The effect of heterogeneous distribution of porosity on the flexural moduli of sintered iron bars

Bar shaped specimens were prepared from iron powder. The specimens possesse d a quasilayered distribution of porosity with porous outer regions and mor e dense core. For such specimens, the effective flexural moduli determined by means of flexural vibration parallel to the quasilayers were systematica lly higher than those determined from vibrations perpendicular to the quasi layers. When the more porous surface regions were more or less removed by g rinding, the difference between "parallel" and "perpendicular" moduli decre ased or even vanished. Such effect of surface regions of less stiffness was also confirmed theoretically by calculating the relevant moduli for model bars with quasilayered distribution of porosity.