress results. The fundamental aim of both experiments was to evaluate the dynamic behaviour and validate the numerical model. The pre-processing software ANSA was used to construct the finite element model and MSC Nastran was used as the FE- solver to simulate static and dynamic stresses on the structure. Transport loads were simulated using the random vibration load case, where a input load is in form of Power Spectral Density (PSD) data which describes the distribution of power into frequency components for a given time series. The input PSD was also in accordance with ASTM D4169-16 DC3, which is used to simulate the same response as in the experiment. During the numerical analysis, the glass and the intermediate PVB layer is assumed to be linear and isotropic. A validation of the numerical model was carried out against the experimental results to evaluate the predictive capability of the developed numerical model. The finite element model leads to good co, The authors want to acknowledge that this work was written in collaboration between two Universities, Philip Oliver Reis from Jönköping University from the Master of Science program Product Development and Materials Engineering and Karthik Vasudeva Murthy from Chalmers University from the Master of Science program in Applied Mechanics. The authors of this report were assigned together by Volvo Car Corporation, to complete this research work.

This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision occurs which causes strong mechanical coupling between the two subsystems. The experimental results show that the operating bandwidth is widened to 14 Hz (14–28 Hz) at an acceleration of 9.81 m/s2, and the peak output power can be 0.35 W at a relatively low operation frequency of 16 Hz. Simulation and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity conversion efficiency by 40–81%.

This book deals with the statistical theory of sound and vibration. The foundation of statistical energy analysis is presented in detail. In the modal approach, an introduction to random vibration with application to complex systems having a large number of modes is provided. For the wave approach, the phenomena of propagation, group speed, and energy transport are extensively discussed. Particular emphasis is given to the emergence of diffuse field, the central concept of the theory. All important notions are gradually introduced—making the text self-contained—to lead the reader to the ultimate result of ‘coupling power proportionality’ and the concept of ‘vibrational temperature’. Further key topics include the analogy between thermodynamics and sound vibration. Applications are concerned with random vibration in mass–spring resonators, strings, beams, rods, and plates but also reverberation in room acoustics, radiation of sound, and sound response., Includes bibliographical references and index., This book deals with the statistical theory of sound and vibration. The foundation of statistical energy analysis is presented in detail. In the modal approach, an introduction to random vibration with application to complex systems having a large number of modes is provided. For the wave approach, the phenomena of propagation, group speed, and energy transport are extensively discussed. Particular emphasis is given to the emergence of diffuse field, the central concept of the theory. All important notions are gradually introduced—making the text self-contained—to lead the reader to the ultimate result of ‘coupling power proportionality’ and the concept of ‘vibrational temperature’. Further key topics include the analogy between thermodynamics and sound vibration. Applications are concerned with random vibration in mass–spring resonators, strings, beams, rods, and plates but also reverberation in room acoustics, radiation of sound, and sound response.

Design and evaluation tests for the JEM (Japanese Experiment Module) pressurized module/experiment module pressurized section and their components were performed under contract with NASDA. The results presented are: lift-off noise of the above module/section, random vibration forecast analysis, impact tests for the upgrade meteoroid/debris shield, cabin mass flow test in the early condition, flow distribution test, 1553B communication protocol interface test, 1553B signal characteristics test, heat treatment process test for vacuum line, and vibrational and flow characteristic test of diffuser etc., 宇宙開発事業団業務委託計画書「宇宙ステーション取付型実験モジュール(JEM)の開発-与圧系設計評価試験(その2)」に基づき与圧部/補給部与圧区システムおよび当該システムを構成する構成機器に関して設計、評価試験を行った。次の結果について報告する。上記与圧部/与圧区の打上げ時音響、ランダム振動予測解析、防御能力強化型いん石防御構造特性試験、初期状態キャビン内マスフロー試験、流量配分試験、1553B通信プロトコルインタフェース試験、1553B信号特性試験、真空系配管の熱処理プロセス試験、およびディフューザなどの振動および風速特性試験。

After discussing H-2 Orbiting Plane (HOPE) communication and data processing system, main electronic equipments, development schedule and technological tasks, requirements for HOPE system, ground system etc. were reviewed. Following items were described: (1) System considerations of communication and data processing system; (2) considerations on environment resistance of equipments; and (3) design considerations of main electronic equipments. Specifications required for communication system in launching phase, inorbit phase and return phase were presented, and constitution of communication system necessary for filling the requirements was considered. Results of study of data processing were shown on the constitution, interface to user equipments, communication protocols to mission equipments and system hardware. Environment resistance of electronic equipments for communication and data processing was investigated on random vibration, sinusoidal vibration, impact, static acceleration, sound and humidity. Points of design of HOPE onboard Unfilled S-Band (USB) / S-Band Single Access (SSA) transponder and data recorder were described, and especially, the technological tasks of heat resistant antenna were presented on materials for case/body, connector and Radio Frequency (RF) cable assembly, structural scheme, resistance to variation, impact, acceleration etc., and tasks of each type of antenna such as Micro Stripline Antenna (MSA), cavity, and Waveguide (WG) type. Also, features, functions, constitution and performance of high gain antenna for Data Relay Tracking Satellite (DRTS) communication were described. Further, technological tasks of communication and data processing system, development of parts and development schedule were briefly introduced., HOPE(H-2打ち上げ型宇宙往還機)通信･データ処理系のシステム、主要電子機器、開発計画、技術的課題に対する検討を行うとともに、HOPEシステム、地上システムなどへの要求事項をまとめ、以下の通り記述する。(1)通信･データ処理系のシステム検討:通信系については、打上げフェーズ、軌道上フェーズ、帰還フェーズに対して要求される諸元を示し、その要求を満たすために必要な通信系の構成について検討を行った。データ処理系については、処理系の構成、ユーザ機器とのインターフェース、ミッション機器との通信プロトコルならびにシステムハードウェアに関する検討結果を示した。(2)機器の耐環境性の検討:通信･データ処理系電子機器の耐環境性をランダム振動、正弦波振動、衝撃、静的加速度、音響ならびに湿度に関して調べた。(3)主要電子機器の設計検討:HOPE搭載用USB(Unfilled S-Band)/SSA(S-Band Single Access)トランスポンダ、データレコーダの設計の要点を述べるとともに、特に耐熱性アンテナに関して、ケース/ボディの材質、コネクタ、RFケーブルアセンブリ、構造様式などの共通の課題や振動･衝撃･加速度などに対する耐性およびMSA(マイクロストリップ)･キャビティ･WG(導波管)のような各タイプ別の課題を示した。また、DRTS(データ中継追跡衛星)通信用高利得アンテナの特徴、機能、構成、性能について述べた。その他、部品開発、通信･データ処理系に係わる技術的課題、開発計画について簡単に触れた。

A spacecraft is subjected to dynamic and static loads during launch. These loads are deterministic and of random nature and cannot be tested under the real conditions due to cost considerations. The spacecraft must therefore sustain certain mechanical loads without permanent deformation with a certain safety factor due to the uncertainties in the actual loading values during launch. The applicable mechanical test requirements and load combination have been first determined for the structure of interest: the SEAM CubeSat. These requirements are found to be steady-state accelerations, random vibration and shock response spectrum loadings. They have been simulated onto the structure globally and locally in order to extract stress values, amend design features when necessary and determine adequate material properties in order for the final design to fulfill the mechanical requirements during launch., En satellit utsätts för dynamiska och statiska belastningar under uppskjutningen. Dessa laster är av deterministisk och av slumpmässig natur och kan inte testas under verkliga förhållanden på grund av kostnadsskäl. Satellitens konstruktion måste därför klara att utsättas för utan permanent deformation med en viss säkerhetsfaktor på grund av osäkerheter i de faktiska belastningarna under uppskjutningen. Mekaniska provningskrav och lastkombinationer har bestämts för en utvald struktur: SEAM CubeSat. Dessa krav visar sig vara accelerationer, slumpmässiga vibrationer och stötar. Strukturen har simulerats globalt och lokalt för att få fram de mekaniska belastningarna. Baserat på resultat från simuleringarna har konstruktionen modifierats och lämpliga material egenskaper har bestämts för att den slutliga konstruktionen ska uppfylla de mekaniska kraven under uppskjutningen.

This work presents and assesses a reduced model of a recently proposed seismic isolation system, namely the Roll-N-Cage isolator. This system incorporates several interesting features and mechanisms in a single unit, among others: isolation, energy dissipation, buffering, high vertical stiffness and strength for supporting heavy loads. Departing from previous studies, which were based on the simulation of the Roll-N-Cage device by uncoupled orthogonal unidirectional models, this work first introduces a reduced-order coupled bidirectional numerical model of the device. Then the efficiency of such a type of control devices, as simulated by the proposed approach, is evaluated for the seismic protection of a cable-supported bridge. The bridge model is derived from the ASCE benchmark cable-stayed bridge by means of an extended version. It was found that the developed model with optimal tuning of the parameters was proved able to match satisfactorily the physical behavior of the RNC devices, which were found able to achieve effective reductions in the seismic effects in terms of both internal forces and accelerations. It was also noted that choosing small buffer stiffness of the buffer or self-stopping mechanism could slightly limit the peak displacements, at cost of a small increment of the deck accelerations and non-remarkable variations of internal forces. Further, a coupled bidirectional model seems to be fundamental to precisely predict the actual behavior of the isolators when the deck motion is affected by a non-negligible interaction in the two (longitudinal-transversal) directions., Postprint (published version)

Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data usually is non-Gaussian. To synthesize non-Gaussian random vibration, both the probability density function (PDF) and the damage effects must be considered. A new method is presented in this paper to synthesize non-Gaussian random vibration that is characterized by running RMS (root mean square). The essential idea is to model the non-Gaussian signal by a Gaussian signal multiplied by an amplitude modulation function (AMF). A two-parameter Weibull distribution is used to model the PDF of the running RMS and to create the AMF. The shock response spectrum (SRS) is used to detect significant shocks within the non-Gaussian signal. A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD), kurtosis, PDF and fatigue damage spectrum (FDS) as the field data.

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology February 1995, Periodic structures which are slightly disordered undergo dramatic changes in mode shapes such that the responses go from being spatially extended to spatially localized. This phenomenon called mode localization, offers an excellent option for passive vibration isolation. In the first part of the thesis, we provide analytical prediction of modes exhibiting moderate localization using a newly developed Jordan Block Perturbation Method. We estimate and compare convergence zones of our newly developed method with perturbation techniques used to describe localized modes. In the second part of the thesis, we provide numerical evidence that complex branch points, which occur for complex disorder values in the mode-disorder relation, are responsible for modal sensitivity. We investigate the effects of the strength of the branch point and their location in the complex plane. In the third part of the thesis we perform an optimization study involving the selection of parameters which ensure a minimum level of localization of all modes. Optimal solutions were found to lie at maximum distances from the branch points, and the convergence basin of each optimum was demarcated by the branch point surface. The number of local optima were found to grow exponentially with the number of pendula. A statistical analysis showed that sampling of 10% provided an estimate that was within 2% of the global optimum, thereby reducing the computational effort for small to moderate systems of pendula. For larger systems of pendula, the problem of obtaining the global optimum in reasonable time still remains an open problem. In the fourth part of the thesis we propose an application for mode localization in vibration isolation. An oceanographic mooring with regularly spaced buoys is investigated for localization of inline elastic oscillations. Localization is found to be useful for confining the harmonics in deep water moorings of 1000 - 4000m., I wish to gratefully acknowledge educational support of the Office of Naval Research contract numbers N00014-89-C-0179 and N00014-90-C-0098. Computational time was supported by Office of Naval Research under grant number N00014-92-J-1269.

This Test Operating Procedure (TOP) is to be used as a guideline for development of Laboratory Vibration Test Schedules (LVTS) for Multiple Degree-of-Freedom (MDOF) scenarios.

There is a need to investigate and improve upon existing methods to predict response of sensors due to flow-induced vibrations in a pipe flow. The aim was to develop a tool which would enable an engineer to quickly evaluate the suitability of a particular design for a certain pipe flow application, without sacrificing fidelity. The primary methods, found in guides published by the American Society of Mechanical Engineers (ASME), of simple response prediction of sensors were found to be lacking in several key areas, which prompted development of the tool described herein. A particular limitation of the existing guidelines deals with complex stochastic stationary and non-stationary modeling and required much further study, therefore providing direction for the second portion of this body of work. A tool for response prediction of fluid-induced vibrations of sensors was developed which allowed for analysis of low aspect ratio sensors. Results from the tool were compared to experimental lift and drag data, recorded for a range of flow velocities. The model was found to perform well over the majority of the velocity range showing superiority in prediction of response as compared to ASME guidelines. The tool was then applied to a design problem given by an industrial partner, showing several of their designs to be inadequate for the proposed flow regime. This immediate identification of unsuitable designs no doubt saved significant time in the product development process. Work to investigate stochastic modeling in structural dynamics was undertaken to understand the reasons for the limitations found in fluid-structure interaction models. A particular weakness, non-stationary forcing, was found to be the most lacking in terms of use in the design stage of structures. A method was developed using the Karhunen Loeve expansion as its base to close the gap between prohibitively simple (stationary only) models and those which require too much computation time. Models were devel

The Element Free Galerkin (EFG) method, which is based on the Moving Least Squares (MLS) approximation, is developed here for vibration, buckling and static analysis of homogenous and FGM plate with curvilinear stiffeners. Numerical results for different stiffeners configurations and boundary conditions are presented. All results are verified using the commercial finite element software ANSYS® and other available results in literature. In addition, the vibration analysis of plates with curvilinear stiffeners is carried out using Ritz method. A 24 by 28 in. curvilinear stiffened panel was machined from 2219-T851 aluminum for experimental validation of the Ritz and meshfree methods of vibration mode shape predictions. Results were obtained for this panel mounted vertically to a steel clamping bracket using acoustic excitation and a laser vibrometer. Experimental results appear to correlate well with the meshfree and Ritz method results. In reality, many engineering structures are subjected to random pressure loads in nature and cannot be assumed to be deterministic. Typical engineering structures include buildings and towers, offshore structures, vehicles and ships, are subjected to random pressure. The vibrations induced from gust loads, engine noise, and other auxiliary electrical system can also produce noise inside aircraft. Consequently, all flight vehicles operate in random vibration environment. These random loads can be modeled by using their statistical properties. The dynamical responses of the structures which are subjected to random excitations are very complicated. To investigate their dynamic responses under random loads, the meshfree method is developed for random vibration analysis of curvilinearly-stiffened plates. Since extensive efforts have been devoted to study the buckling and vibration analysis of stiffened panel to maximize their natural frequencies and critical buckling loads, these structures are subjected to in-plane loading while the vibrat

Recent studies on train passengers' activities found that many passengers were engaged in some form of work, e.g., reading and writing, while traveling by train. A majority of the passengers reported that their activities were disturbed by vibrations or motions during traveling. A laboratory study was therefore set up to study how low-frequency random vibrations influence the difficulty to read. The study involved 18 healthy male subjects of 23 to 32 yr of age group. Random vibrations were applied in the frequency range (1-10 Hz) at 0.5, 1.0 and 1.5 m/s(2) rms amplitude along three directions (longitudinal, lateral and vertical). The effect of vibration on reading activity was investigated by giving a word chain in two different font types (Times New Roman and Anal) and three different sizes (10, 12 and 14 points) of font for each type. Subjects performed reading tasks under two sitting positions (with backrest support and leaning over a table). The judgments of perceived difficulty to read were rated using 7-point discomfort judging scale. The result shows that reading difficulty increases with increasing vibration magnitudes and found to be maximum in longitudinal direction, but with leaning over a table position. In comparison with Times New Roman type and sizes of font, subjects perceived less difficulty with Anal type for all font sizes under all vibration magnitude., QC 20110131

提出了基于相關函數預估計和漸近小波分析的結構系統識別方法,此方法可以從結構隨機環境振動響應中識別出結構的模態參數和物理參數。證明了在廣譜白噪聲環境激勵下,結構隨機振動相關響應的Morlet小波系數圖的脊線值包含了解耦的結構模態信息,可用于結構的模態參數識別。如果知道隨機激勵的功率譜強度,還可以識別結構的質量、剛度和阻尼矩陣等物理參數。三層框架結構數值算例的結果表明上述方法可以準確地從結構隨機振動響應信號中識別出結構參數。蘇通大橋北索塔環境振動測試試驗研究的結果表明此方法對于工程結構環境激振下的結構模態識別具有很好的效果。 In this paper, a covariance-driven wavelet analysis technique is proposed for identifying the characteristics of linear structural systems from random vibration response measurements. Based on the asymptotic wavelet analysis theory, the paper proves that the ridges of Morlet wavelet coefficient magnitudes of structural covariance response under random excitations contain structural modal information and can be used to estimate structural modal parameters. In addition, if the spectral intensity of the random load is known, structural mass, stiffness and damping matrices can also be estimated. Results of a numerical study on a 3-storey frame show that the proposed technique can accurately estimate structural modal parameters and physical properties under random excitations. An experimental study on the north cable pylon of Sutong Bridge further verifies the accuracy and applicability of the proposed technique.

A popular scheme for achieving low phase noise across a large range of offset frequencies is to employ an oscillator at an output frequency with low far-from-carrier noise that is phase-locked to a reference that has low close-to-carrier noise. We investigate the effects of vibration on phase-locked loop (PLL) when two oscillators with different vibration sensitivity are phase-locked. For experimental verification, a 2.5-GHz surface-transverse wave (STW) oscillator integrated with and phase-locked to a reference 10-MHz quartz-crystal oscillator is chosen. The vibration sensitivity of a STW oscillator used for the experiment is slightly lower than the vibration sensitivity of the 10-MHz reference. The PLL is optimized for at-rest operation and then evaluated in the presence of different levels of random vibration., Presented at the Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting (41st) held in Santa Ana Pueblo, NM on 16-19 November 2009. Published in the Proceedings of The Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting (41st), p303-312, 2009. The original document contains color images.

The focus of this research was to examine how well participants could detect and localize tactile signals while riding in moving vehicles. A ride motion simulator (RMS) was used to simulate a Bradley fighting vehicle or high mobility multipurpose wheeled vehicle traversing a cross-country course or gravel road. Two tactile display systems were used to provide signals. The wireless tactile control unit (WTCU) employed a vibrating motor similar to that of a cell phone or pager, and the Tactile Communications System (TACTICS) employed a plunger motor, which creates a tapping sensation. The signal strength of the TACTICS was driven at the optimal operating characteristics (TACTICS 1) or at operating characteristics similar to those of the WTCU system (TACTICS 2). For each system, eight tactors were positioned at 45-degree intervals (cardinal compass points) in two adjustable belts (plunger motor belt and pancake motor belt) worn around each participant's waist. Participants received tactile signals during a baseline (stationary) condition and while moving on the RMS. Results show that the TACTICS 1 performed consistently across all conditions, which may be because of the stronger, more distinct tactile signal generated by the TACTICS 1. Detection of tactile signals was affected by terrain, with fewer signals detected on the crosscountry terrain. Additionally, the south tactor was detected less frequently than the other locations when participants were moving over the cross-country terrain., The original document contains color images. Project No. 62716AH70.

Flight vehicle airframes in today's advanced flight systems are required to optimally integrate a variety of multi-functional requirements to maximize effectiveness with acceptable risk. The X-51A airframe design process and criteria draw upon decades of successful design of both manned and unmanned flight vehicles for production and experimental intent. This paper summarizes the X-51A vehicle mission requirements, system design, design processes used for airframe synthesis, design safety factors, success criteria and issues facing the incorporation of advanced optimization techniques in the development of airframes for vehicles such as the X-51A., See also ADM202420., The original document contains color images. Published in RTO-MP-AVT-145 AC/323(AVT-145)TP/117. Presented at UAV Design Processes/Design Criteria for Structures Meeting p1.7-1-1.7-14 2007. Sponsored in part by DARPA.

The vibration response of a structure excited by a turbulent boundary layer is investigated experimentally and numerically. First, the wall pressure in a high speed acoustic wind tunnel is characterized and the cross-spectral density is approximated using a Corcos model with frequency dependent correlation lengths and a modified Chase model. Both models agree quite well with the measured cross spectrum. Second, based on these turbulence models, the vibration response is predicted and compared to measurements. At lower frequencies both models perform well. In a higher frequency region, however, the vibration response is greatest for length scales that are much longer than the one given by the convection velocity of the turbulence, and in this frequency region only the modified Chase model works effectively., QC 20100525

Remaining life assessment is the process of predicting the future operational life of a product based on estimate of life consumed under its life cycle environmental conditions. Remaining life is typically an output of health monitoring and prognostics. In this thesis, a generic 'Health Status Assessment' methodology has been developed, that provides a guideline for conducting a remaining life assessment for electronic hardware already deployed in the field. The methodology presents the assessor with the possible techniques that can be used and the criteria for implementing each technique. A practical application of the new methodology is demonstrated by assessing the remaining life of an electronic circuit card subjected to shock and random vibration loads in its life cycle environment. During life testing, a mechanical support structure on the board was damaged. Analytical and finite element methods were employed to determine and explain the cause of failure.

Acquisition, Tracking and Pointing (ATP) of space and airborne optical beams is becoming an important research topic as the requirements for the control of the beam are increasing. Arc-second accuracy and nano-radian jitter coupled with stringent pointing requirements test the limits of control systems. A unique Laser Jitter Control Test Bed was built to study means to correct disturbances in a laser relay system. A new technique, the Adaptive Bias Filter (ABF), applies a compensating bias to the reference signal for the adaptive filter, allowing rapid convergence in correcting narrowband disturbances. A second technique, the Adaptive Delay Filter (ADF), was applied in a new way to the adaptive control systems to better correlate the error signal with the reference signal. Experiments using these techniques effectively demonstrated the usefulness of the new control methods, including the use of a combination Linear Quadratic Regulator (LQR) and LMS/ABF filter to remove disturbances caused by colored noise injected into an optical beam. The combination controller results in a 38 dB decrease in jitter caused by a 50 Hz vibration and a 10 dB decrease in an 87 Hz vibration of the supporting platform, and an overall 75% improvement in the broadband jitter experienced by the optical beam., The original document contains color images.