CONICAL PIPE ENVELOPE FORMATION PROCESS

Transcription

1 Pofesso Fydeyk Knap D Robet Kuzel, Eng. Czestochowa Technical Univesity Poland CONICAL PIPE ENVELOPE FORMATION PROCESS Abstact Conical pipes belong to a goup of economical pofiles which find boad application in vaious metal poducts. Until now the conical pipes ae manufactued by following methods: olling on two-high mill in impessions with vaying depth on the olls peimete; foging in leve swaging machine, fomation in combined pocess of dawing and olling, and olling on skew olling mill. Manufactuing of conical pipes belong to complicated engineeing pocesses, and used until now methods do not allow to meet demand fo conical pipes especially the long ones with lage cosswise dimensions, e.g. pipes fo lamp posts. This situation makes it easonable to look fo new pocesses with wide engineeing possibilities when compaed with till now known methods. It seems that the pocess of conical pipe envelope fomation will allow too widen conical pipes assotment. In a conical pipe envelope fomation pocess the lengthwise tensile stesses and cicumfeential and adial compessive stesses act on defomed mateial, and at the same time cicumfeential stesses pevail. In the stain aea the stess condition causes diminishing of oute diamete, incease of wall thickness, and slight pipe elongation. When plastically stained a pipe undegoes unnecessay non-dilatational stains that ae geate on the oute suface than on the inne one. In the pocess a pipe is put in otations, and its adial staining take place though fou olls symmetically aanged in elation to the defomed pipe (Fig. 1). Location of the olls in elation to the pipe is detemined by the conical suface of the fixing sleeve 1 connected with the body 2 by a thead, so when the sleeve is set in otations, this causes its axial displacement, and simultaneously stats adial shifting of olls 4, and though that motion makes it possible to eceive a conical pipe. Conical pipe fomation may occu with inceasing o deceasing daft, and the pipe tape depends on the pocess kinematics conditions, i.e. lengthwise displacement speed of foming olls, and thei adial shifting speed.

2 Fig. 1. Coss-section of the conical pipe envelope olling device 1 fixing sleeve, 2 body, 3 pipe, 4 oll, - designation of paticula element motion duing the pocess Pocess chaacteistics In the pocess of conical pipe envelope foming [5] an input cylindical pipe, put in otations, is dawn between fo olls, symmetically aanged in elation to the defomed pipe, and the oll geneato is declined at some angle in elation to the defomed pipe, so gadual deceasing of oute diamete takes place. Duing the pocess a tansition of a given point though a plastic stain valley is connected with multiple enteing in a zone of diect oll impact, and the total stain is a sum of unit stains esulted fom each oll impact on defomed pipe. Pipe plastic stains that ae expessed by diminishing of oute pipe diamete, and by lengthwise and adial stains, take place as a esult of diect foming olls impact, as well as of zones of non-contacted inteaction on a bounday of zones between foming olls, in which elastic state pevail, and zones of plastic state.

3 Couse and esults of tests While beginning the pocess fistly the pipe was put in otations, and then the fixing sleeve was otated togethe with a mechanism of device body lengthwise displacement in elation to the defomed pipe. The pocess was conducted with otating fixing sleeve, both in diection coesponding, as well as evesed, to the diection of defomed pipe otations. The tests wee caied out with oll lengthwise speed amounting within the bounds of mm pe 1 evolution. Fig. 3 Foming oll While pocess conducting the lengthwise foce that acted on the defomed pipe was ecoded though a stain gauges. To detemine linea and non-dilatational stains in the plastic stain valley of the defomed pipe the pocess was stopped when assumed pipe oute

4 diamete change was achieved, and then the linea and non-dilatational stains wee detemined. Caied out measuements of linea stains in cicumfeential, adial and lengthwise diections (Fig. 4) showed that deceasing of pipe oute diamete is accompanied incease of the pipe wall thickness with slight pipe elongation ε ε ε l D k -ln Dp ε θ Fig. 4 Diagam of linea stain changes in cicumfeential, adial and lengthwise diections Within the whole ange of oute diamete deceasing the wall thickening gows monotonically as pipe diamete deceases, so in adial diection the stains ae positive. Also stains in lengthwise diection ae positive, but thei value is much lesse than adial stains. On the othe hand the stain in cicumfeential diection is negative, as the pipe peimete deceases. Fom among thee linea stains the cicumfeential stain is the highest one as fa as absolute value is concened, next the adial stain is slight lesse, and the lengthwise stain is the smallest one. The cicumfeential stains that expess diamete change, and the adial stains expessed as wall thickness change ae pevailing stains. At fist appoximation it can

5 be assumed that the lengthwise stains ae equal to zeo, the pipe does not changes its length while it is fomed, and the oute diamete decease is accompanied by wall thickness incease. Such scheme of stains elates to stess state that ules in plastified zones. Lengthwise stesses l, adial stesses, and cicumfeential stesses θl act on a defomed pipe. Lengthwise stesses l cause elongation of defomed mateial and its shotening in adial and cicumfeential diections. Radial stesses have simila effect, while cicumfeential stesses cause mateial twisting in cicumfeential diection, and dimension incease in adial diection, i.e. wall thickening. Conditions of stess equilibium must be met between adial and cicumfeential stesses that act in a pipe (Fig. 5). Fig. 5 Diagam of stess patten on valley section Pojecting stesses that act on elementay volume in vetical diection it may be eceived When integated and tansfomed it may be eceived g 0 sinθ = 0 sin θ ' (1)

6 When fiction foces ae taken into account the equilibium condition assumes the fom θ ' ( + µ sin ϕ) dϕ cosϕ l = θ g0 l sinθ 0 Hence = θ g 0 sinθ 1 sin θ ' + µ ( 1 cos 2θ) 4 (2) Above mentioned elationships show dependencies between adial and cicumfeential stesses on the pipe suface. Radial stess on inne suface is equal to zeo, so it is pope to ente mean adial values against the wall thickness. Similaly as in a taditional pocess of pipe dawing [6] it was assumed that a patten of adial stesses is linea, and in this connection the mean adial stess is equal to a half of the adial stess on oute pipe suface. s = 1 2 Fom the equation it may be seen that fo a given value of the stess θ, the adial stesses s ae the highe the highe is the wall thickness to pipe diamete atio. So when thick-walled pipes foming the adial stesses ae highe than in couse of thin-walled pipes defoming. Duing conical pipes foming the cicumfeential and lengthwise stesses pevail. These stesses must meet a condition of plasticity. When using the condition of maximum tangential stesses we may wite = β l θ p (3) Lengthwise stesses l have positive sign, while cicumfeential stesses θ have negative sign. So if l is small, then θ is close to a value of plastifying stesses and they decide the

7 stain chaacteistic, and on the othe hand when l is high then θ is small and stesses l will decisively influence on the stain patten. Radial stesses will influence somewhat, too, especially when cicumfeential stesses θ ae high. Conclusions 1. In the pocess of conical pipe envelope foming the tensile lengthwise stesses and cicumfeential and adial compessive stesses act on defomed mateial, and at the same time cicumfeential stesses pevail. The stess condition that pevail in the stain aea causes diminishing of oute diamete, incease of wall thickness, and slight pipe elongation. 2. Apat fom desied linea stains the pipe undegoes (unnecessay) non-dilatational stains. These stains ae geate on the oute suface than on the inne one. Refeences 1. A. C. Atkins and R. M. Caddel, The Incopoation Of Wok Hadening And Redundant Wok In Rod Dawing Analyses, Int. J. Mech. Sci., 10(10)(1968) T. Z. Blazynski, Metal Foming Tool Pofiles and Flow (London: The Macmillan Pess Ltd., 1976). 3. R. M. Caddel, and A. C. Atkins, The Influence of Redundant wok with dawing ods tough conical dies, Tans. ASME, pape, No 67 WA, Pod R. W. Johnson, and G. W. Rowe, Redundant wok in dawing cylindical stock, Jounal of the Institute of Metals, 67 (1968), F. Knap, and R. Kuzel, Walcowanie obwiedniowe u stożkowych, Rudy Metale 8(42) (1997), L. Sadok, M. Moawiecki, and E. Wosiek, Pzeóbka Plastyczna. Podstawy Teoetyczne (Katowice: Wydawnictwo Śląsk, 1986).