Portable Piezospectroscopy system: non-contact in-situ stress sensing through high resolution photo-luminescent mapping

Abstract

Through the piezospectroscopic effect, certain photo-luminescent materials, once excited with a laser, produce spectral emissions which are sensitive to the stress or strain that the material experiences. A system that utilizes the piezospectroscopic effect for non-contact stress detection over a material's surface can capture important information on the evolution of mechanical response under various conditions. Therefore, the components necessary for piezospectroscopic mapping and analysis have now been integrated into a versatile and transportable system that can be used with photo-luminescent materials in any load frame or on a variety of structures. This system combines compact hardware components such as a portable laser source, fiber optics, spectrograph, charge-coupled device (CCD), and an X-Y-Z stage (with focusing capabilities) with a series of data analysis algorithms capable of analyzing and outputting high resolution photo-luminescent (PL) maps on-site. Through a proof of concept experiment using a compressed polycrystalline alumina sample with sharp machined corners, this system successfully captured high resolution PL maps with a step size of 28.86μm/pixel and located high stress concentrations in critical areas, which correlated closely with the results of a finite element model. This work represents an important step in advancing the portability of piezospectroscopy for in-situ and non-contact stress detection. The instrumentation developed here has strong implications for the future of non-destructive evaluation and non-invasive structural health monitoring.

Quantifying Alumina Nanoparticle Dispersion in Hybrid Carbon Fiber Composites Using Photoluminescent Spectroscopy

“…A laser source with a 532 nm wavelength was used in conjunction with the novel Portable Piezospectroscopy System [32]. The laser power was measured at the probe to be 15.12 mW , and an exposure time of 200 ms was chosen for data acquisition.…”

Damage mapping with a degrading elastic modulus using piezospectroscopic coatings

“…PS data was collected with a prototype portable spectrometer system designed to be easily transported with a quick setup time [17]. Excitation was achieved using a low power, 1.5 mW laser of 532 nm wavelength in a back scattering configuration with a long working distance objective (28 mm).…”

“…These techniques rely on other physical principles to determine the elastic modulus rather than conventional stress/ strain relationships and are currently active fields of research [15,3]. Among these, however, piezospectroscopy stands out as the one technique suitable enough for integration with full-scale mechanical load frames for standard coupon testing [16,17].…”

Evaluating the effect of nano-particle additives in Kevlar® 29 impact resistant composites

“…From literature [16,2,26], the peaks of investigation were identified at approximately 1611 cm À1 and 1649 cm À1 . Spectroscopy readings were conducted on the pristine fibers and compared with literature for agreement, and the measurements were conducted utilizing a portable spectrometer with specification available in published work [27].…”

“…The scanning techniques are continuing to be improved in an effort to develop complete contour maps of the impact region. The techniques have shown great promise for large scale spectroscopic stress mapping [27].…”