Squeak & Rattle Correlation in Time Domain using the SAR-LINE™ Method

A new Squeak & Rattle simulation method was presented at the ISNVH conference 2010 (SAE 201-01-1423). This method, called the SAR-LINE™ method, is based on the evaluation of the relative displacement in time domain due to a random load. A specific challenge for a Squeak & Rattle simulation approach is to correlate the results to a real squeak or rattle phenomenon. This paper presents a new test procedure which enables the correlation between the results of the SAR-LINE™ simulation and the audible rattle occurrence. Three different configurations with increasing complexity were both tested and simulated. A pseudo random signal was used as load and the relative displacement was measured with the Laser Scanning Vibrometer in time domain. The movement in the gap and the rattle sound were recorded in a video sequence. The simulated results along the SAR line can directly be compared with the measured results along the gap. It is shown how the correlation between the rattle occurrence and the simulation results can be performed with the statistical evaluation approach of the SAR-LINE™ method. Beyond this the paper presents also the definition of a new output parameter which can be used for the squeak correlation. The new parameter includes both the time aspect and the main squeak direction which enables the comparison between the squeak occurrence measured with a stick-slip test machine and the simulated results. This type of Squeak & Rattle correlation increases clearly the capability of the SAR-LINE™ method, which is even more important when prototypes are no longer available during the design process.