Analysis of Bi-Axial and Tri-Axial State of Stresses in Plastically Deformed Solid Cylindrical Specimens under Dry Lubrication

Abstract

his paper explains the type of stresses induced in the AA2014 solid cylindrical specimens when deformed plastically between a set of rigid dies. The solid cylindrical specimens machined to different height (h) to the diameter (d) ratios namely h/c1=1, h/d=0.75 and h/d=0.5 were compressed between the two flat cylindrical dies using a 100 ton capacity UTM. These billets were deformed to different strain levels. At each and every stage of the incremental strain, the various elements of the geometry such as contact diameter at the die/billet interface, bulged diameter at the equatorial region and the height after deformation were noted down. The significance of measuring the various elements of the geometry is to predict the value of stresses namely axial stress, hoop stress, hydrostatic stress and effective stress which influence the ductility or formability of the material. The stresses induced in the billets were predicted using the empirical equations and a comparison has been made for uni-axial, bi-axial and tri-axial state of stresses for different aspect ratios. A notified behavior in the value of stresses has been observed for all the aspect ratios and for different state of stresses.