A stereoscopic method for dihedral angle measurement

A new method is presented for the measurement of equilibrium dihedral angles in intergranular inclusions, and illustrated with pure copper containing 1 wt% lead. The method is based on the selective dissolution of inclusions visible along a polished metallographic section. Scanning electron microscopy stereo image pairs are then taken and processed so as to enable a three-dimensional digital reconstruction of the inclusion/matrix interface along each inclusion. Spherical caps describing the Cu/Pb interface over non-facetted orientations are then fitted to the measured digital inclusion envelope reconstructions. Knowing the center and radius of these spheres, the true dihedral angle of each specific inclusion can then be deduced with good precision. It is found that the true dihedral angle in the Cu/Pb alloy is not a unique function of temperature, reflecting the (known) anisotropy of high-angle grain boundary energy in coppe

Tensile strength of axially loaded unidirectional Nextel 610 (TM) reinforced aluminium: A case study in local load sharing between randomly distributed fibres

The tensile failure of unidirectional alumina fibre reinforced aluminium is studied in uniaxial loading along the fibre axis. The tensile strength is measured as a function of matrix yield strength, which is varied by varying the testing temperature, from RT to 600 degrees C. Over the range of matrix yield strength (i.e., of temperature) examined, the fracture mode remains brittle. Batdorf's (J Reinforced Plastics Compos 1982;1:153-164) simple ideal local load-sharing model describes well the observed behaviour, under the condition that it be adapted to account for the actual number of nearest neighbours characteristic of the fibre distribution in the composite. This is shown to be close to three, i.e., at variance with the usually assumed idealized hexagonal or square fibre arrangement patterns. (C) 2011 Elsevier Ltd. All rights reserved

Longitudinal deformation of fibre reinforced metals: Influence of fibre distribution on stiffness and flow stress

A computational analysis of the longitudinal deformation of continuous fibre reinforced metals is presented. Elastic and elastic-plastic matrix behaviour are considered. Analytical approaches are confronted with finite element analyses (FEA) for varying fibre distributions, ranging from single fibre unit cells to complex cells. Analysis of microfields shows that the main cause for deviation from the equistrain rule of mixtures is a stiffening effect of matrix confinement when surrounded by touching fibres arranged as "rings". Comparison with FEA shows that Hill's [J. Mech. Phys. Solids 12 (1964) 199, 213] bounds, although best possible in terms of volume fraction, are of limited value in so far as Hill's upper bound lies far above any practical limit for a fibre reinforced material, whereas Hill's lower bound loses its bounding property when extended to non-linear behaviour via an incremental scheme. This latter effect can be corrected by changing slightly Hill's derivation in a way that preserves the bounding property. Finally, implications are given for the derivation of in situ matrix flow stress curves from, experimental tensile curves on fibre reinforced composites. It is suggested that linear three-point bounds can in practice be used for this purpose. (C) 2004 Elsevier Ltd. All rights reserved

Local Approach of the Charpy Test at Low Temperature

Charpy V-notch impact testing is widely used in the toughness assessment of large forged components, e.g. the pressure vessel for pressurised water reactors (PWR). At low temperature, A508 Cl.3 nuclear pressure vessel steel fails by cleavage fracture. The results reported here are part of both an experimental program and numerical investigations which aim at the establishment of a non-empirical relationship between the lower shelf Charpy V-notch energy, CVN, and the fracture toughness, KIc, of this material. Here, the applicability of the Beremin cleavage fracture model to the Charpy specimen is demonstrated

Transmitted light microscopy of a fibre reinforced metal

A method is presented for studying fibre damage in continuous fibre reinforced composites. It is based on contrasting the transmission of light through intact translucent fibres with the light through fractured or dead-ended fibres. The method is applied in order to detect processing-induced fibre fractures in aluminium reinforced with continuous alumina fibres