EuroWire March 2020

Technical Article

Also, the cost of making a fibre optic strain gauge utilising pseudorandom code is much cheaper than its counterpart of fibre Bragg grating. The economic impact of our project, we believe, is a positive one that will save money, not spend it. 3 Conclusions The IWCS_Fiber project is the creation of a fibre optic strain gauge that utilises pseudorandom code interrogation. This strain gauge must be implemented into a design that can be used in a classroom setting for future mechanical engineering students to use in their instrumentation lab. Working with our faculty mentors we decided it was best to create a pressure vessel that will undergo strain so that the fibre optic strain gauge can be attached to it to measure strain. Real-time strain results will be displayed for the students to see and take home to measure for further data analysis. Right now, at the end of senior design one, all materials are in and ready for build and the code is ready to be tested for correlation. n 4 Acknowledgements We appreciate Jim Hartman and the IWCS for being our sponsors and for giving us the platform to present our research and design regarding fibre optic strain gauges. Also, a special thanks to our mentors Dr Jerry Dhalberg, Dr Garry Hodgins and Mr Franklin Green for guiding us through this endeavour. Courtesy of IWCS Cable & Connectivity Symposium, Charlotte, North Carolina, USA, September/October 2019.

A few weeks into the project, when dialogue became more clear with our faculty supporters that this project had the goal of becoming a lab for students to use in the future, the focus of the project shifted. A fibre optic strain gauge was still the main goal, but how it would be used became very different. We needed to come up with a solution that would be easy for students to use over and over again. We decided that a pressure vessel would be the best way to demonstrate strain in a classroom setting. A cylindrical pipe would be pressurised with a bike pump and the fibre wrapped around the centre of the pipe would be able to determine the strain at each psi. Displaying the strain in real time was now very important in order for the students to see, and also have them record the data and take it home for further interpretation. At this point our project specifications changed from testing strain in com- pression and tension to just tension, and displaying strain in real time instead of having it perform in a large range of temperatures. Also, how we were going to have the strain gauge communicate with the computer changed because we now had to do it in the instrumentation lab, which gave us the option of using the NI boards. We plan on testing both connections through NI board and Ethernet port to see which option works best for communication through LabVIEW. LabVIEW was always going to be used because it is easy to use and our faculty supporter Franklin Green is very knowledgeable on the subject, so we knew if we ran into any troubles he would be able to point us in the right direction. 2.4 Project impact Our project has a direct impact on public welfare in an industrial context. A fibre optic strain gauge that utilises pseudorandom code, when placed in industry, provides a reliable, cost-effective solution to monitoring the safety of weight-bearing structures. Fibre optic strain gauges are able to determine when a structure is no longer safe to use and needs to either be torn down or reinforced. This technology is beneficial to the public and can help minimise deaths and injuries that would have otherwise happened if buildings or bridges collapsed due to high or cyclic levels of stress and strain. With this technology stress and strain can be monitored and failure can be prevented before it happens. As stated above, this project can be used to keep the public safe and prevent the death and injury of humans caused by building or bridge failure. This system can be implemented anywhere in the globe and that is how our project has an impact on a global scale.

▲ ▲ Figure 1 : Model of strain gauge testing apparatus with pressure vessel and media converter with SFP+ module

Bridges and buildings in China can be monitored in the United States. There is no limit to how our fibre optic strain gauge could be implemented across the entire globe. The impact that our project could have on culture is almost non-existent. Because strain gauges already exist and they are placed on structures for our safety, our culture already has a mindset that does not think twice when driving over a bridge or staying in a high rise apartment. The culture that we live in today in the United States has already adapted to this lifestyle where engineering is trusted. There is potential that fibre optic strain gauges could be implemented in a less developed part of the world and it could change the culture there and allow the people to trust the work done by engineers, knowing that if it is going to fail there are systems in place to know beforehand so to reduce the chance of injury. Societal impacts have the most potential in underdeveloped countries as stated above and for the same reasons. To the best of our knowledge we do not believe that our project will have a significant environmental impact. Traditional wire strain gauges and fibre optic strain gauges are both made out of material that can be recycled. They are also one-time use objects and cannot be used again. It is unclear which material is more environmentally friendly to produce: metal or glass. As a result we do not think that our project will have a significant environmental impact. The economic impact of our project has a lot of potential. If used properly our strain gauge would be able to help improve structural integrity through monitoring and regular maintenance. This means that whether the structure is destroyed and replaced or simply reinforced, the bill associated with it will be much less than it would be if it failed with no warning. The cost of potential medical bills, clean up, and any other damage to nearby structures will be far greater.

University of North Carolina at Charlotte Engineering Senior Design Charlotte, North Carolina USA Tel : +1 252 414 8420 Email : whodges3@uncc.edu

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March 2020