For this reason, many analytical, numerical 1– 3, and experimental studies have been conducted over the past decades to investigate structural strain and damage induced by various loading conditions.Įxperimental strain measurement methods can be divided into two major categories: contact-based and non-contact techniques. As a direct indicator of the effects of stress concentration, strain measurement plays an important role in structural health monitoring (SHM) and non-destructive testing. Many cases of structural failure in buildings, bridges, ships, and aircraft are closely related to stress–strain concentration. Moreover, fatigue and fracture cracks due to low level but high-frequency loads would also grow in stress concentration regions and cause damage. For ductile materials, stress concentration might instead cause localized plastic deformation and yielding. Brittle materials will typically fail at such high stress locations due to fracture and cracking. It can occur when there are irregularities in the geometry or material of a structural component.
These findings highlight the potential of S 4 strain measurement technology as a promising alternative or complement to existing technologies, especially when accumulated strains must be detected in structures that are not under constant observation.Ī stress concentration is a location at which the mechanical stress is significantly higher than in the surrounding area. Finite element method simulations also showed closer agreement with S 4 than with DIC results. Strain features were more clearly revealed with S 4 than with DIC. Noncontact strain maps measured with the S 4 films and point-wise scanning were directly compared to those from DIC on acrylic, concrete, and aluminum test specimens, including one with subsurface damage. The new S 4 film improves spectral uniformity of the nanotube sensors, avoids the need for annealing at elevated temperatures, and allows for parallel DIC measurements. S 4 measures strain-induced shifts in the emission wavelengths of single-wall carbon nanotubes embedded in a thin film on the specimen.
This study reports next generation optical strain measurement with “strain-sensing smart skin” (S 4) and a comparison of its performance against the established digital image correlation (DIC) method.
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