Search

The application of statistical energy analysis to vibro-acoustic systems of complex geometry has been made practicable by the introduction of the concept of equivalent mass/equivalent volume. Although previous research at the ISVR has shown that these parameters can be directly measured, it has recently been found that the published formulae for carrying out this calculation are not sufficiently accurate. This is because it has been previously incorrectly assumed that the measurement on the subsystem of interest is unaffected by the presence of other attached subsystems. The paper derives the correct expressions for equivalent mass/equivalent volume for the general case of N -connected subsystems. By utilizing these derived expressions, the paper then proceeds to show that the coupling loss factors can be obtained directly in terms of the measured input power and vibration velocity/sound pressure. The paper concludes by showing that the power balance equations can, by utilizing the above expressions, be framed in terms of the subsystem velocities/sound pressures rather than in terms of subsystem energies. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]