Multistage drawing of axially symmetric part from sheet blank at simple-action presses or multiposition automatic press

FIELD: process engineering.

SUBSTANCE: invention relates to drawing of axially symmetric parts from sheet blanks. Semis are drawn at dies in job-by-job manner, first, at bottom mating that of axially symmetric part to extreme depth and with conical wall. Further jobs include configuring to the shape of axially symmetric part. At final job of drawing, semi-finished product results with wall, shape and sizes corresponding to those of box part with trimming allowances.

EFFECT: higher accuracy of sizes.

10 dwg

The invention relates to a sheet punching and can be used for forging of axisymmetric parts of various configurations of sheet materials, metals and non-metals, mainly for stamping to the extrusion of axisymmetric parts of automobiles, tractors, agricultural machinery, household appliances and other equipment on presses simple steps or multi-position presses-machines.

Known traditional method multistage drawing of axisymmetric sheet blanks, which consists in sequential functional drawing of a cylindrical semi-finished products at a decreasing from operation to operation in diameter and increasing in height and which are described in the following sources of information:

1. Romanovsky VP Reference cold stamping. - L.: engineering, 1979, p. 121, Fig. 103.

2. Forging and stamping: a Handbook in 4 volumes, volume 4 stamping. - M.: Mashinostroenie, 1985-1987, p. 131, Fig. 1).

3. Reference design stamps: stamping. Under the General editorship of L. I. Rudman. - M.: Mashinostroenie, 1988, p. 244, Fig. 4.

4. Storozhev, M. V., Popov E. A. Theory of metal forming. Textbook for universities. Ed. 4th, revised and enlarged extra-M.: Mashinostroenie, 1977, p. 374, Fig. 8.15.

5. Popov E. A. fundamentals of theory of sheet metal forming. Textbook for high schools. Ed. 2nd, revised and enlarged extra-M.: Mashinostroenie, 1977, p. 153, ri�. 53.

As the closest analogue is used the first method, namely: Romanovsky VP Reference cold stamping. - L.: engineering, 1979, p. 121, Fig. 103.

The disadvantage of this known traditional method multistage drawing symmetrical components is that the first and all subsequent drawing operations, except the last, the bottom part of the semi-finished configuration does not match, and the bigger the bottom symmetrical components, resulting in the wall of axisymmetric parts, stretched on the last operation of the extrusion, there are defects such as unevenness and traces of radius of curvature at the bottom of the semi-stretched on all previous operations extrude, surface quality symmetrical components is impaired, and its accuracy decreases. In producing this disadvantage by multistage drawing of symmetrical components leads to a high percentage of defective stamping, unnecessary increase in the rates of consumption of the material on one part and the cost of manufacture of axisymmetric parts. For the removal of defects is required stop the automatic line stamping, completion and debugging of a set of dies for the extrusion and the forming of the symmetrical components, which results in high production costs.

Technical�certification object of the invention is to improve the dimensional accuracy of parts received the hood presses on simple steps or multi-position press machine through the use of multioperational method of symmetrical components extraction with a minimum number of drawing operations and the saving of sheet material from which is made of sheet billet.

The problem is solved due to the fact that in the method of multistage drawing of axisymmetric sheet workpiece presses simple steps or multi-position press machine that includes a consistent and functional hood in stamps from a sheet of semi-finished workpiece configuration from operation to operation approaching axisymmetric configuration items, wherein in the first operation range hoods in the initial stages form a bottom of the first semifinished product corresponding to the bottom of the symmetrical components in subsequent stages pull the first semi-conical wall to the limit, without destruction of the workpiece, depth, subsequent drawing operations are extrusion of semi-finished products with a bottom portion received in the first operation, with a consistent and functional reduction of the angle of taper of the wall of the first semi-finished product, the depth of the extrusion and increase the configuration of semi-finished products from operation to operation closer to the configuration symmetrically� details by means of pushing in the conical wall of the semi-finished product in the matrix of the stamp to the action of force on the clamp die to the cushion of a press or stamp buffer, pressing the edge of the semi-finished product to facilitate extraction without destruction of semifinished product at each operation of the extrusion limit the depth and taper angle of a wall of a prefabricated set of conditions to ensure at all stages of drawing of sheet blanks of gradual increase of the maximum tensile stresses in the dangerous section of the wall prefabricated exhaust, and at the final stage is equal to the yield strength of the blanks, at the end of each operation of the extrusion simultaneously with the extraction performed on the entire surface of the prefabricated edit folds, valid on previous phases hoods, and on the last operation of drawing the shape and dimensions of prefabricated perform the appropriate size and shape of symmetrical components subject to the allowance for trimming the rough edges of the semi-finished product.

The essence of the new method of drawing is characterized by Fig. 1, 2, 3, 4, 5 and 6, in which on the home front view shows a section along the axis of the stamp for the implementation of this method of extraction. Fig. 1 illustrates the initial stage of drawing blanks on the first operation: R is the radius of the outer contour of the blanks in front of the hood, r is the radius of the inner contour of the flange slab, r_pthe radiused edges of the punch, r_m,1the radiused edges of the matrix, the value�ia r _pand r_m,1set from the literature and clarify when debugging stamp for hoods, γ₁- decreasing from operation to operation, the taper angle of the working surface of the punch relative to the vertical, d_p- internal diameter specified on the drawing to the manufacture of axisymmetric parts; Fig. 2 - intermediate i-th stage of the first drawing of sheet blanks to a depth of h_i; Fig. 3 - the final stage of the first drawing of sheet workpiece 9 in the first semi-finished product 10 with a conical wall and limit, without destruction of the workpiece, the height, sheet and billet form a bottom of the first prefabricated, immediately corresponding to the bottom is given by drawing symmetrical components, and the configuration of the bottom of the first semi-finished product does not change for subsequent drawing operations; Fig. 4 - the intermediate step of drawing the first semi-finished product in the die for the second drawing operation; it is shown how from the pillow press or stamp buffer on the clamp die which presses on the edge of the semi-finished product, creates a force that pushes in the process of drawing the conical wall of the semi-finished product in the matrix of the stamp and facilitating the process of extraction without destruction of the material; Fig. 5 - the final stage of the extrusion of the second semifinished product 11 from the first semi-finished product 10; Fig. 6 - the final stage of extraction of the third semi-finished product 12 from the second semi-finished product 11 in stamp� for the third drawing operation; Fig. 7 - sheet blank 9 and semi-finished products 10, 11, 12 with the flange respectively after the first, second and third operations of the extrusion; the last semi-finished product 12 after cutting the rough edges becomes axisymmetric detail and then applied to the destination; Fig. 8 - sheet blank 9 and semi-finished products 10, 11 with the flange and the last semi-finished product without flange 12 respectively after the first, second and third operations of the extrusion; the last semi-finished product 12 after cutting the rough edges becomes axisymmetric detail and then applied to the destination.

Stamps for the implementation of each operation, this method extracts contain the following main functional parts: the punch 1, the matrix 2 and the clamp 3. The punch 1 is fixed to a stationary bottom plate of the stamp 4, the matrix 2 on the movable upper plate 5. Inside the matrix 2 is the ejector 6 stamped semi-finished product, acting on the push rod 7 by means of the device stamp or a press (not shown). Clip 3 through the pushers 8 rests on the pillow press or stamp buffer (not shown) which provides the necessary force to compress the flange blanks and bolting down the conical walls of the previous prefabricated in the matrix stamp for the subsequent drawing of semi-product.

The method is as follows.

Determine the diameter of the blanks �W the condition of equality of the square of the middle surface is given by drawing symmetrical components and blanks with regard to the allowance for trimming the rough edges of the material after the last operation of the hood. Depending on the geometry and the conditions of production symmetrical components the contour of the workpiece can be simplified, for example, use a square sheet blank with cut or uncut edges.

Calculate the elongation factor symmetrical components To be equal to the ratio of workpiece diameter D to the diameter of the middle surface of the wall of symmetrical components: K=D/(d-s), where d is the outer diameter of the wall of symmetrical components, s - thickness symmetrical components equal to the thickness of the workpiece.

If the elongation factor symmetrical components To more than the limit of elongation factor determined by reference literature, designing a multistage extractor symmetrical components, when each subsequent drawing operations as the source of the workpiece is used, the intermediate product obtained at the previous drawing operation, and configuration of semi-finished products from operation to operation, all bring us closer to the axisymmetric configuration details. To reduce the number of operations of the extrusion of axisymmetric parts and, thereby, to reduce the cost of manufacture of axisymmetric parts, on each operation, especially in the first operation of the extrusion, the plastic properties of the workpiece was used to the maximum extent.

Knowing the shape and size of the symmetrical components and the blanks, in the first approx�of the design analysis model the first operation of the extrusion of the material with the pressing of the blanks, set the extrude depth, the angle of taper of the wall of the first intermediate product and other parameters of the die for extrusion. Sheet workpiece 9 (Fig. 1 and 2) is deformed in the first semi-finished product 10 with a conical wall and limiting, without the destruction of the blanks, a height of H₁and from a parent sheet form a bottom of the first prefabricated, immediately corresponding to the bottom is given by drawing symmetrical components on the basis of the following engineering analysis of the process of forming the blanks.

In the first operation of the hood with a clamp slab deformation zone in pulling the prefabricated divided into four sections: 1) the first section of the deformation zone is a flange in the form of a circular ring, which is located between the clamping surfaces of the matrix 2 and clamp 3 stamp and front of the hood has an outer radius R=D/2 and inner radius r, (2) the second section of the deformation zone is the site of the blanks in contact with the edge of the matrix, 3) the third section of the deformation zone is the site of the blanks, without deforming influence of surface forces in the gap between the punch and the matrix, 4) the fourth section of the deformation zone is the site of the blanks, the elements of which are in the process of watiki bent along the edge of the punch and come in contact with the edge of the punch (Fig. 2). Of these four teaching�tkov the main plot have the greatest impact on the danger of ruining a sheet of blank during drawing, is the first section of the deformation in the flange plate stock.

When determining the maximum tensile stress σ_{ρ max}acting in a dangerous, from the point of view of destruction, the cross section of the wall prefabricated exhaust, sequentially determine the stress field in each of the four sites, using as boundary conditions the equality of tensile stresses at the boundary of adjacent parcels.

At each stage of the extrusion dangerous section of the wall prefabricated exhaust is located at the intersection of the wall of the circular conical surface whose vertex lies on the axis of the die, and forming passes through the vertex and edge point of contact of the sheet workpiece with the edge of the punch perpendicular to the median line of the wall. In dangerous section opposite this boundary point to external elementary layers of sheet workpiece applies a tensile stress from bending the blanks on the edge of the punch, and additionally tensile strain from the first three sections of the deformation zone, so these external elementary layers of sheet blanks first, the first to go into a plastic state, and then, when reaching the tensile stress limit strength�and, start to unravel.

Since the drawing process is non-stationary, then the process or working stroke of the stamp, the hood is divided into a large number of i-x stages, i=1, 2, 3, ..., N, where the number of stages N is chosen depending on the depth of the extrusion and other factors. To determine the stress-strain state (SSS) of each element of the first section of the deformation, namely the flange of the sheet workpiece, at each stage of the extrusion accept the analysis model flat axisymmetric stress state and in polar coordinates ρ, θ with the pole on the axis of the stamp solve statically determinate task of two equations with two unknowns σ_ρand σ_θnamely, decide jointly known from theory of plasticity and metal forming equilibrium equation dσ_ρ=-(σ_ρ-σ_θ)dρ/ρ and the equation of plasticity σ_ρ-σ_θ=σ_swhere ρ is the current radius of the element of the middle surface of the flange slab: r≤ρ≤R, σ_ρ- tensile stress acting on the element along the radius, σ_θ- the compressive stress acting on the element in perpendicular to the tensile stress direction, σ_s- increasing at the expense of hardening the blanks yield stress. If the clamp die is not flat, and conical, while working�m the stamp between the clamping surfaces of the matrix and the first clamp form a conical flange of the workpiece and then pull the Central portion of the workpiece by the punch into the opening in the matrix, then the calculations are choosing curvilinear coordinates "x" is the distance from the axis of the stamp the top middle surface of the conical flange to the workpiece and θ is the longitude, and then instead of "x" coordinate used coordinate ρ=xsinβ, where β is the angle between the axis of the stamp and median generatrix of the conical surface of the flange. After substituting the equations of plasticity in the equilibrium equation and integrating the differential equation using the boundary condition that the contour of the blanks when ρ=R, σ_ρ=0, you get a formula for determining the tensile stresses σ_ρin function of the radius ρ on the flange blanks: σ_ρ=σ_sln(R/ρ). According to the latest formula, calculate the maximum tensile stress σ_ρon the inner contour of the flange slab of radius ρ=r on the first i-th stage drawing at i=1: σ_ρ=r=σ_sln(R/r).

Asking a working stroke of the die or forming depth h_1,isucceeding i-x stages of drawing, from the condition of equality of the areas median surfaces known from geometric constructions of semi-finished product and the original slab of radius R calculated current decreasing from stage to stage of the i-th radius R_ithe contour of the blanks. According to the latest formula, calculate the maximum tensile stress σ_{ρ/sub> on the inner contour of the flange slab of radius ρ=r for each i-th stage of drawing: σρ=r=σsln(Ri/r).}

The yield stress σ_sdepending on the intensity of deformation$$\stackrel{}{\epsilon }$$calculated based on the hardening of the workpiece by the formula Zharkova, V. A.,(Zharkov and V. A. Methodology of computer-aided design of technological processes taking into account the anisotropy of the fabricated material. - Forging and stamping production. The pressure treatment of materials, 2007, №1, p. 30-42), where the yield strength σ_Ttensile strength σ_Inand relative uniform elongation δ_pdetermined according to GOST 11701-84 "Metals. Methods of tensile testing of thin sheets and ribbons". The intensity of deformation$$\stackrel{}{\epsilon }$$found from the condition that at i-th stage, drawing the radius R of the outer contour of the slab is reduced to a radius of R_iand the radius of a selected flange element also decreases from the initial value of ρ₀to the current value of ρ. From the condition of equality of the areas received two elementary circular rings of radii R, R_iand ρ₀, ρ first, find the value of ρ₀, � then the value of . When the hood as you move the contour of the blanks flange width, is initially equal to (R-r), gradually decreases. In the initial stages of retraction flange blanks punch to the matrix hardening the blanks prevails over the reduction of the width of the flange and tensile stress on the inner contour of the flange increases. In the final stages of retraction flange blanks punch in the matrix reduces the width of the flange prevails over padding blanks and tensile stress on the inner contour of the flange is reduced. The intensity of deformation on the inner contour of the flange slab of radius r on the i-th stage of the extracts was calculated according to the latter formula when ρ=r:.

In the process of drawing and move the flange of the friction force 2µQ between the two surfaces of the sheet workpiece thickness s and the clamping surfaces of the die and clamp die, which increase the tensile stress σ_ρ=ron increment Δσ_ρ,frrefer to the area of the circular cross-section with the inner contour of the flange of radius r: 2πrs and get Δσ_ρ,fr=µQ/(πrs). Finally, asking the working stroke of the die or forming depth h_ion the i-th stage of drawing and calculating the current i-th radius R_ithe contour of the blanks, find the tensile �atragene on the border of the first section of the deformation zone, namely, on the inner contour of the flange slab with consideration of friction forces: σ_ρ=r=σ_sln(R_i/r)+µQ/(πrs), where Q is the pressing force of the flange clamp stamp from the pillow press or stamp buffer specified by the reference and specify when debugging stamp for hoods, µ - coefficient of friction, which is taken from reference books depending on the applied during the extraction of the lubricant, and depending on the sheet material of the workpiece and the working parts of the die for drawing.

Moving to the center element of the flange slab, initially adjacent to the inner contour of the flange of radius r, moves to the second phase of deformation is bent along the edge of the matrix and moves with the friction of the edge of the matrix, and then straightening off the edge of the matrix and becomes part of the conical wall of the semi-finished product. The influence of bending of the flange element on the tensile stress σ_ρappreciate the correction for the bending Δσ_ρ=σ_Ts/(4r_m,1+2s), for which a stepwise increase of σ_ρin the area of the curve. The influence of the friction element when bending the edge of the matrix take into account multiplierotherwise, exp(µα_i), where α_i- widening from the i-th stage to the (i+1)-th stage of the drawing the angle of coverage of the sheet workpiece edges of the die and punch. The effect of straightening the curved element� off the edge of the matrix include the same amendment Δσ _ρ=σ_Ts/(4r_m,1+2s). Finally, asking the working stroke of the die or forming depth h_1,ion the i-th stage of drawing and calculating the current i-th radius R_ithe contour of the blanks, first from geometric constructions to determine the angle α_icoverage sheet workpiece edges of the die and punch and the radius r_b,1,ithe boundaries of the second section of the deformation zone to the end point of the contact sheet of the workpiece with the edge of the matrix, and then find the tensile stress acting on the boundary of the second section of the deformation zone:

To determine the VAT of the third section of the deformation zone in the conical wall prefabricated exhaust take into account that this site is deformed without the influence of surface forces in the gap between the punch and the matrix, and therefore the same as above for flange, at each stage of the extrusion accept the analysis model flat axisymmetric stress state. First choose curvilinear coordinates: x is the distance from the axis of the stamp the top middle surface of the conical wall to the element of the workpiece, θ is the longitude, and then instead of x use the coordinate ρ=xcosα_i. Next, decide jointly known from theory of plasticity and metal forming equilibrium equation dσ_ρ=-(σ_ρ-σ_{θ )dρ/ρ and the equation of plasticity σρ-σθ=σswhere σρ- the current along the conical wall voltage. As this third phase when the hood is subjected to significantly less plastic deformation than the flange, the equation of plasticity are that the yield stress σsequal to the yield stress σTGOST 11701-84. After integrating the differential equation using the boundary condition that at the boundary of the second section of the deformation zone of radius ρ=rb,1,iand σρ=σ'ρderive the formula for determining the tensile stresses σ"ρin function of the radius ρ in the third section of the deformation zone:.}

In the fourth plot of the deformation, the influence of bending of the sheet workpiece with the edge of the punch on tensile stress estimate corrected for bending Δσ_ρ=σ_Ts/(4r_p+2s), for which a stepwise increase of σ"_ρin the area of the curve.

In the end, you get the following formula Zharkova V. A. to determine the maximum tensile stresses along the conical wall pulling axisymmetric formulation dangerous section, which is on the border of contact of the material with the edge of the punch when ρ=r_c,1,i(Fig. 2):

On defined�nnyh stages of drawing some summands in the latter formula is not necessary to consider; for example, at all stages, after the release of a contour slab from under the clamp die, the first and second portions of the deformation zone pass into the wall prefabricated exhaust and related components do not need to take into account.

From the last formula determines that the larger the radius g of the inner contour of the flange and, consequently, the smaller the surface area of the first main section of the deformation zone in the form of a flange of the blanks, the less stress σ_{ρ max}. Therefore, by increasing the radius of the aperture of the die plates to extrude and, accordingly, the radius r of the inner contour of the flange of the blanks, instead of the previously unacceptable exhaust prefabricated cylindrical wall to the first operation is carried out according to the new method became valid the hood of the semi-conical wall.

Since the VAT wall prefabricated exhaust in dangerous section corresponds VAT sheet specimen during a tensile test according to GOST 11701-84, the danger of destruction of prefabricated judged by the criterion: based on the derived above formula the maximum tensile stress in dangerous section of the wall prefabricated exhaust at all stages of extraction must be less than or equal to the yield stress σ_TGOST 11701-84, namely:

σ_{ρ max}≤σ_T.

PR� the hood as you move the contour of the slab width of the first main phase of deformation namely, the flange is initially equal to (R-r) gradually decreases, while the surface area of the remaining three sections of the deformation zone increases. In the initial stages of retraction flange blanks punch to the matrix hardening the blanks prevails over the reduction of the width of the flange and tensile stress in dangerous section of the wall prefabricated exhaust increases. In the final stages of retraction flange blanks punch in the matrix reduces the width of the flange may prevail, and so can not prevail over the hardening blanks and tensile stress in dangerous section of the wall prefabricated exhaust may fall as well as rise, depending on the parameters of the extrusion. It is therefore important at all stages of drawing of sheet blanks to calculate derived by the above formula, the maximum tensile stress σ_{ρ max}in dangerous section of the wall prefabricated exhaust and compare with the yield strength σ_Tto assess the risk of the destruction of the semi-finished product.

The formula for calculating σ_{ρ max}fair to extract any axisymmetric semi-finished product with both cylindrical and tapered wall. In the first step of extraction, by comparing the values of σ_{ρ max}in dangerous section we extend the semi�of brikama conical wall, the minimum diameter of which is equal to the diameter specified for the manufacture of axisymmetric parts, according to the new method, and semi-cylindrical wall of a diameter equal to the diameter of the same given to the manufacture of axisymmetric parts, by a known method, for the same size blanks and other things equal, conclude that in the first case, according to the new method of extraction of the material with a conical wall of the maximum tensile stress σ_{ρ max}less than or equal to the yield stress σ_Tand the extrusion of semi-finished product without destruction is possible, and in the second case by a known method of extraction of the material with a cylindrical wall of a value of σ_{ρ max}more σ_Tand when the hood is going to happen the gap bottom in a dangerous section of the cylindrical wall of the semi-finished product.

When in the process of drawing a new way of tension σ_{ρ max}reaches the yield limit σ_Tdangerous section of the walls of the semi-finished product will begin to plastically deform and procnames, but the destruction of the semi-finished product is not going to happen, because the drawing process is stopped. At the same time, this hood semi-finished product, when at the last stage of the stress σ_{ρ max}becomes equal to the yield stress σ_Tallows the greatest advantage of the plastic properties of foxes�type of the workpiece on the first operation.

Knowing the tensile stress σ_ρin each element of the deformation, the equations of plasticity are the compressive stress σ_θthat causes the loss of stability of sections of sheet workpiece with the formation of wrinkles. The greatest danger of skladkoobrazovaniem exists on the first section of the deformation, namely the flange of the blanks, so to eliminate such danger in the die used to extrude the clamp. Extraction parameters define and clarify when debugging stamp for hoods so that in the initial stages of drawing folds on pulling the prefabricated were such minimum permissible value, so they can be spread between the working surfaces of the die and punch in the final stages of drawing.

The components of the strain state of the elements of the deformation is calculated by using well known from theory of plasticity and metal forming equations relation between stresses and strains.

So, specifying, in the first and subsequent approximations, the depth of the extrusion, the angle of taper of the wall of the first prefabricated and other settings the first operation of the hood and relying on derived above formula the value of σ_{ρ max}determine the rational parameters of the first operation and die to extrude from conditions that Maxim�Sal tensile stress σ _{ρ max}in dangerous section of the wall prefabricated exhaust at all stages of drawing of sheet blanks gradually increased and in the last stage of extraction was equal to the yield stress σ_Tthe forming depth was marginal - without destruction of the workpiece, the edge of the workpiece at the final drawing, if possible, not slipped out from under the thumb of a stamp in order to rule out a fatal skladkoobrazovaniem the blanks, and that in the final stages of drawing in the lowermost position of the movable part of the stamp edit was carried out (Fig. 3) small, valid on previous phases hood, folds over the entire surface of the semifinished product.

On the second operation of the hood pull the second semi-finished product, the quality of the workpiece using the first material after the first operation of the extrusion, the shape and dimensions of the bottom of the first prefabricated left intact, corresponding to the bottom of the symmetrical components, the first taper angle γ₁wall of the first intermediate product is reduced to γ₂the extrude depth increases from the first limit value H₁up to the second limit, without destroying the semi-finished product, the values of N₂and configuration of the semi-finished product on this second operation closer to axisymmetric configuration details, and from the cushion of a press or stamp buffer on the pressing die pressing �Paradise of prefabricated, creates a force that pushes in the process of drawing the conical wall of the semi-finished product in the matrix of the stamp and facilitating the process of drawing without destroying the semi-finished product (Fig. 4), during the final stages of drawing simultaneously with hood perform correction of wrinkles on the surface of the semifinished product, the minimum allowable during the previous stages of this operation of extraction (Fig. 5).

The parameters of the second operation of the hood is determined by the same methodology developed above for the first operation of the hood, on the basis of the following engineering analysis being drawn into the matrix of the first semi-finished product for the purpose of pulling the second semi-finished product. The deformation zone in pulling the prefabricated divided into four sections: 1) a flange in the form of a circular ring which is in contact with the clamp 3 of the stamp (Fig. 4) and front of the hood has an outer radius of R₂and inner radius r₂where the index 2 stands for the number of operations n=2; 2) section of the semifinished product, which hood had a radius of r_m,1matrix of the first die to extrude and now on the second stamp to extrude in the process of straightening, drawing in increasing the length of the wall of the semi-finished product, and after straightening this the second phase of the deformation zone between the flange and the conical wall to form new elements of the flange of the sheet blank bending radius r_{m 2}the matrix of this second stamp to steal�LCD; 3) the conical section of the wall, deflected in the gap between the punch and the matrix; 4) the site of prefabricated elements which, in the process of drawing curved along the edge of the punch and come in contact with the edge of the punch.

When determining the maximum tensile stress σ_{ρ max}acting in a dangerous, from the point of view of destruction, the cross section of a drawn semi-finished product, which is on the border of contact of stretch of the material with the edge of the punch, sequentially determine the stress field in each of the four sections of the deformation zone, using as boundary conditions the equality of radial stresses at the boundary of the adjacent sections.

Since the drawing process is non-stationary, then the process or working stroke of the stamp, the hood is divided into a large number of i-x stages, i=1, 2, 3, ..., N, where the number of stages N is chosen depending on the depth of the extrusion and other factors. To define VAT each element of the first section of the deformation, namely the flange of semifinished product at each stage of the extrusion accept the same as above for the first drawing operation, the analysis model flat axisymmetric stress state and solve statically determinate task of two equations with two unknowns σ_ρand σ_θnamely, decide jointly known theories of PL�of realism, and the processing of metals by pressure equilibrium equation dσ _ρ=-(σ_ρ-σ_θ)dρ/ρ and the equation of plasticity σ_ρ-σ_θ=σ_swhere ρ is the current radius of the element flange prefabricated, σ_sis the yield stress. After integrating the differential equation using the boundary condition that the contour of the prefabricated when ρ=R_2,iand σ_ρ=0, you get a formula for determining the tensile stresses σ_ρin function of the radius ρ on the flange of the prefabricated: σ_ρ=σ_sln(R_2,i/ρ). According to the latest formula, calculate the maximum tensile stress σ_ρon the inner contour of the flange of the prefabricated radius r₂at the last stage of drawing:, Fig. 5.

Asking a working stroke of the die or forming depth h_2,isucceeding i-x stages of drawing, from the condition of equality of the areas median surfaces known from geometric constructions of the second semi-finished product and the first semi-finished product, counting the current decreasing from stage to stage of the i-th radius R_2,ithe contour of the second semi-finished product. According to the latest formula, calculate the maximum tensile stress σ_ρon the border of the first section of the deformation, namely on the inner contour of the flange pulling of the second prefabricated radius r_2,iat each i-th stage of drawing: .

The yield stress σ_staking into account the hardening of the semi-finished product in the process of drawing is determined by the above formula Zharkova, V. A., in which the intensity of deformation on the inner contour of the flange of the prefabricated radius r₂on the i-th stage, hoods expect when ρ=r₂:.

The second portion of the deformation zone, which hood had a radius of r_m,1matrix of the first die to extrude and now, this second stamp to extrude in the process of straightening, drawing in increasing the length of the conical wall of the semi-finished product, and after straightening this the second phase of the deformation zone between the flange and the conical wall to form new elements of the flange of the sheet blank bending radius r_{m 2}the matrix of this second stamp, the hood, the influence of bending of prefabricated elements on tensile stress σ_ρappreciate the correction for the bending Δσ_ρ=σ_Ts/(4r_{m 2}+2s), for which a stepwise increase of σ_ρon the border of this area of radius r_b,2,i:

.

To determine the VAT of the third section of the deformation zone in the conical wall prefabricated exhaust take into account that this site is deformed without the influence of surface forces in the gap between the punch and the matrix, and therefore the same as above for flange, at each stage of the extrusion accept the analysis model flat axisymmetric stress state and solve known from theory of plasticity and metal forming equilibrium equation dσ_ρ=-(σ_ρ-σ_θ)dρ/ρ and the equation of plasticity σ_ρ-σ_θ=σ_s. As this third phase of the deformation when the hood is subjected to significantly less plastic deformation than the flange, the equation of plasticity accept that at all stages of extraction yield stress σ_sequal to the yield stress σ_TGOST 11701-84. After integrating the differential equation using the boundary condition that at i-th stage of the extrusion on the border of the second phase of the deformation radius ρ=r_b,2,i,derive the formula for determining the tensile stresses σ"'_ρin function of the radius ρ in the third section of the deformation zone:

.

In the fourth plot of the deformation, the influence of bending of the sheet workpiece with the edge of the punch on tensile stress estimate corrected for bending Δσ_ρ=σ_Ts/(4r_p+2s), for which a stepwise increase of σ"'_ρin the area of the curve.

Eventually get the following formula Zharkova V. A. to determine the i-th stage of the second exhaust �maximum tensile stresses along the conical wall pulling axisymmetric formulation dangerous section, which passes through the contact interface of the material with the edge of the punch when ρ=r_c,2,i(Fig. 4):

.

At certain stages of drawing some summands in the latter formula is not necessary to consider; for example, on a recent operation to extrude the cylindrical vertical wall at all stages, after the start of formation of the vertical wall parts, bending the walls of the prefabricated on the edge of the punch is no longer happening, and the last term to consider is not necessary.

Since the VAT wall pulling the second prefabricated in a dangerous cross section corresponds to the VAT sheet specimen during a tensile test according to GOST 11701-84, the danger of destruction of prefabricated judged by the criterion: based on the derived above formula the maximum tensile stress in dangerous section of the wall prefabricated exhaust at all stages of extraction must be less than or equal to the yield stress σ_TGOST 11701-84, namely: σ_{ρ max}≤σ_T. Knowing the tensile stress σ_ρin each element of the deformation, the equations of plasticity are the compressive stress σ_θthat causes the loss of stability of sections of the material with the formation of wrinkles. Extraction parameters define and clarify when debugging a die to extrude so that the initial� stages of drawing folds on pulling the prefabricated were such minimum permissible value, so they can be spread between the working surfaces of the die and punch in the final stages of drawing.

So, specifying, in the first and subsequent approximations, the depth of the extrusion, the angle of taper of the wall of the second semi-finished product and other parameters of the second operation of the hood and relying on derived above formula the value of σ_{ρ max}determine the rational parameters of the second operation and die for drawing air from the environment to the maximum tensile stress σ_{ρ max}in dangerous section of the wall prefabricated exhaust at all stages of extraction was less than or equal to the yield stress σ_Tthe forming depth was marginal - without destruction of the workpiece, forming a fatal skladkoobrazovaniem semi and in the final stages of drawing in the lowermost position of the movable part of the stamp edit was carried out (Fig. 5) small, valid on previous phases hood, folds over the entire surface of the semifinished product.

Similarly for all subsequent n-th of the operations of the extrusion taper angle γ_nthe walls are prefabricated in a consistent and functional in the dies is reduced, the depth of the hood (H_nincrease, the configuration of semi-finished products from operation to operation, all closer to the configuration of symmetrical components, derived by the above formula calculated� the maximum tensile stress σ _{ρ max}in dangerous section of the wall prefabricated exhaust at all stages of extraction and compare with the yield strength σ_Tslab to prevent the destruction of the semi-finished product, and from the cushion of a press or stamp buffer on the clamp die which presses on the edge of the semi-finished product, creates a force that pushes in the process of drawing the wall of the semi-finished product in the matrix of the stamp and facilitating the process of drawing without destroying the semi-finished product at the end of each operation of the extrusion simultaneously with the hood also perform straightening of folds on the surface of the semifinished product, the minimum allowed at the previous stages of the operation of the hood. If the n-th operation on the i-th stage of the drawing tension σ_{ρ max}in dangerous section of the wall prefabricated exhaust will be more than the yield limit σ_Tthen change the parameters of the extrusion so that the stress σ_{ρ max}has become equal to the yield stress σ_T.

On the last operation of drawing out the shape and dimensions of prefabricated perform the appropriate size and shape of symmetrical components subject to the allowance for trimming the rough edges of the semi-finished product, in the final stages of the extrusion simultaneously with the hood also perform straightening of folds on the surface of the semifinished product, the minimum allowable during the previous stages of extraction (Fig. 6). In the end, determine the number of Opera�rd hoods given to the manufacture of axisymmetric parts.

Since the second operation of the hood on all drawing operations from the pillow press or stamp buffer on the clamp die which presses on the edge of the semi-finished product, creates a force that pushes in the process of drawing the conical wall of the semi-finished product in the matrix of the stamp and facilitating the process of extraction without destruction of the material; this reduces the number of drawing operations and to minimize the number of dies for drawing. By reducing the number of dies to extrude the released position on the same multi-press machine, which on this new way stamp axisymmetric detail uses for punching other parts, increasing productivity in manufacturing.

Fig. 7 shows the sheet blank 9 and semi-finished products 10, 11 and 12 with the flange respectively after the first, second and third operations of the extrusion; the last semi-finished product 12 after cutting the rough edges or becomes a part with a flange, or after additional operations drawing only one flange is becoming part without flange and further applied to the destination. When multistage drawing of axisymmetric parts with multi-position press machine prefabricated, for each position, not stretched out to the end, but leave a small flange, as shown in Fig. 7, providing smoothness of prenosological gripper mechanism from position to position.

Fig. 8, as a variant of this method, shown sheet blank 9 and semi-finished products 10, 11 with the flange and the last semi-finished product without flange 12 respectively after the first, second and third operations of the extrusion; the last semi-finished product 12 after cutting the rough edges becomes part and then applied to the destination.

A new method multistage drawing is applicable to the extrusion of axisymmetric workpieces of various configurations. Fig. 9 alternatively, the picture shown multistage drawing on this method of symmetrical components with a flange, on which the last n-th operation hoods stamped with a tapered wall, as shown in Fig. 10, after the forming of axisymmetric parts inserted into one another for ease of transportation.

Through the use of multioperational method of symmetrical components extraction from a great height slab presses simple steps or multi-position press machine, compared with the known method improves the accuracy of the dimensions of the resulting axisymmetric parts with fewer operations extrude, while also improving the quality of the surface, which affects the reduction of scrap rates in production and consumption of sheet material, and in General the cost of manufacture of axisymmetric parts.

With�persons multistage drawing of axisymmetric sheet billet in the die on the press simple steps or multi-position press machine, includes sequential and functional hood from a parent sheet of semi-finished products configuration from operation to operation approaching axisymmetric configuration items, wherein in the first operation range hoods in the initial stages form a bottom of the first semifinished product corresponding to the bottom of the symmetrical components in subsequent stages pull the first semi-conical wall to the limit, without destruction of the workpiece, the depth to subsequent drawing operations are extrusion of semi-finished products with a bottom portion received in the first operation, with a consistent and functional reduction of the angle of taper of the wall of the first semi-finished product, depth of the extrusion and increase the configuration of semi-finished products from operation to operation closer to axisymmetric configuration details by means of pushing in the conical wall of the semi-finished product in the matrix of the stamp to the action of force on the clamp die to the cushion of a press or stamp buffer, pressing the edge of the semi-finished product to facilitate extraction without destruction of semifinished product at each operation of the extrusion limit the depth and taper angle of a wall of a prefabricated set of conditions to ensure at all stages of drawing of sheet blanks of gradual increase of the maximum tensile stresses in the dangerous section �tenki exhaust prefabricated, and at the final stage is equal to the yield strength of the blanks, at the end of each operation of the extrusion simultaneously with the extraction performed on the entire surface of the prefabricated edit the folds made in the previous stages of drawing, and at last drawing the shape and dimensions of prefabricated perform the appropriate size and shape of symmetrical components subject to the allowance for trimming the rough edges of the semi-finished product.