Fatigue failure monitoring of 316L stainless steel coupons using optical fibre based distributed strain sensing

Abstract

We demonstrate the application of optical frequency domain reflectometry to detect, locate and track the propagation of fatigue cracks in simple beam-shaped stainless-steel specimens. To do so we recorded the strain distribution along the entire length of hot rolled and additively manufactured 316L steel specimens with a spatial resolution of 1 mm using an embedded optical fibre, and we evaluated fatigue induced damage under four-point bending load cycles. Our findings are threefold. First, we show that the onset of fatigue damage can be detected using our methodology based on a damage index adapted to optical frequency domain reflectometry measurements, which allows alerting for potential failure. We also show that our optical fibre mounting and embedding technique enables the fibre to survive critical failure of the steel specimen. In addition, we obtain strain profile measurements with a spatial resolution that allows linking the strain distribution with imperfections in the four-point bending set-up.

Structural health monitoring through surface acoustic wave inspection deployed on capillaries embedded in additively manufactured components

“…This principle was further researched [18,19] but to date no successful crack localization has been achieved during an actual fatigue crack event. De Pauw et al post-inserted an optical fibre through the additively created channels and utilized distributed strain sensing to successfully detect and localize fatigue cracks [20].…”

A feasibility study on monitoring of weld fatigue crack growth based on coda wave interferometry (CWI)

“…Recently, various nondestructive testing (NDT) methods [8,9] and structural health monitoring (SHM) approaches [10,11] are applied to detect metal cracks [12] in the early stage of welded structures, including penetration testing (PT) [13], magnetic testing (MT) [14], x-ray radiography [15], eddy current testing (ECT) method [16,17], acoustic emission (AE) [18], ultrasonic techniques [19] and other methods [20]. However, the PT and MT are mainly for the defects on the surface or near surface of materials and not applicable to buried or undersurface defects.…”