Songklanakarin Journal of Science and Technology (SJST) (Jul 2009)
Microstructural simulation of three-point bending test with pre-crack: Effect of sample size and loading configuration
Abstract
Deformation behavior in three-point bending test of Mo-Si-B alloy specimens with pre-crack was investigated byrecourse to finite element analysis (FEA) with heterogeneous microstructures incorporated. The loading configuration wascarried out by moving the top pin down, while the bottom pin remained fixed. The Mo-Si-B alloy consists of hard, brittle T2(Mo5SiB2) phase embedded in a soft matrix of Mo solid solution. The sample contains pre-crack configuration at the middlein order to study the effect of the second phase (T2 particles) onto a crack tip during the bending test. Real optical micrographswere scanned, digitized, and meshed into a two dimensional model with constitutive relations of both phases. It was found that the plastic strain localization was not only caused by the hard T2 particles ahead of the crack tip, but also caused by the top pushing pin. This interaction between two strain fields was also observed if the microstructure were homogeneous. Two methodologies were explored in order to minimize this interaction in order to solely separate the effect of hard T2 particles ahead of the crack tip. The first one was to increase the distance between the top pin and the crack tip, while the second one was to approximate the pushing pin loading by end moment application. It was found that the strain interactionstill appeared in both cases.
