SIMULATION OF ASPERITY PLOWING IN AN ATOMIC-FORCE MICROSCOPE, PART-II- PLOWING OF ALUMINUM-ALLOYS

In this second part, we present results of plowing tests on three comm ercial aluminum alloys using the atomic force microscope technique pre sented in Part 1. Pure (99.99%) aluminum, 5182-O, and 7150-T6 were cho sen as substrates because of their different material properties. Thes e properties create different tribological conditions in processes suc h as rolling, forging, and extrusion where a metal workpiece flows pla stically due to contact with a hard tool surface having many asperitie s. In the present technique, a single plow track was generated with a sharp diamond indentor which simulated a single tool asperity. A serie s of plow tracks was thus generated on each substrate surface over a r ange of plowing speeds and normal forces. The resulting plow track geo metries and plowing forces were measured for input to the theoretical model presented in Part 1. The model was used to predict material flow stress as a function of normal force as well as friction factors at t he different indentor faces. The flow stress predictions from the mode l were compared with flow stress measurements from Vickers microhardne ss tests of each material. This helped to reveal possible scale effect s and highlight tribological phenomena that are peculiar to plowing. T he friction factor was found to be strongly dependent on the ratio of the measured ridge height to the depth of cut. This ratio is known to depend upon material properties such as strain hardening, elastic reco very, densification beneath the indentor, etc., that are not captured within the theoretical framework. Results from some plowing tests with a blunt indentor are reported and comparisons are made with those wit h the sharp indentor. (C) 1998 Elsevier Science S.A.