(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.
(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.
(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.