Understanding the Stick Slip behaviour of plastics and target setting: An OEM Perspective 2019-01-1465

Automotive OEMs are aggressively using different materials in their interior. This trend has increased in recent years due to value proposition and variety of options available for customers in market. Visual harmony, touch haptics, craftmanship and comfort are the driving factors to create different designs and options for customization. New trends like self-driving car and electrification increases the importance of comfort. Excessive usage of different grade plastics with zero gap philosophy can cause to stick slip effect leading to audible discomfort called squeak. Even though systems and subsystems are designed in best approach of structural design and manufacturing tolerances they are vulnerable to extreme environmental conditions and incompatible mating materials can initiate contacts leading to Squeak noise. One way to minimize the possibilities of squeak is by appropriate selection of mating material pairs. In present study, an understanding of stick slip behavior of different plastics is discussed, along with parameters required to focus during material incompatibility testing using a tribology test stand. Friction coefficient of different material pairs are analyzed for observing behavior patterns of squeak w.r.t time the two materials are in contact with each other with defined normal load and sliding velocity. The test results will lead to an initial study of behavior and patterns of friction coefficients and their influence on squeak and to some extent material ageing due to abrasion. Also, an OEM perspective is presented with focus on material selection using objective metrics like coefficient of friction and drive raw material suppliers to create materials which do not create stick slip effect. Finally, an algorithm has been developed using machine learning approach to estimate the stick slip performance and its acceptance as a reliable material pair.