Browsing by Subject "Computer aided engineering"

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    An interactive design framework based on data-intensive simulations: implementation and application to device-tissue interaction design problems
    (2015-02) Lin, Chi-Lun
    This dissertation investigates a new medical device design approach based on extensive simulations. A simulation-based design framework is developed to create a design workflow that integrates engineering software tools with an interactive user interface, called Design by Dragging (DBD) \cite{Coffey:2013ko}, to generate a large-scale design space and enable creative design exploration. Several design problems illustrate this design workflow are investigated via featured forward and inverse design manipulation strategies provided by DBD. A device-tissue interaction problem as part of a vacuum-assisted breast biopsy (VAB) cutting process is particularly highlighted. A tissue-cutting model is created for this problem to simulate the device-tissue contact, excessive tissue deformation and progressive tissue damage during the cutting process. This model is then applied to the design framework to generate extensive simulations that samples a large design space for interactive design exploration. This example represents an important milestone toward simulation-based engineering for medical device prototyping. The simulation-based design framework is implemented to integrate a computer aided design (CAD) software tool, a finite element analysis (FEA) software tool (SolidWorks and Abaqus are selected in this dissertation) and a high performance computing (HPC) cluster into a semi-automatic design workflow via customized communication interfaces. The design framework automates the process from generating and simulating design configurations to outputting the simulation results. The HPC cluster enables multiple simulation job executions and parallel computation to reduce the computation cost. The design framework is first tested using a simple bending needle example, which generates 460 simulations to sample a design space in DBD. The functionality of the creative inverse and forward design manipulation strategies are demonstrated. A tissue cutting model of a VAB device is developed as an advanced benchmark example for the design framework. The model simulates the breast lesion tissue being positioned in a needle cannula chamber and being cut by a hollow cutting tube with simultaneous rotation and translation. Different cutting conditions including cutting speeds and tissue properties are investigated. This VAB device design problem is then applied to the design framework. Critical design variables and performance attributes across three main components of the VAB device (the needle system, motor system and device handpiece) are identified. 900 design configurations are generated and simulated to sparsely populate a large-design space of $10^6$ possible solutions. The design space is explored via the creative design manipulation strategies and several uses cases are established. The bending needle example demonstrates the first success of the proposed simulation-based design framework. The 460 simulations are completed with minimal manual interventions. The functionality of DBD is also demonstrated. The inverse and forward design strategies allow interacting with the design space via dragging on a radar chart widget or directly on the visualization of the simulation. Through the interactions the user is guided to the desired solutions.The VAB tissue-cutting example provides a realistic medical device application of the design framework. The 900 simulations are completed in parallel in the HPC cluster so that the computation time is significantly reduced. The simulation output data is converted to a high-efficiency data format called NetCDF so that the post-compuation for sampling this large design space is made possible. Several use cases are demonstrated. By interacting with the radar chart widget, the user gradually gains the understanding and new insights about the effect of design variable modifications. Next, the direct manipulation strategies via visualization of the simulations are used to solve three issues, including a 'dry tap', moving a leading edge of the tissue sample and narrowing a stress concentration area. These use cases successfully demonstrated the capability and the usability of the design framework.There are two major contributions of this dissertation. The first is the investigation of the new design approach that enables creative design exploration based on extensive simulation data. This success moves a step toward the simulation-based medical device engineering with big data. The second is the FEA simulation model for the VAB tissue cutting process. This model utilizes realistic breast tissue properties to predict cutting forces during the VAB sampling process, which has not been found in the literature. The studies conducted using this model extend the current understanding of the VAB tissue cutting process under different cutting conditions. All of these achievements illustrate the potential for a future medical device virtual prototyping environment.