T. Nakamura et al., FEM SIMULATION OF FRICTION TESTING METHOD BASED ON COMBINED FORWARD ROD-BACKWARD CAN EXTRUSION, Journal of tribology, 119(3), 1997, pp. 501-506
A new friction testing method by combined forward rod-backward can ext
rusion is proposed in order to evaluate frictional characteristics of
lubricants in forging processes. By this method the friction coefficie
nt mu and the friction factor m can be estimated along the container w
all and the conical die surface in the forward rod extrusion using the
oretical calibration diagrams representing the relationship between th
e punch travel, the forward rod extrusion length and mu or m without r
equirements of measuring the forming forces and the paw stress of the
workpiece. The theoretical calibration curves are obtained by rigid-pl
astic FEM simulations in a combined forward rod-backward can extrusion
process for a reduction in area R-b = 25, 50 and 70 percent in the ba
ckward can extrusion. It is confirmed that the friction factor m(p) on
the punch nose in the backward cart extrusion has almost no influence
on the calibration curves. The optimum initial height/diameter ratio
of the workpiece is 1.0-1.1. The influence of the workhardening index
on the calibration curves is insignificant in the range 0.1 less than
or equal to n less than or equal to 0.5. Experimental friction tests a
re carried out in a mechanical press with aluminium alloy A6061 as the
workpiece material and different kinds of lubricants. They confirm th
e analysis resulting in reasonable values for the friction coefficient
and the friction factor.