Model for prediction of temperature distribution in workpiece for surface grinding using fea


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Model for prediction of temperature distribution in workpiece for surface grinding using fea

  1. 1. International Journal of Advanced Research in Engineering and TechnologyRESEARCH IN – INTERNATIONAL JOURNAL OF ADVANCED (IJARET), ISSN 09766480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME ENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print) IJARETISSN 0976 - 6499 (Online)Volume 3, Issue 2, July-December (2012), pp. 207-213© IAEME: ©IAEMEJournal Impact Factor (2012): 2.7078 (Calculated by GISI) MODEL FOR PREDICTION OF TEMPERATURE DISTRIBUTION IN WORKPIECE FOR SURFACE GRINDING USING FEA Gunwant D.Shelake1, Harshal K. chavan2, Prof. R. R. Deshmukh3, Dr. S. D. Deshmukh4 4 Dept. of Mechanical Engineering, JNEC, Aurangabad, MH. India, 1 M.E.(Mfg.) ,2Dept. of Mechanical Engineering ,JNEC, Aurangabad, MH. India, 2 M.E.(Mfg.) ,2Dept. of Mechanical Engineering ,JNEC, Aurangabad, MH. India, 3 Dept. of Mechanical Engineering., JNEC, Aurangabad, MH. ABSTRACT Thermal damage and residual stresses [1] are responsible for defects in grinding process, so it is important to study the factors which affect grinding temperatures. This paper presents an overview of effect of various grinding parameters on grinding temperature. Then general analytical approach consists of modeling the grinding zone as a heat source which moves along the work piece surface. A critical factor for calculating grinding temperatures is the energy distribution [2], which is the fraction of the grinding energy transported as heat to the work piece at the grinding zone.. In this paper, a finite element thermo mechanical model for the calculation of effect of temperature by a surface grinding process on a steel work piece (AISI 52100) is presented. A model giving the energy conducted as heat in the work piece as a function of the grinding wheel [3] speed, the work piece speed, and the cutting depth is proposed Keywords: Thermal damage, temperature distribution, finite element model 207
  2. 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMEI. INTRODUCTIONThe amount of energy per unit volume of material being removed from the work piece duringgrinding is very large. This energy is converted entirely almost into heat, causing a significantrise in the work piece temperature and, therefore thermal damage. In order to analyze thisextensive work has been performed pertaining to the modeling and simulation of grinding.Thermal modeling that can predict the temperature rise within the work piece have beendeveloped. A 2D model was used, with the grinding width large with respect to its length.However, this model is based on the assumption that the total grinding energy is entirelyabsorbed by the work piece, whilst in reality the total grinding energy is distributed not onlyin the work piece but also in the grinding wheel, the chip, and the coolant [4]. The finiteelement method[5] has been employed for modeling the grinding process, in order to achievea greater accuracy and more reliable results. In the present paper, a novel finite elementthermal model is reported, which allows for the calculation of the grinding temperatures andtheir distribution within the work piece. The maximum temperature on the surface and thetemperature fields developed in the subsurface of the work piece during grinding can betheoretically predicted using the model [6]. II. KINEMATICS OF GRINDINGFig. 1 shows a schematic representation of a grinding process. Here a wheel rotating with asurface velocity of Vs moves against the surface of workpiece with relative velocity of Vwp.During the process an amount of a i.e .depth of cut is removed from the surface. The contactlength between wheel and workpiece is calculated from equation (1)in which lc is contactlength, ds is diameter of wheel and a, as mentioned before is depth of cut that is removed inone pass. The heat flux [7] that exerts to the workpiece during grinding can be calculatedfrom equation (2) where q is heat flux into the workpiece, ε is percentage of heat fluxentering into the workpiece, Ft is tangential force that produced during engagement of wheeland workpiece and b is the grinding width. The proportion of heat flux entering theworkpiece can be calculated by equation (3) where uch is the energy required for chipformation having a constant value of 13.8 J/mm3 for grinding all ferrous materials and u isthe total specific energy required for grinding [8], 208
  3. 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME Fig. 1 schematic representation of a grindingIII. THERMAL MODELING OF GRINDINGThe grinding wheel is considered to be a moving heat source, see Fig. 1. The heat source ischaracterized by a physical quantity, the heat flux, q, that represents the heat entering an areaof work piece per unit time and is considered to be of the same density along its length,which is taken equal to the geometrical contact length, lc, which is calculated from therelation [9] ݈௖ = ඥሺܽ. ݀௦ ሻ (1)Where a is the depth of cut and ds is the diameter of the grinding wheel. Fig. 2. Suggested thermal finite element model for surface grindingThe real contact length is expected to be larger to the deflection of the grinding wheel and theworkpiece in the contact area. Assuming the geometrical and real contact lengths areconsidered to be equal. The heat flux can be calculated from the following equation ௙′ ೟ ௩ೞ ‫߳ = ݍ‬ ௟೎ (2)Where, ϵ is the percentage of heat flux entering the workpiece, 209
  4. 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMEf′୲ = the tangential force per unit width of the workpiece,vs =the peripheral wheel speed and lc = the geometrical contact length.The proportion of the heat flux entering the workpiece can be calculated by a formulasuggested by Malkin for grinding with aluminum oxide wheels, as ௨೎೓ ߳ =1− ௨ (3)where‫ݑ‬௖௛ is the energy required for chip formation, having aconstant value of about 13.8 J/mm3 for grinding all ferrous materials, and u is the total specific grinding energy required forgrinding, calculated from ୤′ ୴ u = ୟ୴ ౩ ౪ (4) ౭where v୵ is the workspeed. Note that, in both Eqs (2) and (4), the value of Ft is required inorder to calculate the heat flux and the total specific grinding energy, respectively; it can becalculated from ୮′ ౪ f′୲ = ୴౩ (5)Where Pt is the power per unit width of the workpiece, which was measured during thetesting of the different grinding wheels. Therefore, from Eqs (2)–(5), the heat flux can becalculated for every case. The kind of modeling suggested in this paper is suitable for agrinding process with a very small depth of cut, since there is no modeling of the chip. In anyother case, other assumptions must be made for the chip in order to provide a valid model,since the heat carried away by the chip cannot be neglected. Furthermore, the two coefficientsof the work piece material that are related to temperature, i.e. the thermal conductivity andthe specific heat capacity, along with the density of the work piece must be inserted as inputsto the program. For the material used in the wheel testing, those quantities were taken fromthe FEM program data bank. The first two were considered to be temperature dependent [10].IV. FINITE ELEMENT MODELThe process of grinding is carried out by movement of the grinding wheel against a stationaryworkpiece. During this process, surface of work piece comes into contact with abrasivegrains of grinding wheel and a certain amount of material is removed from it. At any definingmoment contact occurs in a specific length of work piece called contact length in whichthermal exchange and mechanical forces are introduced into the workpiece. The problem of 210
  5. 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMEgrinding can be described by moving an appropriate heat flux and mechanical forces on thetop surface of work piece, mathematically .A two dimensional model was used to simulatemovement of heat flux on the surface of work piece using the ANSYS [11] finite elementanalysis package. Since loading and geometry remains unchanged in the third direction, a twodimensional plane strain model would be appropriate for obtaining temperature and stressfield. The finite element mesh is shown in Fig. 2. AISI 52100 bearing steel which is widelyused for grinding was considered for work piece material. Thermal analysis was carried out,step by step, by exerting calculated heat flux into the contact length.Assumptions made in finite element models are • Grinding process is transient in nature. • Material is homogeneous and isotropic • Material properties [12] are assumed to be linear.V. RESULTSFigure 3a, 3b & 3cshows temperature results when the wheel is approximately at the center ofworkpiece. From figure 3a &3b we can say that maximum temperature occurs at the trailingedge but due to ambient there is no temperature rise after the trailing edge. Fig 3c shows theplot of temperature versus depth at a distance x=0.Due to the coolant on the top surfacemaximum temperature occurs in the sub-surface. Figure 3d shows the temperaturedistribution when the wheel is about to leave the workpiece surface. Fig shows that maximumtemperature occurs when wheel is about to leave the workpiece surface Fig 3a Temperatures counter at the surface Fig 3b Temperature counter at y=-0.1mm 211
  6. 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEMEFig 3c temperature versus depth at X=0 Fig 3e Temperature profile on the surface Fig 3d Temperature distribution in grindingVI. CONCLUSIONIt can be concluded that the Finite Element Model yields a good understanding of the processand aids to make suitable changes to process parameters to affect the desired thermal loadingand which may hence affect the residual stresses [13] in the model. Further, recently there hasbeen some work related to the use of grinding (HSG to be exact) for causing heat treatmentowing to the substantial heat generated and high temperature on the ground surface, the finiteelement model can aid to decide suitable parameters (speed, feed) to determine the bestcourse for attaining such heat treatment. The model also incorporates cooling effects (throughsurface convection) which can be used to compare the cooling effectiveness of the coolants tobe used. Since high temperature occurs at the trailing edge of the grind interface (also calledas the burnout effect), one must ensure that large amount of coolant is used and that itpenetrates the grind zone to be effective. 212
  7. 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME REFERENCES[1] R. J. Gu, M. Shillor,G. C. barber,T. Jen,July 2003:Thermal Analysis of the GrindingProcess.[2] Bin Shen1,Albert J. Shih,Guoxian Xiao, June 2011:A Heat Transfer Model Based onFinite Difference Method for Grinding.[3] T. Brockhof, January 10, 1999: Grind-Hardening: A Comprehensive View.[4] Maklin S., 1989, Grinding Technology: Theory and Application of Machining withAbrasive, SME,Dearbon.[5] D.A.Doman, A.Warkentin, R.Bauer, 1November 2008: Finite element modelingapproaches in grinding.[6] Snoeys ,R., Maris, M and Peters , J., 1978,”Thermally Induced Damages in Grinding,”Annals of the CIRP, p.571[7] Aaron Walsh, February, 2004 :Mathematical Modelling Of The Crankshaft Pin GrindingProcess.[8] Guo, C. And Malkin, S., 1994, " Analytical and Experimental Investigation of Burnout inCreep-Feed Grinding[9] Kohli, S.P., Guo, C., Malkin, S., 1995, "Energy Partition for Grinding with AluminiumOxide and CBN Abrasive wheels", ASME Journal of Engineering for Industry, Vol.117, pp.160-168[10] Jaeger J. “Moving Sources of Heat and Temperature at Sliding Contacts," Proc. Of theRoyal Society of New South Wales, Vol. 76,1942, pp. 203-224[11] Ansys user manual 13.1 2010[12] P.N. Moulik1, H.T.Y. Yang2, S. Chandrasekar*,10 February 2000 :Simulation ofthermal stresses due to grinding.[13] Hédi Hamdi∗, Hassan Zahouani, Jean-Michel Bergheau,26 February 2003:Residualstresses computation in a grinding process. 213