Fabrisonic, a specialist in solid-state metal AM, has once again teamed up with Luna Innovations, a manufacturer of medical, telecommunications, energy and defense technologies, to showcase the potential of its Ultrasonic Additive Manufacturing (UAM) process. In this particular project, the partners were enlisted by NASA to gather data from cryogenic fuel pipes for rocket test stands.
Fabrisonic’s solid-state UAM process is unique in that it can be used to encapsulate sensors, fibers and wires into a metallic substrate. The company has demonstrated this capability time and time again by embedding microphones, thermocouples, ultrasonic inspection sensors and more into solid metal components for a range of applications.
According to the company, there are many advantages to embedding a sensor directly into metal, including enabling the sensor to work in more challenging environments, placing the sensor exactly where it is needed, and allowing for longer operation times compared to more traditional sensor adhesives.
Fabrisonic and Luna Innovations were contracted by NASA to gather valuable data from inside cryogenic fuel pipes, in order to allow NASA to understand pressure and temperature gradients inside the fuel piping closer to the test article, which could give more insight into how an engine is behaving.
Before using the UAM process, NASA gathered data by mounting sensors onto the outside of piping using elbows and ports. This approach was limited in its effectiveness to gather data, so the space agency wanted to find a more accurate and direct way to gather information.
Fabrisonic’s UAM process was able to 3D print sensors directly into the wall of the fuel pipe, which has provided more precise and accurate readings of the thermal and pressure gradients. Luna Innovations provided the sensors for the project. All of the sensors were fiber optic-based because they are the smallest and have the least impact on the pipe’s structure. In terms of collecting data, the fiber optic sensors also have the advantage of collecting data from the entire length of the fiber inside the pipe.
Interestingly, Fabrisonic only 3D printed a small portion of the pipe, where the sensors were embedded. The team started with an existing pipe structure and using milling technology to create a landing strip for the embedded sensors. According to Fabrisonic a “small groove” was cut to positively locate each fiber and the fibers were inserted by hand. Once the fibers were in place, Fabrisonic used its UAM process to print metal material over the landing strip until the original outer diameter of the pipe was rebuilt. Excess printed material was then removed using CNC milling.
In tests, the sensor-embedded pipe performed well. The team submitted the pipe to various temperatures and pressures to calibrate the sensor, including placing the pipe in boiling water and filling it with liquid nitrogen to mimic the effect of cryogenic fuel. The sensors reportedly collected accurate data across these tests.
Going forward, the partners will 3D print a larger pipe section with embedded sensors to be tested at the NASA Stennis Space Center.