Browsing by Subject "Finite element analysis"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Structural Mechanics Characterization of Steel Intermeshed Connections
    (2020-07) Shemshadian, MohammadEbrahim
    This thesis presents the efforts to develop a new class of steel connection named the “Intermeshed Connection” for gravity load resistance in frame structures. The thesis investigates the performance of the connection system using physical testing and numerical simulation, as well as methods for its design. The project herein lays the groundwork to transform the steel building construction industry by advancing the underlying science and engineering precepts for intermeshed connections created from precise, volumetric cutting. Advanced manufacturing techniques, such as high-definition plasma, water jet, and laser cutting, are powerful tools that offer fast operation and precise finish in the process of steel fabrication. To date, this class of advanced manufacturing equipment has only been used to accelerate traditional processes for cutting sheet metal or other conventional fabrication activities (e.g. cutting instead of drilling holes). Such approaches have not capitalized on the equipment’s full potential. The intermeshed connection is intended to exploit this potential by harnessing advanced cutting technologies for volumetric cutting open steel sections, which results in precise steel pieces that can intermesh (i.e. interlock) with each other and form a connection. In such connections, loads transfer mainly through direct contact of the connection components rather than by traditional means through welds or bolts, which facilitates fast assembly and disassembly of steel structures and material reuse. The intermeshed system, if fully automated, can enhance the integration between design, fabrication, and installation. Although the intermeshed connection has multiple interesting features to offer, the idea of cutting of open steel sections poses challenges regarding the load-transfer mechanisms and failure modes for intermeshed connections. For instance, implementation of the cuts would cause discontinuity in the beam or formation of sharp corners in the specimen. The former could interrupt load paths, and the latter could increase stress concentrations. Therefore, to introduce the intermeshed connection system to engineering practice, the structural behavior of these connections needs to be fully understood and adequate performance under gravity loads needs to be demonstrated. The aim of the present study is to provide insight on the structural performance of the intermeshed connection at both global and local levels, and to investigate appropriate design methods. To reach this goal, numerous details of the intermeshed connection were considered, a design procedure was developed, physical specimens were designed and tested, and beams with intermeshed connections were analyzed using sophisticated numerical procedures. This investigation was conducted in a step-by-step state assessment of the intermeshed connection subjected to multiple scenarios of gravity loading and various support conditions. Load resistance and design of these connections were explored to evaluate the mechanics of intermeshed connections including stress and strain concentrations, effective material utilization, failure modes, and connection geometry optimization. Relying on the interaction of individual components, the intermeshed connection demonstrates ample load carrying capacity, stiffness, and ductility, which fulfilled the design requirements. This connection promises to be robust, secure, dismountable and offers the ability to be manufactured within current industrial tolerances and be erected quickly.