Graduate Thesis Or Dissertation
 

Micromechanics of heterogeneous materials under compressive loading

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  • In mining and mineral processing, compressive loading is often encountered during the comminution of ore bearing minerals and in the wear resistant materials used in the comminution circuit. A common thread joining many of the materials that are primarily used under compressive loading is the presence of a high modulus reinforcement, either fiber or particulate, embedded within a lower modulus matrix phase (i.e., a brittle heterogeneous material). Many of these heterogeneous materials are designed or manufactured such that an imperfect interface (i.e., an interface that provides less than complete coherency between the reinforcing phase and the matrix) exists between the reinforcing phase and the matrix (e.g., tough fiber-reinforced ceramics). To date, most research has focused on the response of these heterogeneous materials with imperfect interfaces to tensile loading; however, little is known about their response to compressive loading. The principal objective of this investigation is to develop a better understanding of the micromechanical behavior of these complex materials under compressive loading. Analytical solutions are reviewed and compared with finite element models for the simulation of heterogeneous materials with imperfect interfaces under compressive loading. This comparison shows that a nonlinear numerical approach (finite element method) is necessary to fully simulate the behavior of these materials. To validate the nonlinear model, laser moire experiments were conducted on a model heterogeneous material loaded under uniaxial and biaxial compression. In-plane displacements were measured and found to be in fundamental agreement with the nonlinear finite element model. Subsequently, finite element simulations were developed for a variety of heterogeneous materials with imperfect interfaces. Results show that deleterious tensile stress concentrations are primarily influenced by three factors: (i) the nature of the imperfect interface, (ii) the moduli mismatch between the reinforcement and matrix, and (iii) the volume fraction of the reinforcement. Finally, crack initiation experiments in laboratory models of a heterogeneous material with a frictional imperfect interface were conducted to substantiate the prior work using nonlinear finite element models. Experimental results correlate well with the numerically-predicted micromechanical behavior of a model heterogeneous system under uniaxial compressive loading.
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file details LairdGeorgeII1994.pdf 2017-08-04 公开 下载