RU2697307C1 - First junction puncheon for two-junction drawing of thin shells of revolution with curvilinear surface - Google Patents

First junction puncheon for two-junction drawing of thin shells of revolution with curvilinear surface Download PDF

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RU2697307C1
RU2697307C1 RU2019100875A RU2019100875A RU2697307C1 RU 2697307 C1 RU2697307 C1 RU 2697307C1 RU 2019100875 A RU2019100875 A RU 2019100875A RU 2019100875 A RU2019100875 A RU 2019100875A RU 2697307 C1 RU2697307 C1 RU 2697307C1
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punch
transition
revolution
maximum diameter
workpiece
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RU2019100875A
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Russian (ru)
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Николай Григорьевич МОРОЗ
Игорь Константинович Лебедев
Александр Николаевич Калинников
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ОБЩЕСТВО С ОГРАНИЧЕННОЙ ОТВЕТСТВЕННОСТЬЮ "СИСТЕМЫ АРМИРОВАННЫХ ФИЛЬТРОВ И ТРУБОПРОВОДОВ" (ООО "Сафит")
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21DWORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00Shaping without cutting, by stamping, spinning, or deep-drawing

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to tooling for metal forming, particularly, to puncheons with curvilinear profile for first transition at two-junction drawing of thin-wall shells of revolution with curvilinear surface. Maximum diameter of puncheon makes 0.9–0.95 of the maximum diameter of the bottom and has the shape of a body of revolution with a curvilinear generatrix.EFFECT: homogeneous structure and equal thickness of the material produced in the process of shell drawing.4 cl, 3 dwg

Description

Technical field

The invention relates to tooling for metal forming, in particular, to punches with a curved profile for drawing thin-walled shells of revolution with a curved surface.

State of the art

Currently, in the technology of metal forming, there is a wide variety of methods and their corresponding tools such as molds for drawing shell parts from a thin sheet. [Romanovsky V.P. Handbook of cold stamping. Ed. 6th rev. and add. L. Mechanical engineering. Leningrad branch, 1979. 520 p .; Popov E.A. Fundamentals of the theory of sheet stamping. - M .: Mechanical Engineering, 1977. - 198 p .; Melnikov E.L. Cold stamping bottoms. Ed. 2nd, rev. and add. M Mechanical Engineering, 1986. 192 s].

Numerous methods are known for producing bottoms from a flat billet, consisting in drawing it out while tightly clamping its peripheral part [Romanovsky V.P. Handbook of cold stamping. Ed. 6th rev. and add. L. Mechanical engineering. Leningrad branch, 1979. 520 p. Popov E.A. Fundamentals of the theory of sheet stamping. - M.: Mechanical Engineering, 1977. - 198 p.].

With deep drawing of the bottoms, a quick change in thickness along the generatrix occurs, which in some cases leads to destruction or loss of shape of the workpiece. As a result of this, in practice, to obtain shells of revolution, complex multi-junction processes of drawing an axisymmetric step semi-finished product with a flat end and a radius of curvature are used. For the final molding of the bottoms spend tightening with a hard tool. [Averkiev Yu.A., Averkiev A.Yu. Cold stamping technology. - M.: Mechanical Engineering. 1989 .-- 148-153 p .; Popov E.A., Kovalev V.G., Shubin I.N. Stamping automation technology. - M.: Publishing House of MVTU im. N.E. Bauman, 2003 .-- 134-136 p .; Panchenko E.V., Seledkin S.E. Optimization of the distribution of wall thickness when stamping a spherical billet, Izv. Tula state. Univ., 2004, N3, S. 69-73].

In the presence of friction on the surface of the punch, sections of the workpiece in contact with the working end of the punch experience the action of friction forces that impede the movement of the workpiece relative to the punch and reduce thinning, which leads to the destruction of the shell billet. According to the results of numerous extraction works, it was found that the cross section along which the destruction of the spherical shells during the extraction is located approximately at a radius of 1/3 ... 1/4 of their maximum radius. [Popov EA Fundamentals of the theory of sheet stamping. - M.: Mechanical Engineering, 1977. - 198 p.].

One way to obtain shells of rotation, partially eliminating these disadvantages, is a multi-junction method. In this case, the stamping of the semi-finished product is preliminarily carried out [Melnikov E.L. Cold stamping bottoms. Ed. 2nd, rev. and add. M Engineering, 1986, 192 p.]. The method differs from the well-known in that the preliminary transition is carried out in another set of technological equipment and, possibly, on other equipment. At the same time, obtaining a preliminary semi-finished product can also be a rather complicated technological task. To implement this method, reverse molding is widely used. The main problem in the implementation of this method is to select such a contour of the preliminary transition workpiece so that after the final molding to get the part with minimal allowances and with minimal changes in the structure of the product material used.

The techniques for selecting the contour of the preliminary transition stamp found in the technical literature apply only to individual configurations of parts and are intuitive. For example, in the methodology described in [Luckey S.G. J., Friedeman P. A., Weimann K.J. Desing and experimental validation of a two-stage superplastic forming die / Journal of Materials Processing Technology. 2009. Vol. 209. P 2152-2160], the only recommendation regarding the shape of the stamp of the preliminary transition, is that the length of the generatrix of the contour should not exceed 84% of the length of the generatrix of the contour of the stamp of the final transition.

Some options for choosing the geometry of the profile of the stamp of the first transition, used to implement the reverse drawing of the bottoms, are recommended in [Melnikov EL Cold stamping bottoms. Ed. 2nd, rev. and add. M Engineering, 1986. 192 p.]. According to these recommendations, the profile geometry of the stamp of the first transition is constructed by the selection method so that the ratio of the stamp surfaces of the previous operation to the next is within 0.8 ... 0.95. In [Calculation of the process of reversible gas molding of hollow shells from a sheet EM Seledkin, V.D. Kuhar, M.A. Tsepin, K.Yu. Apatov / Izv. Universities, Non-ferrous metallurgy. 2010. N4. From 52-56] it is also proposed by the selection method to build a preliminary transition contour (or the stamp profile of the first transition).

There are formalized methods for obtaining the contour of the preliminary transition stamp, based on the use of the finite element method and specialized computing software systems. These methods are based on iterative refinement of some initial profile found by modeling the two-transition molding. Such techniques can achieve good results only if all the real effects that occur during the shaping process are taken into account.

Among the methods for designing stamps of preliminary transitions, the most suitable for reverse molding are multi-parameter optimization methods, since they can be used with minimal modification of existing commercial software systems.

However, all the above methods and techniques do not allow the designer of dies to quickly create the design of exhaust dies of the first transition for drawing shells of rotation of arbitrary shape.

A known method of stamping bottoms (SU 1233990 A1, Published: 05/30/1986) from a flat workpiece, which consists in stamping a flat workpiece with a hard clamp on the peripheral part of the workpiece. The hood in this solution is produced in two stages: at the first stage, preliminary preparation of a specially shaped workpiece with a tight clamp on the peripheral part is carried out, and at the second stage, the final extraction of the obtained workpiece with a clamp on the peripheral part of the workpiece is carried out.

The disadvantage is the uncertainty of the structural form of the workpiece of the first hood.

Also known is a method of stamping bottoms (SU 1804933 A1, convention priority 29.05.1990) from a flat billet, comprising a first hood and a second hood, while in the process of the first hood, the depth of the hood is less than the depth of the second hood.

The disadvantage is the uncertainty of the structural form of the workpiece of the first hood.

There is also known a method of stamping bottoms from a flat billet (RU 2172222, Published: 08.20.2001 Bull. No. 23), in which the type and path of deformation of the billet during the first drawing and the amount of plasticity stock of the workpiece after the second drawing are preliminarily determined, and their the results determine the percentage of the depth of the first hood to the depth of the second hood. In this case, upon preliminary determination of the type and path of deformations during the first drawing, the workpiece is discretely deformed to various drawing depths before thinning of the material at the apex appears, and after each discrete drawing, the workpiece deformation value is measured, and upon preliminary receipt of the value of the plastic material stock after the second drawing, a smaller value of the ultimate strain on the diagram of ultimate strains, taking into account the magnitude of the scatter of the values of the component, choose a smaller discrete e depth value of the first drawing.

The disadvantage of this method is the complexity of its implementation when changing the grade of material, taking into account the spread of its mechanical characteristics, which leads to periodic revision of the working parts of the stamp, increasing the time for preparing the stamps for work.

A reasonably close solution is defined in the method of reverse drawing (SU 1180116 A, Published: 09/23/1985) of spherical bottoms from a flat round billet with obtaining a semi-finished product with a surface area equal to the surface area of the bottom at the first transition and a final drawing of the bottom at the second transition by inverting the obtained semi-finished product. In this case, at the first transition, a semi-finished product is obtained with annular corrugations smoothly conjugated with one another, the surface of which is formed by several counter-directed spherical surfaces with a radius of the sphere equal to the radius of the bottom.

An analysis of the available test results on the long and cyclic strength of elongated billet materials used for the manufacture of welded pressure cylinders shows that with an increase in the degree of ultimate deformation (ε.) Of materials during the drawing (stamping) of parts, the cyclic strength of the cylinders significantly decreases. This is due to the fact that with an increase in the degree of deformation (ε ex.) Of materials during the drawing (stamping) of parts, their conditional yield strength (σ 0.2 ) and tensile strength (σ c ) increase, and plasticity indicators (relative elongation δ and narrowing ψ) decrease the more, the lower the energy of the packaging defects of the material. In this case, the hardening curves for each material are located higher and more, the greater the degree and speed of their plastic deformation in the manufacture of blanks. The most intense hardening is characteristic of metals and alloys of austenitic steels, nickel. With an increase in the degree of deformation, the yield strength increases faster than the tensile strength (tensile strength increases by 1.5 ... 3 times, and the yield strength by 3 ... 7 times). In highly hardened metals, the supply of plasticity is running out. This state is extreme, and when you try to continue the deformation, the metal is destroyed.

Hardened metal stores 5 ... 10% of the energy spent on deformation. The stored energy is spent on the formation of structural defects and on the elastic distortions of the crystal lattice of the material. The deformation in polycrystalline materials develops nonuniformly, since individual grains have different orientations and are not found during deformation in the field of a uniaxial stress system. Deformation is unevenly distributed not only in the volume of the material between the grains, but also inside the grains and individual defects. Due to the heterogeneity of deformation in metals, internal residual stresses of various levels arise. The formation of residual stresses as a result of inhomogeneous plastic deformation in high-strength materials can lead to rupture of the finished workpiece.

From the existing level of technology, the closest analogues, both structurally and functionally, to the claimed technical solution are options for choosing the geometry of the stamp profile of the first transition, presented in the monograph [Melnikov E.L. Cold stamping bottoms. Vol. 2, rev. and add. M Mechanical Engineering, 1986. 192 s], and the solution presented in the above method of reversible drawing (SU 1180116 A, Published: 09/23/1985).

However, a common drawback of these analogues is the ambiguity of the use of the proposed solutions in the manufacture of thin-walled shells of rotation of arbitrary shapes.

Disclosure of invention

Based on this analysis, the basis of the present invention, as a device, and not as a method, is the task of creating the design of the punch of the first transition for two-junction reversible drawing, providing a minimum change in the mechanical characteristics of the starting material in the process of drawing shells of rotation of arbitrary shape on both the first and on the second transitions.

The objectives and technical result of the invention of the device were:

- ensuring a homogeneous structure and thickness of the material of the obtained shell of rotation and the exclusion of the influence of these parameters on its deformability and performance as an independent design;

- the exception of oriented microcracks in the material of semi-finished products in the manufacture of them;

- elimination of residual stresses in the semi-finished products of the workpieces during their manufacture.

The technical result is achieved by the fact that the punch of the first transition to obtaining a semi-finished product from a flat round billet for the final drawing of a thin shell (bottom) with a curved surface of revolution by a double-transition drawing by isometric bending (eversion) and subsequent stretching of the obtained semi-finished product is made with a maximum diameter of (0.9- 0.95) of the maximum diameter of the bottom, and has the shape of a body of revolution with a curvilinear generatrix, the coordinates of which y and x correspond to the relation Y c -y = y 0 (1- (x / C) 2 ) 2 , and its maximum depth is (0.3-0.37) of its maximum diameter, where Y s is the current ordinate of a circle with a diameter equal to the maximum diameter of the punch. Moreover, the values of the constants C and y 0 are respectively (0.375-0.45) and (0.215-0.315) also on the maximum diameter of the punch. The technical result is also achieved by the fact that the area of its curved surface in the form of a body of revolution is (0.8-0.9) of the area curved surface of the bottom.

To achieve the result, it is also advisable to perform a punch with a curved surface in the form of a body of revolution formed by the intersection of coaxial opposite directions of the surface with a generatrix corresponding to the ratio Y c -y = y 0 (1- (x / C) 2 ) 2 , and a spherical surface with a radius, equal to the maximum radius of the punch, smoothly conjugated to each other in the zone of intersection along the main radii of curvature of their meridians with a section of a toroidal surface. The intersection line of the oncoming surfaces is on a cylindrical surface with a diameter located in the interval (0.2-0.5) from its maximum diameter.

List of figures

In FIG. 1 shows a general view of the punch.

In FIG. 2 shows a graphical diagram of the surface shape of the punch of the first transition.

In FIG. 3 shows a graphical diagram of the combined structural form of the surface of the punch of the first transition.

The implementation of the invention

Presented in FIG. 2 and FIG. 3 graphic images of the surface shape of the punch of the first transition were obtained by computer simulation using the relation Y c -y = y 0 (1- (x / C) 2 ) 2 under different initial conditions at 0 and C.

To ensure the task, namely, to reduce deformations during drawing, it is advisable to carry out the drawing process in at least two stages.

At the first stage, it is advisable to extract the workpiece with minimal deformations of not more than (10-12)%, and at the second stage, first transform the resulting workpiece into some intermediate shape, which subsequently stretch to the desired geometry with a strain rate not exceeding (8-10) %

Based on this scheme for the implementation of the drawing process to determine the geometry of the workpiece of the first transition, it is advisable to choose the maximum diameter of the workpiece equal to (0.9-0.95) of the maximum diameter of the product obtained at the second transition. This ratio follows from the fact that at the second transition of the hood, in essence, the operations of "distribution" and "hood" obtained at the first stage of the workpiece are combined. In this case, it follows that when the workpiece is “distributed”, the deformations in the deformation zone are close to linear extension and provide the greatest tangential elongation. At a certain magnitude of this elongation, local deformation with the formation of a neck can begin in a certain local zone, which leads to fracture fracture along the forming blank. To eliminate this phenomenon on the basis of numerous analytical and experimental results of the analysis of the features of the operation of a single-stage "distribution" in the manufacture of various kinds of shell structures [see e.g. Popov E.A. Fundamentals of the theory of sheet stamping. - M .: Mashinostroenie, 1977. - 198 p.] Establish restrictions on the magnitude of maximum tensile strains - not more than 10%. Given this restriction on strains that occur during the operation of “distribution” and taking into account the above restrictions on the strain intensity (not more than (8-10)%), we find that the diameter of the punch of the first transition should be in the range (0.9-0.95) of the maximum products obtained in the second transition.

On the other hand, it is well known that during the cold drawing operation, structural changes occur in the workpiece material, leading to its hardening and loss of plastic properties. Therefore, in the manufacture of various kinds of thin-walled shells by cold drawing, restrictions are set on the value of the residual ductility of the shell material. These restrictions impose, respectively, restrictions on the maximum value of the strain intensity during the drawing operation. This is especially true when considering a single-stage hood operation. In this case, as well as earlier when considering the operation of "distribution", on the basis of numerous analytical and experimental results of the analysis of the features of the operation of a single-stage "extraction" in the manufacture of various kinds of shell structures [see e.g. Melnikov E.L. Cold stamping bottoms. Ed. 2nd, rev. and add. M Machine-building, 1986, 192 S.] as a restriction on the maximum value of the strain intensity, a restriction is established - no more than (8-10)%.

Based on the above considerations and limiting ourselves to the requirement that the maximum stretching deformations at the first transition should not exceed (10-12)%, we obtain as a limitation that the total drawing depth of the preform at the first transition should be in the range (0.3-0.37) of its maximum diameter. In this case, the workpiece itself should be presented in the form of a shell of revolution with a surface consisting of a section with a cylindrical surface with a maximum diameter equal to (0.9-0.95) of its maximum diameter, and a section of a complex curved surface that can be transformed in the second stage by isometric bending (eversion) followed by stretching.

As already noted, the two-transition drawing process involves the manufacture of a workpiece at the first transition with a complex curved surface, which at the second transition, by combining deformations in the form of geometric bending (eversion) and stretching, is converted into the final shape of the shell of revolution. A general view of the construction of such a punch is shown in FIG. one.

To design the profile of the meridian of a section of a complex curved surface at the initial stage, the initial surface is selected in the form of a spherical surface with a diameter equal to the diameter of the cylindrical part (see Fig. 2). The fact is that the final shape of the middle surface of the workpiece obtained at the first transition should be almost close to one of the forms of isometric transformation during deformation of its initial spherical shape by means of geometric bending (eversion) of its segment. At the same time, despite significant changes in the shape of the final shell, the internal metric of its middle surface remains practically unchanged (no more than 0.1%) and the deformation of its segment leads to forms close to isometric transformations. So, for example, for structural materials such as steel, the elastic modulus is of the order of 10 6 kg / mm 2 and the ultimate fracture strength is of the order of 10 2 kg / mm 2 , thus, the maximum deformation is of the order of 10 -3 . Due to the fact that the deformation of the segment is axisymmetric, the deformed surface is also a surface of revolution. Any isometric transformation of a segment into a surface of revolution will be a mirror image of a part of the shape of the final shell.

However, the transition of the shell to the deformed state is associated with significant local bending and the formation of narrow transition zones (edges) in the corresponding transformation. To reduce bending deformations and the formation of narrow transition zones (ribs), it is advisable to limit this type of deformation with large deflections of the shells under the condition that the angle of rotation of the normal to the surface during deformation satisfies the dependences ϑ = C (ρ z -ρ), where C and z are some constants , ρ is the relative radius to an arbitrary point when considered in a local coordinate system associated with the center of the shell segment under consideration. The parameter z takes into account a change in the shape of the surface with bending. Based on this condition, the deflection of the axisymmetric shell will be represented in the form of a curve described in the form w = w 0 (1-ρ 2 ) 2 , which is valid with sufficient reliability to describe both small and large movements of flexible shells. Thus, using the accepted considerations, the curve represented as Y c -y = y 0 (1- (x / C) 2 ) 2 , where y and x are the coordinates of the curve, Y is taken as the meridian profile of the complex surface of the punch of the first transition c is the current ordinate of a circle with a diameter equal to the maximum diameter of the punch, and C and y 0 are some constants depending on the depth of the spherical surface with a maximum diameter equal to the diameter of the punch. Several embodiments of this surface shape are shown graphically in FIG. 2. The peculiarity of this shape of the shell profile is that when it is isometrically transformed in the form of geometric bending (eversion), the metric of its middle surface practically does not change. For example, when the shell is drawn from a thin sheet up to 1 mm, local deformations in this case are no more than 0.1%. That is, with this type of transformation, the surface of the workpiece goes into a spherical shape with a sphere diameter equal to the diameter of the cylindrical part of the punch with a level of metal deformation of not more than 0.1%.

Based on the previously accepted restriction that the total drawing depth of the workpiece should be in the range (0.3-0.37) of its maximum diameter, the constants C and y 0 , which determine the shape of the meridian of the surface of the punch, are (0.375-0.45) and (0.215-0.315), respectively also from the maximum diameter of the punch (see Fig. 2).

The proposed embodiment of the punch of the first transition was tested by drawing thin shells of stainless steel, the curvature of the meridian of which is close to the meridian of the spherical shell. Based on the results of the experimental work, it was found that the area of the curved surface of the punch in the form of a body of revolution upon transition to the initial hemispherical surface (half of a sphere with a diameter equal to the maximum on the cylindrical part) should be (0.9-0.95) of the area of the curved surface of the final thin shell (bottom) )

The criterion for determining the quality of transformation and stretching of the workpiece obtained on this punch was the criterion for the absence of corrugation of the finished shell. At the same time, during the drawing operations, oriented microcracks in the semi-finished material are practically excluded, and due to the insignificant level of the drawing deformations, the residual stresses in both the workpieces and in the finished shells during their manufacturing by the double-transition drawing method are significantly reduced.

At the same time, taking into account the fact that a punch is being considered, which ensures the extraction at the second transition of various shells of rotation of arbitrary shape, a range (0.8-0.9) of the area of the curved bottom surface should be established with practical margin as limitations on its surface area.

In the case of the manufacture of shells, the surface of which has a large deviation from the initial hemispherical surface, it is advisable for the surface of the punch to use a surface consisting of a combination of sections of the initial hemispherical surface and the surface, the shape of which is determined by the ratio Y with -y = y 0 (1- (x / C ) 2 ) 2 , smoothly conjugated to each other in the intersection zone along the main radii of curvature of their meridians with a section of a toroidal surface. In this case, the meridians of the used surface sections must have curvatures opposite in sign, that is, the curved surface of the punch is represented as the surface of a body of revolution formed by the intersection of the coaxial counter-directed surfaces under consideration. In this case, the transformation of such a surface reaches large displacements with relatively small deformations of the material used. For design reasons, as a limitation on the surface where the contour of the intersection of the coaxial surfaces forming the form of the punch is located, it should be in the range of cylindrical surfaces with diameters (0.2-0.5) of the maximum diameter of the punch. A general view of such a form of punch meridians is graphically shown in FIG. 3.

Creating the design of the punch of the proposed configuration makes it possible to produce shells with practically no significant change in the structural properties and mechanical characteristics of the material (the deformation of the workpiece material during their manufacturing does not exceed 8%, the volume fraction of the mixture of fine-grained lower bainite and fine-grained mesh martensite does not exceed 10%). In addition, this form allows the use of sheet material subjected to drawing-stamping, with anisotropy of mechanical properties due to the material grade and technological modes of its production, without a significant negative impact on the stable course of the drawing process under various deformation modes. That is, the proposed form of the punch is its rational form in terms of ensuring the task.

With the creation of the proposed device, there was a real opportunity to obtain processes of drawing thin-walled metal shells of rotation of arbitrary shapes that are highly efficient both in terms of productivity and price. The manufacture and testing of the proposed punches of the first transition for the two-transition process of deep drawing of the shells of revolution confirmed their high efficiency.

The present invention can be effectively used to create shell thin-walled structures for various purposes. The invention is intended, in particular, for the manufacture of welded pressure cylinders.

Claims (4)

1. The punch of the first transition of obtaining a semi-finished product from a flat round billet for the final drawing of a thin shell of the bottom with a curved surface of revolution by a double-transition drawing by isometric bending by inversion and subsequent stretching of the obtained semi-finished product, characterized in that it is made with a maximum diameter of (0.9- 0.95) from the maximum diameter of the thin shell of the bottom and is made in the form of a body of revolution with a curvilinear generatrix, the coordinates of which y and x correspond to the relation Y c -y = y 0 (1- (x / C) 2 ) 2 , and its maximum depth is (0.3-0.37) of the maximum diameter, where Y c is the current ordinate of a circle with a diameter equal to the maximum diameter of the punch, and the constant C and at 0 , respectively, are equal (0.375-0.45) and (0.215-0.315) of its maximum diameter.
2. A punch according to claim 1, characterized in that the area of its curved surface in the form of a body of revolution is (0.8-0.9) from the area of the curved surface of the thin shell of the bottom.
3. A punch according to claim 1, characterized in that its curvilinear surface in the form of a body of revolution is formed by the intersection of coaxial counter-directed surfaces with a generatrix corresponding to the ratio Y c -y = y 0 (1- (x / C) 2 ) 2 , and a spherical surface with a radius equal to the maximum radius of the punch, conjugated to each other in the zone of intersection along the main radii of curvature of their meridians with a portion of a toroidal surface.
4. A punch according to claim 3, characterized in that the intersection line of counter-directed surfaces is located on a cylindrical surface, the diameter of which is in the range (0.2-0.5) of its maximum diameter.
RU2019100875A 2019-01-15 2019-01-15 First junction puncheon for two-junction drawing of thin shells of revolution with curvilinear surface RU2697307C1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2821038A1 (en) * 1977-05-31 1978-12-14 Gen Motors Corp Device for pulling spatial metallblechgegenstaenden in one operation
RU2608925C1 (en) * 2015-08-11 2017-01-26 Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский государственный технологический университет "СТАНКИН" (ФГБОУ ВО "МГТУ "СТАНКИН") Male die for drawing of hemispherical parts with flat bottom

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2821038A1 (en) * 1977-05-31 1978-12-14 Gen Motors Corp Device for pulling spatial metallblechgegenstaenden in one operation
RU2608925C1 (en) * 2015-08-11 2017-01-26 Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский государственный технологический университет "СТАНКИН" (ФГБОУ ВО "МГТУ "СТАНКИН") Male die for drawing of hemispherical parts with flat bottom

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
RU 2608925 C1, 26.01.12017. *

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