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Title: The design of mechanical test rigs for the testing of medical devices
Author: Bamford, James Stuart
ISNI:       0000 0004 2689 5025
Awarding Body: University of Teesside
Current Institution: Teesside University
Date of Award: 2004
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The design of biomechanical devices is often difficult because it is not feasible to test them within human or animal patients. Initial designs may be tested using mechanical rigs or finite element models to simulate the complex loading conditions within biological environments. Recent advances in computer technology have allowed computer simulations to become more detailed. However, educated assumptions must be made to simplify the conditions that will effect the device. Highly accurate results can be obtained but it is essential that these results are verified using a mechanical test rig. This will identify if human error or inaccurate assumptions have occurred. Mechanical test rigs were designed to simulate the forces acting within four different biomechanical systems. This involved simulating the forces applied to the lumbar spine, the greater trochanter of the hip, and to the shin; for the testing of inter-vertebral cages, hip protectors and floor coverings, and shin pads respectively. Load cells were used to measure the resultant impact forces applied to the hip and shin. The time-domain data were recorded for each impact and from these data it was possible to calculate the maximum impact force and the total energy absorbed by the greater trochanter. Mechanical testing of intervertebral cages involved pressure sensitive paper to measure resultant pressure trends at the interface between the vertebral end plate and the cages. This instantly revealed pressure trends and computer programs were written to determine the contact area, calibrate pressure values, and to allow the improved visualisation of results. Results from the mechanical test rigs are also suitable for validation of finite element analysis studies. New information has been generated to improve understanding about the pressure trends under intervertebral cages and the key design features have been identified. The hip test rig was used in the design of a novel hip protector, to determine the role of floor coverings in an impact, and to compare numerous hip protectors using typical impact conditions. Results show that a combination of energy absorbent flooring with a hip protector is the best environment for a reduced risk of a hip fracturing. Design recommendations were made regarding the material composition and the thickness of the materials used. This allowed the novel hip protector to be designed as small as possible but still sufficiently reduces the impact force from a person falling onto their hip. The hip test rig was modified to simulate the shin and was used to compare several commercially available shin guards. New information was generated to identify which design features are best to reduce impact forces. Further developments have been made to the first version of the hip impact test rig. The latest version of this hip test rig is currently being used as a benchmark for all hip protectors and is a likely contender as the basis of a standard testing system for a European Standard.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available