Influence of contact friction on the experimental determination of the balanced biaxial strain-ratio using the disc compression test

Abstract

In the present work the disc compression test used to determine the balanced biaxial strainratio r b is analyzed in terms of the influence of contact friction using non-linear finite element analysis (FEA). The FEA results reveal an unexpectedly strong sensitivity of the r(b)-value on contact friction, which is discussed in detail. The most important outcome of the present work is that the FEA can reproduce the r(b)-value imposed by the utilized yield function very well, but only when the prescribed Coulomb friction coefficient has a very small value; for increasing friction coefficients a gradual deviation from the imposed r(b)-value can be observed. This finding implies that in experiments contact friction must be eliminated to a larger extent than commonly expected, otherwise the determined r(b) value using disc compression testing will considerably deviate from the actual one, particularly when r(b) is far from one.