Sandia Senior Design Bonanza - Spring Fatigue Testing

We are displaying a spring fatigue tester for Sandia National Laboratories. We were required to design and manufacture an enclosed testing area for small springs, less than an inch long and only about 1/8 of an inch in diameter. The enclosure was not allowed to exceed 1 foot in any dimension. The springs had to be energized and de-energized in 10 milliseconds and held in an energized state for 50 milliseconds before returning to its de-energized state. To put that in perspective, a blink for the human eye takes 100-150 milliseconds. The springs are only extended 70 thousandths of an inch and we were required to measure the travel distance throughout the test. Our design uses a solenoid and a lever arm to actuate the springs. The lever arm pivots about a point that transfers the ~1/2 inch travel distance of the solenoid to the 70 thousandths of the springs. Using a time-of-flight displacement sensor we measure the distance at a point along the lever arm and a multiplier to calculate how fare the spring is moving. If a spring fails due to fatigue, this information is used to determine where in the energizing cycle the failure occurred. We also are required to take pictures of the springs from various angles. We are using a servo motor to rotate around the springs to achieve this. This being a fatigue test, where failure could happen spontaneously, safety features were necessary to protect the user. The first line of defense is the Plexiglas shielding. There are also fail safes embedded in the enclosure in the form of reed switches. There is a reed switch located on the enclosure door that will turn off the moving systems if it is opened. Similarly, there is a switch for each spring that will trigger if a spring fails and will turn off the test. The solenoid, servo motor, camera, displacement sensor, and safety switches are all controlled through a Raspberry Pi board and program logic. (Demonstration of shortened fatigue test) Table would include informational poster of project and the product.