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Simulation and Experimental Based Analysis of the Laser Beam Welding of DP Steels
摘要： In this paper, heat affected zone characteristics of DP1000 steels was investigated during diode laser beam welding (LBW). A butt-welded joint of specimen in dimension of 300 x 150 mm each (according to EN15614-11:2002) with 1 mm thickness is used for the experimental purpose. The welding thermal cycle and the cooling circumstances in the HAZ was determined by real experiment and the physical simulation. A Gleeble 3500 thermo-physical simulator was used to physically simulate the coarse grain heat affected zone (CGHAZ) on the base material specimens by the utilization of the thermal cycles for t8/5 =2.5 s. The results of the physical simulation were validated by real welding experiments. The properties of the simulated and the real HAZ was examined by optical microscopic, scanning electron microscope and hardness tests.
关键词： Gleeble 3500 physical simulator,t8/5 cooling time,Laser beam welding (LBW),dual phase (DP) steel,Heat affected zone (HAZ) characterization
更新于2025-09-19 17:13:59
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Surface behavior of 16Cr3Al ODS steel—Effects of high laser intensity 1014 W/cm2 in ambiences of air, helium and vacuum
摘要： The behavior of 16Cr3Al ODS steel (oxide dispersion strengthened steel), widely employed structural fusion material, under high-intensity laser radiation with intensity up to 1014 W/cm2 was investigated in air, helium and vacuum surrounding. Employed system was 65 fs laser at 804 nm, with applied pulse energy up to 5.25 mJ. Morphological effects were studied – cracking, crater parameters (depth, cross-section), LIPSS (laser-induced periodic surface structures) formation at the crater periphery, hydrodynamic effects, as well as chemical variations on the surface. Ablation thresholds were also determined for all three ambiences (for 100 applied pulses), and they were 0.30 J/cm2, 0.23 J/cm2 and 0.39 J/cm2 in air, helium and vacuum, respectively. Plasma occurred in all experiments and it was most prominent in vacuum due to strongest laser-material coupling.
关键词： 1014 W/cm2 laser intensity,Laser-induced damages/craters,Nuclear material,Femtosecond laser surface modification,ODS steel
更新于2025-09-19 17:13:59
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Fatigue Life Behavior of Laser Shock Peened Duplex Stainless Steel with Different Samples Geometry
摘要： Two different stress raiser geometries (fillet and notched) were treated by laser shock peening (LSP) in order to analyze the effect of sample geometry on fatigue behavior of 2205 duplex stainless steel (DSS). The LSP treatment was carried through Nd:YAG pulsed laser with 1064 nm wavelength, 10 Hz frequency, and 0.85 J/pulse. Experimental and MEF simulation results of residual stress distribution after LSP were assessed by hole drilling method and ABAQUS/EXPLICIT software, respectively. The fatigue tests (tensile-tensile axial stress) were realized with stress ratio of R = 0.1 and 20 Hz. A good comparison of residual stress simulation and experimental data was observed. The results reveal that the fatigue life is increased by LSP treatment in the notched samples, while it decreases in the fillet samples. This is related to the residual stress distribution after LSP that is generated in each geometry type. In addition, the fatigue crack growth direction is changed according to geometry type. Both the propagation direction of fatigue crack and the anisotropy of this steel results detrimental in fillet samples, decreasing the number of cycles to the fatigue crack initiation. It is demonstrated that the LSP effect on fatigue performance is influenced by the specimen geometry.
关键词： laser shock peening,residual stress,duplex stainless steel,fatigue life,sample geometry
更新于2025-09-19 17:13:59
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Influence of Powder Condition on Surface Properties of Cold-Resistant High-Strength Steel Produced by Direct Laser Deposition Method
摘要： Direct laser deposition (DLD) allows creating parts of complex shapes and configurations in a single process step without using of additional equipment. Such technologies are required in the shipbuilding industry, aircrafts, gas turbines, mechanical engineering etc., where it is necessary to manufacture large-sized and complex products that have a long technological cycle for production using classical technologies. DLD makes it possible to produce parts of various alloys with mechanical characteristics at the level of the wrought alloys. The publication is described direct laser deposition of high-strength cold-resistant steels results. Besides mechanical properties of material, the exploitation properties of the structure are also significantly important. Results of corrosion, abrasive-corrosion and tribotechnical tests are shown.
关键词： corrosion resistance,high-strength steel,abrasive-corrosion resistance,Direct laser deposition,cold-resistant steel,initial powder condition,wear resistance
更新于2025-09-16 10:30:52
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Microstructure and fatigue behavior of a laser additive manufactured 12CrNi2 low alloy steel
摘要： In this research, 12CrNi2 low alloy steel was successfully prepared by laser melting deposition (LMD). The mechanisms driving high cycle fatigue fracture of the as-built LMD 12CrNi2 low alloy steel were investigated and a concurrent process-microstructure-property relationship was established through microstructural analysis. The results showed that the crystal structures of the as-built LMD 12CrNi2 steel mainly consisted of the ferrite and a small amount of Cr23C6 carbides. No preferred texture was observed as a result of the complicated heat flux direction during fabrication. Based on the examination of the fracture surface, fatigue cracks of the as-built LMD 12CrNi2 steel initiated from subsurface defects for all the cases. Crack propagation zones showed a mixed mode of transgranular and intergranular fracture in a brittle manner, whereas the final fracture zones displayed dimples typical of ductile fracture. The kernel average misorientation (KAM) map indicated that the strain localization predominantly occurred at the grain boundaries and slightly appeared at the interior of the ferrite grains. Schmid factor distribution results implied that fatigue cracks originated from grains with {123}<111> slip system due to the prior activation of {123}<111> slip system.
关键词： Fractography,High cycle fatigue,Microstructure,12CrNi2 low alloy steel,Laser additive manufacturing
更新于2025-09-16 10:30:52
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Laser Brazing of Dissimilar Joint of Austenitic Stainless Steel and Pure Copper
摘要： In many industries, there are applications that require the joining of stainless steel and copper components; therefore, the welding of dissimilar stainless steel/copper joints is a common process. For this investigation, the optimal brazing conditions and suitable filler metals for laser brazing of stainless steel/copper lap joints were studied. Tensile shear force increases with increases in the laser spot diameter or in the laser irradiation angle, which is associated with increased bonding width; however, as bonding width approaches 2 mm, tensile shear force reaches a saturated value due to fracturing at the HAZ of the Cu base plate. In order to obtain joints with high tensile shear strength, laser brazing was optimized by using Cu-Si-based filler metal under the following conditions: laser power: 4 kW; spot diameter: 3mm; laser irradiation angle: 80 degrees; irradiation position shift: 0.6 mm; brazing speed: 0.30 m/min; and filler metal feed speed: 0.30 min. Concerning filler metals, it was found that the Ni-Cu type showed relatively large tensile shear force even at high welding speeds in comparison with those of the Cu-Si, Cu, Cu-Ni, Ni-Cu and Ni types, respectively.
关键词： Laser brazing,Copper,Filler metal,Dissimilar material,Stainless steel,Brazing condition
更新于2025-09-16 10:30:52
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Structurally colored stainless steel processed by using femtosecond laser pulses
摘要： Structurally colored stainless steel (SS) surfaces were produced by using femtosecond laser at normal incidence at ambient conditions. The influence of laser polarization on the surface properties was investigated. The surface morphologies, roughness and color of the laser-treated surface were characterized by using environmental scanning electron microscope (ESEM), roughmeter and atomic force microscope (AFM). Results indicated that the circular polarization leads to more random structures than the horizontally linear polarization. Specimen with the highest surface roughness shows the brightest color. Different colors are cyclically exhibited by changing view angles due to different orders of diffraction. This investigation developed the technique of using femtosecond laser in situ preparation of periodic structures on 304 SS, and indicating that laser polarization is an important parameter to control surface structures to achieve different colors.
关键词： polarization,micro/nanostructure,coloration,Femtosecond laser,stainless steel
更新于2025-09-16 10:30:52
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Fatigue Behaviour of Laser Spot Welds in Dual Phase 780 Steel
摘要： High cycle fatigue performance was evaluated on circular shaped laser spot welds (LSW) of dual phase DP780 steels. Fibre laser with two different parameter sets were applied to produce the spot welds. The weld size growth is concomitant to laser power. The failure mechanism under fatigue loading, involving crack initiation and propagation till failure, is explained using analytical stress models and experimental data. Interrupted fatigue tests were done and the crack path was captured by observing under scanning electron microscope. Stress models show that during tensile shear loading of overlapping sheets having spot weld, there is a countering effect of shear stress and bending stress; the latter acts perpendicular to the shear stress and arises from the bending moment along the plane of contact during load transfer. The dominant stress depends on the contact area, i.e. the weld size, which largely controls the crack path route and concurrent fatigue life. Incidentally smaller welds show marginally longer life wherein the stronger axial stress component propels the crack through a longer route consuming more number of cycles. Again, with lowering of fatigue load there is a shift in the mode of failure with transition from interfacial to partial to pull-out failure. However, large welds fail in pull-out mode only irrespective of the fatigue load levels. As compared to the size effect, the weld microstructure has less influence on fatigue crack propagation.
关键词： Laser welding,Stress Intensity Factor,High Cycle Fatigue behaviour,Circular weld,Dual phase steel
更新于2025-09-16 10:30:52
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Multi Response Optimization of Nd:YAG Laser Micro Drilling Characteristics of 304 Stainless Steel using Desirability Function Approach
摘要： Laser micro drilling is a non-traditional machining process for producing micro hole of various sizes and different angle in many modern industrial application, such as aerospace gas turbine, automobile industry, electronics field etc. Laser drilling is extremely high speed with high aspect ratio. However, the quality and accuracy of the holes can be excellent, if the optimal process parameter has set. It is difficult to achieve exact size of hole as per suggested by the equipment manufacturer without any consideration. So this paper addressed to investigate influence of process parameter on drilling characteristics of 304 stainless steel of 1.5 mm thickness material using Nd:YAG laser drilling through desirability function optimization technique. The effect of process parameter taken during machining operation is average power, nozzle stand-off, nitrogen gas pressure to obtain requisite hole quality. The output responses are entry circularity, exit circularity and taper angle were considered performance criteria for the experimentation. Analysis of variance (ANOVA) has been performed to find out the significant process parameter during the micro drilling process. It is found that nitrogen gas pressure is highly influencing factor on the overall response characteristics, which is about 54.62% and nozzle standoff is 2nd highest influencing parameter, which is about 27.69%.
关键词： 304 Stainless Steel,Laser Drilling Machine,Optimization,Desirability,ANOVA
更新于2025-09-16 10:30:52
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Numerical Study on Thermodynamic Behavior during Selective Laser Melting of 24CrNiMo Alloy Steel
摘要： In this paper, a multi-layer and multi-track ?nite element model of 24CrNiMo alloy steel by selective laser melting (SLM) is established by using the ABAQUS software. The distribution and evolution of temperature ?eld and stress ?eld and the in?uence of process parameters on them are systematically studied. The results show that the peak temperature increases from 2153 C and the residual stress increases from 335 MPa to 364 MPa with increasing laser power from 200 W to 300 W; the peak temperature decreases from 2905 C and the residual stress increases from 327 MPa to 363 MPa with increasing scanning speed from 150 mm/s to 250 mm/s; the peak C and the residual stress decreases from 354 MPa to 300 temperature increases from 2621 MPa with increasing preheating temperature from 25 C. Far away from scanning area, far away from starting point, and the adjacent areas with vertical scanning direction, resulting in a uniform temperature distribution, help to reduce the residual stress. Due to the remelting e?ect, the interlayer scanning angle changing helps to release the residual stress of the former layer causing a smaller residual stress after redistribution.
关键词： substrate preheating,?nite element analysis,thermodynamic behavior,selective laser melting,scanning strategy,24CrNiMo alloy steel
更新于2025-09-16 10:30:52