A modular approach for the estimation of forging load for the closed die forging process by computer simulation

Transcription

1 A modular approach or the estimation o orging load or the closed die orging process by computer simulation Dipakkumar Gohil and Mahendrakumar Maisuria Abstract Closed die orging is a very complex process and the measurement o actual orces or real material is diicult and cumbersome. Hence the computer simulation modeling technique has been adopted to get the estimated load requirement. The objective o this research work is to simulate and analyze the closed die orging process. In this research paper, an attempt has been made to compute the load requirement in the closed die orging process by using computer simulation during dierent stages o the process. The results o simulation have been compared with the actual load requirement and the deviation o estimated load and actual load has been reported in the orm o percentage error. I the percentage error is more than the permissible limit then the necessary corrective measures are recommended to get the better simulation results. II. MODELING OF FORGING The modeling and simulation o closed die orging process has been carried out by using analytical and numerical methods [7], []. For the purpose o simulation, a cylindrical shape billet having dierent H/D ratio have been deormed between two die halves as shown in Fig.. The deormation process beore lash ormation has been depicted in Fig. where as Fig. represents the deormation process during the lash ormation stage. Keywords Closed die orging, H/D ratio, Modeling, Modular approach, Simulation. t i H I I. INTRODUCTION N the present highly competitive era, the mass production requirements in the engineering industries have increased the demand or orged components. Forging process, usually involve multiple pre-orming processes ollowed by a speciied inishing process. Process simulation has become an increasingly important tool or the development o new or improved processes. With simulation tools the costs and the time necessary or the development o new products could be reduced signiicantly. The process requires a lot o experience and skill to optimize the quality, costs and lead time []. The objective o this research work is to simulate and analyze the closed die orging process. The main ocus is to estimate the load requirement or the die cavity illing at dierent stages o orging o AISI 6 by a computer simulation technique. The closed die orging process has been divided in to two stages i.e. deormation process beore lash ormation and ater lash ormation []. The designs based on results o simulation are required to be evaluated to make sure that the material would low as per the requirement in the die cavity []. Manuscript received on January 9, 9: Revised version received on February, 9. Dipakkumar Gohil is with the S. V. National Institute o Technology, Surat 95 7, Gujarat State, India (phone: ; ax: ; dbgohil@ gmail.com). Mahendrakumar Maisuria, is with the S. V. National Institute o Technology, Surat 95 7, India ( mbmasuria@ yahoo.com). D o L Fig. Billet and Die geometry: Initial coniguration Fig. Billet and Die geometry: Upsetting w r r L D max max z Fig. Billet and Die geometry: with Flash β β D = L / z t h t h h Issue, Volume, 8

2 A. Estimation o Flow Stresses Forging is a deormation process which involves several variables interconnected by more or less complex unction. The method discussed here, used to simulate the hot die orging process to determine the stresses and the load. The low stress relationship has been implemented as a subroutine [], [], [9]. Where, C = ( ε, T ) m = C& ε () The parameters C and m are available in the material property hand books or dierent billet materials used in various types o orming processes. B. Calculation o Strain The strains in the die cavity as well as in the lash during dierent stages have been calculated as ollows [9], [6]. The strain beore lash ormation, as shown in Fig., could be computed as, ε = ln( H / h) () During lash ormation, as depicted in Fig., the strain in lash, indicated as zone, may be calculated as, ε = ε + tc ln( t c / t ) () At the end o orging, the material is assumed to low in to lash by shearing along the surace indicated by dashed line in Fig.. Thereore the strain in zone i.e. ε is equal to ε tc which is the zone between the shearing line and the die, and the strain in zone is ε may be computed zone as, ε = εtc + ln( hc / h ) ().9 h =.8 t ( L / t ) (5) The mean height o the convergence region as shown in Fig., could be calculated as, h = ( h + t ) / (6) The strain in the convergence region may be obtained as, ε = ε + ln( h / h ) (7) tc c C. Calculation o Strain Rate The strain rates or the various stages o closed die orging are calculated according to the ollowing: Stage I: Deormation process beore lash ormation as shown in Fig. may be computed as, & ε = v / h (8) Stage II: Deormation process ater Flash ormation as depicted in Fig. may be evaluated as, D. Stress Calculation & ε = v / t (9) & ε = v / h () & ε = v / h () The stress beore lash ormation as shown in Fig. may be computed as, = ( + ( D / h)) () µ max The stresses ater lash ormation as represented in Fig. could be calculated as, = ( w / t ) + () Where, µ z = ( K / K )ln( t / K + K r )) + () z z = (( µ r ) / h) + (5) max z K = tan β K K + µ ( + tan K = β ) = h r K tan β = [ {(( h / t ) ) /(( h / t ) ln( h / t ))}] E. Calculation o Force The orce required or deormation process beore lash ormation or the geometry as shown in Fig. could be, F = π [( h / µ )(exp( D / h) ) hd / µ )] (6) I / The orce required or deormation process ater lash ormation or the geometry as shown in Fig. would be, F = F + F (7) II Where, F = π z [( h / µ )(exp( µ L / h ) ) hl / µ = ( π / )(Lw + w )( + ( w / t )) F µ F is the average orce on the billet and F is the average orce on the lash land. III. THE MODULAR APPROACH In the modular approach, the part geometry may be divided in to eight basic regions as shown in Fig., The eight regions are divided in such a manner that, as the top surace descends vertically, as a result o an external orce o unit velocity, the inner and outer suraces o the rings move inward or outward rom the axis as shown in Fig. and 5. The boundaries o these regions may be considered as either rigid tools or as rigid parts o adjacent elements o the work piece. For each o these eight regions shown, a general admissible velocity ield may considered as shown in Fig. and 5 or rectangular and triangular low; both inward and outward, which could be given as below. The parameters A, B, )] Issue, Volume, 8

3 & and & are the radial and axial velocities, respectively. R, z, and α are deined in Fig. 6. u = du / dt w = dw / dt Axis Axis Rectangular Rectangular Triangular Triangular Convex circular Convex circular Concave circular A. Rectangular low inward u& = ( R ) / AR (8) u& = ( B)( R) / AR (9) w& = z / A () w& = ( B) z / AR () B. Rectangular low outward u& = ( R B ) / AR () u& = ( B)( B + R) / AR () w& = z / A () w& = ( B) z / AR (5) C. Triangular low inward u& = cot α( + (/ R)) / (6) w& = ( z cot / R) + (7) α D. Triangular low outward u& = cot α( + (/ R)) / (8) w& = ( z cot / R) + (9) α Concave circular Fig. Inward low o modules O R Fig. 5 Outward low o modules B R N Once the velocity components or any o the eight basic regions are known then the strain rates could be evaluated as, & ε R = δu& / δ R () & ε = δ w& / δ R () & = (& + & ) () ε ε ε θ R & γ R = ( δu& / δ z + δ w& / δ R) () The rate o internal energy dissipation would be calculated or the ield under consideration could be as ollows: E& = ( / ) (& ε + & ε + & ε + (& γ / ) dv + msds & () u& l w& α M Fig. 6 Deinition o various parameters R θ R S A Issue, Volume, 8

4 The irst volume integration in () has to be carried out throughout the entire volume o the part geometry and the second surace integration is required to be carried out or over all suraces. When considering the total rate o energy dissipation may be represented as, E i = n t = ei AV i i i= & (5) The ollowing Fig. 7 represents a modular approach applicable to a typical orging component geometry. X X Y Y Fig. 7 Application o a modular approach Fig. 7 depicts a typical component made by closed die orging process and the dierent modules e.g. Rectangular, Triangular, Concave circular, and Convex circular are represented by dierent hatch pattern. Fig. 8 shows an application o the modular approach or the closed die orging o connecting rod o an Internal Combustion Engine [], []. Section XX Section YY Fig. 8 Connecting rod o an Internal Combustion Engine Section Fig. 9 Sectional details o Connecting rod Issue, Volume, 8

5 IV. SIMULATION ALGORITHM A computer simulation algorithm has been developed consisting o separate subroutines or the two dierent stages o orging process i.e. deormation process beore lash ormation and ater lash ormation [5]. For the process simulation, initially the material is required to be selected rom the material data base. The die parameters, billet parameters, number o stages o deormation process are required to be provided then the algorithm starts computations and simulations using computer graphics as per coding []. C Step Input the value o C and m or Material o Billet B Material Data File START A Material Data File epsilon, epsi_dot sigma_, sigma_max_, F_I u_dot, w_dot Select Material o Billet I Step > n_ No B Input Die parameters: L, h_, w, t_ Yes D Input Billet parameters: H, D_o Input riction parameters: mu_, mu_ Input ram speed and No. o steps or stage I and II: v, n_, n_ epsi_, epsi_, epsi_ epsi dot, epsi dot, epsi dot sigma_z, sigma_z, sigma_max_, F_II u_dot, w_dot Input ram speed and No. o steps or stage I and II: v, n_, n_ I Step > n_ No D volume, height Yes del_h, del_h, theta, h_contact Any moication? No Yes A C END Issue, Volume, 8 5

6 The computer code generates step by step the results or the various output parameters e.g. height, diameter, strain, strain rate, low stress, and load requirement. At the end o the simulation, the algorithm asks or any modiications, i any, may be change o material or dimensions or the purpose o next computations and simulation. V. RESULTS AND DISCUSSION Fig.,, and shows the graph o Actual Load (kn), Estimated Load rom computer simulation (kn) and plotted against the Stroke length (mm) or the H/D ratio o.9,., and. respectively or the lash thickness o mm [8]. From the Fig.,, and, it could be clearly seen that, as the stroke proceeds, the load requirement or the deormation increases. At a particular stroke length, the increase in the load is steep; this is the point where the lash ormation starts. The stroke length or lash ormation to start is dierent or dierent H/D ratio. As the H/D ratio decreases, the billet diameter is required to be increased to maintain the constant volume o the billet material. The actual load and estimated load have been plotted and are in good agreement or all the cases studied as shown in Fig.,, and. The value o percentage error between actual load requirement and the estimated load or the H/D ratio o.9 varies rom. % to. %. For the H/D ratio o., the percentage error ranges rom. % to.7 %. The percentage error or the H/D ratio o. has been ound to vary between. % to.5 %. Further, it has been observed that as the H/D decreases the amount o which is also termed as the deviation rom the actual load requirement reduces which has been observed with H/D ratio o.9 and.. It may be anticipated that the dierence between actual load requirement and the load requirement obtained by computer simulation should urther reduce or H/D ratio o. but it is ound to be increased thereore urther investigation in the actual process as well as in the computer simulation is required, to know the eect o various process governing parameters. Load (kn) Load, % Error Vs. Stroke or H/D=.9 Actual Load Estimated Load Stroke (mm) Fig. Load (kn), Vs. Stroke (mm) or H/D =.9 Load (kn) Load, % Error Vs. Stroke or H/D=. Actual Load Estimated Load Stroke (mm) Fig. Load (kn), Vs. Stroke (mm) or H/D =. Load (kn) Load, % Error Vs. Stroke or H/D=. 7 Actual Load 6 Estimated Load Stroke (mm) Fig. Load (kn), Vs. Stroke (mm) or H/D =. VI. CONCLUSION Finally, it may be concluded that the success o the simulation technique to estimate the deorming load requirement or the closed die orging operation would depend upon the ollowing: The selection o material parameters rom the material property database should match with the actual metallic material. I the percentage error is more than % then the material properties are required to be obtained by the suitable material testing method. The riction conditions prevailing between the die and billet material during the actual deormation process and the simulation are required to be nearly same. Accuracy o the simulation would be governed by the parameters such as the H/D ratio, strain rate, the low o material in the die cavity, and strain hardening property o the actual material. However, due to the complexity o orging operations, the material and process condition, the manuacturing by orging process is still a very much dependent upon trial runs, which Issue, Volume, 8 6

7 results into increased lead-time. An integrated orging simulation and optimization approach would signiicantly improve the overall process o the components manuactured by closed die orging process. C D o F I F II H h h c h L m T t i t t c u& v w w& β max NOMENCLATURE Strain hardening constant Initial diameter o billet Force required beore lash ormation Force required ater lash ormation Initial height o billet Current height o billet Average height o shearing zone at the beginning o lash ormation Current average height o shearing zone Die diameter Strain rate sensitivity exponent Temperature Initial distance between lash lands o two die halves Flash thickness Flash Thickness at the beginning o lash ormation Velocity along the horizontal direction Ram speed Flash width Velocity along the vertical direction Shear plane angle Flow stress ε max Maximum stress beore lash ormation Maximum stress ater lash ormation Strain beore lash ormation ε Strain or zone ε Strain or zone ε Strain or zone ε& Strain rate beore lash ormation ε& Strain rate or zone ε& Strain rate or zone ε& Strain rate or zone ε tc Strain at the beginning o the lash ormation µ Coeicient o riction between die and billet µ Coeicient o shearing riction REFERENCES [] H. Grass, C. Krempaszky, and E. Werner, -D FEM-simulation o hot orming processes or the production o a connecting rod, Computational Materials Science, pp. 8 89, 6 (6). [] Hamzah Ssemakula, Ul Stahlberg, and Kent O berg, Close-die orging o large Cu-lids by a method o low orce requirement, Journal o Materials Processing Technology, pp. 9 7, 78 (6). [] W. Krason and J. Malachowski Eort analysis o the landing gear with possible low during touchdown, NAUN International Journal o Mechanics, Issue, Volume, 8. [] M. Hamedi and H. Pashazadeh, Numerical study o nugget ormation in resistance spot welding, NAUN International Journal o Mechanics, Issue, Volume, 8. [5] L. Tudose, O. Buiga, D. Jucan, and C. Şteanache, Optimal design o two-stage speed reducer using two-phase evolutionary algorithm, NAUN International Journal o Mechanics, Issue, Volume, 8. [6] Tănăsoiu Aurelia and Copaci Ion, Study on the shock caused by collision o railway vehicles, NAUN International Journal o Mechanics, Issue, Volume, 8. [7] Rita C. C. Silva, João N. C. Guerreiro, and Patricia R. C. Drach, Automatic inite element solid modeling, burst and error analyses o corroded pipelines, NAUN International Journal o Mechanics, Issue, Volume, 8. [8] Alexandre Polozine and Lirio Schaeer, Inluence o the inaccuracy o thermal contact conductance coeicient on the weighted-mean temperature calculated or a orged blank, Journal o materials processing technology, pp. 6 66, 95 (8). [9] B. Tomov, R. Radev, and V. Gagov, Inluence o lash design upon process parameters o hot die orging, Journal o Materials Processing Technology, pp. 6 6, (). [] William R.D. Wilson, Steven R. Schmid, and Jiying Liu, Advanced simulations or hot orging: heat transer model or use with the inite element method, Journal o Materials Processing Technology, pp. 9 97, (). [] H. Ou, J. Lan, C.G. Armstrong, and M.A. Price, An FE simulation and optimisation approach or the orging o aeroengine components, Journal o Materials Processing Technology, pp. 8 6, 5 (). [] Shinichiro Fujikawa, Application o CAE or hot-orging o automotive components, Journal o Materials Processing Technology, pp. 76-8, 98 (). [] M. Bakhshi-jooybari, I. Pillinger, P. P. Hartley, and T. A. Dean, Finite element simulation and experimental study o hot closed-die upsetting, Int. Journal Machine Tools Manuacturing, Vol. 6, No. 9, pp. -, 996. [] Hyunkee Kim, Kevin Sweeney, and Taylan Altan, Application o computer aided simulation to investigate metal low in selected orging operations, Journal o Materials Processing Technology, pp. 7-5, 6 (99). [5] Markus Knoerr, Joon Lee, and Taylan Altan, Application o the D inite element method to simulation o various orming processes, Journal o Materials Processing Technology, pp. -55, (99). [6] Biner S. B., A procedure or determination o the strain distribution during simulation o metal orming using model material techniques, Journal o Engineering or Industry, Vol., pp. 9-99, Feb. 99. [7] Boër C. R., Rebelo N., Rydstad H., and Schröder G., Process Modelling o Metal Forming and Thermo-mechanical Treatment, Springer - Verlag, Berlin, Heidelberg, 986. Issue, Volume, 8 7

8 [8] Thomas A. and I. Bannister, The accuracy o orging load estimation in drop orging, Proceedings o 7th International Machine Tool Design and Research Conerence, S. A. Tobias(ed.), pp. -5, 976. [9] Altan T. and Boulger F. W., Flow stress o metals and it s application in metal orming analysis, Trans. ASME, Series B, Vol. 95, pp. 9-8, 97. [] Thomsen E. G., Yang C.T., and Kobayashi S., Mechanics o Plastic Deormation in Metal Processing, Mc - Millan Co., New York, 965. [] Rusino S. E., Forging and Forming Metals, American Technical Society, Chicago, USA, 959. Mr. Dipakkumar Gohil born at Surat, Gujarat State, India on October, 97 has Post Graduated in Mechanical Engineering rom S. V. Regional College o Engineering and Technology, Surat, Gujarat State, India in 998. He is working as a SENIOR LECTURER at S. V. National Institute o Technology, Surat, Gujarat State, India (A Government o India undertaking). He has received many awards and merit prizes during school, college, and in his proessional career which includes a very prestigious National Award, President o India Prize or Outstanding Research Work at the nd National Congress o Indian Society o Theoretical and Applied Mechanics held during December 8 to, 997. He has also received Outstanding Young Person Award oered by Surat Junior Chambers or his remarkable contribution in the ield o engineering and technology. His area o research is advanced manuacturing processes, design and development o smart sensors or mechatronic and robotic applications leading to patents. Further, he has delivered many expert lectures on mechatronic system development at the various national level short term courses and workshops. Apart rom teaching, he has also contributed in the development o sensors and automation or industries. Mr. Gohil is a Lie Member o Indian Society or Technical Education since 998. He has attended, participated & presented a Research Paper at the 7 th World Scientiic and Engineering Academy and Society (WSEAS) International Conerence on System Science and Simulation in Engineering held during November to, 8 at Venice, Italy. Issue, Volume, 8 8