RU2419503C2 - Method of producing bicurved surface shells (versions) - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: set of invention relates to metal forming and may be used in producing bicurved surface shells. Separate parts are preformed. Here, to compensate for welding strains from welding seam shrinkage, parts made from titanium or steel are produced with undercurved edge while parts from aluminium are made with fluted edges all over their edges in the zone of post-welding deformation with width making 8-10 S where S is part thickness.

EFFECT: higher quality of bicurved surface shells.

8 cl, 6 dwg

Description

The invention relates to the manufacture of large-sized shell structures assembled from individual stamped parts (petals and bottoms), welded and equatorial and meridional seams, and can be used in various industries in the manufacture of shells of double curvature.

There are various methods of manufacturing die-welded structures from individual parts, which are pre-deformed on the press equipment by the method of sequential local and rotational-local shaping using machinery and universal specialized equipment. To obtain structures of complex shape or large-sized, when it is impossible to make a structure from one workpiece, a method for dividing the shell into individual elements is used, then a single shell structure is welded from separate preformed elements, see, for example, V.L. Aleksandrov, A.V. Dogadin, V.E. Utkin and others. “The technology of manufacturing submarines" S.-Pb, 2006, p.63, Fig.4.14, which is adopted as a prototype, and the shaping of sheet parts can be performed by one of the known methods specified for example In the Russian Federation patents №21294588, 2,243,843, 2,243,844, 2,323,795.

As analogues of this method, we can note the methods of manufacturing spherical tanks of the Moss type used for gas carriers, as well as the method of manufacturing stamped products for underwater and surface shipbuilding, which is selected as a prototype (see E.N. Moshnin “Technology for stamping large parts ". M., Mechanical Engineering, 1973, p. 9, Fig. 2).

The selected prototype is a method of manufacturing a spherical structure, which is divided into individual parts, all parts are shaped by local deformation of the sheet blanks, after which the parts are welded to each other in a spherical structure.

The disadvantage of this method is that the parts are made according to theoretical dimensions and shape without taking into account welding deformations. After welding, the welds shrink both in the longitudinal and transverse directions, so this design differs from the specified nominal dimensions. The elucidation of the laws of welding deformations is caused by increased requirements to the surface shape of shells after welding and to the bearing capacity of joints in structures. When welding shells, the amount of displacement at the seam after the first pass is 1-5 mm, depending on the rigidity of the welded shell. In addition, it was found that even slight geometric deviations of the joined edges cause a noticeable decrease in strength.

The present invention is aimed at solving the problem of improving the quality of the resulting shells, in particular the accuracy of the shape of the shells with a double curvature of the surface.

The technical result achieved by the implementation of the invention is to reduce the influence of welding strains on a given shape when welding individual parts of the shell.

This technical result is achieved as follows. According to the proposed method, preliminary shaping of individual parts is carried out, during which, to compensate for welding deformations from shrinkage of welds, steel or titanium parts are made with a curvature of edges from their theoretical shape, and aluminum parts are made with bending of edges around the entire perimeter of the parts in the area of subsequent welding strains with a width equal to 8-10 S, where S is the thickness of the parts. Preliminary shaping of sheet parts is carried out on press equipment using universal tooling by the method of successive local pressing or by rotational-local method on a supporting deforming element with the subsequent connection of bent parts into a single structure, mainly by welding. The edges of parts made of steel and titanium alloy are bent, and from aluminum alloys, they are bent, because on the former, due to their low thermal conductivity, so-called “houses” are formed during welding, and on the latter, due to their high thermal conductivity, so-called “dips” appear during welding. The butt and groove edges of the side lobes mating with the bottom are also made with inflection (kink). These defects caused by residual welding deformation from shrinkage of the welds and deflection of the abutting edges of the workpieces are compensated by preliminary inflection for some parts and kink for others.

In a particular case, to eliminate residual displacements and stresses, the welded edges of the parts of the welded joint zone are pre-rolled. In this case, the sheath zone in the place of the future welded joint moves (inflection / kink) by a value of 0.5 S, which can be numerically equal to the axial or radial movement in the weld zone. The edge surface profile is a mirror image of the shell profile after welding. In this case, the welding deformation of the bending of the edge of the shell will lead to compensation of the deformed zone and the residual displacements will be close to zero. To compensate for longitudinal welding deformation, 3/4 of the middle part of the edge of the petals is pre-rolled with a roller, which creates pressure calculated by the empirical formula:

,

,

where b is the width of the rollers, d is the diameter of the rollers, s is the shell thickness, σ _T , E is the yield strength and elastic modulus of the rolled material.

In another particular case, the parts - bottoms are made of increased height by the amount of transverse shrinkage of the weld and its vertical displacement, and the edge of the bottom along the perimeter is formed with an inflection (inflection) depending on the material by an amount equal to 1/2 the difference between the nominal and theoretical diameters of the bottom . In known solutions, the elimination of the vertical component in the zone of the weld on the shell can be made by introducing an allowance.

In another particular case, the welding of parts is performed from the inner concave side of the shell from the middle of the edge to its ends.

The noted patterns and the proposed method were tested in the framework of experimental design work (ROC "Shelf") and on the order of "Triton-NN".

The essence of the proposed method of forming sheet structures with a double curvature of the surface is illustrated by the accompanying drawings:

figure 1 - General view of the torospherical bottom with a double curvature of the surface;

figure 2 - the most convex central dome of the torospherical bottom;

figure 3 - side lobe of the torospherical bottom;

figure 4 - section aa figure 3;

5 is a calculated computer determination of the expected deformation when welding the petals;

6 is a calculated computer definition of the expected deformation when welding the bottom and the annular belt, consisting of welded petals.

The following notations are used in the drawings: s - thickness of the stamped part, h - depth of the stamped bottom, D - diameter of the bottom, d - allowance around the perimeter of the stamped bottom.

The greatest thinning occurring in parts during deformation have approximately the same values. Thinning values of sheet structural elements and boundary deformation values are determined depending on the overall dimensions of the workpieces and the relative radii of the given curvature and the type of stamped material.

At the same time, as recent studies have shown, in particular on the Shelf design and development work carried out under the National Technological Base federal target program (FTP) for 2007-2011, the geometry and thinning of workpieces were within the specified design tolerances.

The most convex part of the welded sheet structure obtained by deformation, in this example, the central spherical dome (Fig. 1, pos. 1 - bottom), is provided with inflection along the abutting edges by the value of its subsequent transverse shrinkage as a result of welding (Fig. 2, 3 ), which is determined by calculation according to OST5.9807-93 and on the basis of experience in the manufacture of such structures.

As shown by the calculation performed using the ANSYS software package (FIGS. 5 and 6) and the experience of manufacturing such structures, welding must be carried out initially from the inside, i.e. along the concave part, and welding is carried out from the middle of the edge to its ends, which reduces the overall shrinkage of the structure.

Taking into account the abovementioned main provisions in the manufacture of this kind of sheet torospherical structure was manufactured at the enterprise of OJSC Severnaya Verf in the framework of the Triton-NN order. The shaping of the bottom R = 2000 mm, thickness t = 10 mm from alloy 1561 with a tolerance of ΔR = 4 mm (for pattern control) and six torospherical petals with a thickness of t = 10 mm with a tolerance of thickness Δ = 3 mm on each joint was carried out on a press Clearing with an effort of 2500 kN. At the same time, it was possible to obtain the required bending quality, acceptable deviations in shape and size, which allowed the assembled structure to successfully pass hydraulic tests.

Claims (8)

1. A method of manufacturing shells with a double curvature of the surface from individual pre-shaped parts made of steel or titanium, consisting of bottoms and petals, welded with equatorial and meridional seams, characterized in that the individual parts are formed with curvature of the edges from their theoretical shape around the entire perimeter parts in an area with a width of 8-10 S, where S is the thickness of the parts. 2. The method according to claim 1, characterized in that when forming the bottoms they are made of increased height by the amount of transverse shrinkage of the weld, and the edge of the bottom along the perimeter is formed with an inflection by an amount equal to 1/2 the difference between the nominal and theoretical diameters of the bottom. 3. The method according to claim 1, characterized in that 3/4 of the middle part of the edge of the petals is pre-rolled with a roller, which creates a pressure calculated by the formula

where
b is the width of the rollers, d is the diameter of the rollers, s is the shell thickness, σ _T , E is the yield strength and elastic modulus of the rolled material. 4. The method according to claim 1, characterized in that the welding of parts is performed from the inner concave side of the shell from the middle of the edge to its ends. 5. A method of manufacturing shells with a double curvature of the surface from individual pre-shaped parts made of aluminum, consisting of bottoms and petals, welded with equatorial and meridional seams, characterized in that the individual parts are formed with bending of the edges from their theoretical shape around the entire perimeter of the parts in zone with a width equal to 8-10 S, where S is the thickness of the parts. 6. The method according to claim 3, characterized in that when forming the bottoms they are made with an inflection by an amount equal to 1/2 the difference between the nominal and theoretical diameters of the bottom. 7. The method according to claim 3, characterized in that 3/4 of the middle part of the edge of the petals is pre-rolled with a roller, which creates a pressure calculated by the formula

where
b is the width of the rollers, d is the diameter of the rollers, s is the shell thickness, σ _T , E is the yield strength and elastic modulus of the rolled material. 8. The method according to claim 3, characterized in that the welding of parts is performed from the inner concave side of the shell from the middle of the edge to its ends.

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