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
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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
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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: 15
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4. All Silica Micro-Fluidic Flow Injection Sensor System for Colorimetric Chemical SensingVedran Budinski, Denis Đonlagić, 2021, izvirni znanstveni članek Opis: This paper presents a miniature, all-silica, flow-injection sensor. The sensor consists of an optical fiber-coupled microcell for spectral absorption measurements and a microfluidic reagent injection system. The proposed sensor operates in back reflection mode and, with its compact dimensions, (no more than 200 µm in diameter) enables operation in small spaces and at very low flow rates of analyte and reagent, thus allowing for on-line or in-line colorimetric chemical sensing.
Ključne besede: optical fiber sensor, spectral absorption microcell, colorimetry
Objavljeno v DKUM: 31.07.2023; Ogledov: 457; Prenosov: 22
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5. Miniature magneto-optic angular position sensorVedran Budinski, Simon Pevec, Stanislav Čampelj, Alenka Mertelj, Darja Lisjak, Denis Đonlagić, 2022, izvirni znanstveni članek Opis: This Letter describes a miniature Fabry–Perot, contactless, magneto-optic sensor for angular position measurement. The sensor utilizes a magneto-optic fluid comprising barium hexaferrite nanoplatelets that become birefringent in the presence of an external magnetic field and a compact fiber-optic sensor system for tracking the liquid’s optical axis direction. An efficient temperature compensation system is provided which allows the use of otherwise highly temperature-sensitive magneto-optic liquids. An unambiguous measurement range of 90° and a resolution of better than 0.05° are demonstrated experimentally.
Ključne besede: Fiber optic sensor, magneto-optic sensor, angular position measurement
Objavljeno v DKUM: 12.05.2023; Ogledov: 623; Prenosov: 99
Celotno besedilo (3,76 MB)
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