Este trabalho tem como objetivo a comparação dos resultados de ensaios de durabilidade em um suporte do eixo traseiro de um veículo leve de passeio, submetido a dois tipos distintos de testes: durabilidade em rodagem real e em simuladores de estradas. Após o término dos ensaios, o componente apresentou resultados diferentes: as trincas podem ser observadas na peça submetida à rodagem real, e os danos não ocorrem no eixo que foi testado em simulador. As discrepâncias citadas podem estar ligadas a possíveis erros, ocorridos durante a transferência dos dados pertinentes ao teste real para o simulador. / The aim of this research is comparing results from durability tests performed at a rear axle bracket of a small passenger car. The part was tested using two different kinds of tests: real (proving ground) durability and simulated (road simulator) durability. After that, the part showed different final results: several cracks can be observed at the part that was tested at the proving ground and no real damage was inflicted at the part that was test at the road simulator. These differences can be related to transferability problems that occurred during data analysis and transfer from real test to a simulated one.

Este trabalho tem como objetivo a comparação dos resultados de ensaios de durabilidade em um suporte do eixo traseiro de um veículo leve de passeio, submetido a dois tipos distintos de testes: durabilidade em rodagem real e em simuladores de estradas. Após o término dos ensaios, o componente apresentou resultados diferentes: as trincas podem ser observadas na peça submetida à rodagem real, e os danos não ocorrem no eixo que foi testado em simulador. As discrepâncias citadas podem estar ligadas a possíveis erros, ocorridos durante a transferência dos dados pertinentes ao teste real para o simulador. / The aim of this research is comparing results from durability tests performed at a rear axle bracket of a small passenger car. The part was tested using two different kinds of tests: real (proving ground) durability and simulated (road simulator) durability. After that, the part showed different final results: several cracks can be observed at the part that was tested at the proving ground and no real damage was inflicted at the part that was test at the road simulator. These differences can be related to transferability problems that occurred during data analysis and transfer from real test to a simulated one.

This research was done as part of a long term project, with the goal to monitor multiple bridges over an extended period of time. Due to the nation’s aging infrastructure and the limited amount of funds to upgrade and maintain it, structural health monitoring (SHM) is very important because it provides in depth information about a structure to be used in decision making. SHM of bridges includes monitoring the effects of traffic loads. This paper discusses the development of a bridge weigh-in-motion (B-WIM) technique that uses the rainflow counting of strain cycles. Typical B-WIM techniques have proven to be accurate but require large algorithms and gauges at multiple locations across the span, and the strain gauge temperature drift must be accounted for. The rainflow B-WIM (RF-BWIM) decreases the processing of the B-WIM and automatically accounts for drift, thus allowing temperature and other analyses of the same bridge to be possible. RF-BWIM also has the potential to decrease the number of sensors required. Strain data taken from an existing long term monitoring system was used to develop the RF-BWIM. The development of the RF-BWIM, as well as a method to determine a virtual gross vehicle weight (C-GVW) used in calculating the RF-BWIM output, is presented.

This thesis presents advanced algorithms for realtime detection of dragline duty, the quantification of its causes and the combined optimisation of dragline motion to minimise cycle time and duty. Draglines are large, powerful, rotating, multibody systems that operate in a similar manner to cranes and certain pick and place robots. Duty is an estimate of fatigue damage on the dragline boom caused by cyclic stresses that are associated with the repetitive dig and dump operation. Neither realtime detection of duty nor the quantification of its causes were previously available. In addition, no previous researchers have optimised the dynamic motion of mining equipment to achieve the combined maximisation of productivity and minimisation of maintenance measures. The advanced duty detection system was developed to improve feedback to dragline operators. The algorithms that were developed are based on the mechanics of dragline motion and fatigue. In particular, fatigue cycles in measured stress are identified at the earliest possible time, based on a novel proof and modification to the rainflow cycle counting algorithm. The contributions of specific causes to each individual stress range are quantified based on the mechanics of operator dependent control and dragline dynamics. In this manner, specific causes of duty are measured. The algorithms confirmed the significant contribution from operator dependent factors and identified the major causes, attributing 28% of the total duty to out-of-plane bucket motion and 15% to dynamic vibration. Further improvements to dragline performance required the development of a dragline dynamic model for offline testing and optimisation. A complete, condensed set of equations for a four-degree-of-freedom nonlinear coupled model of a dragline was derived using Lagrange’s method, allowing direct insight into dragline behaviour not available from previous research. The model was used to investigate the relationship between motor power, operator behaviour, bucket trajectory, productivity and duty during the swing and return phases of operation. Significant potential for increasing productivity and reducing duty was demonstrated. The advanced duty detection system and the dragline model were validated with field measured data, video footage, alternative modelling and expert review. Realtime and end-of-cycle feedback was simulated over many cycles of measured data. Experts from industry and research were consulted to verify the causes of duty based on detailed measured data analysis. The forces, stresses and out-of-plane angle predicted by the dragline model were closely compared with measured data over various indicative cycles. The dragline model was also validated against an alternative model constructed in ADAMS. The development of the dragline model enabled model-based numerical optimisation. Significant nonlinearities in the model and the constraints necessitated the use of the Lagrange multiplier method. The bucket trajectory during the swing and return phase was directly optimised. In order to minimise cycle time and duty, a penalty for duty incurred was added to the cycle time, effectively maximising long-term productivity. For a slew torque optimisation scenario using measured rope lengths, the numerical optimisation performance was shown to be 10-30% better than manual optimisation and 50-60% better than the operator performance. This thesis outlines several significant contributions to improving dragline performance. Underpinning the advanced duty detection system are three significant contributions to fatigue cycle counting algorithms: a proof of the equivalence of two pre-existing algorithms; a new algorithm that enables realtime detection of duty; and an algorithm that can attribute duty to specific causes. These novel feedback tools can provide realtime operator feedback and identify the causes of excess duty and when it was incurred. A complete and condensed set of equations for the four-degree-of-freedom model enabled, for the first time, the optimisation of dragline operation to concurrently reduce duty and increase productivity. The models and feedback algorithms were validated with field measured data. Future work could include installation and extension of the advanced duty detection system. In addition, further modelling and optimisation research could focus on improving the heuristics used for bucket trajectory control, realtime determination of optimum bucket trajectory and testing proposed dragline modifications.

Made available in DSpace on 2016-12-08T17:19:30Z (GMT). No. of bitstreams: 1 1.pdf: 202885 bytes, checksum: 3c12964a828cd6e497b731e66846a800 (MD5) Previous issue date: 2007-12-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nowadays, In due to the big number of studies applied on structural fatigue damage in time domain and frequency domain, besides the increasing of velocity and decreasing of costs on computation area, It is most important the metal-mechanic industries have prevision tools of endurance for their products increasing value, more reliability with big decreasing of development time. After the bibliographic and theoretical research, with the knowledge of all topics of endurance tests and prevision fatigue life methods on time domain and frequency domain, was developed an endurance tests device, based on an theoretical study of the general behavior of test device. Using recourses of Finite Elements Method, the reliability of dynamic simulations were confirmed, and could be founded some need parameters for calculus of theoretical behavior device. With the learn of how the drive system and data acquisition system of tests device works, a perfect control and calibration of this components was executed, ensuring the efficiency and reliability of device. This document is an evaluation of calculation methods of the fatigue life in a frequency domain of specimens under dynamical torsional loading. At first, with an identification of fatigue life curve of specimens in the shape of an hourglass. With the fatigue curve parameters, tests are executed with variable frequency in a limited band. Comparing the experimental results and theoretical results of fatigue life calculus on time domain (Rainflow method)with theoretical results of frequency domain, we can evaluate the reliable level of this last method. / Nos dias atuais, devido ao grande número de estudos aplicados em dano à fadiga estrutural no domínio do tempo e no domínio da freqüência, além do avanço em velocidade e redução de custos na área computacional, é de vital importância que empresas no ramo metal mecânico utilizem ferramentas de estimativa de vida à fadiga para seus produtos proporcionando maior valor agregado, maior confiabilidade com grande redução do tempo em desenvolvimentos. Após uma revisão bibliográfica e teórica adequada, com o aprendizado e implementação de um teste de fadiga e métodos de estimativa de vida no domínio do tempo e da freqüência, foi desenvolvido um dispositivo de testes de fadiga, embasado em um estudo teórico do comportamento geral do dispositivo de testes. Utilizando recursos do Método dos Elementos Finitos (MEF) verifica-se a confiabilidade de simulações dinâmicas, podendo inclusive determinar alguns parâmetros necessários para o cálculo do comportamento teórico do dispositivo. Com o aprendizado do funcionamento do sistema de acionamento e do sistema de aquisição de dados do dispositivo de testes, um adequado controle e calibração destes componentes foi executado, gerando confiabilidade nestes conjuntos. Neste documento é feita uma análise dos métodos de cálculo de vida à fadiga no domínio da freqüência em corpos de prova sujeitos a um carregamento torcional dinâmico. Primeiramente com a determinação da curva de fadiga de corpos de prova testados com a forma de uma ampulheta. Com os parâmetros da curva de fadiga, são executadas testes com freqüência variável em uma banda limitada. Comparando os resultados experimentais e resultados teóricos de cálculo de vida no domínio do tempo (Método Rainflow) com resultados teóricos no domínio da freqüência, pode-se então avaliar o nível de confiabilidade deste último método.

In early 2020, cracks were discovered on the bridge crossing the Torne River at Autio. This resulted in an investigation being launched to determine the structural state of the bridge. In conjunction with this investigation, monitoring equipment was installed on the bridge, which enabled the collection of measured strain at four critical points on the bridge.  In this thesis the measured strain was used to approximate stresses in the prestressing cables and thereby calculate the effects of fatigue on the bridge. Two different structural standards were used to calculate the results: Eurocode 2, and fib Model Code 2010. Likewise, two different cycle-counting methods were used to calculate the results: the Rainflow-algorithm, and the largest-magnitude approach.  Regardless of structural standard or cycle-counting method, the results indicate that the effects of fatigue are neither an issue for the bridge, currently, nor will it be in the expected lifetime of the bridge.

<p>Föreliggande avhandling omfattar en fallstudie av utmattningsrisken för järnvägsbroarna mellan Stockholm Central och Söder Mälarstrand. Ett stort antal utmattningssprickor i broarna över Söderström och Söder Mälarstrand har sedan länge varit kända. I samband med en bärighetsutredning av sträckan har ett stort antal anslutningspunkter i samtliga broar identifierats som kritiska avseende utmattningsrisk. Sträckan är den mest trafikerade i Sverige och de förenklade beräkningsmetoder som anges i Banverkets föreskrift för bärighetsberäkningar är i vissa fall inte tillämpliga.</p><p>De formella bärighetsberäkningarna har visat på flerfaldiga överskridanden i utnyttjandegrad gällande utmattning. I de punkter som beräkningarna visar störst risk för utmattning har inga sprickor påträffats, trots omfattande förbandsbesiktningar. Beräkningarna baseras på typiserade spänningskollektiv och givet antal spännings­växlingar, oberoende av den aktuella trafikmängden. Enligt bärighetsnormen ges möjlighet att beakta den verkliga trafikmängden baserat på historiskt bruttotonnage och typiserade trafiklaster. Dessa beräkningar har utförts och visar på ännu större risk för utmattning, jämfört med den förenklade metoden. I syfte att på ett ännu mer nyanserat sätt uppskatta utmattningsrisken har en metod använts, baserat på uppskattning av den faktiska trafikmängden och dess fördelningar. Beräkningarna baseras på trafikdata tillgänglig från Banverket. Metoden är tillämplig på andra järnvägsbroar på andra sträckor.</p><p>Utöver teoretiska beräkningar har töjningsmätningar utförts. Under 2006 utförde dåvarande Carl Bro AB töjningsmätningar på bro över Söder Mälarstrand och viadukt söder om Söder Mälarstrand, avseende några enskilda tågöverfarter. Under 2008 utförde KTH Brobyggnad omfattande töjningsmätningar på bro över Söderström, avseende all trafik under en månads tid.</p> / <p>The present thesis comprises a case study of the risk of fatigue of the railway bridges chaining between Stockholm Central Station and the district Söder Mälarstrand. A large number of fatigue-related cracks in the bridges at Söderström and Söder Mälarstrand have been known for a long time. During a capacity assessment of the current bridges, a large number of connections have been identified as critical concerning fatigue resistance. The route is the most frequent in all of Sweden and the simplified methods of fatigue assessment defined by Banverket may not always be applicable.</p><p>A conventional capacity assessment has shown numerous exceeds in fatigue resistance, using the stated safety margins. No fatigue cracks have been identified at the locations showing the largest theoretical risk of fatigue, in spite of extensive investigations. The conventional calculations are based on a uniform stress collective and a fixed number of stress cycles, independent of the actual traffic volume. According to the regulations stated by Banverket, the assessment may optionally be performed using historical data of the gross tonnage and standardised traffic loading. Such calculations have been undertaken and show even greater risk of fatigue, compared to the conventional assessment. To estimate the risk of fatigue in more detail, a method has been used, based on estimations of the real traffic volume and its distributions. The analysis is based on available data of the traffic volume and may be applied to other railway bridges on other locations.</p><p>Besides theoretical analyses, field measurements have been performed. In 2006, former Carl Bro AB carried out strain gauge measurements on the bridge passing Söder Mälarstrand and the viaduct south of Söder Mälarstrand. The measurements comprised a small amount of individual train passages. During 2008, the division of Structural Design and Bridges at KTH performed an extensive field measurement programme on the bridge passing Söderström. Continuous measurements collecting data of all traffic during a period of one month was performed.</p>

Föreliggande avhandling omfattar en fallstudie av utmattningsrisken för järnvägsbroarna mellan Stockholm Central och Söder Mälarstrand. Ett stort antal utmattningssprickor i broarna över Söderström och Söder Mälarstrand har sedan länge varit kända. I samband med en bärighetsutredning av sträckan har ett stort antal anslutningspunkter i samtliga broar identifierats som kritiska avseende utmattningsrisk. Sträckan är den mest trafikerade i Sverige och de förenklade beräkningsmetoder som anges i Banverkets föreskrift för bärighetsberäkningar är i vissa fall inte tillämpliga. De formella bärighetsberäkningarna har visat på flerfaldiga överskridanden i utnyttjandegrad gällande utmattning. I de punkter som beräkningarna visar störst risk för utmattning har inga sprickor påträffats, trots omfattande förbandsbesiktningar. Beräkningarna baseras på typiserade spänningskollektiv och givet antal spännings­växlingar, oberoende av den aktuella trafikmängden. Enligt bärighetsnormen ges möjlighet att beakta den verkliga trafikmängden baserat på historiskt bruttotonnage och typiserade trafiklaster. Dessa beräkningar har utförts och visar på ännu större risk för utmattning, jämfört med den förenklade metoden. I syfte att på ett ännu mer nyanserat sätt uppskatta utmattningsrisken har en metod använts, baserat på uppskattning av den faktiska trafikmängden och dess fördelningar. Beräkningarna baseras på trafikdata tillgänglig från Banverket. Metoden är tillämplig på andra järnvägsbroar på andra sträckor. Utöver teoretiska beräkningar har töjningsmätningar utförts. Under 2006 utförde dåvarande Carl Bro AB töjningsmätningar på bro över Söder Mälarstrand och viadukt söder om Söder Mälarstrand, avseende några enskilda tågöverfarter. Under 2008 utförde KTH Brobyggnad omfattande töjningsmätningar på bro över Söderström, avseende all trafik under en månads tid. / The present thesis comprises a case study of the risk of fatigue of the railway bridges chaining between Stockholm Central Station and the district Söder Mälarstrand. A large number of fatigue-related cracks in the bridges at Söderström and Söder Mälarstrand have been known for a long time. During a capacity assessment of the current bridges, a large number of connections have been identified as critical concerning fatigue resistance. The route is the most frequent in all of Sweden and the simplified methods of fatigue assessment defined by Banverket may not always be applicable. A conventional capacity assessment has shown numerous exceeds in fatigue resistance, using the stated safety margins. No fatigue cracks have been identified at the locations showing the largest theoretical risk of fatigue, in spite of extensive investigations. The conventional calculations are based on a uniform stress collective and a fixed number of stress cycles, independent of the actual traffic volume. According to the regulations stated by Banverket, the assessment may optionally be performed using historical data of the gross tonnage and standardised traffic loading. Such calculations have been undertaken and show even greater risk of fatigue, compared to the conventional assessment. To estimate the risk of fatigue in more detail, a method has been used, based on estimations of the real traffic volume and its distributions. The analysis is based on available data of the traffic volume and may be applied to other railway bridges on other locations. Besides theoretical analyses, field measurements have been performed. In 2006, former Carl Bro AB carried out strain gauge measurements on the bridge passing Söder Mälarstrand and the viaduct south of Söder Mälarstrand. The measurements comprised a small amount of individual train passages. During 2008, the division of Structural Design and Bridges at KTH performed an extensive field measurement programme on the bridge passing Söderström. Continuous measurements collecting data of all traffic during a period of one month was performed.

This dissertation deals with three research topics; i) the catcher bearings life prediction method, ii) the Morton effect, and iii) the two dimensional modified Reynolds equation. Firstly, catcher bearings (CB) are an essential component for rotating machine with active magnetic bearings (AMBs) suspensions. The CB's role is to protect the magnetic bearing and other close clearance component in the event of an AMB failure. The contact load, the Hertzian stress, and the sub/surface shear stress between rotor, races, and balls are calculated, using a nonlinear ball bearing model with thermal growth, during the rotor drop event. Fatigue life of the CB in terms of the number of drop occurrences prior to failure is calculated by applying the Rainflow Counting Algorithm to the sub/surface shear stress-time history. Numerical simulations including high fidelity bearing models and a Timoshenko beam finite element rotor model show that CB life is dramatically reduced when high-speed backward whirl occurs. Secondly, the theoretical models and simulation results about the synchronous thermal instability phenomenon known as Morton Effect is presented in this dissertation. A transient analysis of the rotor supported by tilting pad journal bearing is performed to obtain asymmetric temperature distribution of the journal by solving variable viscosity Reynolds equation, energy equation, heat conduction equation, and equations of motion for rotor. The tilting pad bearing is fully nonlinear model. In addition, thermal mode approach and staggered integration scheme are utilized in order to reduce computation time. The simulation results indicate that the temperature of the journal varies sinusoidally along the circumferential direction and linearly across the diameter, and the vibration envelope increased and decreased, which considers as a limit cycle that is stable oscillation of the envelope of the amplitude of synchronous vibration. Thirdly, the Reynolds equation plays an important role to predict pressure distribution in the fluid film for the fluid film bearing analysis. One of the assumptions on the Reynolds equation is that the viscosity is independent of pressure. This assumption is still valid for most fluid film bearing applications, in which the maximum pressure is less than 1 GPa. In elastohydrodynamic lubrication (EHL) which the lubricant is subjected to extremely high pressure, however, the pressure independent viscosity assumption should be reconsidered. With considering pressure-dependent viscosity, the 2D modified Reynolds equation is derived in this study. The solutions of 2D modified Reynolds equation is compared with that of the classical Reynolds equation for the plain journal bearing and ball bearing cases. The pressure distribution obtained from modified equation is slightly higher pressures than the classical Reynolds equations. / PDF file replaced 10-21-2012 at the request of the Thesis Office.

Although a component satisfies all operating static requirements, failures can still occur due to vibration induced fatigue. Vibration induced fatigue is a frequent phenomenon, in cases where the natural frequencies of the structures are excited by the loading. Hence, the methods which consider all dynamic characteristic of the structure should be used to obtain accurate fatigue life predictions. These methods in frequency domain are called vibration fatigue methods which give accurate, reliable and fast results. In this thesis, a numerical code is developed in order to predict fatigue life of structures and it is used for a bracket that is installed on an air platform. However, for verification of the numerical code, a cantilever beam is used as a case study at the beginning. First, finite element model of the cantilever beam is constructed and experimental analyses are performed to verify the finite element model. Then fatigue life is calculated using the numerical code and it is verified comparing the results obtained by both commercial software and performed fatigue tests. For predicting fatigue life of the bracket, flight test is performed in order to obtain acceleration loading. Finite element modeling of bracket and verification of it by experimental analyses are performed and finally, accelerated fatigue life of the bracket is obtained by the developed numerical code, commercial software and fatigue test. It is concluded that the results obtained from the fatigue analyses and fatigue test are considerably close enough to justify that the analysis is significantly accurate.