Research on Squeak Noise from Polypropylene in Frictional Contact with Leather for Automotive Interior Assembly

To explore the mechanisms of squeak generation in automotive interiors, stick-slip experiments on polypropylene versus leather were conducted under various conditions. The friction properties were researched with changes in normal force, velocity, and temperature and static friction coefficients were generally lower at low temperature, higher at room temperature, and intermediate at high temperature and generally increased with an increase in velocity from 1 to 4 mm/s except in some individual cases. The dynamic friction coefficients as a whole presented a significant decrease but displayed similar trends in comparison with the static values. A simplified spring-mass model was built to illustrate the stick-slip physics of movement of polypropylene versus leather. The concomitant squeak characteristics are discussed. Risk priority indexes were acquired to evaluate the level of squeak noise. The inverse of the impulse rate obtained from stick-slip tests was perceived as the crucial threshold for squeak evaluation. A finite element simulation was developed to study the squeak problems of a trimmed vehicle door, and some risk locations were identified by comparing the maximal peak-to-peak amplitude of relative displacement in the main direction with the inverse of the tested impulse rate. The weak area where the squeak originated can be located from the modal contribution analysis for enhancement in the design phase.