Barrelling test of t-section aluminium billet at room temperature

Abstract

During Compression Testing, a solid specimen (T in Cross-Section) is compressed axially between the punch and the bottom plates. As a result of this, the work piece material undergoes compression along with deformation which basically is Bulging at its centre position. In Compression or Upsetting, the presence of frictional constraints between the dies and the work piece directly affects the plastic deformation of the work piece. The friction at the faces of contact retards the plastic flow of metals around the surface and in its vicinity. A conical wedge of a relatively un-deformed metal is formed directly below it while the rest of the cylindrical metal suffers high strain hardening and subsequently bulges out. However, in practice, the use of lubricants greatly reduces the degree of bulging to a great extent. Hence it is necessary to apply a correction factor for the purpose of bulging design of die. For a ductile material like Aluminium used here lateral distortion takes place and due to restraining influence of friction of the load faces, the cross section becomes greater at the centre, the test piece taking up a barrel shape. Hence this is termed as Barrelling. In this particular experimentation the object geometry of Aluminium specimen under different percentage deformation is recorded and the barrelling radius is calculated under the assumption that T-section billet can be considered as summation of rectangular and square billet placed perpendicular to each other. A relation between percentage deformation and the barrelling radius of the T-section specimen is obtained.