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20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
20120140504002
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20120140504002

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  • 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 9 DYNAMIC STABILITY OF MILLING MACHINE BED USING NATURAL FIBRE COMPOSITE 1 Riadh Hasan Hadree, 2 Dr. Mohammad Tariq, 3 Dr. Fouad Alwan Saleh 1 Ministry of transport, General Maritime Transport Company, Republic of Iraq 2 Assistant Professor, Department of Mechanical Engineering, SSET, SHIATS-DU, Allahabad 3 Assistant Professor, Mechanical Engineering Department of Al-Mustansiriya University Iraq ABSTRACT Composites materials find wide applications in all fabricated products. The application of the composites in the machine tool technology is to reduce the vibration and chatter during machining operations. Recently developed composite is granite particles in epoxy matrix. It has high strength, good vibration damping capacity and frictional characteristics. It is used as machine tool beds for some precision grinders. In order to eliminate application limitations imposed by ordinary materials; composite materials may be extended to other commercial utilizations which require durable services at unconventional environmental conditions. Use of composite materials reduces the vibrations of the system as desired which is justified from the experimental observations. With increase in number of layers of composites at an optimum level the vibrations are decreased considerably. Abrupt increase in vibration amplitude has also been observed with increase in number of layers of composites above an optimum limit interposed between the table and work piece. Extensive experiments with different layer combinations along with sandwich plates are carried out to determine vibration response of work specimen with specified machining parameter, i. e., depth of cut and feed rate. The experiments are duly carried out at small feed, low depth of cut and low cutting speed to primarily investigate the scope of damping phenomenon in composite materials. This paper presents the experimental work of the machining of the two different material composites i.e. Glass fibre epoxy polyester epoxy material. The results obtained are compared with respect to each other. Effective damping can be obtained only by proper fixation of the composites to the bed and the work piece. With improper nut and bolt joint there is a danger of additional slip vibrations between the plates. With same fibre phase, lower the matrix phase density more is the damping ability. Keywords: Fibre Composites, Milling Machine, Dynamic Stability. INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING AND TECHNOLOGY (IJARET) ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 5, Issue 4, April (2014), pp. 09-26 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2014): 7.8273 (Calculated by GISI) www.jifactor.com IJARET © I A E M E
  • 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 10 1. INTRODUCTION 1.1 Milling Operation Milling is the process of cutting away material by feeding a workpiece past a rotating multiple tooth cutter. The cutting action of the many teeth around the milling cutter provides a fast method of machining. The machined surface may be flat, angular, or curved. The surface may also be milled to any combination of shapes. The work piece is mounted on the table with the help of suitable fixtures. The desired contour, feed and depth of cut for the job are noted down. A suitable milling cutter for the specified job is selected and mounted on the arbor. The knee is raised till the cutter just touches the work piece. The machine is started. By moving the table, saddle and the knee, for the specified feed and depth of cut, the desired job may be finished. The machine may then be switched off. The different methods of milling are 1) Up milling 2) Down milling Chatter vibrations have damped out on a slotted table Radial Drilling machine using composite structure as a substitute for the base of the work piece [10]. The signal and RMS amplitude, frequency and time period of vibrations are recorded for different number of layers. Mechanical characteristics of an epoxygranite beam against the conventional materials such as cast iron and steel with reference to constant stiffness have been studied [5]. It is observed that, for same stiffness, the epoxy granite structure offers a considerable weight reduction, along with high damping characteristics. New solution with the guide rail assembly technology is presently in use on the basis of a guideway system consisting of a body and a milling table. The dynamics was compared with the use of a frequency response function which had been determined in an impulse test. The proposed solution is characterised by a higher dynamic stiffness, which may directly influence the precision of the machined surfaces [6]. Properties among conventional materials have been taken. Among the major developments in materials in recent year are composite materials, as they offer several outstanding properties as compared to several conventional materials [8]. Hybrid welded steel bed have been proposed as a replacement for cast iron as a machine tool bed material and the results showed that the static and dynamic characteristics were superior to cast iron. The advancements in machine tools to maximize the production by increasing spindle speeds have caused vibration in machine tools [11]. 3D CAD model for the base line and the optimized design has been created by using commercial 3D modeling software CATIA [7]. The 3D FE model has been generated using HYPERMESH. The analyses were carried out using ANSYS and Design Optimization is done with the help of Optistruct. The novel application examples of composite structures to components for the robots, machine tools and automobiles considering the stiffness design issues of composite structures. Mechanical design can be classified into stiffness design and strength design. In the stiffness design, the stiffness or deformation of members is concerned, and the enhancement of dynamic characteristics such as natural frequency or damping capacity of members or systems is also important [2]. Vertical and horizontal slides were constructed of a large CNC machine by bonding high modulus carbon-fibre epoxy composite sandwiches to welded steel structures using adhesives. These composites structures reduced the weight of the vertical and horizontal slides by 34% and 26%, respectively and increased damping by 1.5 to 5.7 times without sacrificing the stiffness. The effects of transverse shear deformation on the modal loss factors as well as the natural frequencies of composite laminated plates by using the finite element method based on the shear deformable plate theory are discussed [12].
  • 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 1.2 Damping mechanism in composite materials Damping mechanisms in composite materials differ entirely from thos metals and alloys. The different sources of energy dissipation in (a) Viscoelastic nature of matrix and/or (b) Damping due to interphase (c) Damping due to damage which is of two types: (i) Frictional damping due to slip in the unbound regions between (ii) Damping due to energy dissipation in the area of matrix cracks, broken (d) Viscoplastic damping (e) Thermoelastic damping Structural damping Rubbing friction or contact among different elements in a mechanical system causes structural damping. Since the dissipation of energy depends on the particular characteristics of the mechanical system, it is very difficult to define a model that represents perfectly str The Coulomb-friction model is as a rule used to describe energy dissipation caused by rubbing friction. Regarding structural damping (caused by contact or impacts at joins), energy dissipation is determined by means of the coefficient of r Damping in Machine Tools Damping mechanisms in composite materials differ entirely from those in conventional metals and alloys. Damping in machine tools basically is derived from two sources damping and interfacial slip damping. Material damping is the damping inherent in the materials of which the machine is constructed. The magnitude of material damping is small comparing to the total damping in machine tools. A typical damping ratio value 0.003. It accounts for approximately the contacting surfaces at bolted joints and sliding joints. This type of damping accounts for approximately 90% of the total damping. 2. MATERIALS AND METHODS In physics, damping is any effect that tends to reduce the amplitude of oscillations in an oscillatory system, particularly the harmonic oscillator. In mechanics, friction is one such damping effect. In engineering terms, damping may be mathematically modeled as a force synchronous with the velocity of the object but opposite in direction to it. If such force is also proportional to the velocity, as for a simple mechanical viscous damper (dashpot), the force F velocity v by F= -cv, where c is the viscous damping coefficient, given in units of N Fig 1 International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 11 Damping mechanism in composite materials Damping mechanisms in composite materials differ entirely from those in conventional metals and alloys. The different sources of energy dissipation in fibre-reinforced composites are: a) Viscoelastic nature of matrix and/or fibre materials (c) Damping due to damage which is of two types: ) Frictional damping due to slip in the unbound regions between fibre and matrix. (ii) Damping due to energy dissipation in the area of matrix cracks, broken fibre n or contact among different elements in a mechanical system causes structural damping. Since the dissipation of energy depends on the particular characteristics of the mechanical system, it is very difficult to define a model that represents perfectly str friction model is as a rule used to describe energy dissipation caused by rubbing friction. Regarding structural damping (caused by contact or impacts at joins), energy dissipation is determined by means of the coefficient of restitution of the two components that are in contact. Damping mechanisms in composite materials differ entirely from those in conventional metals and alloys. Damping in machine tools basically is derived from two sources damping and interfacial slip damping. Material damping is the damping inherent in the materials of which the machine is constructed. The magnitude of material damping is small comparing to the total damping in machine tools. A typical damping ratio value for material damping in machine tools is . It accounts for approximately 10% of the total damping. The interfacial damping results from the contacting surfaces at bolted joints and sliding joints. This type of damping accounts for f the total damping. 2. MATERIALS AND METHODS In physics, damping is any effect that tends to reduce the amplitude of oscillations in an oscillatory system, particularly the harmonic oscillator. In mechanics, friction is one such damping eering terms, damping may be mathematically modeled as a force synchronous with the velocity of the object but opposite in direction to it. If such force is also proportional to the velocity, as for a simple mechanical viscous damper (dashpot), the force F may be related to the is the viscous damping coefficient, given in units of N Fig 1: Mass spring damper system International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – , © IAEME e in conventional reinforced composites are: and matrix. fibres etc. n or contact among different elements in a mechanical system causes structural damping. Since the dissipation of energy depends on the particular characteristics of the mechanical system, it is very difficult to define a model that represents perfectly structural damping. friction model is as a rule used to describe energy dissipation caused by rubbing friction. Regarding structural damping (caused by contact or impacts at joins), energy dissipation is estitution of the two components that are in contact. Damping mechanisms in composite materials differ entirely from those in conventional metals and alloys. Damping in machine tools basically is derived from two sources--material damping and interfacial slip damping. Material damping is the damping inherent in the materials of which the machine is constructed. The magnitude of material damping is small comparing to the total for material damping in machine tools is of the total damping. The interfacial damping results from the contacting surfaces at bolted joints and sliding joints. This type of damping accounts for In physics, damping is any effect that tends to reduce the amplitude of oscillations in an oscillatory system, particularly the harmonic oscillator. In mechanics, friction is one such damping eering terms, damping may be mathematically modeled as a force synchronous with the velocity of the object but opposite in direction to it. If such force is also proportional to the may be related to the is the viscous damping coefficient, given in units of N-s/m.
  • 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 12 An ideal mass-spring-damper system with mass m (kg), spring constant k (N/m) and viscous damper of damping coefficient c (in N-s/ m or kg/s) is subject to an oscillatory force and a damping force, Fୱ ൌ െkx (1) Fୢ ൌ െcv ൌ െc ୢ୶ ୢ୲ ൌ െcxሶ (2) Treating the mass as a free body and applying Newton's second law, the total force F୲୭୲ on the body F୲୭୲ ൌ ma ൌ m ୢమ୶ ୢ୲మ ൌ mxሷ (3) F୲୭୲ ൌ Fୱ ൅ Fୢ (4) Calculation of material damping of Glass fibre polyester In this reinforced composite material, there are different matrix and fibre phases: Reinforcing material --- E-Glass fibre Matrix ---polyester Ef = 80Gpa Em = 3.5Gpa υf = 0.22 υm = 0.25 Gf = 32.7Gpa Gm = 1.4Gpa ηmE & ηfE are taken 0.05 and 0.01 respectively [12]. Applying all the stresses, assuming for a cycle of operations in a system of forces, the net material damping taken from [12] Calculating material damping of Glass fibre epoxy Reinforcing material --- E-Glass fibre Matrix ---epoxy Ef = 80Gpa Em = 3.5Gpa υf = 0.22 υm = 0.25 Gf = 32.7Gpa Gm = 1.4Gpa 2.1 Energy balance approach The loss factor η is commonly used to characterize energy dissipation, due to inelastic behaviour, in a material subjected to cyclic loading. Assuming linear damping behavior η is defined by Vantomme as; η ൌ ଵ ଶπ ∆୵ ୵ (5) where ∆W is the amount of energy dissipated during the loading cycle and W is the strain energy stored during the cycle. Now consideringηଵ , ηଶ and ηଵଶ : ηଵ – normal loading in fibre direction of UD lamina ( longitudinal loss factor) ηଶ – normal loading perpendicular to fibres (transverse loss factor ) ηଵଶ —inplane shear loading (shear loss factor)
  • 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 2.2 Two phase model Fig. 2: Matrix Longitudinal loss factor ( ) is calculated by the following method: (loading in direction 1) The total energy dissipated comprises the sum of that lost in the fibres and matrix. These amounts are proportional to the fractions of elastic strain energy stored in the fibres and matrix respectively; i.e. and are the loss factors for fibres and matrix, associated Using the expressions for the strain energy, From equations (8) and (12) Transverse loss factor ( ) is calculated: (loading in direction 2) As before, is expressed as The strain energy contributions are derived in an analogous manner as for assumption that the same transverse stress development leads to International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 13 (m) and fibres (f) are connected in parallel ) is calculated by the following method: (loading in direction 1) The total energy dissipated comprises the sum of that lost in the fibres and matrix. These ounts are proportional to the fractions of elastic strain energy stored in the fibres and matrix (6) are the loss factors for fibres and matrix, associated with tensile lo sing the expressions for the strain energy, (7) (8) (9) is calculated: (loading in direction 2) (10) The strain energy contributions are derived in an analogous manner as for , b e transverse stress σ2 is applied to both the fibres and the matrix. This (11) International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – , © IAEME ) is calculated by the following method: (loading in direction 1) The total energy dissipated comprises the sum of that lost in the fibres and matrix. These ounts are proportional to the fractions of elastic strain energy stored in the fibres and matrix tensile loading. but now with the is applied to both the fibres and the matrix. This
  • 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 14 Shear loss factor (ηଵଶ ) is calculated: (loading in shear direction) ηଵଶ ൌ η୤ୋ ୛౜ ୛ ൅ η୫ୋ ୛ౣ ୛ (12) where η୤ୋ and η୫ୋ are the loss factors for fibres and matrix associated with shear loading. The strain energy fractions are worked out in the same way as for ηଶ , as it is assumed that the shear stresses on the fibres and matrix are the same. This leads to: ηଵଶ ൌ η౜ృୋౣ୚౜ାηౣృୋ౜୚ౣ ୋౣ୚౜ାୋ౜୚ౣ (13) The coefficients ηfE, ηmE, ηfG, ηmG are calculated from the graphs given in the book “Damping of materials and members in structural mechanics” by Benhamin J. Lazan. These graphs are plotted with E’ & E”, G’ & G”. 2.3 Calculation of material damping of Glass fibre polyester In this reinforced composite material there are different matrix and fibre phases: Reinforcing material (E) Glass fibre Matrix (polyester) Ef = 80Gpa Em = 3.5Gpa υf = 0.22 υm = 0.25 Gf = 32.7Gpa Gm = 1.4Gpa From graphs given in the book “Damping of material and members in structural mechanics” by Lazan ηmE & ηfE are taken; ηmE = 0.05, ηfE = 0.01 ηଵ ൌ η౜ు୉౜୚౜ାηౣు୉ౣ୚ౣ ୉౜୚౜ା୉ౣ୚ౣ ηଵ ൌ ଴.ଶଵଽ଻ହ ଵ଼.ସ଻ହ ൌ 0.0118 ηଶ ൌ η౜ు୉ౣ୚౜ାηౣు୉౜୚ౣ ୉ౣ୚౜ା୉౜୚ౣ ηଶ ൌ ଵ.଴଴଻଻ ଵ଼.ସ଻ହ ൌ 0.0545 ηmG = 0.01, ηfG = 0.015 ηଵଶ ൌ η౜ృୋౣ୚౜ାηౣృୋ౜୚ౣ ୋౣ୚౜ାୋ౜୚ౣ ηଵଶ ൌ ଴.଴଼଺ଷ଻ ଼.ସ଼ଷ ൌ 0.0101 Applying all the stresses, assuming for a cycle of operations in a system of forces, the net material damping according to [12] is given by ηୟ୴ ൌ ηభାηమାηభమ ଺଴ ൌ 0.0012 2.4 Calculating material damping of Glass fibre epoxy Reinforcing material (E) Glass fibre Matrix (epoxy) Ef = 80Gpa Em = 3.5Gpa υf = 0.22 υm = 0.25 Gf = 32.7Gpa Gm = 1.4Gpa
  • 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 15 η୫୉ ൌ 0.03, η୤୉ ൌ 0.01; ηଵ ൌ η౜ు୉౜୚౜ାηౣు୉ౣ୚ౣ ୉౜୚౜ା୉ౣ୚ౣ ηଵ ൌ ଴.ଶ଴ଵଷ ଵ଼.ସ଻ହ ൌ 0.0109 ηଶ ൌ η౜ు୉ౣ୚౜ାηౣు୉౜୚ౣ ୉ౣ୚౜ା୉౜୚ౣ ηଶ ൌ ଴.଺଴଻଻ ଵ଼.ସ଻ହ ൌ 0.0328 η୫ୋ = 0.02, η୤ୋ = 0.015 ηଵଶ ൌ η౜ృୋౣ୚౜ାηౣృୋ౜୚ౣ ୋౣ୚౜ାୋ౜୚ౣ ηଵଶ ൌ ଴.ଵ଺଼ଵଶ ଼.ସ଼ଷ ൌ 0.0198 The net material damping for a single fibre epoxy plate according to Koo & Lee is given by ηୟ୴ ൌ ηభାηమାηభమ ଺଴ ൌ 0.0010 For a single plate of glass fibre polyester and epoxy material damping is 0.0012 and 0.0010 For ‘n’ number of plates: Loss factor for two plates ηଶ ൌ ηଵ ୛ଶ ୛ ൅ ηଶ ୛ଵ ୛ where W1 and W2 are the weights of the plates Considering W1= W2 (homogenous plates) ηଶ ൌ 2ηଵ which implies ηn = n ηଵ Table 1: Material damping of the composite layers Number of plates Glass fibre polyester Glass fibre epoxy 1 0.0012 0.0010 2 0.0024 0.0020 3 0.0036 0.0030 4 0.0048 0.0040 5 0.0060 0.0050 6 0.0072 0.0060 Table 2: Specimen Details Material No. Name of the Material Cross section (mm) 1 Glass Fibre Polyester 210x210x6 2 Glass Fibre Epoxy 210x210x5
  • 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 16 3. EXPERIMENTATION 3.1 Instrumentation The following equipment is needed in recording the amplitude, frequency, period of the vibrations during the machining operation (1) Power supply unit (2) Vibration pick-up (3) Digital Storage Oscilloscope Fig 3: Digital Storage Oscilloscope of Tektronix 4000 series and Vibration pickup 3.2 Digital Storage Oscilloscope Tektronix 4000 series Display: 8x10 cm rectangular mono-accelerator c.r.o. at 2KV e.h.t. Trace rotation by front panel present. Vertical Deflection: - Four identical input channels ch1, ch2, ch3, ch4. Band-width: (-3 db) d.c. to 20 MHz (2 Hz to 20 MHz on a.c.) Sensitivity: 2 mV/cm to 10 V/cm in 1-2-5 sequence Accuracy: ± 3 % Variable Sensitivity: > 2.5% 1 range allows continuous adjustment of sensitivity from 2-1(mV/cm). Input impedance: 1M/28 PF approx. Input coupling: D.C. and A.C. Input protection: 400 V D.C. Display modes: Single trace ch1 or ch2 or ch3 or ch4. Dual trace chopped or alternate modes automatically selected by the T.B. switch.
  • 9. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 17 3.3 Experimental procedure The work specimen of 240mm x 240mm x 10mm is a mild steel square plate. Four holes of 18mm diameter are drilled on the specimen at the corners. The glass fibre epoxy and polyester composite plates are thoroughly cleaned and polished. Plates are fixed on to a bench vice and the edges are filed to clear off the irregularities. All the plates are made to the exact dimensions for the ease of the further operations. Four holes are drilled on each plate and these holes are needed to be coaxial when the plates are placed upon one another and also with the mild steel. All the plates are carefully made homogenously similar to avoid interfacial vibrations and slipping. The work piece is then mounted onto the layered sheets of composites and tightly bolted to slotted table of the milling machine using square head bolts. Initially six glass fibre polyester plates each of 6mm thickness are placed upon the bed along with mild steel. A contact type magnetic base vibration pickup connected to a digital phosphor storage oscilloscope of Tektronix 1000 series is used to pick up amplitude, time period, RMS amplitude and frequency on the mild steel during the machining operation. Fig 4: Composite Six Layers under operation The response signals with respect to amplitude, time period, RMS amplitude and frequency are recorded and stored on the screen of the storage oscilloscope. Then the numbers of layers are reduced to four layers and the observations are recorded. In this way, the experiments are repeated by decreasing the number of layers of various composites. The experiments are conducted for 1, 2, 3, 4, 5 and 6 numbers of layers respectively. The whole process is again repeated using glass fibre epoxy plates each of 5mm thickness. An Up milling cutting operation with constant feed of 18mm/min and depth of cut of 0.03mm is performed during all the experiments. An oil-water emulsion made from animal fat is used as a cutting fluid.
  • 10. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 18 4. EXPERIMENTAL RESULTS AND DISCUSSION Milling operation is carried out to a depth of 3mm while increasing the number of composite plates from one to six. A contact type magnetic base vibration pickup connected to a digital phosphor storage oscilloscope of Tektronix 4000 series is used to pick up amplitude, time period, RMS amplitude and frequency. Finally Mild steel plate alone is machined with no layer under it. Figure 4 shows the experimental set up. Table 3: Experimental Frequency and Amplitude data for Glass fibre polyester S. No. Depth of cut (mm) Feed rate (mm/min) Number of layers Signal Amplitude (mV) Time Period (µs) Frequency (KHz) RMS Amplitude (mV) 1 0.03 18 1 55.4 812.2 1.232 15.3 2 0.03 18 2 35.7 716.7 1.786 11.6 3 0.03 18 3 24.4 413.8 1.154 6.80 4 0.03 18 4 49.8 516.3 2.661 8.92 5 0.03 18 5 53.3 903.6 2.982 10.3 6 0.03 18 6 58.1 231.2 3.465 12.4 Fig 5: Vibration signal for single layer of Glass fibre polyester plates
  • 11. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 19 Fig 6: Vibration signal for two layers of Glass fibre polyester plates Fig 7: Vibration signal for three layers of Glass fibre polyester plates
  • 12. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 20 Fig 8: Vibration signal for four layers of Glass fibre polyester plates Fig 9: Vibration signal for five layers of Glass fibre polyester plate
  • 13. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 21 Fig 10: Vibration signal for six layers of Glass fibre polyester plate Table 4: Experimental Frequency and Amplitude data for Glass fibre epoxy S. No. Depth of cut (mm) Feed rate (mm/min) Number of layers Signal Amplitude (mV) Time Period (µs) Frequency (KHz) RMS Amplitude (mV) 1 0.03 18 1 35.0 864.2 2.728 7.98 2 0.03 18 2 22.4 517.1 1.311 5.23 3 0.03 18 3 42.7 674.2 1.354 8.92 4 0.03 18 4 52.3 231.4 1.722 10.86 5 0.03 18 5 62.8 717.2 2.556 13.41 6 0.03 18 6 68.3 412.4 2.290 17.7
  • 14. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 22 Fig 11: Vibration signal for one layer of Glass fibre epoxy plates Fig 12: Vibration signal for two layers of Glass fibre epoxy plates
  • 15. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 23 Fig 13: Vibration signal for three layers of Glass fibre epoxy plates Fig 14: Vibration signal for four layers of Glass fibre epoxy plates
  • 16. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 24 Fig 15: Vibration signal for five layers of Glass fibre epoxy plates Fig 16: Vibration signal for six layers of Glass fibre epoxy plates
  • 17. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 25 4.3 Discussions The above tables show the variation of signal amplitude with respect to number of layers for different combinations of composites. It is observed that when the numbers of layers are increased, the signal amplitude has decreased for both the composites to a certain extent and then increased abruptly. The maximum amplitude is obtained when no composite material was used indicating that the presence of composite materials decreases the vibration amplitude and increases the counter vibration characteristics of the system. This shows that with increase in the plates the damping can be increased but only to a certain limit and it would have a negative effect with much of progress. Hence optimum level of plates is to be decided to profitably damp out the vibrations. This optimum number of plates is different for glass fibre polyester and glass fibre epoxy. Table 5: Optimum no. of plates and Height of machine too bed Type of composite Optimum no. of plates Height of the machine bed Glass fibre polyester Three (6 + 6 + 6) = 18mm Glass fibre epoxy Two (5 + 5) = 10mm CONCLUSIONS Use of composite materials reduces the vibrations of the system as desired which is justified from the experimental observations. With increase in number of layers of composites at an optimum level the vibrations are decreased considerably. Abrupt increase in vibration amplitude has also been observed with increase in number of layers of composites above an optimum limit interposed between the table and work piece. The results obtained are compared with respect to each other. Out of the two materials, signal amplitudes obtained are less for Glass fibre epoxy material. Therefore, it can be concluded that Glass fibre epoxy material can be used for machine tool structures to reduce the undesirable effects of vibrations. Effective damping can be obtained only by proper fixation of the composites to the bed and the work piece. With improper nut and bolt joint there is a danger of additional slip vibrations between the plates. Hence a proper and intact joint is necessary. On the contrary the optimum number of plates is decided and a single plate of optimum thickness is used as the bed material. The density of the matrix phase plays an important role in damping the vibrations. With same fibre phase, lower the matrix phase density more is the damping ability. Though both the thermosets polyester and epoxy have same material properties like Young’s modulus, Rigidity modulus and Poisson’s ratio, epoxy has more damping ability than polyester because of its low density. REFERENCES [1] Mayank Ladha et al., “Comparative Study of Different Materials on A Drilling Machine with Vibration Signals”, International Journal of Latest Trends in Engineering and Technology (IJLTET) Vol. 3, 2013 pp (145-149). [2] Dai Gil Lee et al., “Novel applications of composite structures to robots, machine tools and automobiles”, Journal of Composite Structures, vol. 66 (2004) 17–39. [3] Jesse Peck and Kurt Massey, “Next Generation Composite Wing Drilling Machine for Vertical Builds”, Electroimpact, Inc. 2011-01-2613. [4] Jan Smolík, “Damping of Prismatic Hybrid Structures”, (2012).
  • 18. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 4, April (2014), pp. 09-26, © IAEME 26 [5] A. Selvakumar and P.V. Mohanram, “ANALYSIS OF ALTERNATIVE COMPOSITE MATERIAL FOR HIGH SPEED PRECISION MACHINE TOOL STRUCTURES”, ANNALS OF FACULTY ENGINEERING HUNEDOARA – International Journal of Engineering (2012). [6] Bartosz Powałka & Tomasz Okulik, “Dynamics of the guideway system founded on casting compound”, Int J Adv Manufacturing Technology (2012) 59:1–7. [7] Swami et al, “DESIGN AND STRUCTURAL ANALYSIS OF CNC VERTICAL MILLING MACHINE BED”, International Journal of Advanced Engineering Technology. [8] Sukhwinder Singh Jolly, “Advancements in Composite Materials and Their Applications in Engineering and Technology”, (International Global Research Analysis), Vol 15, 2012, 2277 – 8160. [9] M. Sulitka1 et al., “MACHINE TOOL LIGHTWEIGHT DESIGN AND ADVANCED CONTROL TECHNIQUES”, Machine Tool Lightweight Design 2008 29-34. [10] Krishna Mohana Rao. G and Vijay Mohan S, “Experimental Analysis of Passive Damping Technique on Conventional Radial Drilling Machine Tool Bed using Composite Materials”, International Journal of Mining, Metallurgy & Mechanical Engineering (IJMMME) Volume 1, Issue 2 (2013) ISSN 2320–4060 pp128-131. [11] S. S. Abuthakeer, et al., “Static and Dynamic Performance Improvement of Conventional Computer Numerical Control Machine Tool Bed with Hybrid Welded Steel”, American Journal of Applied Sciences 8 (6): 610-616, 2011. [12] Koo K. N., Lee. I., “Vibration and damping analysis of composite laminates using deformable finite element”, AIAA, J 31 (4): 728-35, (1993). [13] Singh S. P., Gupta K., “Damped free vibrations of layered composite cylindrical shells”. J Sound Vib 172 (2): 191-209 (1994). [14] Prabhat Kumar Sinha, Manas Tiwari, Piyush Pandey and Vijay Kumar, “Optimization of Input Parameters of CNC Turning Operation for the Given Component using Taguchi Approach”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 4, 2013, pp. 188 - 196, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [15] Kareem Idan Fadheel and Dr. Mohammad Tariq, “Optimization of End Milling Parameters of Aisi 1055 by Taguchi Method”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 5, Issue 3, 2014, pp. 9 - 20, ISSN Print: 0976-6480, ISSN Online: 0976-6499. [16] S. Madhava Reddy, “Optimization of Surface Roughness in High-Speed End Milling Operation using Taguchi’s Method”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 4, 2013, pp. 249 - 258, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

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