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Microstructure and mechanical properties of welding–brazing of Ti/Al butt joints with laser melting deposition layer additive
摘要： Laser welding–brazing of Ti/Al butt joints was performed with coaxial Al–10Si–Mg powders feeding. The experimental results indicated that a sound Ti/Al butt joint could be obtained by an additive layer approach. The influence of the laser melting deposition layers on the weld appearance, interfacial microstructure and tensile properties were investigated. High-quality joints were produced when five and seven layers were deposited. The morphology and thickness distributions of the interfacial intermetallic compounds (IMC) at the brazing interface along the thickness direction of the joint varied with the number of deposition layers. Continuous serrated IMC was obtained in joints produced by seven deposition layers, and the IMC layer was distributed homogenously along the thickness direction. The maximum thickness difference of the IMC was only approximately 0.12 μm. The microstructure of the IMC layer was composed of a nanosized granular Ti7Al5Si12 phase and serrated Ti(Al, Si)3 phase. The maximum tensile joint strength reached 240 MPa, 80% of that of the aluminum base metal, and the lower tensile strength of the other joints was caused by insufficient IMC layer or a porosity defect.
关键词： Tensile strength,Laser melting deposition,Interfacial IMC,Laser welding–brazing,Ti/Al butt joint
更新于2025-09-19 17:15:36
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Microstructural characterization and tensile behavior of Nd:YAG laser beam welded thin high strength low alloy steel sheets
摘要： Laser beam welding (LBW) has many advantages to join high strength low alloy (HSLA) steels compared with conventional fusion welding processes. The present work is focused on joining HSLA plates of 2 mm thickness efficiently through the application of Nd:YAG laser source. Only one process variable i.e. the welding speed was operated between 70 mm/s to 120 mm/s while the rest of the variables were maintained constant. The microstructure evolution of the fusion zone was recorded through optical, scanning and transmission electron microscopy. The fusion zone was observed to be wider but no major defects were present. Fusion zone experienced a change in morphology of ferrite and pearlite depending upon the rate of cooling and exposure time. Fusion zone showcased various ferrites such as acicular ferrite, widmanstatten ferrite, and grain boundary ferrite. Advancement in the welding speed helped in the formation of acicular ferrite. EBSD results presented a descending tendency of prior austenite grain size against increasing welding speed. TEM micrographs affirmed the ferrite transformation and showed the presence of dense dislocations. The changes in hardness and tensile behavior under the experimental conditions were further reported.
关键词： High strength low alloy steel,Microstructure,Tensile strength,Laser beam welding
更新于2025-09-19 17:13:59
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The normal and shear strength properties of laser lap weld
摘要： The study was aimed to clarify the shear strength and the normal strength properties of the lap joint. The welds were characterized with respect to hardness, tensile and fatigue properties. The test materials of this study were low strength carbon steel (LSS) and ultra high strength wear resistant steel (UHSS). The shear strength, perpendicular strength and fatigue resistance of the lap joint laser weld was determined by tensile and fatigue tests. The shear strength of the LSS weld was higher than the strength of the base material. The shear strength of UHSS weld was higher than the LSS weld. However, compared to strength of the base material of the UHSS the weld was weaker even though the weld was harder than the base material. The normal strength of the UHSS and LSS welds was over two times higher than the shear strength of the same welds.
关键词： Shear strength,Laser weld,Normal strength
更新于2025-09-19 17:13:59
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Improved breakdown strength of Poly(vinylidene Fluoride)-based composites by using all ball-milled hexagonal boron nitride sheets without centrifugation
摘要： Hexagonal boron nitride (h-BN) is an ideal candidate to endow ferroelectric polymers with high energy density ((cid:1)(cid:2)) due to its intrinsic high breakdown strength ((cid:3)(cid:4)) of 800 kV/mm. Generally, it is believed that only boron nitride nanosheets (BNNSs) could remarkably improve (cid:3)(cid:4) of composite. Nevertheless, low-yield and time-consuming preparation procedures of BNNSs greatly limits the application of h-BN. To overcome this challenge, in this study, all ball-milled h-BN (B-BN) sheets were entirely used to enhance (cid:3)(cid:4) of poly(vinylidene fluoride) (PVDF) without any further centrifugation. (cid:3)(cid:4) of composites increased as ball-milling time increases at filler content of 8 wt%. Remarkably, PVDF with h-BN ball-milled for 16 h (B16-BN) possesses an impressive (cid:3)(cid:4) value of 506.8 kV/mm, which is 2.86 times that of neat PVDF (272.4 kV/mm) and even 1.33 times higher than that of PVDF/h-BN composites (380.6 kV/mm). (cid:3)(cid:4) of PVDF/B16-BN composites is close to that of PVDF/OH-BNNSs composites at same filler content, suggesting that the centrifugation is not a necessary procedure. Besides, improved dielectric loss, calculated (cid:1)(cid:2), mechanical properties and in-plane thermal conductivity can also be achieved for PVDF/B16-BN composites. These improved properties of PVDF/B16-BN composites indicate that the employment of B16-BN can avoid the weakness of low-yield and time-consuming preparation procedure of BNNSs and broaden its applications in the field of energy storage. Finally, the improved dispersion of OH-BN as well as synergy effect (f) on (cid:3)(cid:4) between OH-BN and OH-BNNSs were discussed to better understand these improved properties of PVDF/B16-BN composites.
关键词： Breakdown strength,No centrifugation,Synergy effect,Hexagonal boron nitride
更新于2025-09-19 17:13:59
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Optimization of Laser Sintering for Demineralized Bone/Polycaprolactone Composite Powder for Bone Tissue Scaffold
摘要： Demineralized bone matrix (DBM) is an excellent bone scaffold material, but is available in only limited sizes. An additive manufacturing (AM) method that retains these properties while enabling customized geometry fabrication would provide bone scaffolds for a larger range of geometries while maintaining the benefits of DBM. This work examines laser sintering (LS) of a blend of demineralized bone matrix (DBM) and polycaprolactone (PCL) using a CO2 laser beam. A comprehensive experimental study was carried out to find the conditions that form defect-free layers while still retaining the favorable biological features of DBM. The results identify a process setting window over which LS can be utilized to constructing complex patient-specific scaffolds. With the identified setting, first, the DBM/PCL blend was fused in the LS machine. Parts were then were further strengthened through a post-processing heat treatment. The shrinkage level, skeletal density, mechanical testing, and porosimetry of the resultant samples were compared to traditional machined DBM blocks. The maximum tensile strength of the samples and post-processing shrinkage depends on heat treatment duration. The tensile strength measurements demonstrate that the post-processing conditions can be tuned to achieve the tensile strength of the demineralized bone strips. Evaluation of the dimensional change suggests that the shrinkage along the laser paths is ~0.3% while thickness shrinks the most (up to ~20%). The porosimetry and density studies showed that the final part achieved over 40% porosity with a density comparable to blocks of DBM.
关键词： laser sintering,porosity,tensile strength,optimization,demineralized bone matrix,shrinkage,additive manufacturing,polycaprolactone
更新于2025-09-19 17:13:59
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Effect of laser texturing on the surface characteristics and bonding property of 30CrMnSiA steel adhesive joints
摘要： The influence of laser texturing on the bonding property of 30CrMnSiA steel joints were investigated. Three patterns including dimple, groove and grid were laser textured on the 30CrMnSiA steel substrate by nanosecond fiber laser. The processed surface was characterized by surface morphology, surface roughness (Ra and Rz) and wettability. The single lap adhesive joints were fabricated and fracture surfaces were observed. The accelerated hygrothermal aging experiments were performed. The results indicated that surface roughness and wettability were both enhanced after laser texturing. The grid patterned substrate was improved pronouncedly, where Ra increased by 400% and Rz was 13 times higher than as-received specimens, and the contact angle was decreased from 65° to 24°. The shear strength of adhesive joints for dimple pattern was not improved evidently, while it was 14.6 MPa and 23.3 MPa in the groove and grid patterned specimens, which was increased by 219%, 348% compared to as-received ones, respectively. The coverage of adhesive layer on the fracture surface was increased and the fracture mode of dimple and groove patterned specimens was adhesive failure and a cohesive failure was achieved for those joints with grid pattern. The bonding property was decreased after hygrothermal aging, and the residual strength of specimens with grid pattern was the highest. The fracture mode was not changed in all adhesive joints.
关键词： Laser texturing,Wettability,Roughness,Adhesive strength,Hygrothermal aging
更新于2025-09-19 17:13:59
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Influence of Post-Weld Processing Techniques on Laser Beam-Welded Ala??3Mga??0.25Sc Alloy Sheets
摘要： Fusion welding in aluminium alloys had always remained an issue for aero- and auto industries. An Al–3Mg–0.25Sc alloy is classi?ed as weldable aluminium alloys. In this study, two welding techniques, keyhole and conduction welding, have been used for joining Al–3Mg–0.25Sc sheets of thickness 1.6 mm. Experiments were carried out using different beam diameter (0.16–2 mm dia), beam power (2–4.5 kW) and laser head speed (ranging from 0.5 to 6 m/min). The results for all autogenous keyhole welding clearly demonstrated a drop in ductility (\ 0.8%) compared to base metal for all beam power and welding speed combinations although the yield strength was reasonably good (175–180 MPa, i.e. [ 50% of base metal). Residual stress-induced distortions affected the ?nal shape of the product, and for that, a suitable stress relief annealing was also required. Hereby, we chose two heat treatment schedules: (1) solution treatment and annealing and (2) retrogression and re-ageing. Retrogression and re-ageing is a precipitation-controlled phenomenon and comprises of an intermediate annealing step between tempering and solutionizing temperature to dissolve the nano-clusters present in the matrix (retrogression) and re-precipitating and growing them by ageing (re-ageing). These two steps were repeated cyclically, and as a result, the strength (190 MPa) and ductility (* 9%) of the material were improved substantially. The improvement of ductility and strength was explained in detail in the light of microstructural studies.
关键词： Strength,Post weld treatment,Weldment,Al-3Mg-0.25Sc alloy,Ductility,Laser welding
更新于2025-09-19 17:13:59
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Influence of surface treatment with infrared nanosecond laser on adhesion performance of adhesion-bonded carbon fiber/epoxy composite
摘要： The surface treatment of carbon fiber/epoxy composites with a pulsed infrared (1064 nm wavelength) nanosecond (7 ns pulse duration) laser has been investigated. It is found that single 1064 nm laser pulse can remove the polymer matrix from composite surface to expose the carbon fibers by expansion of the pyrolysis gas resulting from laser-induced polymer degradation. The influences of laser power density and scan strategy on matrix removal process have been studied. The bonding strength of laser processed, adhesion-bonded CFRP (carbon fiber reinforced plastic) increase with lower matrix residues on the fibers and a linear relation is found. The adhesion-bonding strength of CFRP surfaces, tested by lap-joint shear test, exceeds the strength measured for untreated and abrasion treated (SiC paper) samples. The main origin of fiber damage of the laser-treated surface is mechanical fracture rather than thermal damage as found by laser scanning confocal microscope and scanning electron microscope. The characteristic morphologies and failure modes of shear-tested surfaces are analyzed. The obvious improvement of adhesive strength is achieved by the laser-treated surfaces attributed to matrix removal and carbon fibers protruding. A 1 D model is established to describe temperature and internal gas pressure of the irradiated surface. The new laser treatment method needs less laser energy and low pulse numbers and prove the way to an efficient, low-cost surface treatment for preparation of high quality adhesion bonded CFRP components.
关键词： matrix removal,adhesion strength,1064 nm laser,Carbon fiber/epoxy composite
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Photoluminescence of SnO <sub/>2</sub> nanoparticle ensemble in porous glass with column structure
摘要： In recent years, smart devices have become ubiquitous. Many of these devices are equipped with global positioning system (GPS), Wi-Fi, and other sensors. With their high mobility, the idea of mobile devices as probes has been attracting more and more attention. Mobility and ?exibility offered by smart mobile devices are what traditional ?xed sensors lack. However, mobile devices’ power supplies are quite limited. Although GPS is accurate, its high power consumption somewhat limits its accessibility and sustainability. In contrast, Wi-Fi is less power hungry, but at the same time, less accurate. For the sake of sustainability, by adopting Wi-Fi as an alternative to GPS, longer operation is attainable at the cost of losing some degree of accuracy. In this paper, a Wi-Fi-based algorithm based on log-normal probability distribution of distances with respect to received signal strength is proposed. It is suitable for an outdoor environment, where Wi-Fi access points (APs) are abundant. Simulations are conducted over known AP locations, and results show that the proposed algorithm can save, on average, as much as 35% more battery power than GPS does. The average localization error is ～18 m, and the average velocity estimation error is ～25%.
关键词： Mobile phone sensing,log-normal distribution,positioning algorithm,Wi-Fi-based localization,received signal strength indicator
更新于2025-09-19 17:13:59
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Numerical simulation of temperature distribution and experimentation in laser beam welding of SS317L alloy
摘要： In the present study stainless steel 317L grade was chosen for joining using 400w Nd-YAG laser beam welding process. Tensile strength and temperature distribution are considered as output responses while Welding current, Frequency, Pulse width are taken as process parameters. A butt configuration of 5 mm thick plate of austenitic steel alloy and K-type digital thermocouple was used to observe the temperature experimentally. The welded plates are cut using Electro-discharge machining to prepare Tensile test specimens according to ASTME21 standard. The specimens are tested to get stress-strain graphs and ultimate tensile strengths for all the 9 cases (as per L9 Orthogonal array). Additionally, a 2D transient thermal-structural numerical simulation model was developed to simulate the complete laser welding process. The effect of each parameter has been studied experimentally and numerically. Analysis of variance (ANOVA) has been used for finding out the contribution of each input factor on the output response with the help of MINITAB software. The optimised values of process parameters are utilised to get the thermal profiles and heat-affected zone using finite element simulations. The finite element calculation of process was carried out by a parametric design language APDL available in the ANSYS finite element code. The temperature values obtained using finite element simulation and experiments are matching reasonably good with an error of 12% hence the developed simulated model can be used to study related parameters.
关键词： Tensile strength,Laser beam welding,Optimization,Simulation,FEM,Nd-YAG laser
更新于2025-09-19 17:13:59