Material properties from small specimens using the punch and bulge test

The punch and bulge test provides a technique for the determination of mate rial 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 validate d by comparison with results from experiments, giving good agreement for th e punch force for two differing specimen materials. The finite element anal ysis has enabled punch force-displacement curves, von Mises stresses, equiv alent plastic strains and vertical deflections for the upper and lower surf aces of the disc to be obtained. The finite element model has also been used to determine the relationship b etween 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 o f 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 investigat ed 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 sign ificantly influenced by experimental uncertainties.