Person:
Rosen, David W.

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Now showing 1 - 6 of 6
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    Manufacturing Cellular Materials Via Three-Dimensional Printing of Spray-dried Metal Oxide Ceramic Powder
    (Georgia Institute of Technology, 2007) Rosen, David W. ; Williams, Christopher Bryant
    Cellular materials, metallic bodies with gaseous voids, are a promising class of materials that offer high strength accompanied by a relatively low mass. Unfortunately, existing manufacturing techniques constrain a designer to a predetermined part mesostructure, material type, and macrostructure. In this paper, the authors document their design rationale for the selection of the Three-Dimensional Printing (3DP) additive manufacturing process as a means to fabricate metallic cellular materials. This is achieved by selectively printing a solvent into a bed of spray-dried metal oxide ceramic powder. The resulting green part undergoes reduction and sintering post-production processes in order to chemically convert it to metal.
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    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.
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    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.
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    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.
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    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.
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    Towards the Design of a Layer-Based Additive Manufacturing Process for the Realization of Metal Parts of Designed Mesostructure
    (Georgia Institute of Technology, 2005) Mistree, Farrokh ; Rosen, David W. ; Williams, Christopher Bryant
    Low-density cellular materials, metallic bodies with gaseous voids, are a unique class of materials that have high strength, good energy absorption characteristics, good thermal and acoustic insulation properties, accompanied by an extremely low mass. Unfortunately, current cellular material manufacturing processes severely limit a designer's ability to control the part mesostructure, the material composition, and the part macrostructure. As such, the authors look towards the use of layer-based additive manufacturing (AM) as a means of providing the design freedom that is currently absent from cellular material manufacturing processes. Since current metal-based AM techniques do not offer an adequate means of satisfying the unique requirements of cellular materials, the authors carry out the conceptual design of a new AM process that is dedicated to the manufacture of cellular materials. Specifically, the authors look to the layer-based additive fabrication of metal oxide powders followed by post-processing in a reducing atmosphere as a means of fabricating three-dimensional, low-density cellular metal parts with designed mesostructure. In this paper, the authors detail this conceptual design process and select working principles that are worthy of further investigation. Insights gained as a result of designing an AM process for a specific class of geometry (e.g. considerations for small wall thickness, high quality surface finish, internal voids, and support material) and investigating the use of AM for production-scale manufacturing are also detailed.