汽车轮毂压铸模设计及其型芯加工仿真【机械类毕业-含CAD图纸】
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译文题目： Built-up Edge Investigation Invibration Drilling of Al2024-t6对铝2024-T6钻削积屑瘤研究 Built-up Edge Investigation in Vibration Drilling of Al2024-T6abstractAdding ultrasonic vibrations to drilling process results in an advanced hybrid machining process, entitled vibration drilling. This study presents the design and fabrication of a vibration drilling tool by which both rotary and vibrating motions are applied to drill simultaneously. High frequency and low amplitude vibrations were generated by an ultrasonic transducer with frequency of 19.65 kHz. Ultrasonic transducer was controlled by a MPI ultrasonic generator with 3 kW power. The drilling tool and workpiece material were HSS two-ute twist drill and Al2024-T6, respectively. The aim of this study was investigating on the effect of ultrasonic vibrations on built-up edge, surface quality, chip morphology and wear mechanisms of drill edges. Therefore, these factors were studied in both vibration and ordinary drilling. Based on the achieved results, vibration drilling offers less built-up edge and better surface quality com- pared to ordinary drilling.Keywords: Vibration drilling、Drilling、Ultrasonic、Aluminum 2024-T61. IntroductionDrilling processes constitute a big part of all machining processes (about 40%) 1, which may have a great effect on production costs. A strategy that can reduce these costs is optimizing these processes. A recent method used to improve twist drilling process is adding ultrasonic vibrations to the process. In this method, ultrasonic vibrations are used to improve Ordinary Drilling (OD). This kind of drilling process, that is a hybrid process, is entitled Vibration Drilling (VD) in this paper. In VD the high frequency and low amplitude vibrations are added to OD in direction of feed. Hence, the drill bit has an additional ultrasonic reciprocating motion in the longitudinal direction. Different investigators have reported a variety of improvements in using VD. Babitsky et al. 2 showed that it is possible to drill through thin, exible plates with little deformation by VD in contrast to OD where a back support needed to hold plates against thrust force. They explained that the reduction of deformation of plates in VD is because of a discon- tinuous cutting phenomenon which decreases thrust force. Pujana et al. 3 reported that in VD of Ti6Al4 V, chips intend to break. Azarhoushang and Akbari 4 studied the drilling of Inconel 738- LC. They found that the surface quality improves in VD when compared to OD. Other researchers who applied ultrasonic vibrations to machining processes declared that thrust force and torque decreased by these processes 59. Li etal. 10 developed multi-stage control for vibration condition of VD in order to optimize drilling of laminated composite materials. They changed the vibration condition according to the workpiece material being cut and the cutting situation (entrance, middle and exit of the hole). By this technique, the average deection of drill point, error of the hole diameter and the exit burr height were reduced by over 20%, 80% and 40%, respectively, in contrast to OD. Liao et al. 11 investigated the VD of Inconel 718. The reduction of chips length and torque variations in VD were reported in comparison to OD. Zhang et al. 12 showed that in micro VD in compared with micro OD, tool life increases. They also demonstrated that in VD, because of the drill skidding reduction, hole dimensional accuracy can be improved. Chen et al. 13 developed a voltage controller to keep resonance condition during VD. The reported results showed that by this technique tool life in VD of Inconel 718 enhanced when compared to OD. However, against all mentioned benets for VD, there are some unexpected results. For example, reduction of tool life has been reported in some researches 14,15. The present researchers believe that much more studies need to be done to know VD. To do this, some drilling experiments performed on Al2024-T6. Use of aluminum alloys in industry is growing because they are lightweight metallic materials and have different interesting mechanical and thermal properties 16. But, in dry machining of these alloys, the major problems are built-up edge formation and low quality of generated surface 1620. These problems are more critical in producing of precision workpieces. In this work, built-up edge in VD of Al2024-T6 is studied in detail. Also, the effect of VD on surface quality is investigated and compared to OD. The inuence of machining condition and built-up edge on chip morphology is also presented.2. Vibration drillingFig. 1 shows a schematic conguration of 1D vibration drilling.According to this gure, tool vibrates in drilling operation longitudinally. To impose ultrasonic vibration motions on drill bit, there are three different systems: (1) A system in which drill vibrates and workpiece rotates 4. In this system the rotary motion is applied on workpiece by lathe jaw chuck and the vibrating set (transducer, booster, horn and drill) is xed on the support of lathe machine. By using this system, drilling of workpeices that can be clamped by jaw chuck, would be possible. (2) A system with vibrating workpiece and rotating drill 21. In this system, vibrations are induced to workpiece, therefore, for each new workpiece (with different geometry and material) to be cut a new modal analysis and design are necessary. Hence, the system is only applicable to experimental purposes. (3) A system in which both vibration and rotation are applied to drill 3. In this system, vibration tool rotates and workpiece is fed toward the tool. Drilling various workpieces with different materials, geometry or dimensions is possible by this mechanism. This system is also more capable to be industrialized. In this study, the third system was selected to perform VD. 3. Experimental set-upIn vibration machining processes, designing a vibrating tool which induces the resonance frequency is required. The resonance frequencies of any parts can be found by modal analysis. To achieve longitudinal resonance frequency in VD the modal analysis was performed on the model of vibration tool (horn and drill). As the drill geometry is asymmetric and the results of a 3D analysis can be much more accurate, the 3D models of vibration tool were prepared in CATIA software, and then, transferred to ABAQUS software to do modal analysis. Since geometries of drills were standard and HSS was chosen as tool material because this material has shown good results in drilling of aluminum alloys as 14,2224 have reported, tool geometry and material were xed parameters. Hence, the alternative to vary designs in order to change longitudinal resonance frequency of vibration tool and matching it to the longitudinal frequency of transducer-booster set was horn geometry. This geometry in software was changed as long as the vibration tool longitudinal frequencyFig. 1. Model of VD.came near to 19.65 kHz that is the longitudinal resonance frequency of transducer-booster set.Table 1 shows the tool and horn material specications.Vibration tool model was meshed by TETRA elements (Fig. 2).The smaller the mesh size, the more accurate results can be achieved, therefore, the mesh size changed as far as the error between the two nal consecutive analyses turned into 2%. The next step after meshing is performing modal analysis. The modal analyzer of the software was used and modal analysis was performed.Fig. 3 shows the longitudinal mode shape of the designed vibration tool. The resonance frequency of the longitudinal mode is 19.665 kHz which is close to the longitudinal resonance frequency of transducer-booster set.After the nal design, a vibration tool, considering the achieved dimensions from analyses was fabricated and connected to the transducer-booster set (Figs. 4 and 5).Since the ultrasonic generator, which was used during the experiments, was able to scan the resonance frequencies, the vibration tool set was scanned to nd its longitudinal resonance frequency in practice. Fig. 6 shows the charts achieved by the scan of transducer-booster set, and vibration tool set. It can be seen that the frequency of vibration tool set is 19.99 kHz. The negligible difference between the frequency of transducer-booster set and vibration tool set is due to errors in material properties, manufacturing and assembling of tool.In the next step, a rotary mechanism with the ability to induce both rotation and vibrations to drill was designed. In this mechanism, vibrating set was placed in a steel tube and the tube clamped by jaw chuck. The electricity was transmitted to transducer via two brushes that were in connection with two copperrings and were located inFig. 2. Meshing the vibration tool.Fig. 3. Mode shape of longitudinal resonance frequency.Fig. 4. A schematic picture of vibration tool set.Fig. 5. A picture of vibration tool set.Fig. 6. Scan charts gained by ultrasonic generator: (a) Scan chart of transducer-booster set. (b) Scan chart of vibration tool set.the back of the lathe machine. The workpiece was clamped through a xture on the lathe machine support. Fig. 7 shows the VD set-up.Experimental equipment is as follows: Universal lathe machine (AJAX-AJ 725): to perform drilling experiments. Ultrasonic generator (MPI WG-3000 W): to convert low frequency electrical current to high-frequency electrical current. Laser vibrometer (OMETRON-VH3000+): to measure vibration amplitude. Dynamometer (KISTLER-9257B): to measure thrust force. Optical microscope (Dino-Lite Digital Microscope): to investigate the built-up edge on tool surface. Roughness tester (Mahr, Perthometer M2): to measure surface roughness. Drill: diameter of 5 mm made of HSS. Workpiece material: aluminum 2024-T6 (20 30 85 mm3).Fig. 7. VD set-up.Fig. 8. Experimental equipment. (a) Lathe machine (AJAX-AJ 725). (b) Ultrasonic generator(MPI WG-3000 W). (c) Laser Vibrometer (OMETRONVH3000+). (d) Dynamometer (KISTLER-9257B). (e) Optical microscope (Dino-Lite Digital Microscope). (f) Roughness tester (Mahr). (g) HSS drills. (h) Workpeice. Fig. 9. Thrust force vs. hole number (460 RPM, a = 0). Fig. 10. Thrust force vs. hole number (460 RPM, a = 10 lm). 4. Experiments and resultsSome drilling experiments were performed on Al2024-T6 workpieces and built-up edge, chip morphology and surface quality were studied and compared between OD and VD. All experiments were done without lubricant (i.e. dry cutting).To investigate the inuence of machining parameters, three rotary speeds and three feed rates were chosen for two processes. The values of these parameters are represented in Table 2. Zero amplitude in this table indicates OD conditions. With a new drill, 10 holes with 20 mm depth of cut were made on workpiece for each machining condition. Since built-up edge inuences thrust force, it was studied by comparing thrust force increase between two processes and the built-up edge size was also measured by an optical microscope.Fig. 23. Chip morphology vs. feed rate: (a) 755 RPM, 0.104 mm/rev, a = 0. (b) 755 RPM, 0.348 mm/rev, a = 0.Fig. 24. Surface roughness vs. feed rate.4.1. ResultsFigs. 914 show thrust force diagrams in different machining conditions. Each chart plots thrust forces for constant rotary speed and amplitude, and three different feed rates. In these charts horizontal axes represent number of drilled holes and vertical axes present thrust forces. On the other words, number 1 is related to the rst hole made by a new drill and numbers 210 are the next holes produced by the same drill. It can be seen that thrust force increases for higher feed rates. In general cases, by increasing of feed rate, uncut chip thickness increases and results in increasing of chip thickness and cutting forces. Therefore friction between chip and rake face increases and consequently aluminum adhesion to drill cutters happens.Thrust forces at constant feed rate and different rotary speeds are observed in Figs. 1520. By increasing the number of holes, thrust force increases which is due to adhesion presence enhancement and built-up edge formation.Figs. 21 and 22 show the difference between the amount of forces in the rst hole and the tenth one (force increase value). According to these gures, force increase value increases as the feed rate increases. The reason is aluminum adhesion on drill cutting edges and built-up edge presence in cutting zone; resulting in friction increase and rake angle decrease (tool blunting happens). Therefore the more feed rate, the more adhesion of work material to the tool. Another observation is that the force increase value is less in VD when compared to OD; that is due to the friction reduction in VD which can reduce the formation of built-up edge.In Figs. 21 and 22, it can be seen that by increasing rotary speed the force increase value decreases that is a result of uncut chip thickness reduction which happens by increasing of rotary speed, and then, results in machining forces decrease. Therefore, the bigger rotary speed, the smaller force increase value and the less builtup edge.Figs. 21 and 22 also illustrate the less increase of force increase value in VD in contrast to OD. This result is because of adhesion reduction by adding ultrasonic vibration to the process (VD). Also, as the adhesion and built-up edge presence decrease, a reductionFig. 25. Chip flocking to drill flutes. (a) 460 RPM, 0.208 mm/rev, a = 0. (b) 460 RPM, 0.208 mm/rev, a = 10 lm.Fig. 26. Holes surfaces. (a) 755 RPM, 0.208 mm/rev, a = 0. (b) 755 RPM, 0.208 mm/rev, a = 10 lm.in force increase value happens as a function of rotary speed increase.The effect of feed rate on chip morphology is shown in Fig. 23. Chips breakage happens as feed rate increases. It should be noted that although shorter chips have smaller contact with tool, however, since uncut chip thickness increases as feed rate increases, the machining forces are become larger and the chips move on rake face much more roughly which results in more adhesion, and consequently, higher force increase values.In the present work, the inuence of VD on surface roughness is investigated as well. A comparison has been made among roughness of the rst holes of every 10-hole set. The results are shown in Fig 24. It can be observed that by increasing of the feed rate the surface roughness becomes worse. However, as the rotary speed increases, better surface qualities can be obtained. The reason of obtaining worse surface quality as feed rate increases is higher forces which increase drill skidding and instabilities in drilling process. But, because of smaller uncut chip thickness and lower machining forces, the stability of drilling process increases by enhancing rotary speed and leads to less drill skidding. However, drill skidding makes chips movements irregular and causes chips to strike and scratch holes surfaces.It is also obvious in Fig. 24 that holes produced by VD have better surface nish. This improvement is because of friction reduction between holes surface and drill shank. Astashev and Babitsky in 25 demonstrated the effect of vibrations on dry friction behavior of a contact surface between a bar and a carriage moving on it. They have shown that whenever vibrations induce (in the direction of feed) between two bodies contact surfaces in a system, the system behavior in respect to static force in vibrating conditions is similar to its motion in a linear viscous medium. This phenomenon is recognized as effect of vibrational smoothing of nonlinearities. It may be concluded that the contact between holes surface and drill shank is affected by the effect of vibrational smoothing of nonlinearities, therefore, VD should produce better Ra values compared to OD. Furthermore, this phenomenon (the ef-fect of vibrational smoothing of nonlinearities) happens on the contact surface between surfaces of chips and drill utes. As the axial component of friction force between the surfaces of chips and drill utes decreases, causes chips to move out of drilling hole much easier. In addition, since chips are shorter in VD, because of ultrasonic impact phenomenon, the chips move in drill utes much easier and the impacts between chips and hole surface decrease. Therefore, it might result in less adhesion of chips on holes surfaces.Fig. 27. Adhesion to hole surface. (a) 755 RPM, 0.104 mm/rev, a = 0. (b) 755 RPM, 0.104 mm/rev, a = 10 lm.Fig. 28. Optical microscope photos of drills bits.Fig. 29. Chip surface affected by built-up edge. (a) Chip of first hole, 1255 RPM, 0.348 mm/rev, a = 10 lm. (b) Chip of tenth hole 1255 RPM, 0.348 mm/rev, a = 10 lm.Fig. 30. Chip morphology with hole number. (a) First hole, 755 RPM, 0.104 mm/rev, a = 0. (b) Tenth hole, 755 RPM, 0.104 mm/rev, a = 0. (c) First hole, 755 RPM, 0.104 mm/rev,a = 10 lm. (d) Tenth hole, 755 RPM, 0.104 mm/rev, a = 10 lm.Fig. 31. SEM photos of cutting edges. (a) 460 RPM, 0.104 mm/rev, a = 0. (b) 460 RPM, 0.104 mm/rev, a = 10 lm. (c) 755 RPM, 0.104 mm/rev, a = 0. (d) 755 RPM, 0.104 mm/rev,a = 10 lm.On the other hand, in OD, chips movements in drill utes are difcult and sometimes causes chip ocking to utes (Fig. 25(a) since a higher friction happens between continuous chips and utes surfaces. In OD, chips also strike with holes surfaces strongly and make surface quality worse than that in VD. Fig. 26 shows surfaces of holes produced by OD and VD. According to this gure, holes produced by VD have better surfaces. In contrast to Fig. 26(b), there are more grooves on holes surfaces in Fig. 26(a). This is because of strong impacts that occur between continuous chips and holes surfaces in OD.Generally, built-up edges in machining processes affect surface roughness and chips morphology; because built-up edge pieces separate from cutting edge during machining, and then, adhere to machined surface. In drilling, since there is no direct contact between cutting edges and holes surfaces, built-up edge does not have any effect on surface quality, directly. In drilling, adhesion of chips moving through drill utes to holes surfaces is a damage factor. Fig. 27 compares the adhesion of chips to holes surfaces. The adhesion to holes surfaces which is produced by OD is much more considerable when compared to VD. This outstanding difference is because of more contact time between continuous chips and holes surfaces in OD.Fig. 28 shows the photos taken by optical microscope from drills bits after producing 10 holes. In these photos, adhesion of aluminum to drills bits is obvious. As seen, less built-up edges are formed on tools in VD. The explanation is that friction between tool and chips decreases in VD. In other words, vibrations increase macroscopic viscosity coefcient of contact surfaces which results in seizure length reduction (seizure zone is a place on rake face that chips cease and adhere to tool while moving on rake face) 26. This reduction of seizure length affects friction reduction in machining processes signicantly and causes a reduction in force and chip adhesion to the tool. In addition, because of VD origin, involvement time between tool and work material in VD is much less than in OD which can lead to adhesion reduction.Principally, in drilling with twist drills the material in front of drill bit is pushed to sides by chisel edge with the help of thrust force, and then, by rotation of cutting edges the deformed material is cut 27. Regarding the fact that in OD linear speed of drill bit center is zero, more thrust force is necessary to make plastic deformation in material to be cut. However, in VD the speed of drill bit center is not zero since ultrasonic vibrations are added to feed direction in drilling process. Hence, friction between chisel edge and work material decreases and plastic deformation can be made by less thrust force. Furthermore, the ultrasonic reciprocating motion of drill produces an ultrasonic impact mechanism in VD. This mechanism can create micro cracks in work material and decreases plastic deformation needed for drilling process. Overall, less thrust force and plastic deformation reduce friction and adhesion.In VD, the effective rake angle is bigger than that was made by drill manufacturer. This increase in rake angle also happens during OD, but because of bigger speed (vibration speed plus feed rate) the effective rake angle in VD is much bigger. Therefore, chips can rollover on rake face much easier and cutting force plus friction between chip and tool decrease. These lead to reduction of the pressure in cutting zone which is a factor of adhesion and builtup edge formation.In general cases, built-up edge inuences surface quality and chip morphology. It is because of built-up edge adhesion to machined surface and changing tool cutting angles. As it is apparent in Fig. 29, the built-up edge has affected chip surface. Fig. 29(a) shows a chip produced from rst hole of a 10-hole set and Fig. 29(b) shows the tenth-hole chip of the same 10-hole set. It can be seen that the chip of the rst hole, where there is not yet any built-up edge on drill cutters, has a smoother surface and the chip surface of the tenth hole affected by built-up edge is uneven.Fig. 30 compares the chips shapes of the rst and tenth holes produced by OD and VD. This gure shows that the chips shapes change by increasing the number of holes. It can be explained that by increasing the number of holes, adhesion occurs and results in built-up edge formation. Since built-up edge is broken and formed frequently, tool cutting angles and friction between chip and tool change constantly. Therefore, chip movement on tool rake face changes by increasing of holes number and makes chips shapes irregular. The conic angles of chips are also bigger for chips of the tenth holes. It can be seen in Fig. 30(b) and (d) that chips are less conical in contrast to Fig. 30(a) and (c). It is again as a result of built-up edge presence which causes chips to begin to rollover on rake face much more difcult because of friction increase. This might increase conic angle of chips. The more conical chips, the easier exist of chips from holes.Chips shapes of the tenth holes can be compared between OD and VD in Fig. 30, as well. Shorter chips of VD are as a result of ultrasonic impacts which results in chip breakage. This can be concluded that although chips shapes change by the number of holes in both processes, VD can produce better chips from point of view that shorter chips can exist of holes much easier and make some improvements in drilled holes.As explained, an ultrasonic impact mechanism occurs during vibration machining. The ultrasonic impacts change the thickness along the chips frequently and cause to break the chips in reduced sections. The effect of ultrasonic impacts on chip morphology can be observed in Fig. 30(a) and (c). This gure shows that chips length of VD decreases signicantly and this is a great improvement in drilling, mostly for drilling of materials such as aluminum which produces long chips. Shorter chips are less dangerous for operator and/or machine, and take smaller spaces that make chips transportation easier and less costly. Furthermore, shorter chips in contrast to continuous long ones can exit from drilling hole much easier and with less damage to holes surface and drill bit.The tool damage mechanisms were also studied in this work. As shown in Fig. 31, adhesion of aluminum to tool is apparent here again. Since after each separation of built-up edge a layer of tool might be also separated, therefore by increasing the number of holes (more than 10), adhesion wear will occur. There also exist some grooves on cutting edges that indicate abrasion mechanism occurrence. Photos of cutting edges of drilling tools used in OD show much more serious grooves which are a result of the continuous contact between chips, tool and workpiece that pushes hard particles toward tool surface much stronger. Fig. 31(a), for example, shows a hard-worked aluminum particle that makes a groove on tool edge. It can be also observed in Fig. 31(c) and (d) that abrasion happens in both OD and VD, but, since chips have less involvement with tool, fewer grooves are seen in VD which may be an indication of tool life improvement.5. ConclusionIn this study, a vibration tool (horn and drill) was designed and manufactured by using modal analysis to have a longitudinal resonance frequency near the longitudinal resonance frequency of transducer-booster set. Then a mechanical mechanism by which electrical current can sent from ultrasonic generator to transducer while rotating by jaw chuck was designed, fabricated and set up on the back of lathe machine. By this mechanism, it was possible to apply both vibrations and rotation to the drilling tool. To study and compare the effects of both ordinary and vibration drilling on built-up edge, surface roughness and chip morphology, some experiments were conducted on Al2024-T6 as the workpiece material in different rotary speeds and feed rates. Thrust force increase value and adhesion zone size of aluminum on tool surface were considered as criteria of built-up edge study. The achieved results show that built-up edge and surface roughness can decrease drastically and chips can also be broken to shorter length in VD compared to OD. Friction reduction, because of reciprocating motion of drill, was recognized as the main reason of mentioned improvements in vibration drilling when compared to ordinary drilling. Adhesion and abrasion mechanisms were also found as tool damage mechanisms in both OD and VD, but, VD offered fewer damages in contrast to OD because of less contact and subsequently less friction between chip, tool and workpiece.AcknowledgementsThe second author is thankful to the University of Kashan for the nancial support (Grant No.2559671/1) of this work.References1 R.F. Hamadea, F.A. Ismail, A case for aggressive drilling of aluminum, J. Mater. Process. Technol. 166 (2005) 8697.2 V.I. Babitsky, V.K. Astashev, A. Meadows, Vibration excitation and energy transfer during ultrasonically assisted drilling, J. Sound Vib. 308 (2007) 805814.3 J. Pujana, A. Rivero, A. Celaya, L.N. Lpez deLacalle, Analysis of ultrasonicassisted drilling of Ti6Al4V, Int. J. Machine. Tools Manuf. 49 (2009) 500508.4 B. Azarhoushang, J. Akbari, Ultrasonic-assisted drilling of Inconel 738-LC, Int. J. Machine Tools Manuf. 47 (2007) 10271033.5 B. Vakili Azghandi, M.R. Razfar, An experimental study on the effects of ultrasonic assisted drilling on chip characteristics and tool life, Adv. Mater. Res.325 (2011) 351356.6 V.I. Babitsky, A.V. Mitrofanov, V.V. Silberschmidt, Ultrasonically assisted turning of aviation materials: simulations and experimental study,Ultrasonics 42 (2004) 8186.7 V.I. Babitsky, A.N. Kalashnikov, A. Meadows, A.H.P. Wijesundara, Ultrasonicallyassisted turning of aviation materials, J. Mater. Process. Technol. 132 (2003)157167.8 J. Ramkumar, S.K. Malhotra, R. Krishnamurthy, Effect of workpiece vibration on drilling of GFRP laminates, J. Mater. Process. Technol. 152 (2004) 329332.9 X. Wang, L.J. Wang, J.P. Tao, Investigation on thrust in vibration drilling of fiber-reinforced plastics, J. Mater. Process. Technol. 148 (2004) 239244.10 Z.J. Li, M.S. Hong, L.J. Wang, H.W. Zhao, H. Su, Y.L. Wei, Machining accuracy analysis for step multi-element varying parameter vibration drilling of laminated composite materials, Int. J. Adv. Manuf. Technol. 21 (2003) 760768.11 Y.S. Liao, Y.C. Chen, H.M. Lin, Feasibility study of the ultrasonic vibration assisted drilling of Inconel superalloy, Int. J. Machine Tools Manu. 47 (2007)19881996.12 D. Zhang, X. Feng, L. Wang, D. Chen, Study on the drill skidding motion in ultrasonic vibration microdrilling, Int. J. Machine Tools Manu. 34 (6) (1994)847857.13 Y.C. Chen, Y.S. Liao, J.D. Fan, Autoresonant tuning and control in ultrasonic vibration assisted drilling process, Mater. Sci. Forum 505507 (2006) 823828.14 Chang, S.F. Simon, Gary M. Bone, Burr size reduction in drilling by ultrasonic assistance, Robot. CIM-Int. Manu. 21 (2005) 442450.15 P.N.H. Thomas, V.I. Babitsky, Experiments and simulations on ultrasonically assisted drilling, J. Sound Vib. 308 (2007) 815830.16 P. Roy, S.K. Sarangi, A. Ghosh, A.K. Chattopadhyay, Machinability study of pure aluminium and Al12% Si alloys against uncoated and coated carbide inserts, Int. J. Refract. Met. Hard Mater. 27 (3) (2009) 535544.17 F.M. Kustas, L.L. Fehrehnbacher, R. Komanduri, Nanocoatings on cutting tools for dry machining, CIRP Ann. Manuf. Technol. 46 (1) (1997) 3942.18 M.S. Carrilero, R. Bienvenido, J.M. Snchez, M. lvarez, A. Gonzlez, M. Marcos,A SEM and EDS insight into the BUL and BUE differences in the turning processes of AA2024 AlCu alloy, Int. J. Machine Tools Manuf. 42 (2) (2002)215220.19 G. List, M. Nouari, D. Ghin, S. Gomez, J.P. Manaud, Y. Le Petitcorps, F. Girot, Wear behaviour of cemented carbide tools in dry machining of aluminium alloy, Wear 259 (712) (2005) 11771189.20 J.M. Snchez, E. Rubio, M. lvarez, M.A. Sebastin, M. Marcos, Microstructural characterisation of material adhered over cutting tool in the dry machining of aerospace aluminium alloys, J. Mater. Process. Technol. 164165 (2005) 911918.21 I. Hsu, C.C. Tsao, Study on the effect of frequency tracing in ultrasonic-assisted drilling of titanium alloy, Int. J. Adv. Manuf. Technol. 43 (2009) 127135.22 J. Kouam, J. Masounave, V. Songmene, Pre-holes effect on cutting forces and particle emission during dry drilling,in: 49th Annual Conference of Metallurgists of CIM, Vancouver, BC, Canada, 2010. pp. 253263.23 S. Bhowmick, Minimum Quantity Lubrication Machining Of Aluminum And Magnesium Alloys, Engineering materials Ph.D., University of Windsor, 2011.24 P. Kishore Kumar, K. Kishore, P. Laxminarayana, Prediction of thrust force and torque in drilling on aluminum 6061-T6 alloy, Int. J. Eng. Res. Technol. (IJERT) 2 (3) (2013). 25 V.K. Astashev, V.I. Babitsky, Ultrasonic Process, Machines, Springer, Berlin Heidelberg, New York, 2007.26 C. Cang-Leh, Wave Effects Of Ultrasonic Vibration On Machining, College Of Engineering Ph.D., Pennsylvania State University, 1994.27 Y. Altintas, Manufacturing Automation, Cambridge University Press, 2000. 对铝2024-T6的振动钻削积屑瘤研究摘要钻削过程增加超声波振动衍生出一个先进的复合加工工艺，题为“振动钻削”。 这项研究提出的振动钻具由两个旋转和振动运动被应用到同时钻出的设计和制造。高频率和低振幅振动是由具有的19.65千赫频率超声换能器所产生。超声换能器是由具有3千瓦的功率MPI超声波发生器控制。钻孔刀具和工件材料分别为HSS双长笛麻花钻和Al2024-T6。本研究的目的是调查关于超声波振动对积屑瘤，表面质量，芯片的形态和磨损的钻头刃的机制的影响。因此，在振动和普通钻方面对这些因素进行了研究。基于所取得的成绩，振动钻削相比普通钻提供更少的积屑瘤和更好的表面质量。 关键词：振动钻削、钻孔、超声、铝2024-T61. 介绍钻削过程构成了所有加工过程的重要组成部分（约40）1，这可能对生产成本有很大的影响。一种策略，可以降低这些成本的措施是优化这些流程。一项最新的方法常用于改进扭转钻削过程是增加超声波振动的过程。在该方法中，超声波振动被用来改善普通钻削（OD）。这种钻削过程是一个混合过程，在本文中题为振动钻削（VD）。在振动钻削的高频率和低振幅振动在进给方向被加入到普通钻削。因此，该钻头在纵向方向具有一个额外的超声波往复运动。不同的研究者已经报道了各种各样的改进使用振动钻削。Babitsky等人 2 表明，一个需要持有板块推力支持振动钻削对比普通钻削通过钻透薄，变形小的柔性板。他们解释说，在振动钻削的板的变形的降低是由于不连续的切削现象从而减小了推力。Pujana等人3报道，在Ti6Al4的振动钻削，切削可能被破坏。Azarhoushang和阿克巴里4研究了铬镍铁合金738-LC的钻孔。他们发现，振动钻削相比普通钻削表面质量改善。应用超声波振动加工过程的其他研究人员宣称，推力和力矩降低这些过程5-9。Li等人10 为振动钻削的振动条件开发了一种多级控制，以便优化层压复合材料的钻孔。他们根据工件材料被切割和切割情况改变了振动条件（入口，中间和孔的出口）。通过这种技术，相对于普通钻削，钻点的平均偏转，孔直径和出口毛刺高度的误差分别减少了20，80和40以上。Liao等人11研究了因科镍合金718的振动钻削。在振动钻削相比普通钻削切削的长度和扭矩的变化减少被报告。Zhang等人12表明，在与微振动钻削相比微普通钻削刀具寿命增加。他们还表明，在振动钻削，由于钻头打滑减少，孔的尺寸精度可以得到改善。Chen等人13开发了一种电压调节器，在振动钻削期间以保持谐振条件。所报告的结果表明，通过这种技术因科镍合金718的振动钻削相比普通钻削刀具寿命增强。然而，对振动钻削所有提到的好处，有一些意想不到的结果。例如，刀具寿命的降低，已在一些研究14,15报道。目前的研究认为，更多的研究需要做来了解振动钻削。为此，一些在铝合金-T6上的钻削实验被做。在工业铝合金的使用越来越多，因为他们是轻金属材料有不同的有趣的机械和热性能 16 。但是，在这些合金切削加工中，主要问题是积屑瘤的形成和产生低质量表面16-20。这些问题的关键是精密工件的生产。在这项工作中，对 Al2024-T6的振动钻削积屑瘤进行了详细的研究。同时，研究了振动钻削对比普通钻削表面质量的影响。还介绍了加工条件和积屑瘤对切屑形态的影响。2. 振动钻削图1显示了一个一维振动钻削的结构示意图。根据这个数字，纵向振动钻井工具。对钻头施加超声振动的运动，有三种不同的系统：（1）钻振动和工件旋转的系统4。在这个系统中的旋转运动施加在工件在车床的支撑通过车床卡爪卡盘和振动组（换能器，增压器，角钻）被固定。通过使用该系统，通过爪卡盘夹紧工件钻削将是可能的。（2）系统具有振动工件和旋转钻削21。因此，振动诱导工件，对于每一个新的工件（具有不同的几何形状和材料）进行切割的新的模态分析和设计是必要的。因此，该系统只适用于实验目的。（3具有振动和旋转的系统被应用于钻削 3 。在这个系统中，振动工具旋转和工件被送向工具。通过这一机制，钻各种不同材料，几何形状或尺寸的工件是可能的。该系统也可应用于工业化。在这项研究中，第三个系统被用于进行振动钻削。3. 实验装置在振动加工工艺，设计一振动工具，其诱导的共振频率是必需的。任何部位的共振频率可以通过模态分析被发现。为了获得振动钻削纵向共振频率，模态分析在振动工具（角钻）上进行。作为钻头几何形状是不对称的，这样一个三维分析的结果可以更准确，振动工具的三维模型在CATIA软件进行制备，然后，转移到ABAQUS软件做模态分析。由于钻头几何形状是标准和HSS被选为刀具材料，据14,22-24报道因为这种材料在铝合金钻头方面已经显示出良好的效果，刀具几何形状和材料的参数被固定。因此，设计变化改变，是为了改变振动工具纵向谐振频率和它匹配于传感器 - 增压集的纵向频率为角几何形状。在软件上这种几何形状被改变，只要振动工具纵向频率即换能器助力器组的纵向共振频率达到19.65千赫。表1显示工具和角钻材料规格。由TETRA元件组成的振动工具模型网格（图2）。网格尺寸越小，可以实现更准确的结果，因此，网格尺寸变化只要最后连续分析之间的误差转变为2%。网格划分后的下一步是进行模态分析。该软件的模态分析仪被使用并进行模态分析。图3显示了纵向振动模式的形状设计的工具。在共振频率的纵向模式是一个接近的纵向设置传感器的助推器19.665kHz的共振频率。最终的设计后，振动工具，考虑了从分析制造和连接到传感器增压机组尺寸（图4和5）。由于超声波发生器，这是在实验中使用的，是能够扫描的谐振频率，振动工具集进行扫描，以发现在实践中它的纵向共振频率。图6示出了由传感器助力器组和振动工具集的扫描取得的图表。它可以看出，振动工具集的频率为19.99千赫。传感器助力器组和振动工具集的频率之间的微小差别是由于材料性能，制造和工具的组装错误。在下一步中，设计了一种具有诱导的转动和振动钻能力旋转机构。在该机制中，振动将被放置在一个钢管和爪卡盘夹管。电力经由两个电刷即分别在两个铜图.2.啮合振动图.3.纵向谐振频率的模式形状图.4.振动工具示意图图.5.振动工具的图片集图.6. 由超声波发生器获得的扫描图:(a) 换能器的助推器组扫描图(b扫描图振动工具集环连接，并分别位于所述车床的背面传递到换能器。工件通过在车床机支撑夹具夹紧。图7表示在振动钻削的建立。实验设备如下： 万能车床（ajax-aj725）：进行钻孔实验。 超声波发生器（MPIwg-3000W）：将低频电流到高频电流 激光测振仪（ometron-vh3000+）：测量振动幅度。 测功机（kistler-9257b）：测量推力。 光学显微镜（DinoLite数字显微镜）：研究工具表面的积屑瘤。 粗糙度仪（Mahr, Perthometer M2）：测量表面粗糙度。 钻：5毫米直径的钢。 工件材料：铝合金2024铝（203085mm3）图.7.振动钻削的建立图.8.实验设备:(a)车床（AJAX-AJ725）(b)超声波发生器（MPI WG-3000瓦）(c)激光测振仪（OMETRON- VH3000+）(d)测功机（KISTLER-9257B）(e)光学显微镜（迪诺 - 精简版数码显微镜）(f)粗糙度仪（Mahr）(G)高速钢刀具（h）工件图.9.推力与孔数 图.10.推力与孔数（460RPM，a=10m） 图.11. 推力与孔数（755RPM，a=0） 图.12. 推力与孔数（755RPM，a=10m）图.8.代表在本研究中所使用的设备4. 实验和结果一些钻削实验在Al2024-T6工件和积屑瘤，切屑形态和表面质量进行了研究和在普通钻削和振动钻削之间比较。所有实验均不含润滑剂（即干式切削）下进行。图.13. 推力与孔数（1255RPM，a=0） 图.14. 推力与孔数（1255RPM，a=10m）图.15. 推力与孔数（0.104mm/rev，a=0） 图.16. 推力与孔数（0.104mm/rev，a=10m） 图.17. 推力与孔数（0.208mm/rev，a=0） 图.18. 推力与孔数（0.208mm/rev，a=10m）图.19. 推力与孔数（0.348mm/rev，a=0） 图.20. 推力与孔数（0.348mm/rev，a=10m）图.21.力增加值与进给速度(a=0） 图.22.力增加值与进给速度(a=10m）为了调查的加工参数的影响，三个旋转速度和三个进给速率被选择用于两个过程。这些参数的值在表2中呈现。零幅值在此表中表示普通钻削的条件。随着新钻带有20mm切削深的10孔根据每一个加工条件被加工在工件上。因为积屑瘤影响推力，研究了通过光学显微镜测定比较两个过程和积屑瘤的大小之间的推力的增长。4.1结果图9-14展示推力图在不同的加工条件下的表现。每个图表曲线代表恒定旋转速度和幅度，以及三种不同的进给速率。在这些图表中横轴表示钻孔和垂直轴本推力的数目。换句话说，数字1是相关于由新的钻头所做的第一孔和数字2-10是由相同的钻头所产生的下一个孔。它可以看出，对于更高的进给速率，推进力增大。在一般情况下，通过进给速率增加，未经切割的切削的厚度增加，并导致切削厚度和切削力的增加。因此在切屑与前刀面的增加摩擦从而发生铝的附着力钻头。图.23.切削形态与进给速度:(a)755RPM. 0.104 mm/rev, a = 0. (b) 755 RPM, 0.348 mm/rev, a = 0.图.24.表面粗糙度与进给速度在图15-20推力图中观察恒定的进给速度和不同的旋转速度。通过增加孔的数量，推力增加这是由于粘附性存在增强和积屑瘤的形成。图21和22示出的力在第一孔的力和第十一孔的力（力增加值）之间的差别。根据这些数字，迫使增加值随着进给速率增加而增加。原因是在钻切削刃和切削区产生积屑瘤的存在铝附着力;导致摩擦增加，前角减小（工具钝化发生）。因此，更多的进给速率，加工材料的工具的更密合性。另一个发现是，该力的增加值振动钻削相比普通钻削小; 这是由于在振动钻削摩擦减少这会降低积屑瘤的形成。在图21和22，可以看出，通过增加旋转速度的力的增加值减小即未切割的切削的厚度减少的结果通过旋转速度的增加而发生的，然后，导致加工力降低。因此，旋转速度越大，力的增加值越小和积屑瘤减少。图.25.深度钻削的切削积累(a) 460 RPM, 0.208 mm/rev, a = 0. (b) 460 RPM, 0.208 mm/rev, a = 10m.图.26.孔面 (a) 755 RPM, 0.208 mm/rev, a = 0. (b) 755 RPM, 0.208 mm/rev, a = 10m.图21和22还说明了在振动钻削力的增加值相比普通钻削较小的增长。这个结果是因为加入超声波振动的过程（振动钻削）的密合性降低。此外，作为密合性和积屑瘤的存在减少，在力的增加值的减少发生旋转速度增加的作用。切削形态进给速率的影响示于图23。因为进给速度增加，切削破损发生。应当指出的是，虽然较短的切削与工具较小的接触，然而，由于未切割的切削厚度随进给速率的增加而增加，加工力变大，切削在前刀面上移动得多大致这导致更多的附着力，因此，较高的力增加值。在目前的工作，振动钻削对表面粗糙度的影响也进行了研究。取每10孔集的第一孔的表面粗糙度之间进行比较。其结果示于图24。可以观察到，通过进给速率的增加，表面粗糙度变差。然而，随着转速的增加，可获得更好的表面质量。因是提高钻削过程中钻头打滑和不稳定性较高的力是获得差的表面质量的原因。但是，由于较小的未切割切屑厚度和较低的切削力，从而使钻削过程中通过提高转速来获得稳定，并导致更少的钻削打滑。然而，钻头打滑使得切削移动不规则，造成切削撞击和划伤孔表面。图.27. 孔面的附着力(a) 755 RPM, 0.104 mm/rev, a = 0. (b) 755 RPM, 0.104 mm/rev, a = 10 um.图.28.钻削的光学显微照片图.29.受积削瘤影响的切削表面(a) 第一孔的切削, 1255 RPM, 0.348 mm/rev, a = 10 lm. (b) 第十孔切削 1255 RPM, 0.348 mm/rev, a = 10 um图.30.切削形态与孔数(a)第一孔, 755 RPM, 0.104 mm/rev, a = 0. (b) 第十孔, 755 RPM, 0.104 mm/rev, a = 0. (c) 第一孔, 755 RPM, 0.104 mm/rev, a = 10 um. (d) 第十孔, 755 RPM, 0.104 mm/rev, a = 10 um图.31.切削边缘的SEM照片(a) 460 RPM, 0.104 mm/rev, a = 0. (b) 460 RPM, 0.104 mm/rev, a = 10 um. (c) 755 RPM, 0.104 mm/rev, a = 0.(d) 755 RPM, 0.104 mm/rev,a = 10 um图 24所示它也是显而易见，通过振动钻削生产的孔具有更好的表面光洁度。这种改进是因为孔的表面和钻柄之间的摩擦减小。文献25Astashev和Babitsky提出了在棒料和回车移动之间表面接触的干切削行为的振动的影响。他们已经表明，在一个系统中两个机构接触表面之间的振动感应（以进给的方向），对于该系统的行为，以在振动的条件静力为代表，其以线性粘性介质运动相似。这种现象被认为是非线性的振动平滑的影响。它可以得出结论，孔的表面和钻柄之间的接触是受非线性振动平滑的影响而影响，因此，振动钻削应该相比普通钻削产生更好Ra值。此外，这种现象（非线性振动平滑的作用）发生在钻削和钻槽表面之间的接触面上。在钻削和钻槽表面之间摩擦力的轴向分量降低，使钻削推离钻孔容易得多。此外，由于在振动钻削的切削是较短的，因为超声波冲击现象，在钻槽切削移动排屑容易得多，切削和孔表面之间减少的影响。因此，它可能会导致切削上的孔的表面附着力更小。另一方面，在普通钻削，在钻槽时切削的移动是困难的，有时会导致切削涌向槽（图25（a）在连续芯片和凹槽之间发生剧烈的摩擦。在普通钻削，切削在孔表面发生强烈撞击，并比在振动钻削时表面质量更差。图26示出由普通钻削和振动钻削所产生的孔的表面。根据该图，由振动钻削产生孔具有更好的表面。在对比图26（b）中，在图26（a）中有更槽的孔表面。这是因为在连续的切削和孔表面之间发生强烈的冲击。一般来说，在加工过程中积削瘤影响表面粗糙度和切削的形态;由于在加工过程中积屑瘤块从切削边缘分开，然后，坚持加工表面。在钻削，因为有切削刃和孔的表面之间没有直接接触，积屑瘤不会直接对表面质量产生任何影响。在钻削，切削移动通过切削槽到达孔表面的密合性是损伤因子。图27比较了切削孔表面的密合性。由普通钻削所加工的孔的表面的密合性对比振动钻削更值得考虑。这位明显的差异是因为在普通钻削连续的切屑和孔表面之间有更多的接触时间。图。28表明加工10个孔后，钻头位的光学显微镜所拍摄的照片。在这些照片中，钻头位铝的附着性是显而易见的。可以看出，振动钻削的工具上很少有积削瘤形成。换句话说，振动减少了接触表面的宏观粘度系数，从而导致检区长度减小（检区是当移动到前刀面时切削停止并且黏附在刀具上的前刀面的一个地方）26。这种检区长度的减少影响在加工过程中的摩擦显著减少并且引起的力和切削粘附工具的力降低。此外，由于振动钻削起源，在振动钻削的刀具和工件材料之间介入时间比普通钻削减少不少从而导致密合性降低。原则上，在扭转钻头钻削里，在钻头位的前部的材料在推力的帮助下由凿刃推向两侧，然后，通过切削刃的变形材料的转动被切断27。关于这一事实在普通钻削钻头中心外径线速度是零，更大的推力是必要的，以使塑性变形的材料被切割。然而，在振动钻削的钻头中心的速度不是零，因为超声波振动被加在钻削过程中进给方向上。因此，在横刃和工件材料之间的摩擦减小并且更少的推力能够产生塑性变形。此外，在振动钻削钻头的超声波往复运动产生了超声波影响机制。这种机制可以在加工材料产生微裂纹和减小所需的钻削过程塑性变形。总体而言，较少的推力和塑性变形减少摩擦和粘附性。在振动钻削，有效前角由钻制造商做的更大。在普通钻削期间倾角的增加也发生了，但是因为较大的速度（振动速度加进给速度）振动钻削的有效倾角要大得多。因此，切削可以更容易延展于前刀面和在切削和刀具之间的切削力和摩擦力减小。这些导致切削区的压力减少，它是粘附性和积削瘤形成的一个因素。在一般情况下，积屑瘤影响表面质量和切屑形态。这是因为，积屑瘤的附着在加工表面和改变刀具切削角度。因为它是在图29显而易见的，积屑瘤影响了切削表面。图29（a）示出了从一个孔到第10个孔集的切削过程和 图29（b）示出相同的10个孔集的第十个孔的切削。由此可以看出，那里钻铣刀上尚未有任何积屑瘤，第一孔的切削，具有一个更光滑的表面，并在第十孔的切削表面受积屑瘤影响是不合理的。图30比较由普通钻削和振动钻削产生的第一和第十孔的切削形状。该图显示了切削形状通过增加孔的数量发生变化。它可以通过增加孔的数量，粘附发生并导致积屑瘤的形成进行说明。由于积屑瘤的破裂，经常形成，刀具切削角度和摩擦片和刀具之间的变化不断。因此，对刀具前刀面由孔数量增加改变切削的运动，使得切削的形状不规则。对于第十孔的切削的切削圆锥角度也更大。在图30（b）和（d）可以看出，相对于图30（a）和（c）切削有少圆锥形。再次是由于积屑瘤的存在的结果，导致切削在前刀面开始侧翻的摩擦变得困难得多。这可能会增加切削圆锥角。更多的锥形切削，孔中的切削更容易存在。第十孔的切削的形状可以在图30的普通钻削和振动钻削之间进行比较。，也是如此。振动钻削的较短的切削是受超声波的影响导致切削破损的结果。这可以得出结论，虽然切削的形状由孔在两个进程的数量改变，从图片的观点振动钻削可以产生更好的切削，即更短的切削可以更容易的存在通孔，并在钻孔方面得到更好的改善。如前所述，超声波的影响的机制是在振动加工过程中发生的。超声波冲击沿频繁的切削改变厚度，并导致在缩小部分打破切削。可以在图30（a）和（c）中观察到在切削形态上超声波的影响的效果。该图表明，振动钻削的切削长度显著降低，这是在钻削方面很大的改进，主要用于如铝的材料的切削，它可以加工出长切削。短切削是对于操作员和/或机器较不危险，并采取较小的空间，使切削的运输更方便，成本更低。此外，相比连续长的切削而言短切削出从钻孔中排出容易得多，并与对孔的表面和钻头的损伤较小。在这项工作中对工具破坏机理也进行了研究。如图31所示，铝制刀具的附着性是在这里是显而易见的。由于积削瘤的每一次分离，工具的层也可能分开，因此，因此孔的数量的增长（超过10个），会发生粘着磨损。在切削刃上也存在一些凹槽，这表明磨损机制发生。在普通钻削里被使用的切削刀具的切削刃的照片展示了更严重的凹槽，这是在切削，刀具和工件连续接触的结果，它朝刀具表面强烈的推送硬颗粒。例如图31（a）中展示出了硬加工铝粒子使工具边缘上产生一个凹槽。在图31（c）和（d）也可观察到在普通钻削和振动钻削两者磨损都发生了，但是，由于切削与工具较少介入，在振动钻削里较少的凹槽被看到，这可以是刀具寿命改善的指标。结 论在这项研究中，一个振动工具（角钻）通过使用模态分析被设计和制造，在换能器增压组的纵向共振频率附近有一个纵向共振频率。然后，通过该电流可以从超声波发生器发送一个机械机构到换能器，同时通过卡盘旋转的设计，制造并设置在车床机的背面。通过这种机制，振动和旋转应用到钻削刀具是有可能的。为了研究和比较普通及振动钻削上积屑瘤，表面粗糙度和切屑形态的影响，进行一些实验，该实验选用不同的旋转速度和进给速度的工件材料Al2024-T6。推力增加值和铝对刀具表面粘附力区的大小被认为是积屑瘤的研究标准。所获得的结果表明，积屑瘤和表面粗糙度可以大幅降低，并且在振动钻削的切削相比普通钻削切削也可以被打破，获得更短的长度。由于钻的往复运动，振动切削在对比普通切削时减少摩擦被认为是所提到的改善的主要原因。在普通钻削和振动钻削两者中附着力和耐磨性的机制也被发现作为刀具的磨损机制，但是，振动钻削相比普通钻削获得更少的磨损，这是因为减少接触和随后在切削，刀具，工件之间较少的摩擦。致 谢第二作者是感谢卡尚大学对这项工作提供的财政支持（格兰特No.2559671/1）参 考1 R.F. Hamadea, F.A. Ismail, A case for aggressive drilling of aluminum,
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