Detection of Crack Initiation and Growth Using Fiber Bragg Grating Sensors Embedded into Metal Structures through Ultrasonic Additive Manufacturing

Abstract

Structural health monitoring (SHM) is a rapidly growing field focused on detecting damage in complex systems before catastrophic failure occurs. Advanced sensor technologies are necessary to fully harness SHM in applications involving harsh or remote environments, life-critical systems, mass-production vehicles, robotic systems, and others. Fiber Bragg Grating (FBG) sensors are attractive for in-situ health monitoring due to their resistance to electromagnetic noise, ability to be multiplexed, and accurate real-time operation. Ultrasonic additive manufacturing (UAM) has been demonstrated for solid-state fabrication of 3D structures with embedded FBG sensors. In this paper, UAM-embedded FBG sensors are investigated with a focus on SHM applications. FBG sensors embedded in an aluminum matrix 3 mm from the initiation site are shown to resolve a minimum crack length of 0.286 ± 0.033 mm and track crack growth until near failure. Accurate crack detection is also demonstrated from FBGs placed 6 mm and 9 mm from the crack initiation site. Regular acrylate-coated FBG sensors are shown to repeatably work at temperatures up to 300 ∘C once embedded with the UAM process.

Fiber Bragg Sensors Embedded in Cast Aluminum Parts: Axial Strain and Temperature Response

“…The high compaction forces of the casted aluminum ensure that no slippage of the fiber occurs. This distinguishes the casting from other methods such as additive manufacturing and ultrasonic consolidation, which show highly nonlinear response and delamination behaviors at high temperatures [51,53]. Figure 13.…”

“…A different method to embedded FBG is ultrasonic consolidation, which has the advantage of low temperatures during the embedding process [ 47 , 52 ]. The embedded FBGs showed the same disadvantages as the additive manufacturing methods, such as hysteresis and delamination of the fiber and the metal [ 53 ].…”

Special Issue “Fibre Optic Sensors for Structural and Geotechnical Monitoring”

“…Paper [9] investigates the structural health capabilities of fibre Bragg grating sensors embedded in components made by ultrasonic additive manufacturing. Sensors are embedded during the manufacturing process of standard specimens for laboratory crack tests.…”

Minimizing the wiring in distributed strain sensing using a capacitive sensor sheet with variable-resistance electrodes

“…While most techniques provide spatially discrete data obtained using complex wiring, our technique results in spatially continuous measurement using very few connections. For example, the fiber Bragg grating (FBG), for example, is a popular technique in spatially-discrete distributed strain sensing 14 . Although FBG multiplexing is now a well-controlled technique, FBGs are thermally sensitive.…”