Developing a digital image correlation setup for in situ testing of Achilles tendons
(2024) BMEM01 20241Department of Biomedical Engineering
- Abstract
- Tendons connect muscle to bone and assist in joint motion. To be able to do this, they must withstand large forces and be able to alter their structure under load. If a tendon experiences too high or sudden forces, it will start to tear and eventually rupture. To examine how this happens and how the tendon behaves before rupture, mechanical testing is done. This study focuses on how to combine mechanical testing with digital image correlation. Digital image correlation (DIC) is a non-invasive, optical measurement method that can track different regions of a test sample and calculate local displacements and strains, giving deeper insight about how a tendon behaves under applied strains and loads. In order to do this, it is required to apply... (More)
- Tendons connect muscle to bone and assist in joint motion. To be able to do this, they must withstand large forces and be able to alter their structure under load. If a tendon experiences too high or sudden forces, it will start to tear and eventually rupture. To examine how this happens and how the tendon behaves before rupture, mechanical testing is done. This study focuses on how to combine mechanical testing with digital image correlation. Digital image correlation (DIC) is a non-invasive, optical measurement method that can track different regions of a test sample and calculate local displacements and strains, giving deeper insight about how a tendon behaves under applied strains and loads. In order to do this, it is required to apply a speckle pattern onto the surface of the tendon so that displacements and strains can be tracked by the software. The aim of this project was to develop a DIC setup for in situ testing of Achilles tendons. The study was done on bovine Achilles tendons due to their similarities to human tendons and the project was divided into four main steps. The first step was to prepare bovine for mechanical testing. The second step was to find a speckle pattern that was easily applicable on the surface of the tendon and that gave reproducible results. The third step was to find a loading protocol that would work well in combination with DIC. The fourth and final step was to compare results from mechanical testing with results from DIC to see how well the setup can capture and calculate displacements and strains.
The speckle pattern was applied onto the tendon with an airbrush and the final mechanical testing protocol consisted of preconditioning (2% strain, 5 cycles) and cyclic loading (6% strain, 10 cycles) with additional tests of stress relaxation (8% strain and 16% strain) and ramp to failure (40% strain) to examine the possibilities of the setup. Results show that the setup developed during this project can successfully track and calculate strains and displacements for different parts of the Achilles tendon. However, findings also show that there is room for improvement and further development of the setup to get more reliable results. The difference between applied strain (6%) and calculated strain, in the longitudinal direction, was 3.982 ± 0.309% for the cyclic loading tests indicating that ~ 50% of the strain is lost in the tissue. Slippage was observed at the highest strain for the cyclic loading tests (6%) as well as for the stress relaxation tests (8% and 16%), and from 20% and onwards for the ramp to failure test (40%).
As the method and setup is still in the early stages of testing, further experimentation is required to achieve reproducibility and more accurate results. This method will, in the future, be applied to the testing of human tendons and will give more insight into the local strain response of tendons. (Less) - Popular Abstract (Swedish)
- Experimentell uppställning för mekanisk prövning av hälsenor
”Aj!” Så kan det låta när du skadar din hälsena. Hälsenan är en av de starkaste senorna i kroppen och också den som oftast skadas. Skador på hälsenan kan uppkomma till följd av plötsliga rörelser men även vid repetitiv överansträngning under en längre tid. I värsta fall kan senan gå av helt och hållet. För att kunna förebygga och behandla dessa skador vill man ta reda på vilka delar av senan som utsätts för mest påfrestning under ansträngning. Detta kan göras med hjälp av mekanisk prövning och digital bildkorrelation.
Det vanligaste sättet att undersöka senans materialegenskaper är genom mekanisk prövning. Detta innebär att man spänner fast senan i en klämma i vardera änden... (More) - Experimentell uppställning för mekanisk prövning av hälsenor
”Aj!” Så kan det låta när du skadar din hälsena. Hälsenan är en av de starkaste senorna i kroppen och också den som oftast skadas. Skador på hälsenan kan uppkomma till följd av plötsliga rörelser men även vid repetitiv överansträngning under en längre tid. I värsta fall kan senan gå av helt och hållet. För att kunna förebygga och behandla dessa skador vill man ta reda på vilka delar av senan som utsätts för mest påfrestning under ansträngning. Detta kan göras med hjälp av mekanisk prövning och digital bildkorrelation.
Det vanligaste sättet att undersöka senans materialegenskaper är genom mekanisk prövning. Detta innebär att man spänner fast senan i en klämma i vardera änden som sedan monteras i en mekanisk provmaskin. Senan dras därefter isär och det är då möjligt att mäta den kraft som krävs för att dra senan en viss sträcka. Den här metoden ger information om vilka krafter och töjningar senan upplever över lag. För att kunna mäta hur stora töjningar senan utsätts för i dess olika delar används digital bildkorrelation. Ett mönster appliceras på ytan av senan, och bilder tas medan senan utsätts för ett mekaniskt test. En korrelations-algoritm kan sedan med numerisk analys jämföra bilderna och, med hjälp av mönstret på ytan och ett rutnät, beräkna hur olika regioner av senan har förflyttats under det mekaniska testet. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9167061
- author
- Fritzell, Ebba LU and Eriksson Molin, Minna LU
- supervisor
-
- Kunal Sharma LU
- Maria Pierantoni LU
- Hanna Isaksson LU
- organization
- alternative title
- Experimentell uppställning för mekanisk prövning av hälsenor
- course
- BMEM01 20241
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- additional info
- 2024-17
- id
- 9167061
- date added to LUP
- 2024-06-24 12:53:45
- date last changed
- 2024-06-24 13:02:02
@misc{9167061,
abstract = {{Tendons connect muscle to bone and assist in joint motion. To be able to do this, they must withstand large forces and be able to alter their structure under load. If a tendon experiences too high or sudden forces, it will start to tear and eventually rupture. To examine how this happens and how the tendon behaves before rupture, mechanical testing is done. This study focuses on how to combine mechanical testing with digital image correlation. Digital image correlation (DIC) is a non-invasive, optical measurement method that can track different regions of a test sample and calculate local displacements and strains, giving deeper insight about how a tendon behaves under applied strains and loads. In order to do this, it is required to apply a speckle pattern onto the surface of the tendon so that displacements and strains can be tracked by the software. The aim of this project was to develop a DIC setup for in situ testing of Achilles tendons. The study was done on bovine Achilles tendons due to their similarities to human tendons and the project was divided into four main steps. The first step was to prepare bovine for mechanical testing. The second step was to find a speckle pattern that was easily applicable on the surface of the tendon and that gave reproducible results. The third step was to find a loading protocol that would work well in combination with DIC. The fourth and final step was to compare results from mechanical testing with results from DIC to see how well the setup can capture and calculate displacements and strains.
The speckle pattern was applied onto the tendon with an airbrush and the final mechanical testing protocol consisted of preconditioning (2% strain, 5 cycles) and cyclic loading (6% strain, 10 cycles) with additional tests of stress relaxation (8% strain and 16% strain) and ramp to failure (40% strain) to examine the possibilities of the setup. Results show that the setup developed during this project can successfully track and calculate strains and displacements for different parts of the Achilles tendon. However, findings also show that there is room for improvement and further development of the setup to get more reliable results. The difference between applied strain (6%) and calculated strain, in the longitudinal direction, was 3.982 ± 0.309% for the cyclic loading tests indicating that ~ 50% of the strain is lost in the tissue. Slippage was observed at the highest strain for the cyclic loading tests (6%) as well as for the stress relaxation tests (8% and 16%), and from 20% and onwards for the ramp to failure test (40%).
As the method and setup is still in the early stages of testing, further experimentation is required to achieve reproducibility and more accurate results. This method will, in the future, be applied to the testing of human tendons and will give more insight into the local strain response of tendons.}},
author = {{Fritzell, Ebba and Eriksson Molin, Minna}},
language = {{eng}},
note = {{Student Paper}},
title = {{Developing a digital image correlation setup for in situ testing of Achilles tendons}},
year = {{2024}},
}