DETERMINATION OF FORCES AT THE TRANSVERSE EXTRUSION

Transcription

1 Journal for Tecnology of Plasticity, Vol. (7), Number DOI:.867/jtp DETERMINATION OF FORCES AT THE TRANSVERSE EXTRUSION Belan A.K., Nekit V.A., Platov S.I., Ogarkov N.N., Belan O.A. Nosov Magnitogorsk State Tecnical University, Lenin Street, 38, Magnitogorsk city, Celyabinsk Region, Russian Federation, 55 ABSTRACT In te process of cold bulk stamping tools are exposed to ig stresses. Wile developing tecnology and tool design one sould provide te longitudinal stability of te workpiece and te ig durability of te tool. For tis reason it is necessary to determine te loads wic occur during process. Te paper presents a metod for determination of te force for te transverse extruding, wic was based on te metod of te works balance. Experimental studies ave been performed, wic sowed tat te developed metod allows wit sufficient accuracy to calculate te total load at te die for te transverse extruding. Kay words: cold bulk stamping, upsetting, transverse extrusion, metod of work balance. INTRODUCTION In te process of cold bulk stamping one of te factors limiting te stability and accuracy of te process of upsetting of te ead for one transition is te longitudinal resistance of te rod. Results of previous researces as sown [-] tat in te process of pre-upsetting of te ead wit te lengt to diameter ratio d.5 were is te lengt of te metal under te upsetting ead, d is te diameter of te metal for ead upsetting, metod of transverse extrusion is used. Matrix for transverse extruding as a design tat ensures te ard pinced area of te work piece [5, ]. Upsetting of eads is as follows in Fig.. Te body of te punc (3) moves towards te workpiece (). Most part of te lengt of te upsetting work piece is fixed in te cylindrical bore, te diameter of wic is approximately equal to te diameter of te workpiece. Te work piece is pinced in te working part of te ousing of te punc and die. Te deformation is carried out by a sliding te core witin te punc. As you move te core forward, metal of te workpiece fills te space in te ousing of te punc or matrix, taking te form of te ead. * Corresponding autor s vladimir@nekit.info

2 Fig.. - Te sceme of te process of upsetting wit stamp for transverse extruding - work piece, - te sliding core, 3 - punc, - matrix, 5 - case of te punc. In te process of cold bulk stamping ig tool stresses take place. Terefore, wile developing tecnology and tool design it is important not only to ensure te stability of te work piece, but also to ensure good durability of te tool. For tis reason it is necessary to determine total load of deformation.. METHODOLOGY In te process of transverse extrusion, te kinematic of metal flow is different from te normal process of upsetting. During cold forming of te eads of core products starting from cylindrical blanks by te stamp for te transverse extrusion. One can divide te intermediate workpiece into two areas, depending on te direction of metal flow (Fig. ). In accordance wit tis, it is necessary to consider te conditions of metal flow at bot areas, wic in summary are determining te extrusion force. Axial force on te first area wit sufficient accuracy is determined by te friction conditions of metal on te walls of te punc [6-, ]: P μσ πd, () s were µ is te friction coefficient in te first area, d - diameter of cylindrical area, l - te lengt of te area. σ s - te yield stress in te first area, wic is furter determined as a function of intensity of deformation e i : ei Nei σ ( σ ) C e C e () S i пред Journal for Tecnology of Plasticity, Vol. (7), Number

3 were, С,C are constants, depending on te grade of steel. Tey are determined by calculation according to te tensile tests, N is te coefficient depending on cemical composition of te material (for ferrous metals N = 5). Fig.. - Te settlement sceme for definition of efforts to stamp for transverse extrusion - cylindrical area in wic te metal does not undergo forming. - area, in wic te metal flows only in te radial direction. It sould be noted tat te friction force on te first area decreases wit decreasing lengt l by linear dependence. To determine te loading on te second area of deformation we are using te metod of work balance. Te equation of work balance can be written as: АА АД АТ А, (3) were A А is te work of active deforming forces, A Д is te work of strain in te second section, A Т is te work spent to overcome te friction forces on te end sections of te punc and te matrix, A is te work spent to overcome te resistance of te cylindrical (first) area. Te work of active deforming forces: АА Δ () According to [6] te strain work in te second area is: А Д S i V σ ε dv (5) Te second area can be divided into two typical zones: zone A and zone B (Fig. ). In te zone A te deformation is similar to a conventional upsetting. A caracteristic feature of deformation in tis zone is tat te deformation in te axial direction is constant at any point of te zone: Journal for Tecnology of Plasticity, Vol. (7), Number

4 ε z Δ (6) If we consider te yield stress value σ s averaged over te entire deformation zone we can recorded: πd AДА σ S Δ (7) A caracteristic feature of zone B is tat te deformation force does not act on te contact of te metal wit te tool, te deformation force is transmitted from te side of zone A. If te end surface from te punc and from te die is inclined to te orizontal axis, according to Fig., deformation in te axial direction can be defined as: ε z r tgφ r tgφ (8) d were: current radius; r. Tus, for te axisymmetric stress-strain state in te cylindrical coordinates expressions for te main deformation will ave te form: ε U ; ε θ U ; ε z r φ. (9) According to te law of volume constancy: U U r φ. () Tis differential equation is a linear one of te first order. Te general solution of tis equation can be written as: U φ r c. () 3 Constant c can be determined from te condition tat at te boundary of zones A and B at =r, Δ moving U r. From tis: Δ φ 3 с r r 6 ; φ r Δ φ 3 U r r. () 3 6 Journal for Tecnology of Plasticity, Vol. (7), Number

5 3 Expressions for te main deformation will ave te form: φ r ε c ; 3 (3) φ r εθ c ; 3 () φ εz r. (5) Te formula for intensity of deformation, after te substituting of te expressions for deformations (-) will become: φ 3 5 c φ c φ 3 c εi r r Ten te work of deformation for zone B will be defined as: Were: φ R AДБ σs π k rk3 r kφ k3 rk cr r cln φr 3 3 r kr 3 3 R r R r, R r kr3, kr. (6) 3 Work on overcoming te friction forces on te two end surfaces is defined by te formula: Sear stress at te contact surface 3 3 R r rr r φ АТ πτ k crr, (7) 6 k is defined as: τ k μ σ. S Te expression for determination of total axial force P is obtained after substituting equations (7), (6), (7) into equation (3): АДА АДБ АT, (8) Δ were, P is te axial force on te first section. Journal for Tecnology of Plasticity, Vol. (7), Number

6 3. DISCUSSION OF THE RESEARCH RESULTS In order to analyse equation (8) one can divide te left and rigt part of te equation for te P DA: (9) ДБ Т ДА ДА ДА ДА д / ДА,9,8,7,6,5,,3,,,,,3,,5 r =. Δ/ кр,9,8,7,6,5,,3,, / ДА,,,3,,5 r =, Δ/ кр Fig. 3. Dependencies ДА 6 д 6,9,8,7,6,5,,3,,,,,3,,5 r =.3 Δ/ кр,9,8,7,6,5,,3,, / ДА / ДА,,,3,,5 r =,5 Δ for different values of and r Δ/ кр 6 6 Journal for Tecnology of Plasticity, Vol. (7), Number

7 5 Te ratio ДА depends on te relationsips Δ, r and setting φ (Fig.3). Moreover, according to R Δ te law of volume constancy it is assumed tat: r Te analysis of relationsips presented in Fig. 3 sows tat wit te increase of te parameter and parameter φ (caracterizing te angle of inclination of te side walls of te punc and te matrix), te value ДА grows. Te intensity of tis growt depends on te ratio r. Wit te increase of tis ratio, i.e., wit te decrease in te eigt freely upsetting zone, Δ on te value ДА is somewat reduced.. EXPERIMENTAL INVESTIGATION OF ENERGY-POWER PARAMETERS AT THE TRANSVERSE EXTRUSION To verify te results of teoretical studies of te power parameters, experimental studies ave been curried out. Te eads of cylindrical form ave been extruded into stamp wit a spring-loaded punc. Te tests were performed on te macine for compression tests on MS-. Te experimental setup (Fig. ) as been developed and realized. It provides te simulation of upsetting process in te stamp wit a spring-loaded punc from initial billet wit a diameter of 5.5 mm for producing cylindrical eads of different sizes. In tis installation te work piece (9) wit a lengt L is based on te ejector (7). Work piece is situated witin te cannel of te fixed punc (). Te cannel diameter is approximately equal to te diameter of te work piece. Due to te minimum clearance between te work piece and te tool tigt pressing of te work piece to te walls of te punc in its working cannel occurs. Te deformation is carried out by using moving core (8) inside te punc. As te core is moved forward, under te action of te stop (5) te metal fills te space in te ousing of te punc and takes cylindrical sape of te ead. Deforming force on te work piece is transmitted troug te stop 5 by means of te core (8). Te coaxiality of te application of deforming forces is ensured troug assembling te devices in te corpus (3), wic is mounted on te base (). Experiments were made at te ratio of te lengt of te upsetting work pieces to its diameter ( / d) in te range of.5.. To determine te forces of te upsetting te displacement of te punc corresponding to a certain value of deformation was set and te forces of te upsetting in te macine were recorded. Dimensions of cylindrical eads and results of te measurement of tecnological load are given in Table. Journal for Tecnology of Plasticity, Vol. (7), Number

8 6 Fig.. - Device for simulation of upsetting process of cylindrical eads by te metod of lateral extrusion - matrix; - punc; 3 - body; - base; 5 - stop; 6 - sleeve; 7 - puser; 8 - core; 9 - work piece; L - te lengt of te original billet; l - te lengt of te work piece for forming eads; ead eigt; l - te eigt of te pincing of te workpiece in te cannel of te punc. Table. -Te experimental results of te cylindrical ead upsetting at stamp for transverse extrusion. Force of te upsetting, Head Head KN / d Material diameter igt, Sample [mm] [mm] e i, [%] 3 5 average value Steel Journal for Tecnology of Plasticity, Vol. (7), Number

9 7 5. CONCLUSION To assess te discrepancies between teoretical and experimental values of loads to stamp for transverse extrusion Fig. 8 sows te dependence of P ei, determined by teoretical and experimental ways P teory experiment. 5,,,6,8 e i Fig Cange of deformation force at te die for te transverse extruding depending on te degree of deformation Comparison of teoretical and experimental data sows tat te developed metod allows wit sufficient accuracy to determine te energy-power parameters for te transverse extruding. Discrepancies between calculated and experimental data do not exceed %. It is establised tat te deformation force in te stamp for transverse extrusion is summarized from te force, spent on overcoming te contact friction forces between te working surface of te punc and te deformable metal (3-%), deformation forces in te matrix (6-7%), and te force spent on overcoming te forces of contact friction on te end surfaces of te punc and te matrix ( - 3%). Experimental studies ave sown tat te developed metod allows to calculate wit sufficient accuracy te forces in te stamp for transverse extrusion. Tus, te Researc sowed tat teteoretical results are close to te experimental ones, wic indicates te possibility of using te proposed metod in te practical calculations of te forces in te case of transverse extrusion. Journal for Tecnology of Plasticity, Vol. (7), Number

10 8 REFERENCES [] Te cold forging. Reference. Edited by G. A. Navrotsky. M.: "Masinostroenie", 973, 96p. [] Parsin, V. G., Artyukin V. I., Belan, O. A. Ensuring longitudinal stability during cold forming of workpieces wit te purpose of receiving te eads of core products increased in size. Efficient tecnology for te production of ardware: Sat. scientific. Tr. / under te editorsip of E. N. Teftelev. Magnitogorsk: MGTU,. pp. 5-3 [3] Parsin, V. G., Artyukin V. I., Belan, O. A., Malyseva M. S. Effect of size of te initial bending and eccentric application of deforming forces on te stability of cylindrical workpieces wen landing // Forging and stamping production. Processing of materials by pressure. 5. No. 6. pp. 3-7 [] Belan, A. K., Malyseva M. S., Belan, O. A. Improvement of te process of lateral extrusion on te basis of matematical modelling // Forging and stamping production. Processing of materials by pressure. 8. No. 8. pp. 9 5 [5] Billigmann I. Upsetting and oter metods of die forging. M: Mas-Giz, p. [6] Storozev M. V., Popov E. A. Teory of metal forming. Moscow: Masinostroenie, 97. p. [7] Nekit V. A., Drigun E. M. Hot stamping te bottoms of railway tanks in te conditions of te Magnitogorsk metallurgical combine. Iron and steel.. No. -. pp [8] Nekit V. A., Pustovalov A. A., Nekit A. V. Te metod of determining te critical strain in uniaxial tension. Forging and stamping production. Processing of materials by pressure. 3. No. 3. pp [9] Nekit V. A. O neutral section in te eart of plastic deformation during rolling of strips. Modelling and development of processes of processing of metals by pressure.. No. 8. pp [] Platov S. I., Terentiev D. V., Morozov S. A. Te drawing of wire rod and wire wit regulated surface micro relief Production of rolled products.. No.. pp [] Platov S. I., Ogarkov N. N., Terentiev D. V., Zelezkov O. S., Rubanik V. V., Vassal, J. P. Development of teory and tecnology of designing macines, units and tools in te processes of forming and cutting Bulletin of Nosov G.I. Magnitogorsk state tecnical University.. No. (5). pp. -. [] Movrin D., Penčić M., Dudić S., Čavić M, Milutinović M., Vilotić D. Experimental investigation of contact conditions in tube end forming process by tapering. Journal for tecnology of plasticity. 6/ V., pp.5-5. Journal for Tecnology of Plasticity, Vol. (7), Number

11 9 ODREĐIVANJE SILE DEFORMISANJA U PROCESU TRANSVERZALNOG ISTISKIVANJA Belan A.K., Nekit V.A., Platov S.I., Ogarkov N.N., Belan O.A. Nosov Magnitogorsk State Tecnical University, Lenin Street, 38, Magnitogorsk city, Celyabinsk Region, Russian Federation, 55 REZIME U ovom radu prikazana je metoda određivanja deformacione sile u procesu transverzalnog istiskivanja (istiskivanje u kome se materijal kreće i u pravcu normalnom na pravac kretanja alata). Metoda je zasnovana na principu balansa radova. Polazi se od podele materijala koji se deformiše u dve zone sa različitim brzinskim poljima. U prvoj zoni materijal teče aksijalno i tu se pojavljuje sila trenja između materijala i zida matrice dok se u drugoj zoni javlja i transverzalno kretanje materijala. U cilju verifikacije ove metode izvršena su i eksperimentalna istraživanja koja su pokazala da se eksperimentalni rezultati sa dovoljnom tačnošću slažu sa rezultatima dobijenim ovde prikazanom teoretskom metodom. Razlika između rezultata dobijeni eksperimentom i teoretskom putem nije veća od %. Ključne reči: ladna zapreminska obrada, sabijanje, metoda balansa radova, transverzalno istiskivanje Journal for Tecnology of Plasticity, Vol. (7), Number