Analysis of the Effect of Die Angle Variation on the Behavior of Temperature Profile in Extrusion Process by using ANSYS Poly Flow Software

Transcription

1 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): Vlume-7, Issue-3, May-June 2017 Internatinal Jurnal f Engineering and Management Research Page Number: Analysis f the Effect f Die Angle Variatin n the Behavir f Temperature Prfile in Extrusin Prcess by using ANSYS Ply Fl Sftare Vinay Prakash Pandey 1, Gurmeet Singh Gahir 2 1,2 Mechanical Engineering Department, INDIA ABSTRACT This prject is fcused n achieving the ptimum die angle and vlumetric fl rate fr extrusin prcess. In extrusin prcess, the temperature f the melt might get increased at the die exit, due t the frictin beteen melt and the die surface, hich leads t the degradatin f plastic material prperties. S the basic aim f this prject is t cntrl the melt temperature by gverning different factrs respnsible fr the rise f temperature. When the plastics melt enters the axis-symmetric steel die at a given temperature and at a given fl rate and passes thrugh it, during the prcess heat generatin takes place due t viscus dissipatin. The increase in temperature f the melt ccurs due t the shearing taking place in the die. The amunt f temperature increased during the prcess can be cntrlled by changing the die angle and the vlumetric fl rate f the plastic melt. The 2-d mdel and the meshing fr this rk is generated in GAMBIT sftare, Whereas the verall simulatin is perfrmed n Plyfl mdule f ANSYS sftare. Keyrds-- ANSYS, CFD, Die Angle, Extrusin, GAMBIT I. INTRODUCTION Extrusin is the prcess f cnfining the plastic material in a clsed cavity and then alling it t fl frm nly pening s that it ill take the shape f the pening. Extrusin equipment cnsists f a plasticizing extruder, die assembly, a cling assembly, and haul-ff r inding equipment. Extrusin is a cntinuus prcess, as ppsed t mlding, hich is a cyclic prcess. Extrusin is suitable fr many types f cntinuus plastic prducts that have a unifrm utside shape and can be ciled, cut, r und. The transfrmatin f a slid plastic feedstck material int a mlten viscus fluid takes place in the extruder barrel, thrugh the mechanical shearing actin f a rtating scre and the heat prvided by electrical resistance heaters clamped t the utside f the extruder barrel and die. The cmbinatin f the mechanical, rtating shearing actin f the scre and the heat f the electrical heaters causes the slid plastic feedstck t change int a ht mlten material. The quality f the prduct prduced in extrusin prcess depends n s many factrs like Die design, cling technique used fr the prduct, vlume fl rate etc. The temperature f the melt increases due t viscus dissipatin caused by the shearing taking place in the die. The temperature f the fluidis critical fr the prcess. The viscsity f the fluid changes ith temperature, hich leads t the mdificatin f the shape f the extrudate. The plymer might degrade if the temperature is t high, s a numerical simulatin is f great interest t ptimize the perating cnditins. Temperature f the plastics melt rises inside the die due t shearing and this can be cntrlled by ptimizing die angle and the vlume fl rate. II. METHODOLOGY First f all, e d theretical and practical survey t identify faults in cmpnents prduced by extrusin. By ding s e get t kn that the dimensin f the cmpnent is varying as ell as the prperties f plastics is degrading t sme extent. Different factrs are taken in t accunt hich are respnsible fr the quality f the prduct, and amng these factrs e have cnsidered die angle and vlume fl rate are the crucial factrs hich plays imprtant rle in gverning the quality f the prduct. 494 Cpyright Vandana Publicatins. All Rights Reserved.

2 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): Fr element type (1) (Plastic melt -Isthermal Surface) Gemetrical Mdeling and Meshing Mdeling f 2D axis-symmetric die is dne n GAMBIT. In mdeling prcess, t reduce the time required fr simulatin e have created 2D axis-symmetric die. Map type meshing prcess have been adpted, s that e can get unifrm meshing thrughut the die. 2.2 Simulatin(CFD Analysis) Cmputer based simulatin is perfrmed n plyfl mdule f ANSYS sftare t ptimize the die angle and mass fl rate. Several different simulatins are being perfrmed ith different die angles and mass fl rate, s that e kn its effect n the temperature difference develped during the prcess. 2.3Validatin The results shn in ANSYS are then validated by ding numerical calculatin thrugh Mathematical Mdel. 2.4 Mathematical Mdeling Then e have created a mathematical mdel t calculate the temperature change at the exit f the Die by using 2-D heat balancing equatins (thrugh bth cnductin and cnvectin), heat lss frmulatin via viscus frictin (due t decreasing fl diameter) and als by using Finite element cncepts. The data taken fr calculatin is cnsidered t be standard data. Fr calculatin purpse parameters like dimensins f the die, plastics material prperties, temperature f melt at the inlet and the die material is selected. We have divided the prblem int three dmains: Dmain-1: Fr Cylindrical axis-symmetric prtin Applying the heat balance equatin fr nde 0 Q Q Q Q 4 0 k f 2. 1 T 1 T 0 + h af. 1 T T 0 + k f 2. 1 T 3 T 0 + k f. 1 T 4 T 0 N, applying the heat balance equatin fr nde 1 Q Q Q Q 5 1 h af. 1 T T 1 + k f 2. 1 T 0 T 1 + k f 2. 1 T 6 T 1 + k f. 1 T 5 T 1 The abve t equatins clarifies h the further mre equatins fr several ndes can be structured. Fr the element type (2) (Steel Die) Applying the heat balance equatin fr nde 0 Q Q Q Q Cpyright Vandana Publicatins. All Rights Reserved.

3 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): k d 2. 1 T 1 T 0 + h af + h ad 2. 1 T T 0 + k f 2. 1 T 3 T 0 + h f 2. 1 T 3 T 0 + k f + k d 2. 1 T 4 T 0 N, applying the heat balance equatin fr nde 1 Q Q Q Q 5 1 h ad. 1 T T 1 + k d 2. 1 T 0 T 1 + k d 2. 1 T 6 T 1. 1 T 5 T 1 Fr crner nde pints f the die + k d Q Q Q Q W f k d. 1 T 1 T 0 T 2 T 0 + k d + k f k f k d 4. 1 T 3 T 0 T 3 T 0 + h f k d k f 4. 1 T 4 T 0 + π 3 σ yd 2 i V i ln d i d f Dmain-3: Fr the extruding cylindrical axis-symmetric prtin Applying the heat balance equatin fr nde 0 Q Q Q s 0 k d 2. 1 T 1 T 0 + k d 2. 1 T 2 T 0 + h ad. 1 T T 0 Dmain-2: Fr Frustum axis-symmetric prtin Fr nde pints f Plastic melt and Steel die prtins, the prcedure t cnstruct the equatins is same. But at the intersectin f the nde pints f fluid and die prtin, the heat equatin ill be frmulated as flls; Applying the heat balance equatin fr nde 0 Q Q Q Q Q s 0 + W f k d k f 4. 1 T 1 T 0 + k f k d 4. 1 T 2 T 0 + h f 2. 1 T 2 T 0 + k f. 1 T 3 T 0 + k f + k d 2. 1 T 4 T 0 + π 3 σ yd i 2 V i ln d i d f Fr the extrudate cylindrical axis-symmetric prtin Applying the heat balance equatin fr nde 0 Applying the heat balance equatin fr nde Cpyright Vandana Publicatins. All Rights Reserved.

4 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): k d + k f 2 Q Q Q Q Q T 1 T 0 III. + k f k d 4. 1 T 2 T 0 + k f. 1 T 3 T 0 + h f 2. 1 T 3 T 0 + k d 2. 1 T 4 T 0 + h af + h ad 2. 1 T T 0 PRIOR APPROACH 1. Ajibye & Adeyemi (2006)Studied abut the effect f die land length n the extrusin pressure. It as fund that extrusin pressure increases ith increase in cmplexity f die gemetry, fr die length, the extrusin pressure is lest fr square sectin and highest fr rectangular sectin & fr a particular reductin in area extrusin pressure increases ith increasing die length and vice versa. 2. Grdn et al (2007) have used the adaptable die design methd, in cnjunctin ith upper bund methd that alls the rapid evaluatin f a large number f die shapes and discvery f the desired die that prduces the desired utcme. A duble ptimizatin prcess is used t determine the values fr the flexible variables in the velcity field and secndly t determine the die shape that best meet the given criteria. 3. Karl Pepliński, ArkadiuszMzer (2010) as presented the methdlgy f numerical simulatin fr the die design. A cmmercial cmputer fluid dynamics prgram Ansys Plyfl as used t design the die passage. The bjective is t determine the die passage that results in a balanced mass fl exiting the die that clsely matches the target prfile. The die land shape mdify ith using ptimizatin algrithm is very helpful t btain gemetry and dimensin f extrudate desired prfile. 4. D.Y. Yang, K.J. Kim (2007) have rked n varius industrial extrusin prblems ith high cmplexity are simulated by emplying efficient numerical schemes such as the arbitrary Lagrangian Eulerian Finite element methd and mismatching refinement ith the dmain decmpsitin. And a ne methdlgy f shape ptimizatin technique t reduce cmputatin time fr the design f the extrusin prcess is intrduced. The mechanical prperties like anistrpy f extruded prduct are analyzed by the cntinuum apprach and discussed fr practical examples, and the texture develpment and mechanical prperties in the aluminum extrusin prcesses are predicted by emplying rate independent crystal plasticity mdel based n the smth yield surface ith runded-ff crners. 5. Patrick Ulysse (1999) have rked n an apprximate mdel has been develped t imprve ur understanding f fl cntrl at the exit f an extrusin die. He deals ith the design f traditinal die fl crrectr used in flat faced aluminum extrusin dies. The numerical mdel uses the finite-element methd cmbined ith techniques f mathematical prgramming. Analytical sensitivity has been develped frm the discretized finite element equatins in rder t cmpute the necessary derivatives during ptimizatin. The mdel includes thermal effects and the extruded utlet material is assumed t be temperature dependent and strain rate. Figure 1: Flchart fr numerical simulatin using Ansys Plyfl [Karl Pepliński, ArkadiuszMzer (2010)] In all the abve research rks, authrs have dne their research rk n identifying the effect f die land length n the extrusin pressure r the ther have rked n the die design t get desired shape f the prduct but they have nt rked n ptimizing the die angle r mass fl rate t cntrl the temperature f the prduct at the die exit. Apprpriate die angle and mass fl rate can help us t achieve desired shape and size f the prduct. Mrever, by cntrlling the temperature f the meltat die exit e can imprve the quality f the prduct because the higher temperature may leads t degradatin f material prperties. 497 Cpyright Vandana Publicatins. All Rights Reserved.

5 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): Secndly, there is need t validate the results shn in ANSYS r any ther sftare. Validatin can be dne in many ays either e can perfrm the same analysis in t different sftare ith the same input values, r e can validate ur results thrugh numerical calculatin n the basis mathematical mdel. By studying abve prjects e fund sme deficiencies and there is scpe t d sme further rks. S e have chsen t d ptimizatin f die angle and mass fl rate t imprve the quality f the prduct. This ill be dne n the basis f maximum temperature achieved by the melt near the die exit r e can say n the basis f rise f temperature f the material hich is in direct cntact f the die all during extrusin prcess. TABLE I SYMBOLIC ABBREVIATION IV. OUR APPROACH This is a cupled prblem f nn-isthermal fl f a fluid and heat cnductin in an axis-symmetric steel die. When the plastics melt enters the axis-symmetric steel die at a given temperature and at a given fl rate and passes thrugh it, during the prcess heat generatin takes place due t viscus dissipatin. The increase in temperature f the melt ccurs due t the shearing taking place in the die. The temperature f the fluid is critical fr the prcess as the plymer might degrade if the temperature is t high. The viscsity f the fluid changes ith temperature, hich leads t the mdificatin f the shape f the extrudate. The prblem invlves fl, heat transfer by cnductin and cnvectin, and heat generatin by viscus dissipatin. Energy mmentum and incmpressibility equatins are slved in the fluid dmain. The energy equatin fr heat transprt prblems is slved in the slid (die) dmain. S a numerical simulatin is f great interest t ptimize the perating cnditins. Mrever, the die angle and the vlumetric fl rate are having direct impact n shearing rate f plastics melt. Aim: - As this is a cupled prblem f nnisthermal fl f a fluid and heat cnductin ina axissymmetric steel die. Fr simulatin purpse e are taking standard values fr the parameters like melt temperature, vlumetric fl rate, and dimensins f die. Then further e ill vary the die angle and the vlumetric fl rate t bserve its effect n the melt temperature and lcal shearing. Our aim is t design the die ith ptimum angle and t select ptimum vlumetric fl rate hich ill results in minimum rise f melt temperature. Gemetry Building and Meshing- Gemetry is created in the GAMBIT sftare. Standard Die dimensins and parameters are selected and the same values ill be taken fr validatin purpse. Bundaries and Sub-Dmains selectin The mst imprtant step f CFD analysis is t define the sub-dmains and bundary cnditins f the gemetry. SD1 is fr mlten plastic material and this is a fluid dmain. SD2 is fr extrudate and this is als a fluid dmain. SD3 is fr slid die and this is a slid dmain. 498 Cpyright Vandana Publicatins. All Rights Reserved.

6 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): Thermal bundary cnditins 1. Definitin f the Fluid Sub-Task Material data Thermal bundary cnditins 2. Defining Numerical Parameters 3. Outputs setting V. RESULTS Bundary 1 is fr inlet Bundary 2 is fr axis-symmetric line Bundary 3 is fr utlet Bundary 4 is fr extrudate free surface Bundary 5 is fr die surface Bundary 6 is fr hle internal surface After creating the gemetry and defining bundary cnditin meshing prcess is dne. Basically Mapped mesh ptin is used t generate unifrm mesh thrughut the surface f the gemetry. Then the file is saved in.msh frmat, s that t imprt in ANSYS (Ply fl). Different steps flled in Ply Fl t perfrm analysis are as flls:- 1. Prject and Mesh- Imprt.msh file in PlyFl 2. Definitin f Mdels, Materials, and Bundary Cnditins 3. Definitin f the Fluid Sub-Task Generalized Netnian nn-isthermal fl prblem Shear-rate dependence f viscsity Viscsity is defined by the Bird-Carreaula as F γ = n (λγ ) 2 m 1 2 Temperature dependence f viscsity Fr this prblem, e have assumed that the dependence f viscsity n temperature flls the Arrhenius la. The Arrhenius la is given as: H T = exp α α T T 0 T α T 0 Fig-1 Temperature cntur fr the base mdel(standard Dimensins ) Fig-2 Temperature cntur fr the 2 nd trail(decreased Die angle) Fl bundary cnditins 499 Cpyright Vandana Publicatins. All Rights Reserved.

7 .ijemr.net ISSN (ONLINE): , ISSN (PRINT): On the basis f abve results, a relatinship is established beteen the die angle and rise in the temperature f plastic melt adjacent t die all. And e can cnclude that by decreasing the Die Angle the frictinal resistance get reduced hich results in decrease f maximum temperature. Thrugh the table given bel e can see that if e reduce the Die Angle, the maximum temperature near the Die alls decreases. Fig-3 Temperature cntur fr the 3 rd trail(further Decreased Die angle) The abve figure shs us the effect f change in die angle n the temperature f the plastics melt hile fling thrugh die. Our aim is t cmpare the variatin f die angle ith different intrinsic parameters like temperature, pressure, velcity, etc ithut changing the ther physical and mechanical prperties f Plastic Melt such as initial and final crss sectinal area, discharge, entrance temperature, die temperature, etc. 1 st Case-In the first case, As e can see in the Fig-1 the maximum temperature cntur is shn at the exit lcatin f the die and that is abut Kelvin, this is because f the surface frictin beteen die internal all (fl ay) and the fluid. When the plastics melt enters steel die its temperature is mlding temperature (470K) but hen it exits the die the melt temperature rise t the maximum temperature f K. This heat generatin takes place due t viscus dissipatin. Mrever e can bserve slight inflatin f the extruded surfaces at the exit lcatin f the die. The reasn behind inflatin is rise in melt temperature. 2 nd Case In secnd case(fig-2)e have decreased the die angle by2. The maximum temperature btained at exit is 479 Kelvin and this is significantly less than the prir analysis. This shs us the temperature ill get reduced n decreasing Die angle. This is due t resistance in the fluid fl reduces. Thus heat generatin further reduces. S temperature in the fluid gets reduced. 3 rd Case In this case, (Fig-3) als e have further reduced the die angle by 2. Frm the image e can easily bserve that the maximum temperature 477 Kelvin is much less in cmpare t prir cases. This is due t the fact that the frictin beteen the fluid particles and the die surfaces reduces n reducing the die angle. Reductin in frictin leads t the reductin in heat generatin. Temperature cmparisn chart f analysis dne n Dies ith different die Angles REFERENCES [1] Karl Pepliński, Arka diusz Mzer, Design f extrusin die fr Plastic prfile using Ansys Plyfl Sftare. [2] Carneir, O. S., Nbrega, J. M., Pinh, F. T., Cmputer aided rhelgical design f extrusin dies fr prfiles, Jurnal f materials prcessing technlgy, 114, pp , [3] Carneir, O. S., Nbrega, J. M., Pinh, F. T., Fl balancing in extrusin dies fr thermplastic prfiles, Internatinal Plymer Prcessing, 3, pp. 1-11, [4] Yilmaz, O., Hirkkpru K., A methd t btain balanced fl in prfile extrusin dies, ANTEC, pp , 2009 [5] GAMBIT Sftare [6] ANSYS POLYFLOW User's Guide, Ansys Inc., [7] Fundamentals f engineering heat & mass Transfer, By R.C. Sachdeva. [8] Manufacturing Science, By Amitabha Ghsh & Ashk Kumar Mallik. VI. CONCLUSION 500 Cpyright Vandana Publicatins. All Rights Reserved.