Yeoman et al., A constitutive model for the warp-weft coupled non-linear behavior of knitted biomedical textiles, Biomaterials, 31 (32), 2010:8484–8493
Knitted textiles have been used in medical applications due to their high flexibility & low tendency to fray. In this paper, a constitutive model for soft tissue was utilised to represent the non-linear warp-weft coupled mechanics of knitted textile structures. The constitutive relationship was implemented in an FEA model, where it was verified & validated under warp & weft uniaxial tensile tests. A genetic algorithm (GA) with step-wise increases in resolution & linear reduction in range of the search space was developed for the optimization of fabric model coefficients, for a number of physical fabric samples. For three fabrics tested, the predicted mechanics correlated well with physical data, however, the model exhibited limitations in approximating the linear elastic behaviour of the fourth fabric. With proposals to address this limitation & to incorporate time-dependent changes in the fabric mechanics associated with tissue ingrowth, the constitutive model offers a tool for the design of tissue regenerative knit textile implants (click link below for published abstract).
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Yeoman et al. The Use of Finite Element Methods & Genetic Algorithms in Search of an Optimal Fabric Reinforced Porous Graft System, Annals of Biomedical Engineering, 37 (11) 2009:2266-2287
The mechanics of arteries result from the properties of the soft tissue constituents & the interaction of the wall layers, predominantly media & adventitia. This concept was adopted in this study for the design of a tissue regenerative vascular graft. To achieve the desired structural properties of the graft, most importantly a diametric compliance of 6%/100 mmHg, finite element methods & Genetic Algorithms (GA) were used in an integrated approach to identify the mechanical properties of an adventitial fabric layer that were required to optimally complement an intimal/medial polyurethane layer with various interconnected porosities. The combination of finite element methods & genetic algorithms was shown to successfully optimize the mechanical design of the composite graft. The method offers potential for the application to alternative concepts of modular vascular grafts & the incorporation of tissue ingrowth & biodegradation (click link below for published abstract).
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Yeoman et al., Investigating the potential advantages of a new design metacarpophalangeal joint, Proc. IMechE Vol. 223 Part H J. Engineering in Medicine, 2009:839-847
This paper investigates a new metacarpophalangeal joint design aimed at treating patients with moderate to severe forms of arthritis affecting the index, long, ring, & little fingers. Current small joint arthroplasty designs, including those for the metacarpophalangeal joint of the hand, have had limited success owing to mechanical failures & can be divided into two main families: single-piece elastomer implants & surface articulating implants. The design proposed consists of metacarpal & proximal phalangeal articulating housings & a central flexible spanning elastomer rod that maintains the alignment of the metacarpal & proximal phalangeal components. A finite element model was used to assess the design, & the wear of the articulating bearing surfaces for different material combinations. This finite element analysis showed the design would endure the long term loading conditions & the articulating surface & elastomeric rod wear rates are acceptable (click link below for published abstract).
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