The ring compression test as simulation test for the investigation of friction in hot metal forming

Abstract

Forces and flow of material in metal working decisively depend on friction between workpiece and tool, which can be described by the friction factor m. For investigation of the influence of friction in hot forming of steel and for measurement of the friction factor, the ring compression test is used as simulation test. The influences of material, reduction, strain rate, temperature, and lubricant are discussed.

Effect of natural boundary conditions on the upper-bound analysis of upset forging of ring and disks

“…(8)) proposed by Yang and Kin [12] whereas the VUB solution employed the stream function (Eq. (24)) that is modified in this work by adding an additional higher order term to the one producing the UB solution. As mentioned previously, we do modify the stream function in this manner so that both the VUB and corresponding traditional UB solutions can be numerically determined under the same degree of freedom through the optimal scheme.…”

“…Before deformation models have achieved the goal of predicting the bulge profile as well as the forming load of the upset ring, none of them can account for natural boundary conditions that, in a certain sense, physically reflect the effect of the interfacial frictional condition as observed experimentally [1,2,7,8,12,19,[23][24][25]. Experimental results of upset rings and disks, [7,8,19,23,25], show that various types of lubricants applied on the interface considerably influence the shape of the bulged profile and the forming load.…”

“…-(24), the VUB solution was numerically determined under the same degree of freedom as the corresponding UB solution.…”

Effect of natural boundary condition and the neutral surface of nonlinear type on the upper-bound solution to upset forging of rings using a variational approach

“…Nagpal et al (1978) used the stream function to define a kinematically admissible velocity field for the analysis of the problems of the upset forging of rings, where the axial velocity is derived as a function of the axial and radial directions to account for the effect of material hardening and temperature on the forming process. Although most velocity fields mentioned in the foregoing have been demonstrated properly in predicting the bulge profile as well as the forming load of the upset ring, none of them can account for natural boundary conditions that, in a certain sense, physically reflect the effect of the interfacial frictional condition as observed experimentally (Lee and Altan, 1972;Nagpal et al, 1978;Yang and Kin, 1986;Liu, 1972;Male and Cockcroft, 1964;Saida et al, 1970;Male and Depierre, 1970;Pawelski et al, 1989;Hsiang and Huang, 1991;Moon and Van Tyne, 2000). Experimental results of upset forgings of rings and disks (Lee and Altan, 1972;Nagpal et al, 1978;Liu, 1972;Male and Depierre, 1970;Hsiang and Huang, 1991) show that various types of lubricants applied on the interface considerably influence the shape of the bulged profile and the forming load.…”

Simulation studies on ring upsetting using the Abaqus software

“…Cockford is cited by many authors, including Gieżyńska [5], Sofuoglu and Gedikli [16]. Further studies of this method were conducted among others by Wang and Lenard [18] and also Pawelski et al [15]. It should be noted that, using current advancement of computational methods (FEM), nomograms for determining friction coefficients can be built on the basis of deformation of samples which are not ring-shaped.…”