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Waveguide optimization and its evaluation of a doped polymer optical ???ber designed for visual detection of stress
摘要： A fiber-optic strain sensor using a fluorophore-doped polymer optical fiber (POF) was fabricated at various waveguiding conditions. The effects attributed to each structural feature of the sensor were characterized by observing the sensor?s response. Two fluorophores, Coumarin 540A and Rhodamine 6G, were used to dope the core and the cladding of a poly(methyl methacrylate)-based POF, respectively. Using doped POFs with different numerical apertures (NAs), the changes in the fluorophore peaks upon the application of stress were analyzed by applying macrobending (s) to the fiber. Although the sensor response did not show linearity with respect to the NA, it was found that the shape of the Coumarin 540A-attributed peak was a factor that represented the sensor?s sensitivity. As a result, the double-cladding structure demonstrated its effectiveness in improving the stress sensitivity.
关键词： double-cladding structure,fluorophore-doped,polymer optical fiber,numerical aperture,fiber-optic strain sensor,stress sensitivity
更新于2025-09-23 15:21:01
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The influence of substrate tilt angle on the morphology of laser cladding layer
摘要： Laser cladding technology has been increasingly used in processes of mechanical part and component repairing and remanufacturing. However, current research on the morphology of laser cladding is carried out on the premise of substrate level, it cannot be directly applied to the inclined substrate for laser cladding. This paper studied the influence law of tilt angle on the morphology of laser cladding through geometric parameters and profile of the laser cladding. Results show that substrate tilt angle mainly affects five geometric parameters such as the width and height of the layer cladding, peak shift, elevation side width and reduction side width. And a theoretical model for these geometrical parameters has been established for prediction in this paper. Meanwhile experimental profiles of laser cladding results verified the consistency between the laboratory data and model predictions, which is developed for tilted substrates. It will greatly expand the application range of laser cladding technology on complex parts such as gears.
关键词： Inclined substrate,Theoretical model,Layer geometric characteristics,Coaxial powder feeding,Laser cladding
更新于2025-09-23 15:21:01
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A Synchronously Self-Q-Switched and Self-Mode-Locked Fiber Laser with a Compound Resonator
摘要： We demonstrate a synchronously self-Q-switched and self-mode-locked output pulse ?ber laser based on a linear compound resonator and an LD cladding-pumped Yb-doped double-clad ?ber. A maximum average output power of 332.1 mW is achieved. We observe that the maximum pulse envelope width is 8 μs, and the pulse energy is 3.83 μJ for the self-Q-switched pulse envelope. At the same time, the achieved maximum pulse width is 37.8 ns and pulse energy is 17.61 nJ for the self-mode-locked pulse. We observe the pulse splitting of the self-Q-switched envelope as well and achieve 14 subpulse packets for L1 = 180 mm. There are 75 self-mode-locked pulses in single packets.
关键词： cladding-pump laser,?ber laser,self-Q-switch,compound resonator,pulse splitting,self-mode-locking
更新于2025-09-23 15:21:01
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Sustainable manufacturing: re-contouring of laser cladding restored parts by machining method with cutting energy management
摘要： Laser cladding has been commonly utilized for restoring high value-added parts. However, the poor surface quality becomes key technological barrier which restricts its widespread applications. In the paper, re-contouring strategies by machining method are explored for minimal energy consumption as well as required surface roughness. Firstly, the effect of structural characteristics of the laser-cladded workpiece on specific cutting energy was explored by means of layer-by-layer turning and orthogonal cutting. Results indicated that the specific cutting energy increased, and the machining chatter/vibration exacerbated with decreasing coating thickness under fixed cutting parameters. The reason can be summarized as a result of the effect of elastoplastic deformation behavior across the interface. Then, the influences of depth of cut and feed on specific cutting energy in finish turning were addressed. Results indicated that the specific cutting energy reduced with increasing depth of cut and feed in the form of power functions. In addition, energy efficiency decreased with an increase in uncut chip thickness and cutting speed. On basis of this work, large feed and low cutting speed with the adoption of wiper inserts were recommended for minimizing energy consumption within surface roughness requirement.
关键词： Energy efficiency,Sustainable manufacturing,Specific cutting energy,Laser cladding,Surface quality
更新于2025-09-23 15:21:01
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Influence of Plasma Transfer Arc Cladding of NiCrBFe filler powder on microstructure and tensile properties of Titanium Grade 2 and Ti 6Al-4V alloy dissimilar joint prepared by laser beam welding
摘要： The present investigation deals with the effect of Plasma Transfer Arc Cladding (PTAC) of 60%Ni30%CrB10%Fe filler powder on microstructure and tensile properties of Titanium Grade 2 and Ti 6Al-4V alloy dissimilar joint done by laser beam welding. In laser beam welding, full depth of penetration was achieved using the laser beam power of 1300 W, welding speed of 200 mm/min and focus distance of 10 mm. Tensile studies showed that all the failures occurred in the fusion zones of as-welded, dissimilar weldments and PTAC coated samples. Failure analysis was performed using Comsol software and the results were obsersed as well-in accordance with the experimental results. Finite element studies showed the better accuracy results while comparing both experie-mental and simulation results. The microstructure and mechanical properties studies were conducted on as-welded, dissimilar weldments and PTAC coated samples by scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), and X-ray diffraction (XRD) respectively. XRD displayed the slight presence of compressive residual stress in PTAC coated samples. The microstrcture studies conducted at the fusion zone revealed that more amount of coarse grain boundaries were converted into α-Fe. The avearge heat inputs (Hi) were applied in the coated samples that converted the α + β phase structure into TiNi + TiCrFe boundarys. PTAC coated samples showed the average hardness value of 313 HV and dissimilar weldments exhibited the hardness value of 290 HV. The present study concluded that the corrosion resistance of coated materials was improved owing to the better tensile and bending strength of material.
关键词： Mechanical Properties,Plasma Transfer Arc Cladding,Finite element analysis,NiCrBFe filler powder,Laser beam welding
更新于2025-09-23 15:21:01
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Prediction of solidification cracking by an empirical-statistical analysis for laser cladding of Inconel 718 powder on a non-weldable substrate
摘要： This paper presents an empirical-statistical approach to predict solidification cracking during laser cladding of Inconel 718 powder on A-286 Fe-based superalloy. This approach is based on a linear regression analysis and empirical-statistical correlations between the key processing parameters (laser power, P; powder feed rate, F; and scanning speed, V) and the geometrical attributes of single laser cladding tracks. These correlations were used for the development of a processing map which assesses the effects of the geometrical characteristics on the solidification cracking and the required conditions to obtain crack-free clads. Scanning electron microscopy was used for microstructural characterization. Thermodynamic calculations using the non-equilibrium Scheil solidification model were also employed. The empirical-statistical analysis showed that the processing parameters directly associated with the height and angle of single laser cladding tracks are and, respectively. The processing map revealed that the dilution ratio is the governing macrostructural attribute required to avoid solidification cracking. Indeed, a substrate dilution ratio lower than 25% shifts the cladding composition to an alloy regime, which has lower susceptibility to solidification cracking. The role of this macrostructural feature in reducing the susceptibility of the fusion zone to solidification cracking is thoroughly discussed.
关键词： Thermodynamic simulation,Inconel 718,Processing map,Solidification cracking,Laser cladding,Dilution ratio
更新于2025-09-23 15:21:01
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GaN/InAlN chirped short period superlattice as strain free top cladding for blue laser diode
摘要： This work presents the theoretical study on strain-free chirped short-period superlattices (C-SPSL) as the top waveguide core and cladding layers for InGaN laser diodes (LDs) emitting at 450 nm. The total 530 nm thick layers of reference LD containing 100 nm p-GaN waveguide, 30 nm Al0.15Ga0.85N electron blocking layer (EBL) and Al0.065Ga0.935N cladding layers are replaced by 300 nm thick C-SPSL which contains the 33-periods of 10 monolayers (ML) GaN/ 2 ML In0.18Al0.82N, 48-periods of 6 ML GaN/2 ML In0.18Al0.82N, and 97-periods of 2 ML GaN/ 2 ML In0.18Al0.82N. The optical confinement factor of reference LD is 3.28% whereas for C-SPSL LD it is 3.42%. The better optical confinement at reduced thickness using C-SPSL is due to the high refractive index contrast. The strain in the C-SPSL is negligible. The electron leakage has reduced from 2.54 kA-cm-2 to 0.166 kA-cm-2 at ~10 kA-cm-2 injected current density, whereas the hole transportation has improved by 2.31 kA-cm-2. The C-SPSL configuration also favours the electron blocking effect, thus EBL is not required in C-SPSL design. The light output power at a current injection of 500 mA (10 kA-cm-2) is 248 mW for the new structure and ~143 mW for reference LD. The slope efficiency is improved from ~0.55 W/A to ~0.89 W/A. Also, the dynamic resistance from I-V characteristic is ~ 1.12 Ω which is lowered to ~0.94 Ω.
关键词： superlattice cladding,strain-free top cladding,Short-period superlattice,InGaN Laser Diode
更新于2025-09-23 15:19:57
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Microstructure and Wear Behaviour of SS420 Micron Layers on Tia??6Ala??4V Substrate Using Laser Cladding Process
摘要： Ti–6Al–4V is commonly used material in automobile, aerospace, biomedical and marine due to its excellent properties. However, their uses are reduced because their its poor tribological performance. In the current study, stainless steel 420 alloy powder was cladded on Ti–6Al–4V base material using high-power Yb: YAG disc laser. Then, the cladded surfaces were evaluated to reveal their new phase formation, hardness changes and improved wear properties. Besides, the various wear mechanisms and their corresponding rough averages were studied. Results showed that the microhardness of laser cladded specimen is 613HV while base material shows 303HV. The wear rate of laser cladded specimen reduces remarkably compared to un-clad specimen. The identi?ed major wear mechanisms are abrasive, adhesive and oxidation wear. The worn-out cladded surface shows lesser roughness than base material.
关键词： Wear mechanism,Microstructure,Ti–6Al–4V,Roughness,Laser cladding,SS420
更新于2025-09-23 15:19:57
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The restoration of the friction surfaces by laser cladding
摘要： The paper deals with laser cladding of wear-resistant coatings for restoring friction surfaces. It describes the modes of cladding technological process, and presents the results of wear tests. Wear-resistant coating based on the Ni-Cr-B-Si and alumina system, which exceeds 30HGSA steel by 11.5 times by wear resistance.
关键词： wear-resistant coatings,alumina,friction surfaces,Ni-Cr-B-Si,laser cladding
更新于2025-09-23 15:19:57
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Plastic strain localization induced by microstructural gradient in laser cladding repaired structures
摘要： Laser Cladding is an additive manufacturing technology well suited for the repair of complex metallic components. The repair is a two-step process: first, one removes the worn region and then, the initial geometry is reconstructed locally. The aim of this work is to study the influence of the microstructural gradient on the strain localization in repaired structures. More precisely, we perform in-situ SEM tensile tests completed by EBSD observations of the microstructure in the interface neighborhood between the base material and the repaired region. Furthermore, we monitor the evolution of the local plastic strain distribution at the grain level until failure. This is performed by Digital Image Correlation methods and superposition of grains contours and strain maps. The observations of grain size and plasticity are compared with predictions provided by a Hall-Petch model. The study emphasizes the importance of the microstructural gradient in the vicinity of reparation interface, more precisely it reveals that this gradient induce multiaxial strains and that the strain localization phenomenon is governed mainly by a grain size effect.
关键词： Laser Cladding repair,Additive manufacturing,SEM in-situ tests,strain localization,microstructural gradient
更新于2025-09-23 15:19:57