Abstract
Metal pickup is a phenomenon that can be observed during dynamic braking with automotive disc brakes. Hard metallic particle agglomerations embedded in the friction materials rubbing surface can lead to severe disc scoring, accelerated wear and deterioration of the friction surface of either brake disc or brake pad [1]. Knowing, how the mechanism of metal pickup generation works, would be very helpful for material development and for failure mode analysis in the various and still existing cases all over the friction industry. This paper describes the experimental observation during the generation and dynamic growth of metal pickup in the friction interface. A commercial friction couple of an organic brake pad and a cast iron brake disc material are used on a small sample tester. This high load tribometer enables us to replicate real vehicle driving conditions under lab conditions. The friction force is measured whilst the test generates the metal agglomeration in the friction surface. The observed characteristic of the friction behaviour can be seen in direct relation to the generation of the metal pickup process in the friction interface. The exact number of brake applications needed to generate the metal pickup can therefore be narrowed down to a maximum of 12. The measured friction power indicates a steep rise as the metal pickup materialises. The presented methodology showed a close correlation to the generation of the metal pickup, so the exact moment and dynamic growth can only be estimated with a certain amount of uncertainty. The paper describes the continuation of the research work of metal pick up which was last reported 2011[1]. The newly developed experimental setup now for the first time allows a measurement of the friction force in the phase when the metal fish is generated. The work will be continued with further experiments and simulations.
KEYWORDS – metal pick up, high load tribotester, wet friction, asperity contacts