1. Monitoring surface state of AA7075-T6 during dynamic loading with FBG sensorMarijana Milković, Matej Njegovec, Jožef Predan, Jure Javornik, Denis Đonlagić, Nenad Gubeljak, 2023, izvirni znanstveni članek 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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2. A short-range quasi-distributed strain and temperature sensing system utilizing a standard telecom laser diodeJure Javornik, Denis Đonlagić, 2025, izvirni znanstveni članek Opis: This article presents a short-range fiber-optic quasi-distributed sensing device suitable for strain and temperature measurement. The sensing assembly consists of an fs laser inscribed reference mirror and a sensing array of equidistantly positioned mirrors. Utilization of the reference mirror and proper sensor geometry selection provides the possibility for a high-resolution spectral interrogation of the sensing array while relying on an ordinary, cost-effective distributed feedback (DFB) telecom laser diode. Beside the telecom DFB diode, the entire interrogation system includes only an additional detector, optical coupler, analog interface and a microcontroller. Measurement resolution better than 1 µε was demonstrated experimentally at a sampling rate exceeding 65 samples per second, while utilizing a sensing device with a typical length of 50 mm and spatial resolution of approximately 2 mm. To demonstrate the application potential of the proposed measuring device, a few different packages and sensor configurations were demonstrated and tested, including a system for tactile sensing applications and a short-range quasi-distributed temperature measurement probe.
Ključne besede: optical fiber sensors, short-range quasi-distributed fiber-optic sensor, strain/temperature sensing device, cost-effective interrogation system, tactile sensing, phase subtraction
Objavljeno v DKUM: 03.02.2025; Ogledov: 0; Prenosov: 7
Celotno besedilo (6,44 MB) |
3. Gas sensing system based on an all-fiber photothermal microcellMatej Njegovec, Jure Javornik, Simon Pevec, Vedran Budinski, Tomaž Gregorec, Benjamin Lang, Manuel Tanzer, Alexander Bergmann, Denis Đonlagić, 2024, izvirni znanstveni članek 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: 16
Celotno besedilo (15,77 MB) |
4. Photothermal gas sensing with a custom-made, fiber-coupled Fabry–Pérot etalonManuel Tanzer, Benjamin Lang, Matej Njegovec, Vedran Budinski, Simon Pevec, Jure Javornik, Denis Đonlagić, Alexander Bergmann, 2024, izvirni znanstveni članek Ključne besede: photothermal gas, etalon, interferometry, Fabry-Perot
Objavljeno v DKUM: 29.08.2024; Ogledov: 77; Prenosov: 32
Celotno besedilo (2,37 MB) |
5. Izdelava mikrostruktur s femtosekundnim laserjem : magistrsko deloJure Javornik, 2022, magistrsko delo Opis: Magistrsko delo opisuje sistem za obdelovanje optičnih vlaken in steklenih kapilar, ki je bil izdelan kot razširitev že obstoječega fs laserskega sistema. Opisana sta metoda pridobivanja ultrakratkih laserskih sunkov in teoretično ozadje njihove interakcije z obdelovanim materialom. Nadalje je obravnavan postopek izdelave senzorjev, ki uporabljajo odprto mikrocelico, izdelano iz steklene kapilare na obdelovalnem sistemu. Podani so spektralni odzivi izdelanih senzorjev in rezultati meritev njihovih mehanskih lastnosti. Predstavljeni so mikrofluidni kanali, mikrovijaki in mikroresonatorji, ki so bili izdelani na vrhu optičnega vlakna. Prav tako smo opozorili na zmožnost vpisovanja zrcal v jedro optičnega vlakna s fs laserjem s povzročanjem lokalne spremembe lomnega količnika. Izmerjene so bile optične in mehanske lastnosti vpisanih zrcal pri različnih energijah ultrakratkih sunkov in pri različnih konfiguracijah zrcal. Predstavljena sta bila dva primera uporabe vpisanih zrcal v praktičnih primerih.
Ključne besede: Ultrakratki sunki, femtosekudni laser, mikrostrukture, vpisana zrcala, mikrocelica
Objavljeno v DKUM: 24.10.2022; Ogledov: 617; Prenosov: 117
Celotno besedilo (5,20 MB) |
