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Analysis of the laser drilling process for pilot holes in complex shaped components
摘要： In contrast to mechanical drilling, laser drilling can be applied directly to complex surfaces. The laser holes can thereby serve as pilot holes for mechanical deep hole drilling to produce high quality bore holes. This article examines the influence of pulse power, pulse duration and focus distance on the laser drilling process for curved surfaces using a Nd:YAG-Laser for the stainless steel X2CrNiMo17-12-2 and the case hardening steel 20MnCr5. By varying the laser parameters holes were produced that met the requirements for pilot holes in terms of diameter tolerances, drilling depth, conicity and material influences to enable the process combination.
关键词： process combination,laser processing,manufacturing technology,laser drilling,laser assisted processes
更新于2025-09-12 10:27:22
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Experimental Investigation Of Quality Characteristics In Nd:YAG Laser Drilling Of Stainless Steel (AISI 316)
摘要： Micro-machining of advanced engineering materials such as stainless steels, titanium alloys, nickel alloys, and ceramics is a challenging task due to properties like high strength to weight ratio, toughness, slenderness ratio, and low thermal conductivity. Stainless steel of grade AISI 316 has wide applications in medical science, automobile engineering, aviation, and aerospace industry due to their favourable material properties such as low thermal conductivity, high corrosion resistance, and high strength to weight ratio. Micro-machining of AISI 316 with high aspect ratio is a difficult task due to excessive heat generation, micro- structural changes, and tool breakage. Laser beam machining (LBM) process is a suitable alternative machining process, since it localizes the heat source to control the micro-structural changes. The difficulty arises during laser drilling because of spatter area and heat affected zone (HAZ), which adversely affects the quality of laser drilled holes. The present study attempts to experimentally investigate the effect of laser process parameters such as pulse width, laser energy, pulse frequency, and flushing pressure on the performance measures such as spatter deposition and heat affected zone (HAZ) during drilling operation. To reduce the total number of experimental run and obtain maximum information for the experimental trials, Taguchi L27 has been adopted. Analysis of variance (ANOVA) is performed to identify significant laser parameters influencing both the performance measures. From the study, it is revealed that pulse width is the most significant parameter in the formation of spatter and HAZ. From the results, it is identified that spatter area initially increases with increase in pulse frequency and then decreases for any level of pulse width. As pulse frequency increases, laser power increases resulting in more heat input into the material. This causes increase in vapour pressure inside the laser drilled hole, more material ejection, and increase in spatter area. However, laser supported absorption (LSA) waves developed at higher value of pulse frequency brings about blockage of laser energy from the material surface as an engrossing plasma, which results in reduction of material ejection and reduction in spatter area. It is observed that HAZ increases with increase in pulse width and pulse frequency. It may be due to higher average power of the laser beam, which is directly proportional to pulse width and pulse frequency. Higher the value of pulse width, higher will be the laser thermal energy and higher HAZ.
关键词： Laser Drilling,Nd:YAG Laser,HAZ,Spatter
更新于2025-09-12 10:27:22
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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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A Particle Strength Exchange Method for Metal Removal in Laser Drilling
摘要： A meshfree Particle Strength Exchange (PSE) method is developed for metal removal in a simplified laser drilling problem. To this end, the problem of transient state heat transfer is solved by exerting a static laser beam with a Gaussian intensity distribution, as the external heat source. The proposed PSE scheme is a fully Lagrangian approach, which is straightforward to implement as compared to alternative meshfree methods currently adopted in the state of the art. The performance of the PSE method in solving the heat transfer problem at hand is assessed through a case-study on single-pulse laser heating of a metal workpiece. The simulation results are finally verified against both numerical and experimental data available in the literature, demonstrating the suitability of the proposed approach in addressing the thermal issues of complex manufacturing processes.
关键词： Heat transfer,PSE,Meshfree methods,Laser drilling
更新于2025-09-12 10:27:22
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Modelling the influence of laser drilled recast layer thickness on the fatigue performance of CMSX-4
摘要： This paper introduces a novel approach to fatigue life prediction modelling considering the laser drilling effect on film cooling holes of turbine vanes. The methodology proposed is based on a stress-life model such as the Basquin law and the introduction of manufacturing damage effect. The proposed empirical model gives a unique versatility compared to other stress-life models by considering surface damage such as the recast layer produced by the laser drilling process. The proposed empirical model has been thoroughly tested and validated using existing fatigue data. The statistical analysis shows that the proposed model is adequate for estimating the fatigue life of laser drilled specimens considering the recast layer thicknesses effect. The proposed model also can estimate the life of untested specimens even when only a small sample of fatigue data is available, thereby reducing the required testing data.
关键词： Fatigue life,recast layer,laser drilling,surface defects
更新于2025-09-12 10:27:22
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Comparison between ps- and μs-laser radiation for drilling holes for force transmission elements in CFRP-preforms
摘要： Current lightweight strategies in automobile, aerospace and wind energy applications include composite structures consisting of metal and fiber reinforced plastics for minimum weight, maximum force transmission and high material efficiency. Therefore, economic and technological beneficial material processing for the integration of force transmission elements such as inserts are crucial for these high performance materials. Current state of the art of machining carbon fiber reinforced material is to drill or mill the work piece after the consolidation process. Conventional mechanical and water jet processes lead to high tool wear and often non-repairable defects in the work piece such as delamination, fiber pullout, cracks in matrix and fibers, and deformation. Laser processing of the consolidated material can prevent force induced defects but leads to degradation of the matrix and leaves freestanding fibers inside the drilling hole which can damage the protective surface of subsequently inserted force transmission elements. This is especially critical for lifetime and performance during operation of the structural part. One solution is to drill the so called preform, prior to the infusion process, insert force transmission elements and subsequently infuse the preform with resin. Ultra sonic excited cutting knifes are not applicable for cutting hole diameters of a few millimeters with high aspect ratios. Punching as well as water jet cutting drop out due to force induced interaction with the textile or necessity of a subsequent drying process. Laser material processing could be an adequate solution to circumvent the above mentioned issues. Within this work, non-crimp carbon fiber (NCF) layers are investigated regarding laser processing via ultra-short pulsed and microsecond (fiber laser) radiation. The influence of different process parameters such as scanning speed, repetition rate and laser power are being evaluated regarding geometrical and materialographical quality such as conicity, textile swelling and heat affected zone (HAZ). The temperature distribution during laser processing is important for the estimation of when and where the knitting yarn, which keeps the carbon fiber plies together, disintegrates. Without the knitting yarn swelling occurs which is not desired for subsequent process steps.
关键词： force transmission elements,CFRP-preforms,microsecond laser,ultra-short pulsed laser,laser drilling
更新于2025-09-11 14:15:04
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Delamination-free millisecond laser drilling of thermal barrier coated aerospace alloys
摘要： Millisecond (ms) pulsed laser drilling is currently state-of-the-art in producing acute angle film cooling holes over aero-engine and gas-turbine components made from uncoated nickel superalloys. After laser drilling, most of these components are coated with a high-temperature thermal barrier coating (TBC) to maintain the temperature of the component at a level appropriate for its application. It is desirable to produce holes over the TBC coated components; however, the current state-of-the-art ms laser drilling of acute angle holes over TBC coated materials results in a high level of coating delamination and hence is not used in manufacturing industries. The recent introduction of ms quasi-continuous wave (QCW) fiber lasers has had a significant impact on industrial laser drilling. This paper reports the results of a fundamental investigation carried out on ms QCW laser drilling of angular holes over TBC coated superalloys and provides a pragmatic solution to the issue of TBC delamination. In addition to the investigation on traditional percussion and trepanning laser drilling processes, a new method of drilling called 'laser drilling post-laser TBC decoating' is evaluated with the aim of achieving delamination-free laser drilling of TBC coated aerospace alloy.
关键词： millisecond,thermal barrier coating,laser,drilling,angular,fiber,trepanning,TBC,hole,quasi-CW
更新于2025-09-11 14:15:04
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Coaxial waterjet-assisted laser drilling of film cooling holes in turbine blades
摘要： Film cooling holes (FCHs) of nickel-based single crystal turbine blades were drilled by 532 nm Nd:YVO4 nanosecond laser in coaxial waterjet-assisted environment. Microstructure of the side wall of the FCHs was mainly investigated by means of transmission electron microscopy. The average thickness of heat affected zone (HAZ) around FCHs decreases with increasing of water flow rate. The main phase within HAZ evolves from β-NiAl to β-NiAl + γ-Ni with the increase in the water flow rate. Some γ-Ni particles in the HAZ twined along (111) plane. A small portion of the FCHs are free of HAZ when drilled by coaxial waterjet-assisted laser drilling at a laminar water flow rate ≥ 3.1 m/s. There are no processing-induced defects including HAZ, microcrack, and phase transformation around the FCHs when drilled at the water flow rate ≥ 5.1 m/s. The FCHs with high surface quality can be drilled by the coaxial waterjet-assisted laser drilling. Finally, effects of fluid water on drilling quality of the FCHs were discussed.
关键词： turbine blades,film cooling holes,Coaxial waterjet-assisted laser drilling,heat affected zone (HAZ),transmission electron microscopy (TEM)
更新于2025-09-11 14:15:04