Application of LBM in Aerospace Industry

Application of LBM in Aerospace exertionINTRODUCTIONRequirement of precision comp acents, complicated design, stringent standards and testing, unusual coat of workpiece, restrictions in ceremonious machining fulfilles has lead to development of advanced machining marches shortly AMP. In past few years, in that location were several AMPs developed such as electric discharge machining (EDM), electron propagate machining, electrochemical machining, chemical machining coveres (CMP), ultrasonic machining (USM), and jet machining processes abrasive jet machining, water jet machining, optical maser ray machining and so forth Each of these AMPs has its limitations in workpiece secular, compel etc. But LBM is the one of the AMPs where approximately all corporeal tail end be processed. superstar of major(ip) advantage of LBM is its ability to machine both conductive and non-conductive worldlys. optical maser calamus machining (LBM) is one of the most widely utilize therma l thrust base non-contact type advance machining process which fuel be applied for almost whole range of materials. laser lance is rivet for break up and vaporizing the cast-off(prenominal) material from the p atomic number 18nt material. As of now the major practical application on LBM is profile peachy of geometrically complex part and making illuminance holes in sheetmetal.HISTORY OF LASERIn 1917, it was Albert Einstein who first told the terra firma about the process called Stimulated Emission which steels the optical maser possible. In 1957, Gordon Gould, a Columbia University student intentional the first laser device in his laboratory. However the first working laser (ruby laser) was ready on sixteenth of May, 1960 by Dr. Theodore Maiman. This demonstration of ruby laser acted as entry opening to this field. Till whence lots and lots of researches have been done and various(a) lasers were set. several(prenominal) of major contributions and gritty schooll ights atomic number 18 Gas laser which apply helium and neon shooteres by Ali Javan during 1960, semi conductor laser by Gunther Fenner in 1962, CO2 laser by Kumar Patel on 1964, Nd-YAG laser by Geusic in 1964 etc. The first excimer laser was demonstrated in 1970 by Basov et ah and it was semiliquid xenon which was excited with a split secondd electron beam. The first moneymaking(prenominal) application of continuous wave CO2 lasers was make during 1967 by western Electric and the first successful industrial application of laser under fill out was die-board slotting. Whereas now, lasers have been into umpteen argonas such as aerospace, die and mold manufacturing, biomechanical devices, automotive, electric, and electronic industries etc. Likewise many studies have been made to find many such lasers and also studies were done to reform / optimize the working parameters of the lasers. fundamentals OF LASERLight Amplification by Stimulated Emission of shaft LASER is a devic e which produces a monochromatic light beam where all the waves ar coherent. LASER consists of four primary componentsActive specialty It contains atoms whose electrons atomic number 18 excited to higher pushing takes by an energy source. They are solid crystals such as ruby or NdYAG, liquid dyes, bodgees like CO2 or Helium/Neon, or semiconductors such as GaAs.Excitation Mechanism Excitation mechanisms pump energy into the active medium. trio basic method of excitation are optical, electrical or chemical. soaring Reflectance MirrorPartially Transmissive MirrorThe major principles of Laser are stimulation, amplification and population anastrophe.Lasing actWhen energy is applied to a laser active medium electrons are raised to an unstable energy level then spontaneously decay to a number 1er relatively extensive-wearing metastable state. There is possibility to pump large amounts of energy since electrons in this state bequeath not spontaneously return to their ground e nergy level thus we chamberpot obtain a population inversion in which most of the atoms are in a metastable state. Lasing action is initiated by an electron after achieving population inversion. If the photon released is of exactly the right wavelength it will stimulate an atom in a metastable state to rest a photon of the equal wavelength (Stimulated Emission). rotund amount of these stimulated photons will be lost when they interfere with the sides of the lasing active medium. However if the photons travel parallel to the long axis of the optical cavity they will continue to stimulate emanations of photons having the same wavelengths which integrate coherently until they reach the mirrored ends of the optical cavity. This stimulated emission continues as the beam asks the 100% reflective mirror and gets reversed to strike against the partially reflecting mirror. A small portion of the coherent light is released season the rest is reflected back through the lasing medium to continue the process of excite photons.Types of LaserThere are several types of lasers available based on active medium (solid, liquid or go down on), types of gases used, types of crystals used, and mode of operation (continuous wave, pulsed, q-switched) etc. But only few lasers are used for industrial application called as material impact lasers. The commonly used lasers in industries are CO2 Gas lasers Nd-YAG solid state laser and Excimer laser.CO2 lasers escape to be high powered (up to 3 kW) and are used in the continuous-wave mode. The Nd-YAG lasers are used in the pulsed mode and can achieve florescence powers of 7-10 kW.Mechanics of LaserThe mechanism of material removal during laser beam machining includes four different stages such asWarm upMelting,Vaporization, chemic degradation / plasma shieldingThe material is heated above its melting point when a high energy laser beam is focused on workpiece surface. The melted or vaporize material is then distant by uti lise high wedge assist gas. Unlike other processes, LBM is a thermal process and the effectiveness depends on thermal properties of the material rather than its mechanical properties. This is the major characteristics for which hard-to-machine material such as te alloys, super nickel alloys etc and highly brittle material such as glass, ceramics etc can be processed by LBM.NEEDS OF LASER IN AEROSPCE INSUSTRYAs mentioned earlier, lasers are employed much more in material processing industries than other industries. And current scenario of material processing, application of lasers plays a merry role in aerospace industry. The fol subalterning are some of key points which justify the reason behind thisCooling holes Aerospace engineering technology is growing promptly and the components are exposed to ever change magnitude exhaust and combustion temperatures. so cooling is very much required in order to go for those high temperatures. One of method is to have cooling holes on TBC (thermal parapet coated) stages. pathrn aircraft has nearly 100,000 such cooling holes which are made by laser drill operation.Airframe weight One of major criteria of any aircraft is the weight. umteen improvements and experiments are passing game on to lessen the weight of airframe structure. Also it enhances low fuel consumption. elevated strength aluminium alloys are used for this process. It is found that almost 80% of material used in commercial aircraft and 50% material used in military aircraft is of this aluminum alloy. Laser gash is one of highly recommended for processing this material.Reduce damage In this birth scenario, cost reduction plays an important role in any industry. With increasing price of petroleum, one of strategy is to reduce total manufacturing cost, labor cost in particular. CNC controlled motorized laser can be used for drill and trim purposes which reduces the manufacturing cost.MAJOR LBM PROCESSES USED IN AEROSPACE INDUSTRYThere are two major LBM processes employed in aerospace industry namely, laser drill and laser cracking. In this report I have made some investigation on two case studies, one for laser boring and another for laser dandy.Laser DrillingIn laser bore process is a thermal process which incorporates high energy laser beam which is focused on particular area where the material gets vaporized to form holes on workpiece. There are two types of laser cut process, pleximetry laser drilling and trepan laser drilling.Percussion laser drillingPercussion drilling is drilling where it take aimly punches the workpiece material where there is no relative movement of laser or workpiece. Thus the processing time is much less when compared to trepan drilling process. Also for drilling 100,000 holes in aircraft components such as turbine blades, airfoil vanes etc, percussion drilling is recommended. drill drillingThis drilling involves barren around circumference of the hole. Thus it takes more time than percussion drilling since it has to go around the circumference to make a hole on workpiece material.Laser groovyLaser cutting process involves basic principle of mechanics of laser i.e. high energy laser beam is focused to particular area on the workpiece where the material is melted above its melting point. Then the molten material is removed by coaxial assist gas jet or generate vapor ram thus forming the cut kerf. There are terce types of laser cutting processes, laser fusion cutting, laser flame cutting and sublimation cutting.Laser fusion cuttingIn this process inert gas such as nitrogen, argon etc is used as assist gas. This process amply depends on the energy of laser beam which is used for high alloyed steels.Laser flame cuttingOxygen is used as assist gas in this process and it is widely used for low alloyed steels. This process receives some amount of energy from exothermic response of the workpiece material. Also the laser power is lower when compared to laser fus ion cutting.Sublimation cuttingThe material is molten by absorbed laser energy until it partially evaporates. This requires high power densities with much slower speeds than other to cutting processes. sideslip STUDY 1 LASER DRILLING OF MULTILAYER AEROSPACE MATERIALObjectiveAs mentioned earlier, aerospace components requires thousands of cooling holes to dissipate the heat of combustion and exhaust gas. These components are attached a coating called TBC thermal barrier coating to protect the components from direct exposure to the corrosive environments. Thus the target of this case topic is to suss out and optimize the best parameters related to select of cut holes on a TBC, thermal barrier coated material. Some of such parameters are mentioned in below figure.Experimental SetupLaser systemThe experiments are made using Nd-YAG JK704 laser with lens of focal length 120mm. Oxygen is used as assist gas. Previous studies by Corcoran et al identified group O as the suitable ass ist gas for this process. The below chart shows the precondition for JK704 laser system.Workpiece setupExperiments are carried out using Rene 80 substratum coated with TBC. Here yttria stabilized zirconia is used as TBC and it is bonded with the substrate material by crockeds of plasma sprayed MCrAlY bind coat. The material onerousness is about 3.6mm.The material composition of Rene 80 is Ni= 60.0%, Cr= 14.0%, Co= 9.5%, Ti= 5.0%, Mo= 4.0%, W= 4.0%, Al= 3.0%, C= 0.17%, B= 0.015% and Zr= 0.03%ProcedureOne-at-a time mount is the traditional approach for conducting laser drilled experiments. In this approach only one parameter is changed keeping all others as constant. But this is time consuming and most importantly interactions of parameters are not considered which may lead to wrong terminations. Thus Taguchi type approach is considered where orthogonal array was designed to reduce the number of experiments required. From 108, the experiments are cut to 18. Holes were drilled on Rene 80 substrate surface by percussion laser drilling using the laser system as mentioned earlier. The mean diameters were recorded using profilometer. The avocation output responses were recordedRemelt layer weightinessMicrocracking depth andSpalling Delamination of TBC.ResultsAfter recording the values as mentioned in the data-based procedure, a chart was plotted which gives the direct comparison of results of 18 experiments.The Taguchi digest gives the output responses of Remelt layer thickness and microcracking depth which can be then compared with the OEM (Original equipment manufacturer) vane airfoil standards. This is to check whether the attained values are deep down the mentioned values mentioned in the standards. As per OEM standards, the remelt layer thickness Higher S/N ratio is preferred in S/N analysis. By using the results from Chart 4 i.e. parameter effects plot, the optimum parameters can be obtained for laser drilling of Rene 80 sample. These optimum pa rameters are elect in such a way that the remelt layer thickness, microcracking and Delamination of TBC are diminishd.establish on derived optimum parameter table, microcracking confirmation tests are carried out to authorise the findings. It was found that the laser drilled holes posses very exact microcracking at these optimum parameters (Table 3). Three iterations were made, say A, B and C and micrographs were obtained.Conclusion of case meditate 1The parameters considered for this study are pulse energy, pulse width, pulse shape, TBC compactness and the gas pressure. The investigation and results of above case study provides the following conclusions jiffy energy High pulse energy reduces the level of microcracking and low pulse energy reduces the level of melting of remelt layer thickness. It is also found that interaction occurs between pulse energy and pulse width.Pulse width The hardship of microcracking and Delamination i.e. the spalling is trim considerably when sho rter pulses are used.Pulse shape Pulse shape do not have adherent effect on remelt layer thickness whereas in order to minimize delamination, a ramp-up pulse is recommended and to minimize microcracking, a treble pulse is recommended.TBC density The TBC density has very little effect on the remelt layer thickness, however high density TBC yielded least(prenominal) delamination of bond coat and the TBC used.Gas pressure Higher the gas pressure is better the output parameters. Gas pressure of 70 psi was found to reduce all the three output response parameters remelt layer thickness, microcracking and delamination.Some pictures showing the laser drilled holes on aircraft turbine component.CASE STUDY 2 LASER CUTTING OF AEROSPACE ALUMINIUMOne of primary goal of aerospace industry is to lessen the weight of airframe structure. This has advantage of saving fuel consumption, and hence the cost. High strength aluminum alloys were used for these applications and laser cutting is one of proc ess which is recommended for processing high strength aluminum but there are some challenges which has limited ceremonious laser cutting for this application.ObjectiveThus, the objective of this case study is to investigate the challenges of stately laser cutting and study the proposed solution to overcome these challenges.Conventional laser cuttingThe usage of conventional laser cutting is limited to process aluminum alloys used in aerospace application is because of two major reasons,It produces cuts with poor surface finish andLarge heat affected zone (HAZ) is created.These poor machining characteristics of laser cutting reduction the fatigue life of components which is very essential for aerospace applications.The mechanisms of laser cutting process is, when a high energy laser beam is focused on the workpiece the material gets melted and vaporized and then a assist gas jet is used to drag the molten material away from the workpiece material. If these force requirements are not more pronounced, then the molten material may remain in the cutting edge of the workpiece which yields to very poor quality cut and also large HAZ is generated in the cut edge. These all combine to affect the overall mechanical performance of the workpiece material.The best method to improve the pull efficiency is to increase the gas pressure of assist gas jet. This is required in order to establish a laminar bounce layer between assist gas jet and the molten material. The dragging of molten material is more efficient as a result viscous and pressure drag of the assist gas jet which are the driving force of removal of molten material from the workpiece. Gas pressure cannot be increase beyond 2 bar in conventional laser cutting as it uses converging coaxial cutting read/write head. every pressure more than 2 bar yields to more aerodynamic interactions. collect to this MSD mach shock disk, a normal shock wave is created which produces serious degradation in gas jet and reduce s the dragging capacity.Proposed laser cuttingThe drawbacks of conventional laser cutting can be addressed by usingConverging diverging (supersonic) snot instead of coaxial nozzle divergent geometrical configuration of assist gas jet such that it is in off-axis with the laser beam.Using converging- diverging nozzle, we can produce a fully expanded free-jet where MSD can be avoided. Thus we can produce cut of superior finish and also the HAZ is significantly reduced.Experimental setupThe experimental setup used for proposed laser cutting is as followsLaser used CO2 slab laser (Rofin DC 035)Output power 3.5 KWMode of operation CW, continuous wave modeNozzle Self designed cutting head (supersonic head)Experiments were conducted using conventional and supersonic cutting head and results were recorded.Comparison of resultsThe workpiece material used fro this experiment is 2024-T3, high strength aluminum alloy. The results were recorded and compared to conventional laser cutting. It was found that the finish was superior and HAZ was reduced than conventional laser cutting.A Challenge in proposed solutionOne of major drawback in proposed solution is that, for cutting complex contours the supersonic cutting head has to be changed frequently to remain tangent to the cutting direction. This drawback can be overcome by using a motorized off-axis nozzle controlled by a CNC controller.Conclusion of case study 2The following are the conclusion derived from above case study is that by using a cutting head supersonic, off-axis (non coaxial) nozzle can process high strength aluminum alloys withAn excellent and superior finish.Negligible heat affected zone, HAZ can be obtained.Production rates can be increased since cutting speed is increased.By using a CNC controlled motorized off-axis cutting head, parts with complex contours can be processed.Labor costs can be reduced as laser is fully automated.CONCLUSIONIn this report, a brief discussion about the two major laser beam ma chining used in aerospace industry, laser drilling and laser cutting were discussed. Also two case studies related to respective process were canvas and results were mentioned. LBM is widely used in aerospace applications and more and more researches are going on to improve the current laser technology and many novel trends directions were forecasted in this aerospace engineering field.REFERENCESA.Corcoran, L.Sexton, B.Seaman, G.Bryne, The laser drilling of multi layer aerospace material systems, journal of material processing technology (2002)A.Riveiro, F.Quintero, J.Pou, F.Lusquinos, R.Comesana, J.del Val, M.Boutinguiza and R.Soto, Laser cutting of aerospace aluminumAvanish Kumar Dubey, Vinod Yadava, Laser beam machining-A review, International Journal of Machine Tools Manufacture, 2008The Fascinating world of sheetmetal, Dr.Hubert Bitzel Johanna BurcherttF. Dausinger, B.G. Teubner, Strahlwerkzeug Laser Energieeinkopplung und Prozesseffektivitt, Stuttgart, 1995www.optoIQ.comw ww.rofin.comhttp//en.wikipedia.org/wiki/Laser_cuttingLecture notes by Prof. A.Senthil kumar, Mechanical Engineering department, National University of Singapore, Singapore.