Fundamental abrasive contact at high speeds: Scratch testing in experiment and simulation

Abstract

The understanding and experimentation of abrasive wear mechanisms at high speeds is still poorly investigated in literature. This is mainly due to a lack of suitable, well-instrumented test rigs for fundamental, single abrasive wear events. Standard scratch tests, which are often utilized for studies of abrasion phenomena, operate in the low-speed range up to some mm/s, while applications suffering from abrasive wear often operate at speeds exceeding 1 m/s (e.g., rolling, grinding, machining). Numerical approaches, especially particle-based methods, allow the simulation of such fast deformation processes, but rely on hardening models that require a precise knowledge of material parameters. Thus, the Johnson-Cook material model was parametrized using data from high-speed compression tests of pure aluminum. A series of scratch tests with increasing depths were then simulated using the particle-based Material Point Method (MPM). Experimentation was done on a pendulum scratch test rig equipped with a Rockwell C diamond cone. By adjusting the balance point of the swing arm of ∼1 m length, a velocity of 6.8 m/s was achieved at its tip as measured with a high-speed camera. Scratches of several depths were performed, and their force signals acquired. Post-test analyses comprised topography measurements and EBSD on cross-sections of the scratches to investigate the microstructural changes due to the high-speed wear event. Scratch topographies and abrasive mechanisms compared favorably between experiment and simulation for the aluminum. The extent of strain hardening was significantly reduced compared to low-speed experiments. The calibration of the high-speed force sensor was successful and now allows the investigation of new alloys and determination of material parameters under high-speed abrasive conditions.