Optimal Design of Feeder for Sand Casted Steel Dumbbell: Simulation Studies for Techno-Economic Feasibility

Transcription

1 Amercan Journal of Mechancal Engneerng, 2014, Vol. 2, No. 3, Avalable onlne at Scence and Educaton Publshng DOI: /ajme Optmal Desgn of Feeder for Sand Casted Steel Dumbbell: Smulaton Studes for Techno-Economc Feasblty Hader Hussan 1,*, A. I. Khandwawala 2 1 Research Scholar, Bhagwant Unversty Ajmer (Rajasthan), Inda 2 Ex. Professor, Mechancal Engneerng Department, SGSITS, Indore, Inda *Correspondng author: hader @gmal.com Receved June 10, 2014; Revsed July 14, 2014; Accepted July 27, 2014 Abstract In the castng technology, defect free castng had been the prmary goal snce the ncepton of the technology. However n the present castng arena, emphass on the precse and defect free castng has got greatly ncreased due to energy savng, envronmental and economy consderatons apart from the strngent product qualty standard requrements. In order to acheve ths level, computer smulaton s nevtably necessary. FEM based smulaton software s used to fnd soldfcaton related defects specally shrnkage porosty very precsely. In the present work ANSYS, an FEM based versatle software has been used for hot spots dentfcaton n a two feeder system. The feeders have been desgned and optmzed. ANSYS has been used for transent thermal analyss and then optmzaton process has been performed. Path of two feeder optmzaton for steel sand castng on ANSYS have been searched. Conductve and convectve heat transfer has been taken n to consderaton. The whole process s performed usng tradtonal modulus approach also. The results are compared. The comparson reveals that ANSYS optmzer provdes better results for castng havng two feeders. It saves materal and energy thus resultng nto economy and envronmental benefts too. Hence t may be recommended as superor over modulus approach for two feeder system n sand castng. Keywords: feeder desgn optmzaton, FEM, modulus approach, sand castng, shrnkage porosty, steel Cte Ths Artcle: Hader Hussan, and A. I. Khandwawala, Optmal Desgn of Feeder for Sand Casted Steel Dumbbell: Smulaton Studes for Techno-Economc Feasblty. Amercan Journal of Mechancal Engneerng, vol. 2, no. 3 (2014): do: /ajme Introducton Sand castng s the most wdely used process for both ferrous and non ferrous metals, and accounts for approxmately 90% of all castngs produced. Fnte Element Method (FEM) s a powerful computatonal tool that s used to numercally solve many engneerng problems. Most of the Research on the area of castng processes modelng uses FEM as a solver to the castng Process model. The numercal smulaton of soldfcaton process usng ether Fnte Dfference or Fnte Element Methods (FDM/FEM) nvolves the followng steps: [1] 1. Formulatng an accurate mathematcal model of the soldfcaton process. 2. Specfyng accurate values for thermal propertes of materal nvolved. 3. Performng the analyss to obtan the temperature hstory of castng and mould ponts. 4. Post processng the results to vsualze the soldfcaton pattern and dentfy defects. Feeders are desgned to compensate the soldfcaton shrnkage of a castng, and make t free of shrnkage porosty. Feeder desgn parameters nclude the number, locaton, shape and dmensons of feeder. Feed path and feedng dstance nfluence the locaton and number of feeders. The volume of the feeders must be mnmzed to ncrease the yeld. The crteron s gven by for gettng feeder yeld C F3 : CF3 = Nv c c/ Nv c c+ v f (1) In sand castng, sand mxed wth bnders and water s compacted around wood or metal pattern halves to produce a mould. The mould s removed from the pattern, assembled wth cores and metal s poured n to the resultant cavtes. After coolng, moulds are broken to remove the castng. After castng s removed from the sand moulds, sand mould s destroyed [2]. In sand castng, molten lqud metal s poured nto a cavty whch takes the negatve shape of the object and the mould s made from sands. Heat removal s by heat transfer n sand mould, the governng equatons for heat transfer are [3] 2 T T = α t 2 x (2)

2 Amercan Journal of Mechancal Engneerng 94 (,0) T0 T x = (3) ( 0, ) ( Temperature at metal end) T t = T M (4) (, ) 0 T t = T (5) The method of steepest descent may appear to be the best unconstraned mnmzaton technque snce each one-dmensonal search starts n the best drecton. The use of negatve of the gradent vector as a drecton for mnmzaton was frst made by Cauchy n In ths method we start from ntal tral pont X1 and teratvely move towards the optmum pont [4]. Fnte element analyss based software ANSYS 12.0 has been used. Modal of castng s done n Pro E wld fre and cylndrcal feeders have been created n ANSYS modelng. Element selecton and materal property feedng s done latter. Convectve load have been consdered after proper meshng. Proper boundary values of temperature have been provded and then transent thermal analyses have been performed. DB log fle has been assgned to ANSYS optmzer and then desgn varable, state varable and objectve functons have been provded [5]. They are heght of feeder, maxmum temperature dfference of feeder and respectve castng zone, nverse of feeder yeld respectvely wth sutable allowances and factor of safety. Frst order optmzaton has been performed through ANSYS Desgn optmzaton works entrely wth the ANSYS Parametrc Desgn Language (APDL) and s contaned wthn ts own module (/OPT). Desgn optmzaton s largely concerned wth controllng user-defned, APDL functons/parameters that are to be constraned or mnmzed usng standard optmzaton methods (e.g., functon mnmzaton, gradents, desgn of experments). The ndependent varables n an optmzaton analyss are the desgn varables. The vector of desgn varables s ndcated by: [6] [ ] X= XX X X (6) n Desgn varables are subject to n constrants wth upper and lower lmts, that s, ( 1, 2, 3,, ) X X X = n (7) Where: n = number of desgn varables. The desgn varable constrants are often referred to as sde constrants and defne what s commonly called feasble desgn space. Now, mnmze f = f( X) (8) Where: f = objectve functon Subject to ( ) g ( X) g = 1, 2, 3,, m (9) ( )( 1, 2, 3,, ) h h X = m (10) ( ) ( 1, 2, 3,, ) W W X W = m (11) g, h, W = state varables contanng the desgn, wth underbar and overbears representng lower and upper bounds respectvely. (nput as mn, max on OPVAR command) m 1 +m 2 +m 3 =number of state varables constrants wth varous upper and lower lmt values. The state varables can also be referred to as dependent varables n that they vary wth the vector x of desgn varables [6]. In FEM, the feld varables are the temperatures at all nodal ponts that vary wth tme. Thermal propertes lke thermal conductvty, densty, specfc heat also vary wth temperature and hence the problem becomes non lnear transent n nature Galerkn s weghted resdual approach has been reported [7]. The advantage of usng FEM s the ablty to handle complex boundares, the ease n mplementng boundary condton. But ths method requres much effort for formulaton of problem, data preparaton and need long processng tme [8]. In general, FEM s preferred as t allows a wder choce of element shapes and better accuracy, whle FDM based smulaton programs are faster and easer to execute. Recent advances have been n the areas of automatc preprocessng (mesh generaton), adaptve re-meshng for better accuracy n crtcal regons, heat transfer models for consderng the effect of varable ar gap and mould coatngs, convectve and radaton heat transfer and mprovng the effcency of computaton[9]. Feeder optmzaton has been performed usng topology optmzaton [10], poson equaton approxmaton [11] and genetc algorthm [12]. P. Prabhakara Rao gves advantages of computer smulaton based desgn enumerated. The procedures thus descrbed have been demonstrated wth the above case study of applcaton of Pro CAST smulaton at G.S alloy Foundry. It s demonstrated that the foundres can derve mleage by resortng to FEM smulatons of the castng process for process development and optmzaton. [13] The applcaton of castng smulaton software s n the foundres not only mnmzes the wastages of resources requred for fnal castngs, but also mproves / enhances the qualty and yeld of castngs, whch mples hgher value addton and lower producton cost. The expermental study represents the effect of szes of rsers and necks on the soldfcaton behavor of the alumnum alloy castngs. The smulated results are more or less smlar wth expermental results [14]. The applcaton of computer aded method, sold modelng, and castng smulaton technologes n foundres can able to mnmze the bottlenecks and non value added tme n castng development, as t reduces the number of tral castng requred on the shop floor. In addton, the optmzaton of rser neck reduces or completely removes the occurrence of shrnkage defect n the castng. The applcaton of castng smulaton software based on fnte element method and vector element method shows good results and matched wth the expermental results [15]. Over sze feeder leads to not only the loss of materal but also to the loss of energy requred for moldng and remoldng the materal agan and agan. In fact the repeated moldng-remoldng consumes huge amount of fuel ultmately contrbutng to the global warmng whch s the greatest havoc for modern cvlzaton. Hence the optmal desgn of feeder system must be seen not only from the materal savng pont of vew, t must smultaneously be pursued from the envronmental

3 95 Amercan Journal of Mechancal Engneerng consderatons too [16]. The modern castng processes not only requre hgh precson and accuracy, they requre energy effcency and envronmental consstency too. The present work s a determned step n ths drecton. 2. Objectve of the Study The shrnkage porosty defect s one of the very common soldfcaton defects of sand castng process. It occurs n the thckest sectons of castng whch s possessng lastng freezng pont. The components gets fal due to nsde porosty. As sand castng have the bggest part n manufacturng of world. The practcal approach of desgn of feeder had normally hgh factor of safety and due to that over sze feeders have normally been desgned and tested on shop floor. Ths consumes lot of money and tme. So there s requred a faclty of feeder desgn whch s cheap n the affordable rang of small & medum scale castng ndustry. The ANSYS optmzaton tool can gve the better desgn but one have to fnd out the way of formulate the castng problem n t. We do not found the work done by researcher wth ANSYS optmzaton tool n mult feeder desgn of feeders for sand castng process. In ths work we have fulfll the objectve of to fndng out the way of desgnng the two feeders for sand castng of steel and we found t better on conventonal modulus approach. 3. Data Collecton Mult feeder optmzaton has been performed on a dumbbell castng of Steel. Two feeders have been desgned. Volume = M 3, Surface Area = M 2 Feeders can be optmzed by modulus approach. The thckest secton has hghest value of modulus. The optmzaton can be performed on ANSYS Optmzaton of Dumbbell Castng wth Modulus Approach and Ansys For removng shrnkage porosty defect, two feeders are desgned here by modulus approach and ANSYS 12.0 desgn optmzer for dumbbell castng. Dumbbell has been consdered n four sectons A, B, C, D. Frst modulus approach has been used and then ANSYS Optmzer appled. Modulus Approach- Table 1. Dumbbell castng data (Secton wse) s Volume M 3 Surface Area M 2 Modulus=V/A A 2.16 x x B 1.5 x x x 10-3 C 6.4x x x 10-3 D 1.5 x x x 10-3 Modulus Approach For medum sze Dumbbell Castng wth two feeders- Dameter of Feeder = MM Heght of Feeder = MM Dameter of Second Feeder = MM Heght of Second Feeder = 63.3 MM, feeder yeld by Modulus method s =51.12% The process of analyss of ths case wth Desgn optmzer of ANSYS 12.0 (An FEM Based general purpose software) has been search out for two feeders. Here we have taken heght of feeders as a desgn varables, State varable S1 = FT1-CT1 (always postve), State varable S2 = FT2-CT2 (always postve) wth sutable allowances and factor of safety so that hot spot must not reman n casted part. It should be n respectve feeder. FT= maxmum feeder temperature for respectve zone, CT= maxmum castng temperature of catchment. Followng are the graphs as a result of optmzaton. Fgure 1 s showng the temperature accordng to coolng. It can be seen that hgher temperature are wth feeders as compare to casng. Ths assures that the shrnkage porosty wll be n feeders only. Fgure 1. Dumbbell shape castng of Steel

4 Amercan Journal of Mechancal Engneerng 96 Fgure 2. Dumbbell shape castng wth optmzed feeders Fgure 3. Feeder 01 Temperature remaned hgher than correspondng castng zone 01 temperature durng entre optmzaton process.

5 97 Amercan Journal of Mechancal Engneerng Fgure 4. Feeder 02 temperatures remaned hgher than correspondng castng zone 02 temperature durng entre optmzaton process. Fgure 5. Inverse of feeder yeld whch s contnuously dropped durng optmzaton

6 Amercan Journal of Mechancal Engneerng 98 Fgure 2 s showng the temperature varaton on the central plane of Castng and Feeders. Fgure 3 and Fgure 4 are showng that maxmum temperature of Feeder remaned hgher than respectve castng zone temperature. Fgure 5 s showng the nverse of feeder yeld (objectve functon) whch s contnuously drop durng optmzaton. Here objectve s to acheve hgher feeder yeld. 5. Result and Analyss In the vew of outcome of modulus approach and fnte element method based ANSYS 12 desgn optmzaton tool, we can say that the two feeders are desgned effcently for dumbbell shape steel castng. Feeder yeld comes out from modulus method for Steel s equal to = 51.77%. Feeder yeld obtaned from ANSYS 12 desgn optmzer s equal to = 88.92%. So net advantage ganed by ANSYS 12.0 desgn optmzer s 37.15%. Optmzaton on ANSYS works better for small castngs. Importng IGES fle, Modelng, Meshng, n ANSYS may put produce problems for complcated complex shapes n transent thermal analyss and requred deep knowledge of desgn optmzaton tool and castng process. After optmzaton of feeder desgn, the suggested value can be checked by anmaton on the center plane and temperature contour can be plotted at every tme step. Two feeder desgn optmzaton can be performed on ANSYS 12 whch s low prced general purpose FEM based software. ANSYS optmzer s producng precse feeder desgn as compare to modulus approach for desgn of feeder but optmzaton process on ANSYS requres more tme, advance and powerful computer system and sklls relatvely. The ANSYS would be a effcent tool for desgn and smulate feeders n vrtual envronment for sand castng ndustry globally. Acknowledgements The authors are thankful to the Bhagwant Unversty for provdng the support & faclty and Dr Josh, Prof. n Mechancal Engneerng, SGSITS, Indore for useful techncal suggestons. References [1] Rav B., Metal Castng-computer aded desgn and analyss PHI, [2] Jan R.K., Producton Technology, Khanna Publshers, Delh, 15 th Edton Auguest, 1995 [3] Qn Rongshan, Workshop: Heat management, Lecturer 7, Graduate Insttute of Ferrous Technology, POSTECH computatonal metallurgy laboratory Korea, lecturer notes, seen on web n dec., [4] Rao S.S., Optmzaton; Theory and Applcaton, Wley Eastern Lmted, [5] ANSYS help-thermal Tutoral, Frst order optmzaton, ANSYS Inc. [6] [7] Josh Durgesh and Rav B., comparson of fnte element method and vector element method for castng soldfcaton smulaton, Indan Foundry Journal, vol. 54 no. 9 September , 2008, PP [8] Venkatesan A., Rajadura A., Effect of Ar-Gap on Castng Soldfcaton, Amercan Foundary Socety, 2006, PP [9] Rav B. and Srnvasan M.N., castng soldfcaton analyss by modulus vector method, Internatonal Journal of Cast Metals Res., 1996, PP [10] Tavakol R. And Davam P., Optmal rser desgn n sand castng process wth evolutonary topology optmzaton, Struct multdsc optm, accepted on 8 June 2008, PP [11] Tavakol Rohalla and Davam Parvz, Optmal rser desgn n sand castng by topology optmzaton wth SIMP method I : Posson approxmaton of nonlnear heat transfer, equaton, Struct multdsc optm, accepted on 29 October 2007, Sprnger-Verlag. 2008, PP [12] Elzabeth Jacob, Roschen Saskumar, B. Praveen and V. Gopalakrshna, Intellgent desgn of feeders for castngs by augmentng CAD wth genetc algorthms, Journal of Intellgent Manufacturng, 15, 2004, PP [13] P. Prabhakara Rao, G. Chakraverth, A.C.S. Kumar, G. Srnvasa Rao, Modelng and Smulaton of Soldfcaton n Alloy Steel Sand Castngs, Internatonal Journal of Thermal Technologes, Vol. 1, No. 1 Dec. 2011, PP [14] T. Nand, R. Behera, A. Chanda and G. Sutradhar, Study on Soldfcaton Behavour of LM6 Castngs by Usng Computer- Aded Smulaton Software, Indan Foundry Journal, Vol. 57, No. 3, March 2011, PP [15] Behera Rabndra, Kayal.S, Sutradhar. G, Soldfcaton behavor and detecton of Hotspots n Alumnum Alloy castngs: Computer Aded Analyss and expermental valdaton, Internatonal Journal of Appled Engneerng Research, Dndgul, Volume 1, No 4, 2011, PP [16] Belmra Neto, Carolen Kroeze, Leen Hordjk, Carlos Costad, Modellng the envronmental mpact of an alumnum pressure de castng plant and optons for control, Envronmental Modelng & Software, Volume 23, Issue 2, February 2008, PP