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UBC Theses and Dissertations

A comparison between XFEM and SPH in solving two-dimensional fracture mechanics problems, with applications in food breakdown modeling Pourahmadi-Meibodi, Baharan


Masticatory performance and the occlusal force are two of the main clinical metrics that are used to evaluate the masticatory function objectively. A comprehensive evaluation of masticatory function requires a correlative inspection of these two metrics. The complex multi-variant nature of the human mastication and the limitations of visualization and clinical measurement techniques, complicates the clinical investigation of masticatory function. A biomechanical model of oral food breakdown has the ability to bypass these difficulties. The currently available food breakdown models are either highly dependent on experimental data or are focused on food engineering applications. In this thesis, we attempted to solve these issues by building a two-dimensional fracture mechanics model to simulate the oral food breakdown. The different computational methods available to solve fracture mechanics problems have limits and strengths, which affects the accuracy of their solution. Extended Finite Element Method (XFEM) and Smoothed Particle Hydrodynamics (SPH) method use two very distinct approaches to solve fracture mechanics problems; comparing the effectiveness of these two methods can provide valuable insights into the computational possibilities. As the classical SPH formulation for solid mechanics suffers from numerical deficiencies, we first performed a set of modifications to build a corrected SPH model for solid and fracture mechanics. We solved fracture mechanics benchmark tests using XFEM and the modified version of SPH and investigated their strengths and weaknesses thoroughly. The SPH method eventually was selected to model the food breakdown procedure. We simulated the food breakdown following one chewing stroke using our two-dimensional SPH fracture model and measured the corresponding occlusal force and masticatory performance for a range of different food properties. The food breakdown model was able to simulate the experimental correlation between masticatory performance and the food properties. Although the simulated measurements for occlusal force were in accordance with the previous experimental studies, further detailed clinical investigation is required to validate the force pattern during chewing. The simplified biomechanical model of oral food comminution described in this work can be regarded as the first step toward building a patient-specific model to pre-assess the patient’s masticatory function following a maxillofacial reconstructive surgical plan.

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