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Prediction of quality characteristics of laser drilled holes using artificial intelligence techniques
摘要： Micro-drilling using lasers finds widespread industrial applications in aerospace, automobile, and bio-medical sectors for obtaining holes of precise geometric quality with crack-free surfaces. In order to achieve holes of desired quality on hard-to-machine materials in an economical manner, computational intelligence approaches are being used for accurate prediction of performance measures in drilling process. In the present study, pulsed millisecond Nd:YAG laser is used for micro drilling of titanium alloy and stainless steel under identical machining conditions by varying the process parameters such as current, pulse width, pulse frequency, and gas pressure at different levels. Artificial intelligence techniques such as adaptive neuro-fuzzy inference system (ANFIS) and multi gene genetic programming (MGGP) are used to predict the performance measures, e.g. circularity at entry and exit, heat affected zone, spatter area and taper. Seventy percent of the experimental data constitutes the training set whereas remaining thirty percent data is used as testing set. The results indicate that root mean square error (RMSE) for testing data set lies in the range of 8.17–24.17% and 4.04–18.34% for ANFIS model MGGP model, respectively, when drilling is carried out on titanium alloy work piece. Similarly, RMSE for testing data set lies in the range of 13.08–20.45% and 6.35–10.74% for ANFIS and MGGP model, respectively, for stainless steel work piece. Comparative analysis of both ANFIS and MGGP models suggests that MGGP predicts the performance measures in a superior manner in laser drilling operation and can be potentially applied for accurate prediction of machining output.
关键词： Laser drilling,ANFIS,Genetic programming,Stainless steel,Artificial intelligence,Ti6Al4V,Surface cracks
更新于2025-09-12 10:27:22
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Melt pool monitoring for laser beam melting of metals: assistance for material qualification for the stainless steel 1.4057
摘要： Laser Beam Melting of Metals (LBM-M) is an additive manufacturing technique that is successfully applied for the manufacturing of complex parts, small batch series and prototypes. In LBM metallic parts are generated layer by layer directly from sliced CAD data. For each layer a thin powder layer is deposited and subsequently, irradiated by a focused laser beam, which is guided by a galvanometer scanner. A major drawback of this relatively new manufacturing technology is a limited material portfolio. Today, the whole procedure of material qualification is time-consuming and resource intensive because a fast and reliable modelling of the process is not yet possible. In this work we are going to show the results of a qualification procedure applying a coaxial melt pool monitoring system to determine suitable processing parameters for a material, which has not yet been processed. In this work, a stainless steel material was exemplarily used to proof the feasibility. Furthermore, we are discussing the usability of this methodology for the material qualification in LBM-M in general.
关键词： Laser Beam Melting,Additive Manufacturing,Stainless Steel,Material Qualification,Quality Assurance,Selective Laser Melting,Process Stability,Melt pool Monitoring
更新于2025-09-12 10:27:22
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The passivity of selective laser melted 316L stainless steel
摘要： The passive film properties of as-received selective laser-melted 316L stainless steel (SLMed 316L SS) without obvious pores were studied and compared with those of wrought and solution-annealed (SA) SLMed 316L SSs. Among the samples, the as-received SLMed 316L SS had the lowest passive current density, which was attributed to two factors: the super high sub-grain boundary density increased the number of nucleation sites for passive film formation, and the micro-galvanic effect between the sub-grain boundary and the inner sub-grains also accelerated the rapid formation of a thick protective layer. The poor passivation and re-passivation abilities of the SA SLMed 316L SS were ascribed to the extensively precipitated nanosized oxide and sulfide particles, especially those at the grain boundary.
关键词： Cellular structure,Passive film,Stainless steel,Selective laser melting,AFM
更新于2025-09-12 10:27:22
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Direct laser welding of pure titanium to austenitic stainless steel
摘要： Direct butt joining of pure titanium to 316L stainless steel with continuous Yb:YAG laser was performed with variation of the beam offset from joint line. Mechanical properties of samples were evaluated by tensile tests and three-point flexural tests. The fractured surfaces and cross sections of welds were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Tensile properties of welds were strongly determined by the beam offset from joint line and are well described by Weibull statistics. Ultimate tensile strength of 174 ± 69 MPa and ultimate flexural strength of 297 ± 48 MPa were obtained. Brittle fracture took place in the diffusive interface rich in λ1 and FeTi phases.
关键词： titanium,stainless steel,Laser,dissimilar welding
更新于2025-09-12 10:27:22
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Parametric study of laser welding of copper to austenitic stainless steel
摘要： Welding of copper to stainless steel is challenging because of sharp difference in thermophysical properties of materials and the presence of miscibility gap in Fe-Cu system. The parametric study of continuous Yb:YAG laser welding between copper and austenitic stainless steel 316L has been performed. The influence of laser power, welding speed and beam offset from joint line on weld composition, microstructure and tensile properties was studied. The corrosion behaviour of the welds was evaluated in 0.1M NaCl with the potentiostatic pulse testing method, salt fog and immersion tests. In function of copper dilution in the melted zone, different types of microstructure were observed: homogenous solid solution (≥2 at.% Cu), copper-rich net between austenite cells (2-5 at.% Cu) and formation of Cu-rich droplets (> 20 at.% Cu). Selective corrosion of Cu-rich microstructures took place in the melted zone. Tensile properties of the welds were determined by the formation of heat-affected zone in solid copper, where ductile fracture took place.
关键词： stainless steel,copper,corrosion,laser,dissimilar welding
更新于2025-09-12 10:27:22
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A Study of Laser Beam Welding, Gas Tungsten Arc Welding and High Temperature Brazing Processes on Micro hardness and Tensile Strength of AISI Type 316 Stainless Steel
摘要： Thin wall joints for elevated temperature (~550 °C) applications can be prepared by Laser Beam Welding (LBW), Gas Tungsten Arc Welding (GTAW) and High Temperature Brazing (HTB) methods. The joints have been made and tests such as helium leak test (HLT), micro hardness test and tensile test were carried out. A study has been performed on these joining techniques to recognize the suitable method for high temperature applications. No observable leak was identified during HLT. Microstructures shows dissimilarity in solidification morphology due to disparity in heat sources. It has been identified that the joint made by brazing process having higher micro hardness value. Further, it has been observed that LBW joints have better mechanical properties than GTAW joints and HTB joints.
关键词： GTAW,Micro hardness,AISI 316 stainless steels,Tensile properties,High temperature brazing,Microstructures,Nd:YAG Laser
更新于2025-09-12 10:27:22
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Two pass laser welding of TC4 Titanium alloy to 301L stainless steel via pure V interlayer
摘要： Pulsed laser welding of TC4 Titanium alloy to SUS301 L stainless steel with V sheet as inter-layer was applied. V does not form any intermetallic compound with Ti and Fe. V is used as an interlayer for joining Titanium alloy and stainless steel that the laser successively focused near the Titanium alloy-V and V-stainless steel interfaces. In this way, only two weld zones and unmelted V interlayer can be produced, but also by microstructure of residual solid V interlayer situated between two separately formed weld zones. The unmelted V interlayer acted as a barrier to mixing of the two base materials. The unmelted part of V interlayer also acted as a diffusion barrier between Ti and Fe to avoid the Ti-Fe intermetallics. The tensile strength of joint was 587 MPa accordingly.
关键词： Microstructure,Weld zone,Welding,TC4 Titanium alloy,SUS301L stainless steel,V Interlayer
更新于2025-09-12 10:27:22
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Effect of Laser Beam Welding on the Cyclic Material Behavior of the Press-hardened Martensitic Chromium Steel X46Cr13
摘要： For the application of high-strength materials in welded joints, a point of principle is how the strength of the sheet metal is affected by cyclic loading and by welding. For the investigation of the cyclic material behavior of the press-hardened martensitic chromium steel X46Cr13, strain-controlled fatigue tests were performed and evaluated. The aim of compensating the limitations in the weldability of this press-hardened material is achieved by a reduced heat input of the laser beam welding and a defined heat treatment. The effect of laser beam welding on the fatigue properties is shown by the cyclic behavior of butt joints. The cyclic material behavior is the basis of strain-based fatigue assessment approaches. Both cyclic stress-strain curves and strain-life curves are used for the fatigue life estimation. No clear difference between the press-hardened base material and butt joints has been found in the cyclic stress-strain curves. Transient effects are found by comparison of hysteresis loops of the initial loading, at the cyclically stabilized state and at crack initiation. Cyclic hardening is concluded from the initial loading and the cyclically stabilized state. By comparison of strain-life curves, a difference in the number of cycles to crack initiation between the base material and butt joints is found. Cycles to crack initiation of butt joints tested under strain control result in over 50 % of the base material’s fatigue strength at 1·106 cycles to failure.
关键词： high manganese TWIP steels,high-strength steel,MnCr steels,butt joint,laser beam welding,Martensitic stainless steel,integral fatigue life estimation method,press-hardening,cyclic material behavior
更新于2025-09-12 10:27:22
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Wear Tribo-Performances of Laser Cladding Colmonoy-6 and Stellite-6 Micron Layers on Stainless Steel 304 Using Yb:YAG Disk Laser
摘要： Stainless steel material has been widely used in aeronautical, chemical and nuclear industries due to good corrosion resistance. However, the material has less hardness and wear resistance. In this study, two various depositions namely Colmonoy-6 and Stellite-6 have produced on 304 Stainless steel. Besides, the coating was examined to reveal their metallurgical, mechanical and tribological properties. In addition, wear mechanism, wear debris and roughness averages were studied. The outcomes indicate that both coatings show with dendrite structure due to rapid cooling rates. Hardness of the clad surface has improved than substrate material. The results of friction coefficient of specimen with Colmonoy-6 is lower than that of specimens Stellite-6 and substrate. Also, wear resistance of Colmonoy-6 has increased 49 times than substrate sample, which reveals that Colmonoy-6 laser cladding plays role on wear resistance. Adhesive and abrasive are the major wear mechanisms in the present study.
关键词： Wear debris,Microstructure,Stainless steel 304,Roughness,Wear performance,XRD,Laser cladding,Hardness
更新于2025-09-12 10:27:22
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Computational Investigation of Melt Pool Process Dynamics and Pore Formation in Laser Powder Bed Fusion
摘要： In the laser powder bed fusion additive manufacturing process, the presence of porosity may result in cracks and significantly affects the part performance. A comprehensive understanding of the melt pool process dynamics and porosity evolution can help to improve build quality. In this study, a novel multi-physics computational fluid dynamics (CFD) model has been applied to investigate the fluid dynamics in melt pools and resultant pore defects. To accurately capture the melting and solidification process, major process physics, such as the surface tension, evaporation as well as laser multi-reflection, have been considered in the model. A discrete element method is utilized to model the generation of powder spreading upon build plate by additional numerical simulations. Multiple single track experiments have been performed to obtain the melt pool shape and cross-sectional dimension information. The predicted melt pool dimensions were found to have a reasonable agreement with experimental measurements, e.g., the errors are in the range of 1.3 to 10.6% for melt pool width, while they are between 1.4 and 15.9% for melt depth. Pores are captured by both CFD simulation and x-ray computed tomography measurement for the case with a laser power of 350 W and laser speed of 100 mm/s. The formation of keyholes maybe related to the melt pool front wall angle, and it is found that the front wall angle increases with the increase in laser line energy density. In addition, a larger laser power or smaller scanning speed can help to generate keyhole-induced pores; they also contribute to produce larger sized pores.
关键词： additive manufacturing,melt pool,computational fluid dynamics (CFD),stainless steel,discrete element method (DEM),keyhole
更新于2025-09-12 10:27:22