Measurement of Young's modulus and tensile failure properties of green powder compacts

Abstract

The paper describes a series of tests that use an instrumented die, unconfined compression of a cylinder, three point bending and Brazilian disc test to explore the elastic modulus and tensile failure in powder compacts. Through the use of common powders test methods are benchmarked against each other. The results show that modulus data from the instrumented die does not depend on data reduction method, however it does exhibit the influence of die dilation at high pressures, made evident in a reduction in modulus at higher density levels. Modulus data from the unconfined compression of a cylindrical compact lead to a lower level of modulus in comparison with the instrumented die test, due principally to the removal of confining and frictional effects at the die wall. Modulus data obtained from three point bending are again lower than that obtained from the unconfined compression test. At this time, this is attributed to the anisotropy within the compact and the relationship between sample compression and tensile loading direction. Powder tensile properties have been determined from the three point bending and Brazilian disc test in which a cylindrical sample is compressed across its diameter. In this instance, diametral compression leads to a lower failure stress, attributed to the influence of compact anisotropy. With regard to powder behaviour, lubricant addition level for DistaloyAE has only a small effect on Young's modulus as determined by the unconfined compression test. The modulus of the DistaloyAE powder increases at the higher density attributable to increased bonding between particles under this condition.