Investigation of Influencing Parameters for Tribological Conditions in Dry Forming Processes

doi:10.1007/s40195-015-0343-4

Abstract

Abstract:

Environmental awareness and a growing demand for efficient resource utilization encourage the realization of lubricant-free forming processes. A first step in accomplishing dry sheet metal forming is to gain knowledge about the changing tribological conditions and to ide.jpgy the relevant influencing parameters. The commonly used flat strip drawing test was selected to investigate the tribological conditions in the flange area of deep drawing processes. The influencing factors of contact pressure and varying drawing velocities were analyzed under dry and lubricated conditions. Additionally, the tool and workpiece surfaces were characterized. Besides lubrication, the contact pressure mainly determines the tribological conditions. In lubricated tests higher normal pressure reduces friction, whereas without lubrication higher pressure results in slightly increasing friction. A changing drawing velocity affects the friction when lubricant is applied. In dry experiments, no influence of velocity was found. Results of surface characterization reveal adhesion as main wear mechanism under dry conditions. Based on the investigated influence of the process parameters, an increase in process understanding for dry forming operations is derived.

Key words: Deep drawing, Tribology, Friction, Dry forming

Jennifer Steiner, Marion Merklein. Investigation of Influencing Parameters for Tribological Conditions in Dry Forming Processes[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(12): 1435-1441.

Figures/Tables 10

Fig. 1 Schematic diagram of the setup of flat strip drawing test

Fig. 2 Dimension and initial topography of friction jaw a and sheet metal strip b

Table 1 Experimental design and test parameters (nAA6014 = 3)

Velocity V_rel (mm/s)	50, 100 and 150
Normal Pressure p_N (MPa)	1.0, 1.5 and 2.0
Lubricational condition	Lubricated with 2.0 g/m² KTL N 16 and dry condition

Fig. 3 Resulting friction coefficient under a lubricated and b dry conditions

Fig. 4 Schematic diagram of the wear mechanism under dry conditions with aluminum alloys

Fig. 5 Comparison of drawing force-drawing length curve for strips No. 1 and No. 3

Fig. 6 Evaluation of areal percentage of adhesion

Fig. 7 Correlation of friction coefficient and areal percentage of adhesion under dry condition

Fig. 8 Surface morphologies after strip drawing tests for friction jaw a-f and strip No. 1 g-i under different normal pressures: a, d, g 1.0 MPa; b, e, h 1.5 MPa; c, f, i 2.0 Mpa

Fig. 9 Reduced peak height (Spk) of tool surface and areal fraction of adhesion for dry tests

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