Structural Health Monitoring Systems, Making Aerospace Travel Safer

The year was 1982 when the United States of America was on its way to reach the final frontier with its first operational space shuttle. To reach this goal, NASA built the sophisticated space shuttle Columbia to send their astronauts to space. This shuttle was the first of its kind and required many new electrical systems and structural materials. Some of these systems in the shuttle were either too complicated or too far out of reach to be checked by an astronaut. To monitor these systems, NASA implemented structural health monitoring systems. This was a crucial aspect of the space shuttle, which allowed a successful mission.

strain gauge picStructural Health Monitoring (SHM) is the observation of any type of structure or system in order to track its health. This type of monitoring is done using strain gauges and a data logger. Strain gauges are used to collect the loads applied to the structure. These are placed in multiple places in order to monitor the entire system. Data loggers are used to record the data in order for review. The data collected is able to be streamed live as well as recorded and reviewed later.

The study of a systems’ health using vibrations and sensors began in the late 1970’s and early 1980’s. At this time, NASA was launching their first space shuttles and they needed a way to monitor the elaborate and hard to reach systems installed in those shuttles. Into the 1990’s, as NASA created new vehicles, the space rover and the international space station, SHM was input into each of these systems. In these situations, the SHM systems test components that space debris struck. These SHM systems, which aircraft industries later adopted, tested the longevity of aircrafts and tested aircrafts that have gone through many cycles. The surge in the SHM in the aerospace industry came from the increased use of carbon fiber-reinforced materials that more and more aircraft manufacturers have begun to use. The cracks that occur in this material are not able to be seen by the naked eye and therefore require such monitoring.

Though SHM has not been in the aerospace industry for that long, much research and advancement in this field has been done. The sensors used for the collection of data have decreased dramatically. Strain gauges are small enough to fit in any spot that needs to be recorded. Since the size has decreased so much, the weight has gone down as well. This allows for a lighter aircraft or the possibility of redistributing that weight elsewhere. Another improvement is the decrease in the size of the data loggers. Some can be as small as a roll of quarters. Like the strain gauges, the data loggers’ weight will affect the aircraft in a minimal way.

Current research in this field usually begins on a smaller scale. A model of a wing or part of the aircraft is constructed and the possible loads, stresses, strains, and twists are applied to the model. The strain gauge records that data and sends it to the data logger. With that, one can tell if any changes have occurred, which would signify the structure is weakening. The advantage here are the max loads and circumstances that initiate failure are recognized at a smaller price and without as much endangerment.

On a larger scale, aircrafts are tested with SHM by placing strain gauges throughout the inside of the parts that would like be tested before assembly. That aircraft is then flown and the data collected. This application is not only used for tests, but is also seen in commercial airlines. The aircrafts in that industry are cycled a large amount at a rapid pace. The SHM in the complex system allows for a quicker check during stops while at the same time allowing for the calculation of when the aircraft may fail.

SHM will continue to be used in aircrafts and other aerospace vehicles. It will allow a way to monitor the structure and systems of the vehicle. Over time, it will only get better as the technology that powers it improves. These improvements to structural health monitoring systems will prevent even more failures and allow for safer travel through the air.

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