Abstract In many engineering applications, there are systems that exhibit a series of collisions in a certain amount of time, for example the impact of floating ice in ships and the rubbing between stationary and rotary parts in turbomachinery. In many of these situations, it is of vital importance to know how the impacts affect the overall system behavior for the correct functioning or the prediction of faults in the system. This can be done by proposing models that can represent the system when it is subjected to sudden impacts in its oscillation movement. However, due to the nonlinear and non-smooth characteristic of the impact phenomenon, the implementation of impacts in mechanical systems may be a challenging task. In this manner, this paper aims in proposing a vibro-impact model of two adjacent portal frame structures, being one of them driven by an unbalanced DC motor positioned on top of it. The portal frames were modeled as continuous beams by means of the Euler-Bernoulli beam theory. In order to model the impact between the structures, three different models were considered: using the Hertz theory of elastic bodies to model the contact force using a nonlinear damping; using a spring and a damper in parallel, viscoelastic or spring-dashpot system, to model the force; and considering the impact to be instantaneous and using the coefficient of restitution to adjust the velocity after the contact. To validate the impact models, an experimental procedure was performed and the measurements compared with the simulations.

Abstract This work presents an analysis of an ocean wave energy harvesting system. This system is composed of a direct current (DC) power generator attached at the middle-top of a floating platform. A pendulum is connected to the generator’s shaft. It is considered that the ocean waves motion swings the platform in the vertical direction, which transfers energy to the pendulum, making possible to convert mechanical energy, induced by the ocean wave, into a rotational motion due the pendulum and after in electric energy due the generator. With the objective to optimize the harvested power, several analyses of the pendulum parameters, ocean wave amplitude and frequency were carried out. This work was based on the Brazilian’s coast characteristics. Numerical and experimental results were performed which shows the efficiency of the conversion of mechanical energy provided by the pendulum into electric power.

Para avaliar o comportamento da suspensão do pulverizador autopropelido, foram desenvolvidos modelos físicos e matemáticos em função da excitação ocasionada pelas irregularidades do solo. Neste trabalho, estas irregularidades são representadas por obstáculos de uma pista normalizada segundo a norma ISO 5008. As equações do movimento são obtidas a partir dos modelos matemáticos de meio veículo. As simulações numéricas são executadas nos softwares Matlab® e Simulink®. A partir da entrada conhecida, podem-se determinar as características dos elementos da suspensão para obter níveis desejáveis de conforto e segurança. Foram analisadas quatro diferentes configurações do sistema, variando-se a relação de rigidez a partir de um modelo considerado padrão. Constatou-se que o aumento da relação de rigidez resulta na redução da aceleração vertical e no aumento do curso da suspensão, melhorando o conforto e diminuindo a segurança.

To evaluate the behavior of the suspension of self-propelled sprayer were developed physical and mathematical models as a function of excitement caused by irregularities in the soil. In this work, these irregularities are represented by obstacles of a track standard from ISO 5008. The motion equations are obtained from half car model. The numeric simulations are executed in software Matlab® and Simulink®. From a known entry, the characteristics of the suspension elements can be determined for obtain desirable levels of comfort and safety. Four settings with different stiffness ratio were simulated. It was found that the increase of stiffness ratio results in the reduction of vertical acceleration and in the increase of suspension travel, improving the comfort and decreasing safety.

Neste trabalho, foram feitas algumas análises sobre o comportamento dinâmico simulado de dois tipos de suspensões passivas das barras dos pulverizadores tracionados. Estas análises foram conduzidas em condições virtuais de pista de prova normalizada ISO 5008, com dois níveis de velocidade de deslocamento do pulverizador (5 km h-1 e 15 km h-1) e em dois perfis de pista existentes na norma (acidentada e suavizada). Foram utilizados nas simulações os softwares MATLAB®; SIMULINK® e Visual Nastran®. Os resultados mostram que a suspensão do tipo trapezoidal teve melhor desempenho em baixas frequências de excitação (w < 0,2 Hz), enquanto a suspensão do tipo pêndulo simples teve melhor desempenho nas demais condições das pistas normalizadas.

In this paper we conducted several analysis of the simulated dynamic behavior of two passive suspension types of the trailed sprayer booms. The suspension analysis was conducted under conditions of a bump track test ISO 5008, with two levels of speed (5 km h-1 and 15 km h-1) and two track profiles proposed in these standards (bumpy and smooth). It was used the simulations software MATLAB®; SIMULINK® and Visual Nastran ®. The results obtained showed that suspensions of trapezoidal type have good performance at low frequencies input (w < 0,2 Hz) while suspensions of simple pendulum type have good performance in others conditions.