Experimental and analytical techniques for the assessment of in vitro implant migration in polymer foam models
Experimental and analytical techniques for the assessment of in vitro implant migration in polymer foam models
The first phase of this thesis examined the use of two polymer foams as a suitable analogue material to cancellous bone. Fatigue characterisation of the polymer foam materials showed the materials to be qualitatively similar to cancellous bone in their behaviour. However, quantitative differences existed as compared to cancellous bone and also between the analogue materials themselves; the foams showed less modulus degradation and accumulated strain compared to cancellous bone. Relationships were established for life, secondary strain rate, modulus reduction and accumulation strain in terms of normalised stress and life fraction. In the absence of established data for the fatigue properties of cancellous bone/analogue materials, the approach employed here could form the basis for the selection of a suitable analogue in vitro test medium for assessing the performance of implants.
A combined Finite Element and Continuum Damage Mechanics method was used for the fatigue/migration simulation. Life fraction was used as the damage parameter and a coupled analysis was conducted based on the relationships for modulus and accumulated strain. The algorithm used an iterative procedure where each iteration simulated a number of cycles. The models were capable of simulating the given input behaviour satisfactorily for uniaxial compression tests of both the materials. However, under very high stress levels the models were sensitive to localisation of damage, and underpredicted life. The method was extended to a bonded, foam and metal plate model of migration, simulating an idealised model of the implanted proximal tibia. In the simulations, the effect of the stress concentration near the plate edges was found to dominate the model behaviour; it caused a significant underprediction of migration. However, a similar trend was observed between the FE models and the experiments in terms of migration pattern and how it varied with load.
University of Southampton
Palissery, Vinu
2fd7a215-281f-4d6a-a108-d1c376300485
2004
Palissery, Vinu
2fd7a215-281f-4d6a-a108-d1c376300485
Palissery, Vinu
(2004)
Experimental and analytical techniques for the assessment of in vitro implant migration in polymer foam models.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The first phase of this thesis examined the use of two polymer foams as a suitable analogue material to cancellous bone. Fatigue characterisation of the polymer foam materials showed the materials to be qualitatively similar to cancellous bone in their behaviour. However, quantitative differences existed as compared to cancellous bone and also between the analogue materials themselves; the foams showed less modulus degradation and accumulated strain compared to cancellous bone. Relationships were established for life, secondary strain rate, modulus reduction and accumulation strain in terms of normalised stress and life fraction. In the absence of established data for the fatigue properties of cancellous bone/analogue materials, the approach employed here could form the basis for the selection of a suitable analogue in vitro test medium for assessing the performance of implants.
A combined Finite Element and Continuum Damage Mechanics method was used for the fatigue/migration simulation. Life fraction was used as the damage parameter and a coupled analysis was conducted based on the relationships for modulus and accumulated strain. The algorithm used an iterative procedure where each iteration simulated a number of cycles. The models were capable of simulating the given input behaviour satisfactorily for uniaxial compression tests of both the materials. However, under very high stress levels the models were sensitive to localisation of damage, and underpredicted life. The method was extended to a bonded, foam and metal plate model of migration, simulating an idealised model of the implanted proximal tibia. In the simulations, the effect of the stress concentration near the plate edges was found to dominate the model behaviour; it caused a significant underprediction of migration. However, a similar trend was observed between the FE models and the experiments in terms of migration pattern and how it varied with load.
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Published date: 2004
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Local EPrints ID: 465420
URI: http://eprints.soton.ac.uk/id/eprint/465420
PURE UUID: 55dba910-36b1-4ea5-945b-97ee0e83627e
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Date deposited: 05 Jul 2022 00:52
Last modified: 16 Mar 2024 20:10
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Author:
Vinu Palissery
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