Material properties from small specimens using the punch and bulge test

Abstract

The punch and bulge test provides a technique for the determination of material properties from small specimens. Although the test has been in use for a number of years, the behaviour of the specimen is not fully understood. A finite element analysis of the test has thus been undertaken and validated by comparison with results from experiments, giving good agreement for the punch force for two differing specimen materials. The finite element analysis has enabled punch force-displacement curves, von Mises stresses, equivalent plastic strains and vertical deflections for the upper and lower surfaces of the disc to be obtained.

The finite element model has also been used to determine the relationship between the specimen yield stress and the punch force for elastic-perfectly plastic specimens. It is shown that a linear law applies over a 6:1 range of yield stresses and thus the punch and bulge test represents an effective method of yield stress measurement from small specimens.

The effect of experimental artefacts on the punch force has been investigated through finite element analysis and physical experiment. The punch force is shown to be effectively insensitive to small uncertainties in the test fixture and experimental conditions. Yield stress results are thus not significantly influenced by experimental uncertainties.