Organizational Unit:

George W. Woodruff School of Mechanical Engineering

Permanent Link

https://hdl.handle.net/1853/70728

Parent Organization

Organizational Unit

College of Engineering

Includes Organization(s)

Organizational Unit

Advanced Mechanical Bipedal Experimental Robotics Lab

Organizational Unit

Computational Reactor and Medical Physics Laboratory

Organizational Unit

Cryo Lab

Organizational Unit

Environmentally Conscious Design and Manufacturing

Organizational Unit

Fusion Research Center

Show 4 more

ArchiveSpace Name Record

https://finding-aids.library.gatech.edu/agents/corporate_entities/120

Full item page

Publication Search Results

Now showing 1 - 10 of 26

Analysis of Mesostructure Unit Cells Comprised of Octet-truss Structures

(Georgia Institute of Technology, 2006-08) Johnston, Scott R. ; Rosen, David W. ; Reed, Marques ; Wang, Hongqing Vincent

A unit truss finite element analysis method allowing non-linear deformation is employed to analyze a unit cell comprised of n3 octet-truss structures for their stiffness and displacement compared to their relative density under loading. Axial, bending, shearing, and torsion effects are included in the analysis for each strut in the octet-truss structure which is then related to the mesostructure level (unit cell). The versatility of additive manufacturing allows for the fabrication of these complex unit cell truss structures which can be used as building blocks for macro-scale geometries. The finite element calculations are compared to experimental results for samples manufactured on a Stereolithography Apparatus (SLA) out of a standard resin.
Design of a Graded Cellular Structure For an Acetabular Hip Replacement Component

(Georgia Institute of Technology, 2006-08) Johnston, Scott R. ; Rosen, David W. ; Wang, Hongqing Vincent

The state-of-the-art porous coatings become more and more popular in uncemented prostheses to make bone grow into implants for biological fixation. In this paper, graded cellular structures are proposed for uncemented prostheses to enhance stability on implant-bone interfaces. As an example study, the authors develop a new acetabular implant with gradient porosity for hip replacement. A gradient porous acetabular component with cellular structure could match the bone’s elasticity. Material is adaptively distributed from high porosity at the bone-implant interface to solid metal at the joint’s articulating surface. The new acetabular prosthesis would replace metal-on-polyethylene bearing with metal-on-metal bearing for less wear. The design problem of acetabular component is formulated and a requirement list is elaborated. A detailed design of the prosthesis with a graded cellular structure is presented. The design concept is validated with a comparison to the existing products according to the design requirements.
Design Synthesis of Mesoscopic Cellular Structures With Unit Truss Approach and Particle Swarm Optimization Algorithm

(Georgia Institute of Technology, 2006-08) Williams, Chris ; Rosen, David W. ; Wang, Hongqing Vincent

Cellular material structures have been engineered at the mesoscopic scale for high performance and multifunctional capabilities. However, the design of adaptive cellular structures - structures with cellular configurations, sizes, and shapes designed for a specific geometric and loading context - has not been sufficiently investigated. In this paper, the authors present a design synthesis method with the use of unit truss approach and particle swarm optimization algorithm to design adaptive cellular structures. A critical review is presented to show the pros and cons of the new design synthesis method and an existing homogenization method. The research extends the application of additive manufacturing in the design of new materials for high performances and benefits its long-term growth.
Design of General Lattice Structures for Lightweight and Compliance Applications

(Georgia Institute of Technology, 2006-07) Rosen, David W. ; Johnston, Scott R. ; Reed, Marques

The primary goal is to design parts with lattice mesostructure and demonstrate that they have better structural and/or compliance performance, per weight, than parts with bulk material, foams, or other mesostructured approaches. Mesostructure refers to features within a part that have sizes between micro and macro-scales, for example, small truss structures, honeycombs, and foams. The versatility of additive manufacturing allows for the fabrication of these complex unit cell lattice structures which can be used as building blocks for macro-scale geometries. A method and software system have been developed to synthesize lattice mesostructure parts and compliant mechanisms in 2D and 3D. Underlying the synthesis method is a new analytical model of unit lattices, used to compose larger structures. Axial, bending, shearing, and torsion effects are included in the analysis for each strut in the lattice structure which is then related to the mesostructure level (unit cell). A unit lattice finite element analysis method allowing nonlinear deformation is employed to analyze a unit cell comprised of n[3] unit structures for their stiffness and displacement compared to their relative density under loading. Aerospace and biomedical applications are demonstrated.
Why Are Intervals and Imprecision Important In Engineering Design?

(Georgia Institute of Technology, 2006-02) Aughenbaugh, Jason Matthew ; Paredis, Christiaan J. J.

It is valuable in engineering design to distinguish between two different types of uncertainty: inherent variability and imprecision. While variability is naturally random behavior in a physical process or property, imprecision is uncertainty that is due to a lack of knowledge or information. There are many sources of imprecision in design. Sequential decision making introduces imprecision because the results of future decisions are unknown. Statistical data from finite samples of environmental factors are inherently imprecise. Bounded rationality leads to imprecise subjective probabilities. Expert opinions and judgments often are imprecise due to a lack of information or conflict. Behavioral simulations and analysis models are imprecise abstractions of reality. Knowledge of a decision maker's preferences may be imprecise due to bounded rationality or other constraints. Consequently, the engineering design community needs efficient computational methods for interval data and imprecise probabilities in order to support decision making in the design process. This paper introduces these sources and needs, with the aim of forming a foundation for future collaboration with the reliable engineering computing community.
Computational Methods for Decision Making

(Georgia Institute of Technology, 2006-02) Bruns, Morgan Chase ; Paredis, Christiaan J. J. ; Ferson, Scott

In this paper, we investigate computational methods for decision making based on imprecise information in the context of engineering design. The goal is to identify the subtleties of engineering design problems that impact the choice of computational solution methods, and to evaluate some existing solution methods to determine their suitability and limitations. Although several approaches for propagating imprecise probabilities have been published in the literature, these methods are insufficient for practical engineering analysis. The dependency bounds convolution approach of Williamson and Downs and the distribution envelope determination approach of Berleant work sufficiently well only for open models (that is, models with known mathematical operations). Both of these approaches rely on interval arithmetic and are therefore limited to problems with few repeated variables. In an attempt to overcome the difficulties faced by these deterministic methods, we propose an alternative approach that utilizes both Monte Carlo simulation and optimization. The Monte Carlo/optimization hybrid approach has its own drawbacks in that it assumes that the uncertain inputs can be parameterized, that it requires the solution of a global optimization problem, and that it assumes independence between the uncertain inputs.
Applying Information-Gap Decision Theory to a Design Problem having Severe Uncertainty

(Georgia Institute of Technology, 2006-01) Duncan, Scott Joseph ; Paredis, Christiaan J. J. ; Bras, Berdinus A.

Often in the early stages of the engineering design process, a decision maker lacks the information needed to represent uncertainty in the input parameters of a performance model. In one particular form of severely deficient information, a nominal estimate is available for an input parameter, but the amount of discrepancy between that estimate and the parameter’s true value, as well as the implications of that discrepancy on system performance, are not known. In this paper, the concepts and techniques of information-gap decision theory (IGDT), an established method for making decisions robust to severely deficient information, are examined more closely through application to a design problem with continuous design variables. The uncertain variables in the chosen example problem are parameters of a probability distribution, so the relationship between IGDT and design approaches considering precise and/or imprecise probabilities is explained. Insight gained from a walkthrough of the design example is used to suggest the types of problems an IGDT approach will or will not effectively solve as well as potential limitations that could be encountered when solving more complex problems.
Eliminating Design Alternatives Based on Imprecise Information

(Georgia Institute of Technology, 2006) Recuk, Stephen Joseph ; Aughenbaugh, Jason Matthew ; Bruns, Morgan Chase ; Paredis, Christiaan J. J.

In this paper, the relationship between uncertainty and sets of alternatives in engineering design is investigated. In sequential decision making, each decision alternative actually consists of a set of design alternatives. Consequently, the decision-maker can express his or her preferences only imprecisely as a range of expected utilities for each decision alternative. In addition, the performance of each design alternative can be characterized only imprecisely due to uncertainty from limited data, modeling assumptions, and numerical methods. The approach presented in this paper recognizes the presence of both imprecision and sets in the design process by focusing on incrementally eliminating decision alternatives until a small set of solutions remains. This is a fundamental shift from the current paradigm where the focus is on selecting a single decision alternative in each design decision. To make this approach economically feasible, one needs efficient methods for eliminating alternatives—that is, methods that eliminate as many alternatives as possible given the available imprecise information. Efficient elimination requires that one account for dependencies between uncertain quantities, such as shared uncertain variables. In this paper, criteria for elimination with and without shared uncertainty are presented and compared. The set-based nature of design and the presence of imprecision are introduced, elimination criteria are discussed, and the overall set-based approach and elimination criteria are demonstrated with the design of a gearbox as an example problem.
Intention Aware Interactive Multi-Modal Robot Programming

(Georgia Institute of Technology, 2003-10) Paredis, Christiaan J. J. ; Khosla, Pradeep K. ; Iba, Soshi

As robots enter the human environment, there are increasing needs for novice users to be able to program robots with ease. A successful robot programming system should be intuitive, interactive, and intention aware. Intuitiveness refers to the use of intuitive user interfaces such as speech and hand gestures. Interactivity refers to the system's ability to let the user interact preemptively with the robot to take its control at any given time. Intention awareness refers to the system's ability to recognize and adapt to user intent. This paper focuses on the intention awareness problem for interactive multi-modal robot programming system. In our framework, user intent takes on the form of a robot program, which in our context is a sequential set of commands with parameters. To solve the intention recognition and adaptation problem, the system converts robot programs into a set of Markov chains. The system can then deduce the most likely program the user intends to execute based on a given observation sequence. It then adapts this program based on additional interaction. The system is implemented on a mobile vacuum cleaning robot with a user who is wearing sensor gloves, inductive position sensors, and a microphone.
Environmental Benchmarking of Medium-sized TVs Sold in North America, Europe and Asia (China)

(Georgia Institute of Technology, 2003) Carlier, Taco ; Duncan, Scott Joseph ; Boks, Casper B. ; Stevels, Ab ; Bras, Berdinus A.

The environmental benchmarking procedure as developed by the Design for Sustainability Lab of Delft University of Technology and the Environmental Competence Centre of Philips Consumer Electronics has been applied to TVs sold in the market in three continents: North America (USA), Europe and Asia (China). For each region three or four products of different brands have been considered. In total some fifty parameters, which are relevant for the environmental performance have been measured. These measurements allow making calculation of 2002 another project was completed in life cycle performance of the products (based on the Eco Indicator 95 system). The results show big differences in all categories; no brand scores consistently best in all focal areas. It will be concluded that although TVs are seemingly a mature product, different design tradition, different supplier base and difference in speed of latest technology make that in practice differences up to 50% in life cycle performance have been found. Also between products sold in the three regions of the world clear differences were found (although not as big as between best and worst brand performances.) Only partly this observation can be explained by differences in for instance environmental legislation. It will be speculated to what extent the structure of the value chain is responsible. It will be concluded that environmental benchmarking is a powerful tool to systematically track down design improvements and to check on supplier relationships.