A study of the response of submerged mast-like structures to shock loads has been carried out. An analytical model has been developed which uses a lumped parameter system whose equations of motion are solved by the use of finite difference time integration techniques. The effects of the stiffness and damping inherent in the supporting restraints are successfully included into the analysis by assuming that they provide linear rotational stiffness and a viscous type of damping. An analysis of hydrodynamic interaction effects has been developed in order to investigate how the frequency response of the structure is affected by submergence. Changes in both the frequency and the damping characteristics are predicted as a function of the depth of submergence. Methods of incorporation of these hydrodynamic forces into the time domain solution of the lumped mass system are investigated and are found to be most accurate for slender structures. In order to develop a fuller understanding of the hydrodynamic response, two experimental investigations have been carried out. The first is laboratory based and uses carefully controlled free vibration tests to excite a number of modal frequencies of a rigidly clamped vertical mast in both submerged and partially submerged conditions. Results show that the frequency changes are closely predicted by the hydrodynamic analysis developed in this thesis and also show that hydrodynamic damping is a linear function of amplitude of deflection for the first natural response mode over the mast's elastic range of response. To investigate the shock response of submerged structures, a second test rig is used to subject a slender mast to a shock load radiating from an underwater explosion. The structural significance of the higher modal frequencies is evaluated through the use of Fourier Analysis and digital filtering techniques. The instrumentation performance including both damped and undamped transducers is assessed in order to make recommendations for future shock trials. The experimental investigation has shown that both the direct pressure loading and the movement of the supports are important factors in the mast response and that their combination produces important high frequency response modes.

Standards and regulations for dimensioning of load-bearing structures are based on the response of load-bearing structures subjected to loads without variation in time. In the event of an accidental load, e.g. a collision or explosion, causes the load to have a rapid variation in the time resulting in a dynamic response. Previous studies have shown that structures that respond in a certain way under static load have shown a completely different behavior under dynamic influence and therefore it is of interest to study the dynamic response of structures.By testing concrete beams with varying amounts of shear reinforcement subjected to impact loading, the purpose of this report is to analyze how the beams responds in terms of crack width and vibrations when they are exposed to a dynamic load. For comparison, reference tests have also been performed on beams subjected to a quasi-static load.The result of the project shows that the shear reinforcement comes into play as the beams with a larger amount of reinforcement have more capacity to hold the flexural shear cracks together. There is also an indication that the dynamic flexural shear capacity could be lower than static shear capacity as the shear cracks had an increased inclination during dynamic loading for some of the beams. This results in a decreased flexural shear capacity as only one stirrup carried the load across the shear crack.Measured signal shows that beams failing respond when impacted by the similar to a plastic collision, while beams responding with a flexure dominated mode without going to failure instead answer similar to an elastic collision. Furthermore, there is indication that the natural frequencies change significantly due to both flexural cracks and flexural shear cracks.

No description available.

Conveyor chains are often subject to repetitive shock loads during normal operations. This can cause accelerated wear in the chain leading to premature chain replacementor chain failure (Otoshi, 1997, p. 4). In this thesis a new approach for reducingshock load related wear in conveyor chains is proposed. The scope and objective ofthis project is to investigate the shock load phenomenon and develop a dynamic pinlink chain plate. A study into chain wear and shock loads of chain driven conveyorswas made to identify problem areas. Additionally, a Simulink model was created tosimulate the influence of shock loads on conveyor chains. Common wear as a result ofshock loads are identified as pin failure, bushing failure, scuffing, chain plate failure,fatigue and chain elongation, (Otoshi, 1997, p. 76-78). Nine concepts were drafted and evaluated using methods described in (Ulrich &Eppinger, 2016). The concepts were simulated using Finite Element Analysis (FEA)and two concept iterations, Concept B v.3 and Concept C v.3, were manufacturedfor static tensile tests using two different setups and Digital Image Correlation (DIC)system for additional strain measuring. The breaking load for Concept B v.3 andConcept C v.3 is 105 and 70 kN respectively. The approximate yield strength ofConcept B v.3 is 11 kN and 40 kN for Concept C v.3. The Fatigue limit was estimatedto 10 kN for Concept B v.3 and 20 kN for Concept C v.3. A nonlinear FEA for Concept C v.3 and Concept B v.3 provided additional insightinto the behaviour of the pin link chain plates during high stress concentrations. While neither the linear static nor nonlinear static analyses managed to accuratelypredict the behaviour of Concept B v.3, the simulated results of Concept C v.3 werein line with the observed tensile tests. From the results it is concluded that a dynamic chain plate in the form of ConceptC v.3 has the potential to reduce the magnitude of the force in the chain imposedby shock loads, while still following the current ISO standard for conveyor chains. The resulting design proposition provides an easy to manufacture high strength chainplate with increased elastic properties.Future work should be focused on determining the fatigue life and shock load resistanceof the developed chain plate. It is recommended that material selection is focused onwear and fatigue resistant materials and that both simulated and physical dynamictesting is performed.

Cascade Drives specializes in high-performance electromechanical linear actuators (EMA). The company has developed a range of linear rack and pinion actuators based on a patented load distribution technique that allows multiple pinions to interact with a single gear rack. A project where one of their EMAs is to be implemented into an excavator boom is about to be initiated. It is suspected that extreme shock loads are present in such applications. The shock loads could potentially cause problems for the structural integrity of the gear train. This master thesis focused on defining requirements for an overload protection mechanism and identifying and evaluating possible solutions that could be implemented into the EMA to protect it from damage. At the start of the thesis, a pre-study had already been conducted. The author found that the forces present during shock loading warrant some protection strategy to be researched and implemented into the EMA. A comprehensive multibody dynamics model (MBD) of the EMA was developed in MSC Adams (View) to validate the result from the pre-study. The MBD model was later expanded to include a torsional stiffness model derived from physical tests and the flexibility of the excavator boom itself, which was extracted from flexible body simulations of the excavator boom assembly in Adams. The expanded MBD model simulations revealed that a protection mechanism was needed in the thought application. Three protection mechanisms/strategies were simulated and evaluated in the MBD environment. A slipping solution in the form of a friction clutch, a disconnecting solution in the form of an electromagnetic clutch, and an active solution in which the electric motor was controlled to produce maximum torque in the opposite direction of motion at the point of impact to dampen the loads through the gear train. Running the motor in reverse at impact proved to be an insufficient strategy. Even for an idealized motor that combined the maximum torque from the strongest motor and the rotational inertia from the lightest motor available for the EMA, simulations resulted in loads above the static load limit through the gear train. The friction clutch was shown to be plausible but inefficient. The slipping torque of a friction clutch had to be detuned way below the static load limit due to the delays in peak torque throughout the gear train, which meant that the overall actuating force of the actuator was severely hampered. The electromechanical disconnecting clutch was proved to be the most promising alternative. The disconnecting clutch completely disengages the upstream components from the downstream components in the drive train, meaning that the overall system performance remained unchanged. The response times needed depended on where the clutch was installed, from around 16ms if only the motor was disengaged up to 17ms if both the motor and the brake were disengaged. Further analysis of triggering strategies and response times has to be conducted to definitely decide if an electromagnetic clutch is a viable option. Still, the result from this thesis shows that it is a promising path. / Cascade Drives är specialiserade på högpresterande elektromekaniska linjära ställdon. Företaget har utvecklat en rad linjära ställdon av kuggstångskonfiguration som bygger på en patenterad lastfördelningsteknik som möjliggör för flera pinjonger att interagera med en enda kuggstång. Ett projekt där ett av deras ställdon ska implementeras i en grävmaskinsbom är på väg att inledas och man misstänker att det i en sådan applikation kan uppstå extrema chocklaster, vilka potentiellt kan orsaka stora skador på ställdonets drivlina. Detta examensarbete fokuserade på att kravställa och analysera ett överbelastningsskydd och att identifiera och utvärdera olika möjliga lösningar som kan implementeras i ställdonet för att skydda det från skador. En förstudie kring problemet har redan genomförts där författaren fann att de krafter som uppstår vid chocklaster motiverar att någon form av skyddsstrategi undersöks och implementeras i ställdonet. En omfattande multibody dynamics (MBD) modell av ställdonet utvecklades i MSC Adams (View) för att validera resultatet från förstudien. MBD-modellen utvidgades senare till att innefatta en torsionsflexmodell härledd från fysiska tester och även flexibiliteten hos själva grävmaskinbommen som extraherades från flexible body-simuleringar av grävmaskinens bomaggregat i Adams. Resultat från de utökade MBD-modellsimuleringarna visade att en skyddsmekanism behövs för att skydda drivlinan i ställdonet mot överlast i den tänkta grävmaskinsapplikationen. Tre olika skyddsmekanismer/strategier simulerades och utvärderades i MBD-miljön. En glidande lösning i form av en friktionskoppling, en frånkopplande lösning i form av en elektromagnetisk koppling, och en aktiv lösning där elmotorn reglerades till att producera maximalt vridmoment bakåt vid tidpunkten för kollisionen för att minska belastningarna i drivlinan. Att köra motorn bakåt vid kollision visade sig vara otillräckligt. Även för en idealiserad motor som kombinerade det maximala vridmomentet från den starkaste motorn som simulerades med rotationströgheten från den lättaste motorn som simulerades resulterade simuleringar i krafter genom drivlinan överstigande den statiska maxbelastningen. Friktionskopplingen visade sig vara en möjlig men ineffektiv lösning. Friktionskopplingens utlösningsmoment måste trimmas ner långt under den statiska maxbelastningen på grund av tiden det tar för maxbelastningen att propagera genom drivlinan. Detta innebar att ställdonets totala prestanda minskade rejält. Den frånkopplande elektromekaniska lösningen visade sig vara det mest lovande alternativet. Det faktum att den frånkopplande kopplingen helt kopplar bort komponenterna uppströms från komponenterna nedströms i drivlinan innebar att systemets prestanda förblev oförändrad. Svarstiderna som krävdes berodde på var kopplingen var installerad, från cirka 16ms om bara motorn skulle kopplas ur och upp till 17ms om både motorn och bromsen kopplades ur. Ytterligare analyser av utlösningsstrategier och svarstider måste genomföras för att definitivt avgöra om en elektrisk frånkopplande koppling är ett bra alternativ, men resultaten från denna avhandling visar att det är en lovande väg.

Neste trabalho avaliou-se o desempenho de um reator anaeróbio operado em batelada seqüencial e contendo biomassa imobilizada (ASBBR) em espuma de poliuretano quando submetido a diferentes tempos de alimentação e cargas orgânicas volumétricas, além da aplicação de cargas de choque orgânicas. O reator, com mistura por recirculação da fase líquida e mantido à 30 ± 1 ºC, tratou soro de queijo reconstituído e possuiu 2,5 L de volume reacional. Os resultados mostraram que o tempo de alimentação utilizado exerceu maior influência sobre o desempenho do reator para maiores valores de carga orgânica volumétrica. Durante a operação com carga orgânica volumétrica de 3 gDQO/L.d, a alteração do tempo de alimentação não influenciou na eficiência de remoção de matéria orgânica filtrada, que foi de 98%. Sob carregamento orgânico volumétrico de 6 gDQO/L.d, verificou-se tendência de queda daquela variável para maiores tempos de enchimento: 99, 98 e 97%, para tempos de alimentação de 2, 4 e 6 horas, respectivamente. Na operação com carga orgânica volumétrica de 12 gDQO/L.d, o aumento do tempo de alimentação resultou em queda mais significativa da eficiência de remoção de matéria orgânica filtrada: 97, 95 e 93%, para tempos de alimentação de 2, 4 e 6 horas, respectivamente. Em todas as condições, a aplicação de cargas de choque de 24 gDQO/L.d causaram o aumento da concentração de ácidos no efluente. No entanto, apesar desse aumento, o reator retomou rapidamente sua estabilidade, sendo a alcalinidade otimizada ao afluente suficiente para manter o pH próximo do neutro durante toda a operação. Independente da carga orgânica volumétrica aplicada, a operação com tempo de alimentação de 2 horas foi aquela que proporcionou maior estabilidade e menor suscetibilidade do processo às cargas de choque orgânicas. / This work assessed the performance of an anaerobic sequencing batch reactor containing immobilized biomass (ASBBR) on polyurethane foam when submitted to different feeding times, volumetric loading rate and organic shock loads. The reactor, in which mixing occurred by recirculating the liquid phase, contained 2,5 L reaction medium and was maintained at 30 ± 1 ºC for treating reconstituted cheese whey. Results showed that the effect of feeding time on reactor performance was more pronounced at higher volumetric loading rates. During operation at volumetric loading rate of 3 gDQO/L.d, changing feeding time did not affect filtered organic matter removal efficiency, which amounted to 98%. At volumetric loading rate of 6 gDQO/L.d, removal efficiency showed a tendency to drop at higher feeding times: 99, 98 and 97%, for feeding times of 2, 4 and 6 hours, respectively. At volumetric loading rate of 12 gDQO/L.d, increase in feeding time resulted in a more significant drop in filtered organic matter removal efficiency: 97, 95 and 93%, for feeding times of 2, 4 and 6 hours, respectively. Application of shock loads of 24 gDQO/L.d caused increase in acids concentration in the effluent, at all conditions. However, despite this increase, the reactor readily regained stability and optimized alkalinity supplementation to the influent was sufficient to maintain near neutral pH during the entire operation. Regardless of applied volumetric loading, operation with feeding time of 2 hours was which yielded maximum stability and reduced susceptibility of the process to organic shock loads.

Neste trabalho avaliou-se o desempenho de um reator anaeróbio operado em batelada seqüencial e contendo biomassa imobilizada (ASBBR) em espuma de poliuretano quando submetido a diferentes tempos de alimentação e cargas orgânicas volumétricas, além da aplicação de cargas de choque orgânicas. O reator, com mistura por recirculação da fase líquida e mantido à 30 ± 1 ºC, tratou soro de queijo reconstituído e possuiu 2,5 L de volume reacional. Os resultados mostraram que o tempo de alimentação utilizado exerceu maior influência sobre o desempenho do reator para maiores valores de carga orgânica volumétrica. Durante a operação com carga orgânica volumétrica de 3 gDQO/L.d, a alteração do tempo de alimentação não influenciou na eficiência de remoção de matéria orgânica filtrada, que foi de 98%. Sob carregamento orgânico volumétrico de 6 gDQO/L.d, verificou-se tendência de queda daquela variável para maiores tempos de enchimento: 99, 98 e 97%, para tempos de alimentação de 2, 4 e 6 horas, respectivamente. Na operação com carga orgânica volumétrica de 12 gDQO/L.d, o aumento do tempo de alimentação resultou em queda mais significativa da eficiência de remoção de matéria orgânica filtrada: 97, 95 e 93%, para tempos de alimentação de 2, 4 e 6 horas, respectivamente. Em todas as condições, a aplicação de cargas de choque de 24 gDQO/L.d causaram o aumento da concentração de ácidos no efluente. No entanto, apesar desse aumento, o reator retomou rapidamente sua estabilidade, sendo a alcalinidade otimizada ao afluente suficiente para manter o pH próximo do neutro durante toda a operação. Independente da carga orgânica volumétrica aplicada, a operação com tempo de alimentação de 2 horas foi aquela que proporcionou maior estabilidade e menor suscetibilidade do processo às cargas de choque orgânicas. / This work assessed the performance of an anaerobic sequencing batch reactor containing immobilized biomass (ASBBR) on polyurethane foam when submitted to different feeding times, volumetric loading rate and organic shock loads. The reactor, in which mixing occurred by recirculating the liquid phase, contained 2,5 L reaction medium and was maintained at 30 ± 1 ºC for treating reconstituted cheese whey. Results showed that the effect of feeding time on reactor performance was more pronounced at higher volumetric loading rates. During operation at volumetric loading rate of 3 gDQO/L.d, changing feeding time did not affect filtered organic matter removal efficiency, which amounted to 98%. At volumetric loading rate of 6 gDQO/L.d, removal efficiency showed a tendency to drop at higher feeding times: 99, 98 and 97%, for feeding times of 2, 4 and 6 hours, respectively. At volumetric loading rate of 12 gDQO/L.d, increase in feeding time resulted in a more significant drop in filtered organic matter removal efficiency: 97, 95 and 93%, for feeding times of 2, 4 and 6 hours, respectively. Application of shock loads of 24 gDQO/L.d caused increase in acids concentration in the effluent, at all conditions. However, despite this increase, the reactor readily regained stability and optimized alkalinity supplementation to the influent was sufficient to maintain near neutral pH during the entire operation. Regardless of applied volumetric loading, operation with feeding time of 2 hours was which yielded maximum stability and reduced susceptibility of the process to organic shock loads.