COMPRESSIVE DEFORMATION OF AMORPHOUS PD40NI40P20

In uniaxial compressive deformation of Pd40Ni40P20 glass the angle between the plane of the shear bands and the compression axis is observed to be approximately 42°, increasing with compressive strain. This indicates that the yield process is dependent on the normal stress acting on the slip plane. The yield stress in plane strain compression is almost equal to the yield stress in uniaxial compression. Both these observations show that yielding in this glass is controlled by a Mohr-Coulomb or Tresca criterion, rather than the von Mises criterion appropriate for crystalline metals, and this confirms that the flow mechanism is intrinsically different from that in crystalline metals and similar to that which operates in amorphous polymers which dilate during flow.