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Opis: The AA7075-T6 material is widely used in aerospace applications due to its favourable strength-to-weight ratio and cost-effectiveness. The material undergoes a process of cold rolling and subsequent stretching to form metal sheets. This process generates residual compressive stresses on the surface of the material. Surface changes in the material are observed at low stress levels, resulting in variations in residual stresses and surface roughness. This article presents an approach to monitor the surface state changes of AA7075-T6 material during dynamic loading using Fiber Bragg Grating (FBG) sensor. Numerical Finite Element Method (FEM) simulations analyse the transfer of deformations from the damaged surface through the adhesive layer to FBG with different cladding thicknesses. Loading induces microcrack-related intensity changes in the FBG optical spectrum and deformation response. The magnitude of the response is greater, when the cladding thickness of the optical fibre is thinner. Experimental results show that the FBG optical spectrum response varies with cumulative number of dynamic cycles.
Ključne besede: AA7075-T6, dynamic loading, Fiber Bragg Grating (FBG) sensor, surface condition
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 6
Celotno besedilo (1,20 MB)
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Opis: This article presents an all-silica microwire optical sensor designed for both fast response time and high-resolution temperature detection. The sensor consists of a thin optical microwire created at the tip of an optical fiber, configured as a temperature sensitive Fabry–Perot interferometer (FPI). For the purposes of achieving rapid response times, the sensing section of the sensor has a diameter of 11 µm. Experimental bench tests were set up to evaluate the sensor’s static and dynamic performance. The results indicate a sensor system resolution of about 5 mK and demonstrate a bandwidth of 38 Hz that corresponds to a response time of 4 ms in still air. The sensor’s functionality is shown through a basic periodic gas compression method detecting small temperature fluctuations. In addition, the sensor was demonstrated for operation up to 600 ◦C.
Ključne besede: Fabry-Perot, high-resolution temperature sensor, micromachining, microwire optic sensor, optical fibers, short response time
Objavljeno v DKUM: 12.02.2025; Ogledov: 0; Prenosov: 6
Celotno besedilo (8,03 MB)

Opis: Laserski viri z nastavljivo valovno dolžino, ki se uporabljajo za branje optičnih vlakenskih senzorjev imajo pogosto zelo kompleksno zgradbo, uporabljajo gonilna vezja, ki so kompleksna in zahtevna za uporabo, obenem pa so zelo draga. S pojavom VCSEL laserske diode z nastavljivo valovno dolžino se je pojavila cenovno ugodnejša različica, ki ima manj kompleksno zgradbo in je enostavnejša za uporabo. V diplomskem delu je predstavljena izgradnja gonilnika VCSEL lasersko diodo z nastavljivo valovno dolžino vse od načrtovanja in izgradnje sistema pa do programiranja algoritmov za nastavljanje valovne dolžine in prikaza rezultatov.
Ključne besede: nastavljiv laserski vir, nastavljiva VCSEL, gonilnik laserske diode
Objavljeno v DKUM: 14.10.2024; Ogledov: 0; Prenosov: 21
Celotno besedilo (3,71 MB)

Opis: This article presents an all-fiber, miniature Fabry-Perot gas sensor based on photothermal absorption spectroscopy with a custom-made and cost-efficient interrogation system. The sensing gas microcell has a diameter of 125 μ m and a length of 1 mm, and allows for free gas exchange within the optical resonator through micromachined slits. High light intensity and confinement are ensured by delivering the excitation light directly into the gas microcell through a lead-in single-mode fiber. This enhances the photothermal effect and provides a short system response time. The interrogation system utilizes the modulation of an excitation laser diode with a fixed frequency while locking the probe laser onto the gas microcell’s quadrature point (QP) and observing the variations of the reflected optical power. To show the potential of the proposed system, nitrogen dioxide (NO2 was measured in dry air. Thereby, a limit of detection of 20 ppm could be achieved for 10 s integration time. Furthermore, the small dimensions of the sensor allow for improved dynamic performance with photothermal modulation frequencies as high as 7 kHz.
Ključne besede: Fabry–Perot interferometer, FPI, fiber gas cell, fiber gas sensor, nitrogen dioxide, NO2, photothermal effect
Objavljeno v DKUM: 29.08.2024; Ogledov: 96; Prenosov: 13
Celotno besedilo (15,77 MB)

Opis: This paper presents a fiber optic sensor for the detection of corrosion processes that occur on metal surfaces. In the proposed sensor design, a sensing fiber with an inscribed high-order Bragg grating is attached to the observed metal surface. A broadening of high-order Bragg grating spectral characteristics is observed and used to detect small and highly localized longitudinal strain variations that occur along the fiber as a result of corrosive rust flakes' formations beneath the sensing fiber. The proposed approach provides a straightforward fabrication method, the possibility for unobtrusive mounting, including mounting of the sensor beneath the corrosion-protective layers, and consistent corrosion detection yields.
Ključne besede: optical fiber sensors, corrosion, impact of corrosion, optic sensors
Objavljeno v DKUM: 09.02.2024; Ogledov: 320; Prenosov: 26
Celotno besedilo (1,58 MB)
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