The influence of cylinder lubrication on piston slap

A model has been developed for determining the time history of piston slap impact force. This model takes into account the influence of the oil film on the impact behaviour, which was found to be an important factor. However, it was also found that entrapped gas bubbles in the oil are equally significant. Three test rigs were designed and built to study these effects on the impact phenomenon and extensive tests were carried out. The impact force time history has been determined using Reynolds' theory. Results have shown that Reynolds' theory for fluid film squeezing can be applied for oil film damping determination. However, the experimental results have also shown that when gas is entrapped during the impact, this theory considerably overpredicts the magnitude of the impact. An eight-degree-of-freedom lumped parameter model was developed through the dynamic analysis of each component of an internal combustion engine's reciprocating system. The effective damping factor derived from this model was found to be inversely proportional to the oil film thickness cubed, as expected from Reynolds' theory. A dynamic model has been proposed, where the oil film mixed with bubbles is considered to be analogous to a serial spring and damping system. By incorporating a spring in series with this damper, the effect of the bubbles can also be predicted

O uso de geotecnologias na elaboração de mapas de ruído The use of geotechnologies in the noise mapping

A elaboração de mapas de ruído com o apoio das geotecnologias é uma poderosa ferramenta para visualização e compreensão do comportamento do ruído em determinada área. Nesta pesquisa avaliaram-se os níveis de pressão sonora em uma região de aproximadamente 18 ha, composta por indústrias, residências, criação de animais e uma avenida movimentada no entorno do município de Campo Grande (MS). Efetuaram-se análises semivariográficas das amostras e os mapas de ruído foram desenvolvidos utilizando-se krigagem, que se mostrou adequada, desde que os dados coletados fossem representativos e os pontos de amostragem coerentes com a situação que se queria avaliar. Os mapas de ruído permitiram identificar as regiões mais críticas, as fontes e suas respectivas áreas de influência, além de verificar onde são ultrapassados os limites normativos de pressão sonora.<br>Geotechnologies application in noise mapping consists in a powerful tool to visualize and understand the sound distribution in a specific area. This research was done at the city of Campo Grande, Mato Grosso do Sul, Brazil, in an area of approximately 18 ha, where there are industries, residences, animal breeding and an avenue. Sound level pressures were explored, semivariografic analysis were done and noise maps were developed using kriging, that demonstrated to be appropriated, since that the collected data were representative and the sampling points coherent with the situation that needed to be evaluated. The noise maps permitted to identify the most critical regions, the sources and their influence areas, as verify where the normative limit values for sound pressure exceed