EFFECT OF BLANK RADIUS ON DRAWING STRESSES IN HYDROFORMING DEEP DRAWING PROCESS

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1 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN EFFECT OF BLANK RADIUS ON DRAWING STRESSES IN HYDROFORMING DEEP DRAWING PROCESS D.R.Uday Kuma, D.P.Ravinde Reddy, D.A.V.SitaRamaaju 3 Associate pofesso, Dept.of Mechanical Engineeing, Mahatma Gandhi Institute of Technology, Gandipet, Hydeabad. 575.Telangana. India. Pofesso& Head, Dept.of Mechanical Engineeing, Chaitanya Bhaathi Institute of Technology, Gandipet, Hydeabad. 575.Telangana. India. 3 Pofesso & Diecto of admissions,dept.of Mechanical Engg., JNTUH college of Engineeing, Kukatpalli, Hydeabad Telangana. India ABSTRACT Hydo foming deep dawing is an impotant pocess used fo poducing cups fom sheet metal in lage quantities. Hydaulic pessue can enhance the capabilities of the basic deep dawing pocess fo making cups. This pape pesents effect of adius of blank on dawing stesses in hydo foming deep dawing pocess though casto oil medium. In hydo foming deep dawing pocess, the methodology fo applying the hydaulic pessue on blank peiphey in adial diection. It is obtained though the punch movement within the fluid chambe, which is povided in punch and die chambes. These two chambes ae connected with the bypass path and it is povided in the die. Duing the pocess punch movement within the fluid chambe the pessue is geneated in fluid and it is diected though the bypass path to blank peiphey, the thick fluid film is ceated on the uppe and lowe sufaces of the blank and subsequently educes fictional esistance and is to educe tensile stesses acting on the wall of the semi dawn blank. The blank is taking at cente place in between blank holde and die suface with suppoting of high pessuied viscous fluid. The dawing stesses ae poduced in the cup wall at die entance adius along the dawing diection duing the fomation cup in this pocess though punch foce.the shea stesses acted by viscous fluid on the both sides of blank, so apply viscosity phenomenon to this analysis. The Dawing stesses ae detemined in tems of pocess paametes, blank geomety and to study on effect of blank adius on these stesses. Keywods:- Viscosity of oil, dawing stess, shea stess, deep dawing, hydo foming. INTRODUCTION The advantages of sheet hydo foming ae impoving the mateial fomability, eduction of fiction foce, the accuacy of the foming pat and the eduction of foming stages. The hydo fomed components ae used in the aeospace, automotive and othe industies. In deep dawing a sheet metal blank is dawn ove a die by a adiused punch. As the blank is dawn adially inwads the flange undegoes adial tension, cicumfeential compession and Dawing stesses ae poduced in dawing diection of cup[-4].the latte may cause winkling of the flange if the daw atio is lage, o if the cup diamete-to-thickness atio is high. A blank-holde usually applies sufficient pessue on the blank to pevent winkling [5-6]. Radial tensile stess on the flange being dawn is poduced by the tension on the cup wall induced by the punch foce. Hence, when dawing cups at lage daw atios, lage adial tension ae ceated on the flange and highe tensile stess is needed on the cup wall. Bending and unbending ove the die adius is also povided by this tensile stess on the cup wall. In addition, the tension on the cup wall has to help to ovecome fictional esistance, at the flange and at the die adius. As the tensile stess that the wall of the cup can withstand is limited to the ultimate tensile stength of the mateial, in the field of hydo foming deep dawing pocess the special dawing pocesses such as hydo-foming [7], hydo-mechanical foming [8], counte-pessue deep dawing [9-], hydaulic-pessueaugmented deep dawing []. The pocess is an automatic co-odination of the punch foce and blank holding foce, low fiction between the blank and tooling as the high pessue liquid lubicates these intefaces and elimination of the need fo a complicated contol system. The pessue on the flange is moe unifom which makes it easiest to choose the paametes in simulation. The pessue in the die cavity can be contolled vey feely and accuately, with the appoximate liquid pessue as a function of punch position, the pats can dawn without any scatches on the outside of the pat and also obtained in good suface finish, suface quality, high dimensional accuacy and complicated pats[- Volume, Issue, Novembe 4 Page 4

2 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN ].In the hydo foming deep dawing pocess the pessuied fluid seves seveal puposes ae suppots the sheet metal fom the stat to the end of the foming pocess, thus yielding a bette fomed pat, delays the onset of mateial failue and educes the winkles fomation. The advantages of hydaulic pessue foming deep dawing techniques, inceased depth to diamete atio s and educes thickness vaiations of the cups fomed ae notable. In addition, the hydaulic pessue is applied on the peiphey of the flange of the cup, the dawing being pefomed in a simultaneous push-pull manne making it possible to achieve highe dawing atio s then those possible in the conventional deep dawing pocess.. NOTATION p adius of punch cp cone adius on punch d adius of die opening cd cone adius on die t thickness of blank j adius of blank σ adial stess hoop stess dθ angle made by element at job axis P h blank holde pessue P adial pessue of fluid Shea stess acting by the fluid on each side of element Total Shea stess acted by the fluid on the Element d width of element adial distance of blank element fom job axis yield stess Radial stess at die cone. d (dy) distance between uppe suface of the blank element and blank holde (dy) distance between lowe suface of the blank element and die suface dy distance maintained by blank element fom both blank holde and die suface shea stess acted by fluid on uppe suface of the blank element shea stess acted by fluid on lowe suface of the blank element du velocity of the blank element elative to blank holde and die suface dynamic viscosity o absolute viscosity o Viscosity of fluid, the total shea stess acting by the fluid on the blank element A h height of the gap thickness of fluid 3. EVALUATION AND EFFECT OF BLANK RADIUS ON DRAWING STRESSES 3. Detemination of Radial Stess Hydo foming deep dawing Pocess as shown in fig.. In the hydo foming deep dawing Pocess, a high pessue is poduced in the fluid by the punch penetation into the fluid chambe. This pessuied fluid is diected to the peipheal suface of the blank though the bypass holes and also this high pessue fluid leak out between the blank and both the blank holde and die. This ceates a thick fluid film on uppe and lowe suface of the flange and subsequently educes fictional esistance. Duing the pocess the shea stesses ae acting by fluid on the both sides of semi dawn blank at a gap, which is povided between the blank holde and die suface and the semi dawn blank is taking place at middle of the gap. The height of the gap is moe than the thickness of the blank. The adial stesses ae geneated in the blank in adial diection due to punch foce applied on it So these stesses ae geneated in cicula blank mateial duing in the hydo foming deep dawing pocess. The vaious stesses acting on the blank element duing the pocess is shown in fig..evaluation of adial stesses, let us conside a small element of blank d in between blank holde and die suface in adial diection at a distance fom the job axis of the cicula blank with in the fluid egion (fig..). The viscous fluid contact on the both sides of blank element, due to this, the viscous foce is acted by fluid on the both sides of the blank element. The total shea stess acting by the fluid on the element (i.e. shea stess is acting by the fluid on the each sides of element and it is same).then shea foce F is given by, d F x A c Whee A c fluid contact aea of element But A c d d + dd Volume, Issue, Novembe 4 Page 5

3 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN Fig. Hydofoming Deep Dawing pocess Fig.. Acting of Stesses on the element duing dawing pocess Apply the equilibium condition in adial diection, i.e. Net foces acting on the element in the adial diection equal to eo. F, d d d () t As, ae the two pinciple stesses, the equation is obtain by using Tesca s yield citeia () Combined eq. () and eq. () d d d t Integating d t C t Whee C is constant, it is obtained fom bounday condition., d d (3) That bounday condition : at j Whee is the coefficient of fiction between blank and both the blank holde and die suface The bounday condition is Sub. in eq. (3) we get C j j t Component C is sub. in eq.(3) j ( j ) (4) t This equation (4) epesents distibution of adial stesses in the blank duing the hydo foming pocess. 3.. Radial stess at die cone ( d ) Radius of die opening we know that fom eq. (4), at d d d j ( j ) t d d Volume, Issue, Novembe 4 Page 6

4 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN j d ( j d ) (5) d t The equation (5) epesents adial stess distibution in the blank at die cone and is acting in adial diection duing the dawing pocess. 3.3 Dawing stess In hydo foming deep dawing pocess, the blank slides along the die cone duing dawing pocess with fluid contact media. The adial stess at beginning of die cone in this pocess is given by eq.5. The Coefficient of fiction between the blank and both the blank holde and die suface is negligible, so fictional foce is eo. To develop the elation between dawing stess at die thoat along the dawing diection and adial stess at die cone in adial diection d. This elation can be evaluated by using simple belt pulley analogy. In this analysis the fluid fiction is consideed and also these stesses ae aleady in tems of fluid viscosity ae defined. The elation between and d with fluid contact is shown in fig.3. Fig.3. Relation between dawing stess [ ] and adial stess at die cone [ d ] duing dawing pocess in fluid medium In conventional deep dawing pocess the above analogy is given by T e whee T and T ae tensions, ө Included angle at cente of pulley made by T and T (o) T Contact angle, µ coefficient of fiction between pulley and belt. This eq. is apply to this hydo foming pocess with consideations of T x A* and T d x A*, whee A* contacting aea of and d & it is same and µ (Coefficient of fiction between the blank and both the blank holde and die suface & no diect contact between the blank and both the blank holde and die suface), d x x A * A* e d, d d x e e d (6) so in hydo foming deep dawing pocess, The dawing stess in the cup wall at die entance adius along the dawing diection is equal to adial stess occued at beginning of die cone in adial diection. But we know that adial stess at die cone in adial diection fom eq.[5] j Z d Z ( j d ) (7) d t This equation epesents the distibution of dawing stess in the cup wall at die entance adius along the dawing diection in the pocess. Volume, Issue, Novembe 4 Page 7

5 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN VISCOSITY PHENOMENA In this hydofoming deep dawing pocess, the blank is inteaction with the fluid, then the viscosity is comes into the pictue. Duing the pocess the shea stesses and shea foces ae acting by the fluid on the blank in the gap, which is the egion between blank holde and die suface. Duing the hydofoming deep dawing pocess, the blank is taking place at middle of the gap. The effect of viscosity phenomenon in this pocess as shown in below fig.4. Fig.4.Blank element between blank holde and die suface within fluid egion Newton s law of viscosity is applied to this pocess fo evaluation of dawing stesses.let us conside a small element of blank in between blank holde and die suface with in the fluid egion i.e gap. as shown in fig.4. dy,because the blank element is taking place at middle of the gap But dy but, Because of dy dy dy du dy du dy du du Accoding to Newton s law of viscosity, dy dy Let us, dy h t The total shea stess acting by the fluid on the blank element A + du But dy, Whee du u u 4 u A h t 4. Dawing stess in tems of viscosity A du A dy j The dawing stess Z ( j d ) (Fom eq.7 ), d t 4u Substitute, we get dawing stess in tems of viscosity ht 4 u h t (8) Volume, Issue, Novembe 4 Page 8

6 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN j 4 u j d (9) d h t t 5. MAGNESIUM ALLOYS Magnesium is the highest of the commecially impotant metals, having a density of.74 gm/cm 3 and specific gavity.74.applications fo magnesium alloys include use in aicaft, missiles, machiney, tools, and mateial handling equipment, automobiles and high speed compute pats. Like aluminum, magnesium is elatively weak in the pue state and fo engineeing puposes is almost always used as an alloy. Even in alloy fom, howeve, the metal is chaacteied by poo wea, ceep and fatigue popeties. Stength dops apidly when the tempeatue exceeds C, so magnesium should not be consideed fo elevated tempeatue sevice. Its modulus of elasticity is even less than that of aluminum, being between one fouth and one fifth that of steel. Thick sections ae equied to povide adequate stiffness, but the alloy is so light that it is often possible to use thicke sections fo the equied igidity and still have a lighte stuctue than can be obtained with any othe metal. Cost pe unit volume is low, so the use of thick sections is geneally not pohibitive. Fo engineeing applications magnesium is alloyed mainly with aluminum, inc, manganese, ae eath metals, and iconium to poduce alloys with high stength to-weight atios. On the othe positive side, magnesium alloys have a elatively high stength-to-weight atio with some commecial alloys attaining stengths as high as 3 MPa. High enegy absoption means good damping of noise and vibation. While many magnesium alloys equie enamel o lacque finishes to impat adequate connection esistance, this popety has been impoved makedly with the development of high puity alloys. Fo this analysis thee types of Magnesium alloys consideed namely AZ3B-O, HK3A-H4 and AZ6A-F. Magnesium alloy AZ3B-: composition (%): 3.5 Al,.6Mn,.Zn and Tensile stength 4MPa, Yield stength 5MPa. Magnesium alloy AZ6A-F: composition (%): 6.5Al,.Zn and Tensile stength 48MPa, Yield stength Mpa. Magnesium alloy HK3A-H4: composition (%):3.Th,.7Z and Tensile stength 8MPa, Yield stength 5Mpa. 6. RESULTS & DISCUSSION The dawing stess distibution in the blank duing the hydofoming deep dawing is given by eq.9 j 4 u j d d h t t The following pocess paametes and yield stess values of magnesium alloys ae consideed fo evaluation of dawing stesses of magnesium alloys with casto oil fo successful fomation of cup in hydofoming deep dawing pocess. p 5 mm, d 3mm, c 5 mm, Radial pessue of fluid P, Punch speed u 5mm/sec, h mm, Type of mateials used :Magnesium alloys, Yield Stess values ( ) of Magnesium alloys: AZ3B-O 5MPa, HK3A-H4 5 MPa and AZ6A-F MPa. Type of fluid used: casto oil, viscosity.985n sec/m, adius of blank j 8mm, 85mm,9mm,thickness of blanks t 4mm. The evaluation of values of dawing stesses ( ) in the blanks of magnesium alloys with a given fluid and given thickness of blanks fo diffeent adius of blanks as follows. Substitute the above values in above equation we get genealied equations fo evaluation of dawing stesses duing the pocess with espect to thickness of blanks of magnesium alloys with casto oil medium. j j The esults of dawing stesses fo magnesium alloys with espect to adius of blank as j 8mm,85mm,9mm, at t 4mm with casto oil medium ae pesented in fig.5. Volume, Issue, Novembe 4 Page 9

7 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN Fig.5. Effect of blank adius on dawing stesses of magnesium alloys Fom this figues the dawing stesses ae inceasing with inceasing the adius of blank. This is due to viscosity of oil and shea stesses acted by this fluid duing the pocess. It is also the function of pocess paametes, yield stess and fluid pessue. Fom fig.5 the magnesium alloys at t 4mm with casto oil viscosity, ange of dawing stesses of AZ3B-O is N/m N/m, HK3A H4 is N/m 554N/m and AZ6A-F is N/m N/m.The inceasing ode of dawing stesses ae AZ3B- < HK3A- H4 < AZ6A- F. The dawing stess is in highe value when adius of blank is highe value. At lowest adius of magnesium alloys, the dawing stess is highe in AZ6A-F and lowe in AZ3B-O and medium values in HK3A- H4. 7. CONCLUSIONS In this analysis the dawing stesses ae evaluated with in the ange of adius is 8mm - 9mm, at constant thickness of magnesium alloys blanks. The dawing stesses ae inceasing with inceasing the adius of blanks. These effects ae due to viscosity of casto oil acted on the blank of magnesium alloys duing the foming pocess. The highest value of dawing stess occued in AZ6A-F as N/m at j 9mm and lowest value occued in AZ3B-O as N/m at j 8mm.The pecentage of incease in dawing stesses of each magnesium alloy with in the ange of given blank adius and at given thickness is.5%. The ode of inceased amount of dawing stesses of magnesium alloys as AZ3B-O < HK3A H4 < AZ6A F. Highe values of dawing stesses ae obtained in high adius of blanks. These dawing stesses ae used to get good esults of deep dawability, suface finish and accuacy in poducts of magnesium alloys. The winkling is educed due to the blank suppoted by high pessuied viscous fluid. The highe values of dawing stesses ae give the minimiing the dawing time and highe in foming limits. ACKNOWLEDGEMENT One of the authos (D.R.Uday Kuma) thanks the management and pincipal of Mahatma Gandhi Institute of Technology fo encouaging and ganting pemission to cay out this wok. REFERENCES [] Hillie, M.J., The mechanics of some new pocesses of cup dawing, J. Appl. Mech. 36 (969) [] Yossifon, S., Sweeney, K., and Altan, T., On the acceptable blankholde foce ange in the deep dawing pocess, J. Mate. Pocess. Technol. 33 (99) [3] E.Doege, K.Dode, Pocessing of magnesium sheet metals by deep dawing and stetch foming, J.Mat. Tech. 7 8 (997), pp.9 3. [4] E.Doege, K. Dode and F.P. Hamm, Sheet metal foming of magnesium alloys, Poceedings of the IMA- Confeence on Magnesium Metallugy, Clemont-Feand, Fance, Octobe 996. pp [5] J.M. Alexande, An appaisal of the theoy of deep dawing, Met. Rev. 5 (9) (96) [6] D.F. Eay, E.A. Reed, Techniques of Pess-woking Sheet Metal, pentice- Hall, New Jesey, 974, pp. 7. [7] W.Panknin, W. Mulhause, Pinciples of the hydo fom pocess, Mittleilungen de foschungges Blechveebeitung 4 (957) [8] B. Lasen, Hydomechanic foming of sheet metal, Sheet Met.Ind. (Feb.977) Volume, Issue, Novembe 4 Page

8 IPASJ Intenational Jounal of Mechanical Engineeing (IIJME) Web Site: A Publishe fo Reseach Motivation... editoiijme@ipasj.og Volume, Issue, Novembe 4 ISSN [9] K. Nakamua, Sheet metal foming with hydaulic counte pessue in Japan, Ann. CIRP 36 () (987) [] K. Nakamua, T. Nakagava, Factue mechanism and factue contol in deep dawing with hydaulic countepessue..i. JSTP 5 (84) (984),pp [] S.Thiuvaudchelvan, A novel pessue augmented hydaulic-deep-dawing pocess fo high daw atios, J. Mate. Poc.Technol. 54 (995) [] K. Lange, Handbook of Metal foming, McGaw-Hill, New Yok, 985, pp...4. [3] S.Yossifon, J.Tiosh, on the pemissible fluid-pessue path in hydofoming deep dawing pocesses analysis of failues and expeiments, Tans. ASME J. Eng. Ind. (988) [4] S. Thiuvaudchelvan, W. Lewis, A note on hydo foming with constant fluid pessue, J. Mate. Pocess. Technol. 88 (999) [5] S.H. Zhang, J. Dancket, Development of hydo-mechanical deep dawing, J. Mate. Pocess. Technol. 83 (998) 4 5. [6] D.Y. Yang, J.B. Kim, D.W. Lee, Investigations into the manufactuing of vey long cups by hydomechnical deep dawing and ioning with contolled adial pessue, Ann. CIRP 44 (995) [7] K. Obelande, The hydomechanical deep dawing of sheet metals-ii, Blech Rohe Pofile 4 (98) AUTHOR BIOGRAPHY D.R.Uday Kuma woking as Associate Pofesso in Depatment of Mechanical Engineeing, Mahatma Gandhi Institute of Technology, Gandipet, Hydeabad, Telangana, India. He obtained B.E in Mechanical Engineeing fom Andha Univesity, Vishakhapatnam, Andhapadesh and M.Tech in Poduction Engineeing fom JNTUH, Hydeabad, Telangana state. He did his Ph.D in Mechanical Engineeing in the field of Metal Foming fom JNTUH, Hydeabad, Telangana,India.. He published 38 Technical papes in vaious intenational jounals and confeences. He taught 5 subjects in the field of Mechanical Engineeing.He published one book with LAP Lambet academic publishing, Gemany. His aeas of inteest include Hydo foming, Sheet metal foming, Bulk metal foming, Finite element analysis, Special manufactuing pocesses, Stess analysis and computational fluid dynamics. He is a eviewe and editoial boad membe fo Intenational jounals such as IJMET, IJARET, IJPTM, IJPRET, IJTE, IJDMT, IJIERD, IJAIEM, IIJME and IJRET. D.P. Ravinde Reddy woking as a Pofesso & Head, Dept. of Mech. Engg., Chaitanya Bhaathi Institute of Technology, Hydeabad.Telangana,India. He Obtained B.Tech in Mechanical Engineeing fom Kakatiya Univesity, and M.E in Engineeing Design fom PSG College of Technology, Coimbatoe and did his Ph.D entitled Investigation of Machining paametes in othogonal cutting and themal stess vaiation of cabon epoxy matix composites fom Osmania Univesity.Recipient of Raja Rambapu Patil National awad fo Pomising Engineeing Teache by ISTE fo the yea in ecognition of his outstanding contibution in the aea of Engineeing and Technology. Published ove Technical papes in vaious jounals and confeences. Pincipal Investigato fo the AICTE Sponsoed Poject on Factue Based Design of Ceamic Matix Composites and Fibe Geometic Modelling. Chief Coodinato fo the UGC Sponsoed Poject on Tool Wea and Othogonal Cutting of Cabon Composites. Pincipal Investigato fo NSTL sponsoed eseach poject on Design of Composite popelle fo highe cavitation Pefomance.His cuent eseach inteests include CAD, FEA, Manufactuing and CFD D.A.V.Sitaamaaju eceived his Ph.D in Mechanical engineeing fom Indian Institute of Technology, Madas,India in.he is cuently Pofesso of Mechanical engineeing and Diecto of admissions,jawahalal Technological Univesity Hydeabad,Hydeabad,India. HePublished ove 5 t ech n i ca l papes in vaious jounals and confeences. His cuent eseach inte est include altenate fuels, IC.engines, Manufactuing and CFD. He is esouse peson fo vaious technical confeences and wokshops. Volume, Issue, Novembe 4 Page