Determination of Correlated and Uncorrelated Blocked Forces on an Engine Valve Cover

摘要

Inverse force determination is routinely used to identify input forces when they are not directly measurable. Inverse forces can be determined with and without the source structure attached though the process is simpler if the source structure is attached. If the source structure is attached, the inversely determined forces are referred to as blocked forces. In this research, blocked forces are determined for a plastic engine cover bolted to a base forced by an electromagnetic shaker. At frequencies below 400 Hz, blocked forces are determined and validated using routine approaches where phase is included in both transfer function and operational response measurements. Above 400 Hz, it is demonstrated that predictions are improved if phase is ignored and blocked forces are assumed to be uncorrelated with respect to each other. It is also shown that the blocked forces can be used to drive models and predict the effect of design changes.