Rotating systems are subject to vibrations due to the presence of external or internal sources and this causes damage to the health of the equipment and tends to generate high maintenance costs. As an alternative to solve this type of problem, vibration attenuators can be used, allowing the equipment to work safely. Currently, several attenuation methods have been investigated for monitoring the functioning of mechanical structures, especially compact attenuating systems, such as, for example, those that use shape memory alloys. In this context, the present work presents the semiactive control of vibrations of a flexible rotor using nitinol wires heated by electric current. The displacements of the bearing in which the wires act are analyzed for different heating temperatures and compared to the rotor without the actuator. By analyzing the experimental results, we note the efficiency in reducing the amplitude, in addition to changing the natural frequency, making the safer system. Resumo: Sistemas rotativos estão sujeitos a vibrações devido a presença de fontes externas ou internas e isso provoca danos à saúde do equipamento e tende a gerar gastos elevados de manutenção. Como alternativa para solução desse tipo de problema pode-se utilizar os atenuadores de vibrações, permitindo que os equipamento trabalhem de maneira segura. Atualmente, diversos métodos de atenuação têm sido investigados para o monitoramento do funcionamento de estruturas mecânicas, principalmente os sistemas atenuantes compactos, como, por exemplo, os que utilizam as ligas de memória de forma. Nesse contexto, o presente trabalho apresenta o controle semiativo de vibrações de um rotor flexível utilizando fios de nitinol aquecidos por corrente elétrica. Os deslocamentos do mancal em que os fios atuam são analisados para diferentes temperaturas de aquecimento e comparados com o rotor sem o atuador. Pela análise dos resultados experimentais, nota-se a eficiência na redução da amplitude, além da alteração da frequência natural, tornando o sistema mais seguro.

Metaheuristic algorithms have become popular lately as an optimization method due to their similarity to natural adaptation events. In this context, such algorithms have the ability to cover several areas, in which for control systems such algorithms present a new way of developing and adapting control laws that are adapted and improved for different situations in which the dynamic system can be found. This work aims to utilize the metaheuristic algorithm particle swarm optimization in which three populations of gains, generated in different ways, are optimized by the algorithm and adapted for different situations of parameters of the analyzed system. Resumo: Algoritmos meataheurísticos se tornaram populares ultimamente como método de otimização devido a sua similaridade com eventos naturais de adaptação. Neste contexto, tais algoritmos possuem a capacidade de abranger diversas áreas, em que para sistemas de controle tais algoritmos apresentam um novo meio de desenvolver e adaptar leis de controle que são adaptadas e melhoradas para diversas situações em que o sistema dinâmico pode ser encontrado. Este trabalho visa utilizar o algoritmo metaheurístico particle swarm optimization em que três populações de ganhos, gerados de formas diferentes, são otimizados pelo algoritmo e adaptados para diferentes situações de parâmetros do sistema analisado.

Vibration is an essential subject for the design of rotordynamic systems, being responsible for compromising the integrity and causing risks to operational functioning. This work deals with an experimental investigation of the semi-active vibration controller for a rotordynamic system using shape memory alloy (SMA) elements. SMAs are smart materials that present thermomechanical coupling represented by solid phase transformations that promote either stiffness change or hysteretic dissipation. In this regard, they are useful in controllers employing thermal actuation from electric current through the Joule effect. This paper presents a proof of concept of a controller using SMA elements. An experimental apparatus is proposed considering a typical rotor system using SMA wires at the bearings. In this regard, proper temperature variations allow the system to cross critical resonant conditions.

In internal combustion engines, studies of the effects of fuel adulteration focus on problems that occur in the fuel system and pollutants, but little attention is paid to lubricants. Some of these research studies are focused on detecting adulteration rather than the impact of this tampering on the internal combustion engine and lubricant degradation. This work evaluates, in addition to the problems in the supply system, the early degradation of the lubricant from the physical and chemical changes it undergoes when using adulterated gasoline in an internal combustion engine. For that, a 160cc Honda stationary engine mounted on a bench and connected to an alternator through a transmission belt was used. Fuels adulterated with ethanol, kerosene, and thinner were used in proportions of 5, 10, 15, and 20%. The cycles were 40 h each, which is equivalent to approximately 2000 km covered. To measure the engine time and rotation, a tachometer/hourmeter was used, where the time of each cycle was recorded. Particle quantifier analysis (PQA) tests and infrared spectrometry (sulfation, nitriding, oxidation, and total acid number (TBN)) were performed, in addition to changes in engine behavior in relation to rotation. The results showed changes in rotation according to the concentration and type of contaminants. Engine wear was small for the 2000 km covered. The sulfation, nitriding, oxidation, and TBN levels were altered, indicating the degradation of the lubricating oil.

Rotating systems are subject to external and internal excitations that cause undesirable vibrations, taking to degradation of the structural integrity of the system and the users health. In the industrial area, for example, the vibration attenuation can allow rotating systems to operate more efficiently and safely, providing less frequent periodic maintenance and avoiding expensive cost. In this context, the control of vibrations has been the object of concern of research centers and the specialized literature is full in proposals of solutions for this subject. This work presents a theoretical proposal of the mathematical modeling of a rotating machine containing shape memory alloy wires, whose purpose is to promote the damping of lateral vibrations caused by perturbation forces, mainly unbalance forces. This work intends to construct a theoretical knowledge, in a research area of restricted and relevant domain.