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外文翻译--高速数控铣床混合聚合物混凝土床身的设计与制造【中英文文献译文】

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外文翻译--高速数控铣床混合聚合物混凝土床身的设计与制造【中英文文献译文】,中英文文献译文,外文,翻译,高速,数控,铣床,混合,聚合物,混凝土,床身,设计,制造,中英文,文献,译文
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Design and manufacture of hybrid polymer concrete bedfor high-speed CNC milling machineJung Do Suh Dai Gil LeeReceived: 22 September 2006/Accepted: 11 June 2007/Published online: 23 January 2008? Springer Science+Business Media B.V. 2008AbstractTo maximize the productivity of precisionproducts such as molds and dies, machine tools shouldbe operated at high speeds without vibration. As theoperation speeds of machine tools are increased, thevibration problem has become a major constraint ofmanufacturing of precision products. The two impor-tant functional requirements of machine tool bed forprecision machine tools are high structural stiffnessand high damping, which cannot be satisfied simul-taneously if conventional metallic materials are usedfor bed structure because conventional high stiffnessmetals have low damping and vice versa. This paperpresents the application of hybrid polymer concretefor precision machine tool beds. The hybrid polymerconcrete bed composed of welded steel structure facesandpolymerconcretecorewasdesignedandmanufactured for a high-speed gantry type millingmachine through static and dynamic analyses usingfinite element method. The developed hybrid machinetool bed showed good damping characteristics overwide range of frequency (g = 2.935.69%) and wasstable during high speed machining process when thespindle angular speed and acceleration of slide were35,000 rpm and 30 m/s2, respectively.KeywordsPolymer concrete ? Machine tool ?Damping ? Precision machining1 IntroductionModern precision machine tools are required toproduce precise products at high machining speeds.To achieve the requirement, machine tools must havehigh damping as well as high structural stiffness.Modern machine tools are usually equipped with highspeed spindle systems rotating up to 35,000 rpm andmoving frames operating up to 30 m/s2accelerationand deceleration (Suh and Lee 2002). At these highoperation speeds, machine tool structures are vulner-able to vibration, which results in poor surface finishand inaccurate dimensions of products (Suh and Lee2004). Besides, chatter, a kind of self-inducedvibration, adversely affects tool life (Clancy andShin 2002). The vibration of a machine tool isfrequently caused by the low damping: if theJ. D. SuhFuel Cell Vehicle Team1, Advanced Technology Center,Hyundai Motor Company, 104, Mabuk-Dong,Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-912,Republic of KoreaD. G. Lee (&)Department of Mechanical Engineering,Korea Advanced Institute of Science and Technology,ME3261, Guseong-dong, Yuseong-gu,Daejeon-shi 305-701, Republic of Koreae-mail: dgleekaist.ac.kr123Int J Mech Mater Des (2008) 4:113121DOI 10.1007/s10999-007-9033-3damping of machine tool structures is too low, selfinduced or regenerative vibrations are bound to occurduring high speed operation because the naturalfrequencies of machine tool structures can not beincreased indefinitely. Machine tool structures madeof metallic materials cannot have both high stiffnessand damping characteristics because conventionalmetallic materials are inferior in damping character-istics. Therefore, auxiliary dampers such as a dampeddynamic absorber, Lanchester vibration damper, andhydraulic damper have been used to increase damp-ing. However, their effects are confined in pre-determined modes and frequencies (Ema and Marui2000). Although the stiffness of machine tool struc-tures can be increased either by employing higherstiffness materials or by increasing the sectionalmodulus of structures, the damping and stiffness ofmetallic structures cannot be increased simulta-neously. The best way to obtain both high dampingand high structural stiffness is to employ sandwichstructures composed of high stiffness faces and highdamping cores such as polymer concrete. The poly-mer concrete is a high potential material for machinetool bed structures due to its high damping charac-teristics with moderate stiffness and low cost (Kimet al. 1995; Cortes and Castillo 2007): Although thepolymer concrete is more expensive (depending onresin binder systems, their prices range from $300/m3to $2,000/m3), if it is compared with conventionalcement concrete ($50/m3$80/m3), the conventionalcement concrete is not suitable for the machine toolapplication due to its inferior strength and impactresistance (Cortes and Castillo 2007).This paper presents the design and manufacture ofa hybrid polymer concrete machine tool bed thatconsists of sandwich structures of welded steel facesand polymer concrete core. The static and dynamicanalyses of the hybrid bed were performed after thebasic properties of polymer concrete were measured.The developed hybrid polymer concrete bed hasbeen incorporated in high-speed gantry-type mill-ing machine (FV400, Daewoo Heavy Industries &Machinery Ltd., Korea). The dynamic characteristicsof the structure were measured by impulse dynamictests. Compared with damping factors of steel or caseiron bed structure (g = 0.20.3%), the hybrid polymerconcrete exhibits superior damping characteristics(g = 2.935.69%).2 Characteristics of polymer concreteThe polymer concrete is composed of aggregatesbound with polymer matrix which is usually epoxy orunsaturated polyester. Although epoxy resin hasbetter material properties, unsaturated polyester resinYJ-100 K (Aekyung chemical Ltd., Korea) wasemployed as a binding material, in this work, becausethe polyester is less expensive and suitable for largestructures such as machine tool bed due to its diversecuring rate. Moreover, the material properties ofpolymer concrete is determined not by the bindingmaterial but by the volume fraction of aggregate,independently of binding material; the higher volumefraction of aggregate may result in the higherstiffness of polymer concrete.The aggregates were grouped by their meshnumberssuchas#1.01.5,#1.53.2,#3.26.4,#6.412.0 and larger than #12 that is classified assand. To determine the approximate mixing ratio ofaggregates, it was assumed that the smaller aggre-gatesoccupythevoidformedbythelargeraggregates, which is general concept of linearpacking theory. For example, gravels #1.0#1.5 formvoid about 40 % of the apparent volume, and thisvoid may be filled with gravels #1.5#3.2 and soforth. The tentative mixing ratio was determined bythe linear packing theory and the optimal mixing ratiofor the dense packing of polymer concrete wasdetermined by several trial and error experiments asshown in Table 1.Figure 1 shows the measured damping factors ofpolyester and granite as raw materials for polymerconcrete by impulse dynamic test depicted in Fig. 2.The measured damping factors range from 2% to 4%over wide range of frequencies and the values aremuch higher than those of conventional metallicmaterials. Also, properties of polymer concrete weremeasured by impulse dynamic test (ASTM C215-91).Table 1 Composition of polymer concreteGravel (Mesh #)Sand Polyester1.01.5 1.53.2 3.26.4 6.412.0Wt.%30.315.47.17.130.010.0Vol.% 26.713.66.36.326.421.8114J. D. Suh, D. G. Lee123Tables 2 and 3 list the sizes of specimens andmechanical properties, respectively. Figure 3 depictsmeasured damping factors with respect to frequen-cies. In addition, shear strength between polymerconcrete and steel with respect to the surfaceroughness of steel was measured as shown in Fig. 4ausing Instron4206 (Instron Co., USA) at a crossheadspeed of 0.1 mm/min. Specimens were composed ofpolymer concrete and steel rod embedded in polymerconcrete shown in Fig. 4b. The surfaces of steel rodswere treated using abrasive papers of various meshnumbers followed by co-curing with polymer con-crete. From the experimental result in Fig. 5, it wasfound that the shear strength increases as the surfaceroughness increases.0.000.020.040.060.08050100150200250300Frequency Hz ro t ca f gn i pmaDPolyesterGraniteFig. 1 Damping factors g of raw materials for polymerconcrete under flexural vibration w.r.t. frequenciesPCFFT AnalyzerImpact hammer String AmpAmpAccelerometer Specimen Fig. 2 Impulse dynamic test to measure the mechanicalproperties of polyester and graniteTable 2 Size of concrete specimens for impulse dynamic testsSpecimenLength (mm)Height (mm)Width (mm)124097972360979734809797Table 3 Properties of polymer concreteDensity (kg/m3)E (GPa)G (GPa)m226025.210.50.20.000.020.040.060.080.10100100010000Frequency Hz ro t ca f gn ipmaDSteelPolymer concreteFig. 3 Damping factors g of polymer concrete under flexuralvibration w.r.t. frequenciesFig. 4 Measurement of the shear strength between polymerconcrete and steel: (a) Photograph of test using instron, and (b)Photograph of specimen (mm)Design and manufacture of hybrid polymer concrete bed1151233 Design and manufacturing process3.1 Design of hybrid bed from the perspective ofaxiomatic designThe functional requirements (FRs) of the machine toolbed are as follows (Tobias 1965; Kim et al. 1995).FR1: Increase structural stiffnessFR2: Increase structural dampingSince outer dimensions of the bed were pre-deter-mined considering assembly with other parts, basicdesign concept was determined as a sandwichstructure composed of steel faces and polymerconcrete core. The damping of a sandwich structurecomes largely from the damping of core material.Therefore, design can be decoupled by followingdesign parameters (DPs) (Suh 2001).DP1: Thickness of steel plates composing the steelbase (Face of sandwich structure)DP2: Damping characteristics of polymer concreteFR1FR2?X0xX?DP1DP2?1Additional advantage of the sandwich structure is thatthe steel faces not only increase structural stiffnessbut also work as a mold for polymer concrete duringmanufacturing.Figure 6 shows the high-speed gantry-type millingmachine tool structure investigated in this work,whose specifications are shown in Table 4. Themachine tool bed is a hybrid structure composed ofwelded steel base in Fig. 7 and polymer concrete corefilled its inside cavity. The machine tool bed of thistypehastwofunctions,i.e.,thelinearmotormounting and the LM-guide mounting. A movingframe, Y-slide, is guided by the LM-guide and drivenby the linear motors mounted on the vertical columnsof the machine tool bed as shown in Fig. 6. There-fore, the vertical columns should resist inertia forceof the moving frame and pulling force of 21 kN ofthe linear motors which bends the vertical columnsinward. Consequently, the vertical columns are majorsources of large deformation during operation, andwere selected for the main design part. Furthermore,their displacement during vibration is relativelylarger than other parts because the vertical columnsare the weakest parts of the structure.05101520250.400.600.801.001.201.40Ra m aPM h t gne r t s r aehSFig. 5 Shear strength between steel and polymer concretew.r.t. surface roughness of steelFig. 6 Machinetoolstructure(FV400,DaewooHeavyIndustries & Machinery Ltd., Korea)Table 4 Specifications of the machine tool (FV400, DaewooHeavy Industries & Machinery Ltd., Korea)SpecificationValueSize (X 9 Y 9 Z, mm)1830 9 600 9 1850Transfer range (X 9 Y 9 Z, mm)600 9 400 9 400Transfer acceleration (X, Y, Z-slide, m/s2)14, 14, 20Mass (X, Y, Z-slide, kg)550, 1100, 290Clearance of linear motor (mm)0.9 0.3LM-guide deformation limit (lm)30Attraction force of linear motor (kN)21Maximum spindle speed (rpm)35,000116J. D. Suh, D. G. Lee123Figure 7 shows the welded steel base and DPsrelated to DP1. X1X3, Y1Y6and Z1Z3representthicknesses of steel plates. To determine the DPs, thestatic and dynamic characteristics were calculated byFEM using ANSYS 6.0 (USA). Also, dampingfactors were estimated using the energy relationduring vibration. To simulate the actual static loadingand deformation, the six supporting points on thebottom surface were fixed while the pulling andinertia forces were applied to the LM-guides and thelinear motors respectively as shown in Fig. 8 andTable 5. The inertia forces Fxand Fzwere applied tothe two points on each LM-guide while the inertiaforce Fyand pulling force Fpwere applied to the partson which linear motors are mounted. Additionally,the vertical columns are resisted by the LM-blocksand the LM-rails of 2.0 9 109N/m elastic stiffness inthe X-direction, and 2.5 9 109N/m elastic stiffnessin the Z-direction.Figure 8 and Table 6 show the results of deforma-tions when the boundary conditions and DPs inTables 5 and 7 were applied. From the results inTable 6, it was found that the stiffness of structure islargely dependant on the plate thicknesses in theX-direction but not on plate thicknesses in theY-direction. Figure 9 and Table 8 show the resultsof dynamic analyses from which it was found thatmajor deformation during vibration occurred in thevertical columns and the 1st vibration mode shape ofthe vertical column was similar to the deflection shapeof a cantilever beam by concentrated loads on a freeend. The higher natural frequencies were obtained asthe thicknesses of steel faces in the X-directionincrease but the increases were not remarkable. It isdue to that the increase in thicknesses of steel faces inthe X-direction not only increases the structuralFig. 7 Welded steel basefor the machine tool bed (Xiand Yirepresent thethickness of the steelplates): (a) Top view, and(b) Bottom viewFig. 8 Static deflection of the machine tool bed by theattraction force and the inertia forceTable 5 Boundary conditions for static analysisLocationB. C.Source6 points on the bottom surfaceFixed?Linear motor15.1 kNInertia force Fy21 kNPulling force FpLM-guide7.6 kNInertia force Fx-5.7 kNInertia force FzDesign and manufacture of hybrid polymer concrete bed117123stiffness but also increases its mass which impedes theincrease of natural frequency.However, it is well known that the 1st mode haslarge portion of vibration energy due to its largedeformation amplitude than other higher modes.Therefore, damping of the 1st mode was estimatedusing strain energy approach in which the damping ofa sandwich beam corresponding to the vertical columnwas calculated from damping properties and strainenergies stored in steel faces and polymer concretecore, respectively. To estimate damping of the bedstructure, the vertical column was assumed to be asandwich cantilever beam composed of X-directionsteel faces and polymer concrete core as shown inFig. 10. As shown in Fig. 11, when concentratedloads P1and P2in Fig. 10 are adjusted properly, i.e.P1/P2is 1249, the corresponding static deflection issimilar to the amplitude of the 1st mode of vibration.In this work, it was postulated that the total strainenergy is the sum of the strain energies stored in steelfaces and polymer concrete core and dissipatedenergies are proportional to their damping factorsand strain energies; The total strain energy U in unitwidth of beam is calculated from strain energies in thesteel faces USand the concrete core UC.Table 6 Deformation of the machine tool bed under inertiaand attraction forces (lm)CaseLinear motorLM-guideMax dmMin dmD dmMax dgMin dgD dg148.86.542.314.56.58.0251.26.544.715.06.58.5355.66.549.115.56.68.9448.86.842.014.56.87.7551.56.844.715.06.88.2655.76.948.815.56.98.6Table 7 Dimensions (mm) of the steel plates composing thesteel baseCaseX1X2X3Y1Y2Y3Y4Y5Y6Z1Z2Z3120202010101010101010502021520151010101010101050203102010101010101010105020420202010555510105020515201510555510105020610201010555510105020Fig. 9 Mode shapes ofvibration of the machinetool bed : (a) 1st, (b) 2nd,(c) 3rd, and (d) 4th118J. D. Suh, D. G. Lee123U US UCZZASrz;S?22ESrzx;S?22GS !dzdxZZACrz;C?22ECrzx;C?22GC !dzdx2whereSandCrepresent steel and concrete while ASand ACdesignate areas occupied by steel and polymerconcrete, respectively. The stress in the steel facesand polymer concrete core are calculated as follows.rz;SES? M ? xD3rzx;SV ? EC?RT?C0X dXDV ? ES?RxT?CX dXD4rz;CEC? M ? xD5rxz;CV ?Rx0EC? X dXD6where x and T?Crepresent distance from its neutralaxis to the point under concern and to the steel face,respectively. M, V and D represent bending moment,shear force and flexural rigidity, respectively. Oncethicknesses of steel faces and polymer concrete coreare defined, the ratio of strain energies in the steelfaces and the core concrete is determined. In thatcase, damping factor g of the vertical column iscalculated by the following (Rao 1978; Sun and Lu1995).g WD2pUWD;S WD;C2pUS UCgS? US gC? UCUS UC7where WDrepresents the energy dissipation percycle of vibration. Since the 1st vibration frequencyis close for all cases in Table 8, the damping factorofconcretegCwasassumedtobe8.8%byextrapolation at 100 Hz from Fig. 3, while thedamping factor of steel gSwas assumed to be0.2%. For Case 1Case 3 in Table 7, the calculatedvalues of g were 3.3%, 3.4% and 3.7%, respec-tively. For Case 4Case 6, the calculated value of gwerealso3.3%,3.4%and3.7%becausethecorresponding plate thicknesses in the X-directionwerethesameasCase13whiletheplatethicknesses in the Y-direction were neglected. Fromthe damping estimation, the calculated dampingfactors increased as the thicknesses of steel faces inthe X-direction decreased. Consequently, Case 4 inTable 7 was determined as the design values formanufacturing because the machine tool structureshould have high stiffness and the damping factorof 3.3% is large enough for machine tool bedstructure.Table 8 Natural frequencies obtained from FE-analysis (Hz)Case1st2nd3rd4th1104108185203210310717919939910417219141041061852035102105179198699102172190Polymer concrete Steel 674424P1P2821382X1X2X3ZXtCFig. 10 Schematic drawing of the vertical column to estimatethe damping factor of the 1st vibration mode0.00.20.40.60.81.000.20.40.60.81Normalized position Z / Zmaxtnemeca lps id dez i l amroN / XXxamAmplitude ofthe 1st mode shapeStatic deflectionFig. 11 Comparison between the 1st vibration mode ampli-tudeandstaticdeflectionoftheverticalcolumnbyconcentrated loads in Fig. 10Design and manufacture of hybrid polymer concrete bed1191233.2 Manufacture of polymer concrete machinetool bedThe polymer concrete bed was manufactured bypouring polymer concrete into the steel base inFig. 12, followed by room temperature curing. Thesteel base composed of welded steel plates waspositioned up side down for the pouring process andthus void space in Fig. 12a was easily filled with thepolymer concrete. Detailed manufacturing processesfor polymer concrete are as follows.(a)Cleaning aggregates with water to remove saltcontained in aggregates.(b)Mixing of aggregates and polyester resin withthe pre-determined weight or volume ratio.(c)Packing with vibrator to induce self packing bygravity and to obtain homogeneity of concrete.(d)Curingofpolymerconcreteatroomtemperature.(e)Assembling and mounting other parts such asthe LM-guide and the linear motor.Figure 13 shows the photograph of the polymerconcrete bed manufactured in this work.4 Dynamic characteristics of the polymerconcrete machine tool bedThe dynamic characteristics of the polymer concretebed were measured by the impulse dynamic test usingFFT analyzer (B&K, Denmark) where six points ofthe bed were fixed as shown in Fig. 9a. For themeasurements, a dual channel FFT analyzer (B&K2032), a charge amplifier (B&K 2626), an impulsehammer (B&K 8202), an accelerometer (B&K 4374),and a force transducer (B&K 8200) were used. Thenthe test results were compared with those calculatedby FE-analysis. Figure 14 and Table 9 show themeasured FRF (frequency response function) anddamping factor with respect to frequency where thedamping factor g was calculated by the half powerFig. 12 Photograph of the welded steel base for the machinetool bed: (a) Bottom view, and (b) Top viewFig. 13 Photograph of the polymer concrete machine tool bed0.0000.0050.0100.0150.0200.02550Frequency HzFRF100150200250Fig. 14 FRF of the polymer concrete machine tool bed120J. D. Suh, D. G. Lee123bandwidth method using the FRF obtained from theimpulse dynamic test (Nashif et al. 1985).g f2? f1fr8where (f2- f1) and frrepresent the half power bandwidth and the corresponding natural frequency,respectively. From the impulse dynamic test, it wasfound that the hybrid machine tool bed had largedamping factors over the wide range of frequency;The damping factors g were 2.935.69% dependingon natural frequencies. Compared with steel or caseiron bed structure (0.20.3%), those are superiorvalues.In case of the 1st mode, the calculated andmeasured damping factors were 3.30 and 4.13,respectively. The difference may be attributed tothe neglect of damping occurring in the interfacebetween the steel and the polymer concrete layerduring the calculation.5 ConclusionIn this study, a polymer concrete bed combined withwelded steel structure, i.e. a hybrid structure, wasdesigned and manufactured for a high-speed gantry-type milling machine. The optimal mixing ratio ofaggregates for polymer concrete considering packingwas obtained experimentally. Then the mechanicalproperties of polymer concrete as well as adhesionproperties to steel adherand with respect to its surfaceroughness were measured. The dynamic characteris-tics of the hybrid polymer concrete bed weremeasured by impulse dynamic test. From the impactdynamic test, it was found that the hybrid machinetool bed had l
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本文标题:外文翻译--高速数控铣床混合聚合物混凝土床身的设计与制造【中英文文献译文】
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