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- 2019
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- supercontinuum generation
- Nonlinear
- photonic crystal fiber taper
- liquid filled photonic crystal fiber
- fiber optic sensor
- temperature sensor photonic crystal fiber
- Electrospinning
- fiber rod
- quantum dot-converted LEDs component
- Scattering
- Optoelectronic Information Science and Engineering
- Beijing University of Posts and Telecommunications (BUPT)
- Dalhousie University
- Soochow University
- Technical University of Ostrava
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Investigation of cut quality in fiber laser cutting of CFRP
摘要： Fiber laser cutting of CFRP sheets was investigated using a 2 kW multi-mode fiber laser, focusing on how the cut quality factors, such as kerf width, kerf depth, matrix evaporation width, matrix recession width, kerf taper angle, matrix damage zone, and cut surface morphology, change as laser power, laser scanning speed, and the number of laser passes are varied. By designing a systematic experiment on a large process window, several important parameters for kerf width, kerf depth, matrix evaporation width, and matrix recession width were identified, and using them, it was verified that the beam scanning speed is a dominant factor for minimizing thermal damages. Also, circular rings were observed in each carbon fiber at the cut surfaces, and it looked as if they were generated when each fiber was thermally fused in the radial direction. A larger number of laser passes was found to contribute to a smooth surface morphology, because of the formation of highly-fused surfaces, which prevents fiber delamination and pull-outs. Optimum process conditions were also identified by comparing various cut quality factors.
关键词： Fiber laser cutting,Optimal process conditions,Cut quality factors,Thermal damage,Carbon fiber reinforced plastic (CFRP)
更新于2025-11-28 14:24:20
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Laser cooling arc plasma effect in laser-arc hybrid welding of 316L stainless steel
摘要： Current laser-plasma interaction theory supports that the plasma energy e.g. electron temperature would increase by the effect of inverse bremsstrahlung (IB) absorption, when a laser beam passed through the plasma. However, in this paper, we found an interesting laser cooling arc plasma effect (LCAPE) during kilo-Watt fiber laser-TIG hybrid welding. Based on theoretical modelling and experiments, we observed that a temperature decrease of more than 5000 K at the tail of the argon plasma occurred under different process parameters during hybrid welding of 316L stainless steel. We proposed the LCAPE is caused by the laser-induced metal vapor. The mechanism mainly includes the convection cooling and enhanced radiation of the arc plasma by the metal vapor. Our findings could broaden the theory of laser-plasma interaction and provide a theoretical reference to the modulation and control of plasma in industries.
关键词： Cooling effect,Stainless steel,Laser-arc hybrid welding,Arc plasma,Fiber laser
更新于2025-11-28 14:24:20
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Dynamic keyhole behavior and keyhole instability in high power fiber laser welding of stainless steel
摘要： A three-dimensional numerical model, considering the real-time multiple reflections of a laser beam, adiabatic bubble model and shear stress, was developed to study the dynamic keyhole behavior and keyhole instability in fiber laser welding of stainless steel. The inner dynamic keyhole behavior and weld defect formation were directly observed in a high resolution assisted by transparent glass. The numerical and experimental results showed that the keyhole width reached the quasi-steady state earlier than the keyhole depth did during fiber laser welding of stainless steel. Due to the large recoil pressure at rear keyhole wall caused by the irradiation of laser energy reflected by the bulge at the front keyhole wall, the rear keyhole wall was severely deformed at keyhole bottom and keyhole middle. The rear keyhole wall was collapsed due to the high surface tension pressure and hydrostatic pressure. The whole keyhole collapse was attributable to the capillary instability of the keyhole associated with large depth/width ratio and the strong flow of the bulges at the keyhole wall. When the laser power was increased, the keyhole depth/width ratio was increased, so the keyhole was more capillary instable. The average inclined angle of the front keyhole wall was decreased.
关键词： Bubble formation,Dynamic keyhole behavior,Keyhole instability,Fiber laser welding
更新于2025-11-28 14:24:20
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Effect of Heat Input on Porosity Defects in a Fiber Laser Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy
摘要： Porosity defects are still a challenging issue in the fusion welding of molybdenum and its alloys due to the pre-existing interior defects associated with the powder metallurgy process. Fiber laser welding of end plug and cladding tube made of nanostructured high-strength molybdenum (NS-Mo) alloy was performed in this work with an emphasis on the role of welding heat input. The distribution and morphology of porosity defects in the welded joints were examined by computed tomography (CT) and scanning electron microscopy (SEM). Preliminary results showed that laser welding of NS-Mo under low heat input significantly reduced the porosity defects in the fusion zone. The results of computed tomography (CT) showed that when the welding heat input decreased from 3600 J/cm (i.e., 1200 W, 0.2 m/min) to 250 J/cm (i.e., 2500 W, 6 m/min), the porosity ratio of the NS-Mo joints declined from 10.7% to 2.1%. Notable porosity defects under high heat input were related to the instability of the keyhole, expansion and the merging of bubbles in the molten pool, among which the instability of the keyhole played the dominant role. The porous defects at low heat input were generated as bubbles released from the powder metallurgy base metal (BM) did not have enough time to overflow and escape.
关键词： fiber laser welding,molybdenum alloy,porosity defects,heat input
更新于2025-11-28 14:24:20
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Influence of laser parameters on tensile shear strength of copper welds
摘要： The electrification of the power train in the automotive industry leads to the requirement of electrical connectors with high ampacities. These connectors are often realized using ultrasonic bonding technology. Substitution of ultrasonic welding by laser welding allows an increase of ribbon cross section by a factor of 5 and thus a similar increase of the maximum transferred current. The increased cross section leads to higher loads (at least by a factor of 5) applied to the weld seam during the process. To minimize the heat input, the weld seam strength in shear direction shall be maximized. The influence of different laser parameters on the ultimate tensile shear stress in lap joint configuration is investigated, based on representative specimen geometries (10 × 0.3 mm2). The variable parameters are: laser wavelength (IR around 1050 nm + frequency doubled 515 nm), focal diameters (42–300 μm), different temper conditions of the base material, process parameters (laser power 0.6–4 kW and feed rate 50–800 mm/s), and welding strategies (single pass welding, spatial beam modulation). The material used is Cu-ETP (>99.9% Cu). For all the investigated parameters, the observed failure mode is “fracture in the fusion zone.” The ultimate tensile shear stress for all experiments is around 188 N/mm2 even for parameter changes in the order of one magnitude. This is in contrast to the assumed relation between laser parameters and the mechanical properties. This contrast will be discussed.
关键词： load-carrying capacity,ductile welds,wobbling,fiber laser welding,shear strength
更新于2025-11-28 14:24:20
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Laser in-situ synthesis of high aspect ratio TiB fiber bundle reinforced titanium matrix composite coating
摘要： In this study, coatings are fabricated with laser cladding technique on titanium alloy substrate using TiB2 powder (0.5 μm, 5 μm and 50 μm) as the cladding materials. The effects of different TiB2 particle sizes and different laser powers on the microstructure of laser cladding layer are investigated. The results reveal that the cladding layer of high aspect ratio TiB fiber bundle is formed when using 0.5 μm TiB2 as the cladding material under the condition of high laser power (2.5 kW) of TiB fiber bundle are formed when using 5 μm and 50 μm TiB2 as the cladding materials under the condition of different laser powers. Combined with the evolution of microstructure in the cladding layers, the formation mechanism of high aspect ratio TiB fiber bundle is discussed. Meanwhile, the cladding layer of high aspect ratio TiB fiber bundle exhibits the advantages of high hardness and high wear resistance, and the predominant wear mechanisms of TiB fiber bundle are cutting and fracture.
关键词： TiB fiber bundle,Microstructure,Wear,Laser cladding,Hardness
更新于2025-11-28 14:24:20
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Influence of Al-Si coating on microstructure and mechanical properties of fiber laser welded 22MnB5 steel
摘要： Fiber laser welding of as-received 22MnB5 steel with Al-10wt.%Si coating in butt configuration was performed. The influence of Al-Si coating on microstructure transformation and mechanical properties including tensile tests, fatigue tests and Erichsen cupping tests was investigated. Ferrite with Al enrichment (1.37 wt%) was found in the fusion zone (FZ) of coated welded joints with 15% area proportion, while nearly entire martensite structure composed the FZ in the case of de-coated joint. The strain localization was more likely to accumulate at the martensite/martensite interface rather than the ferrite/martensite interface due to the higher kernel average misorientation (KAM) values. Microhardness of the FZ in coated welded joints dropped by 50HV compared with that of de-coated welded joints. However, tensile properties were not affected since failure occurred at base metal (BM). Fatigue samples of coated welded joints showed better performance than the de-coated ones, suggesting that the ferrite in the FZ had positive effect on fatigue lives under cycling load conditions. The Erichsen cupping tests showed similar Erichsen values (5.60 mm and 5.67 mm) for de-coated and coated welded joints. An opposite effect of ferrite on Erichsen cupping tests was obtained. The peak force required for deformation dropped by 35% with Al-10wt.%Si coating.
关键词： Microstructure,Al-Si coating,Mechanical properties,Fiber laser welding,22MnB5 steel
更新于2025-11-28 14:24:20
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Polarization induced non-reciprocal phase controlled all-fiber loop mirror based inclinometer
摘要： An optical fiber inclinometer based on non-reciprocal phase change effect in a single-mode fiber loop mirror (FLM) is proposed. The phase of light waves in FLM is controlled by two-phase shifters (PSs). The relationship between the inclination angles and phase differences of the two-PSs, and transmitted light power was derived by Jones calculus. The signature of the birefringence obtained through simulation on the output light has been confirmed by experimentation. From the results, it was found that when the birefringence of the two-PSs are different, two measurement sensitivities (17.07 × 10?3 deg?1 and 21.37 × 10?3 deg?1) can be realized with one angle measurement system. We also report a method for changing measurable ranges, and measurement sensitivity. Since the angle can be directly measured from the transmitted light power, the results of this work contribute to the realization of simple and low-loss inclinometers using standard single-mode fiber.
关键词： Optical fiber inclinometer,Tilt measurement,Fiber optics,Sagnac interferometer,Fiber loop mirror
更新于2025-11-28 14:24:03
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Helical Long-Period Gratings Inscribed in Polarization-Maintaining Fibers by CO2-Laser
摘要： We demonstrate fabrication of helical long-period gratings (HLPGs) in a polarization-maintaining fiber using CO2-laser. The maximum polarization dependent loss (PDL) of the grating was measured to be more than 30 dB at the resonance wavelength. The HLPG was found to have a high index sensitivity of -7248.6 nm/RIU when the surrounding refractive index changes in the range of 1.4470-1.4600, temperature sensitivity of 158.8 pm/°C, and strain sensitivity of 3.17 pm/με. The twist sensitivities based on intensity variation were measured to be 5.98 dB/ (rad/m) (co-directional twist) and -5.97 dB/ (rad/m) (contra-directional twist), respectively. The demonstrated grating devices have promising applications as high-sensitivity fiber sensors, PDL compensator etc.
关键词： optical fiber sensors,Fiber gratings,polarization-maintaining fibers,helical long-period gratings
更新于2025-11-28 14:24:03
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High Sensitivity Polarimetric Optical Fiber Pressure Sensor Based on Tapered Polarization-Maintaining and Fiber Bragg Grating
摘要： In this paper, we propose a high sensitivity polarimetric optical fiber pressure sensor (OFPS) using a polarization-diversity loop composed of a polarization beam splitter, polarization controllers, and a sensor head. The sensor head consists of 8-cm-long tapered panda-type polarization-maintaining fiber (PMF) and a fiber Bragg grating (FBG) directly spliced with PMF, and the sensor head is located inside a pressure chamber. A pressure-induced birefringence change due to the photoelastic effect can be greatly enhanced at the tapered section of PMF, thereby increasing the pressure sensitivity of the sensor head. The tapered PMF was fabricated using a fusion splicer, and the tapered length and center waist diameter of the tapered PMF segment were ～350 and ～56.82 μm, respectively. At the polarization-diversity loop, PMF is used as a birefringent element to create an interference spectrum due to polarization interference. A pressure-induced birefringence change of PMF results in a wavelength shift of the interference spectrum. Because the PMF birefringence also has a cross sensitivity to temperature, the FBG is utilized for the compensation of the temperature effect on it. The resonance wavelength of the FBG is sensitive to ambient temperature changes but insensitive to changes in pressure. This spectral response of the FBG can be used to compensate additional ambient temperature changes occurred at the sensor head. The pressure sensitivity of our sensor was measured as approximately ?27.70 nm/MPa, and an adjusted R2 value representing the sensor linearity was measured as ～0.9903 in a measurement range of 0–0.5 MPa. Our fabricated sensor exhibits the highest pressure sensitivity among previously reported polarimetric OFPS.
关键词： Polarization-Maintain Fiber,Optical Fiber Sensor,Sagnac Interferometer,Pressure
更新于2025-11-28 14:24:03