RU2610194C1 - Way of stabilisation of shape and dimensions of hulls built in moulding stands - Google Patents

Abstract

FIELD: shipbuilding.

SUBSTANCE: invention refers to the area of shipbuilding in the part of production of metal hulls built in moulding stands. A hull is secured in a moulding stand and a vibration generator is installed to the deck plating above intersections of members so that rotation axis of the vibration generator is headed aslant the processing hull. Whereupon, first, the vibration generator is installed perpendicularly to the centerline in the center of the deck, then it is reinstalled to one board and then, to another one, being installed on the plating above intersections of stiffeners, and after that, the process is repeated in other sectional areas firstly located sternwards and secondly, forward.

EFFECT: invention allows decreasing residual welding deformations in hulls before release from securing to a moulding stand and increasing of accuracy of constructional dimensions and shape of hulls.

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Description

The invention relates to the shipbuilding industry in the manufacture of metal hulls of ships built in patterned stands, to reduce residual welding deformations obtained in the process of assembly and welding.

It is known that after welding of any metal structures, welding deformations inevitably occur, leading to a change in the shape and size of the structure, as well as a change in the properties of the metal in the heating zone. It is not possible to completely eliminate deformations even when using welding technologies such as laser and hybrid laser-arc, which provide only a significant reduction in deformations compared to traditional arc methods. However, there are a number of technological methods that contribute to the reduction of welding strains.

There is a method of reducing welding deformation of sections of ships and ships by assembling and welding in a fixed state (Shipbuilding technology: studies for universities. / Alexandrov V.L. et al. - St. Petersburg: Profession, 2003). The essence of the method is to exclude or limit the formation of welding strains at certain technological stages of assembly of the structure due to the significant rigidity of the assembly equipment (conductors, beds, technological fasteners). In this case, residual deformations of the structure after its detachment from the snap will be formed under the conditions of the structure's own rigidity and therefore will be less. The main disadvantages of this method are the need to manufacture metal-intensive technological equipment and its low efficiency in the case of manufacturing structures with an asymmetric arrangement of welds relative to the central axes of the finished structure.

Also known is a method for editing products (patent No. 1733158), including ship's welded structures, the essence of which is that the product is laid on two supports, after which it is bent by a static load applied through an elastic bond, and then exposed to a vibration load. When bending by a static load, a bending stress is created equal to the difference between the stress of the yield strength of the workpiece material under vibration and the bending stress created by the vibration load. The disadvantage of this method is that the application of a load through an elastic coupling reduces the vibrator power needed to achieve resonant frequencies, and in turn, a decrease in the yield strength of the workpiece material when exposed to vibration reduces the required static load.

As a prototype of the invention, a typical technological process of low-frequency vibration processing (HBO) of parts, assemblies and housing structures after their manufacture is selected, described in RD5 R. GKLI.0104-216-95 “Guiding document”.

To solve this problem, a low-frequency vibration processing of the hulls of ships built in the patterned stands, until they are released from fixing.

The specified technical result is achieved in a method of stabilizing the shape and size of the hulls of the vessels, in which the hull of the vessel is fixed in the pattern stand and to the skin of the deck, vibration exciters are installed above the nodes of intersection of the stiffeners so that the axis of rotation of the exciter is directed across the vessel hull being processed.

The invention is illustrated by the following figures:

FIG. 1 - Scheme of manufacturing a ship's hull in stands with patterned contours.

FIG. 2- Scheme of cross sections for the location of the exciter.

FIG. 3 - Diagram of permutation of the vibration exciter along the cross section.

FIG. 4 - Technological complex for low-frequency vibration processing VTU-01M.

The hull of the vessel 1 is fixed in the pattern stand 2. Then, in the center of deck 3, vibration exciter 4 is installed to the lining at the intersection of the mid-frame plane and the diametrical plane (DP) so that the axis of rotation of the vibration exciter 4 is perpendicular to the DP (Fig. 3 and Fig. 2).

Next, conduct low-frequency vibration processing at a resonant frequency in pos. 1 cross section AA. HBO is performed at two or three clearly pronounced resonant frequencies, but not leading to overload of the exciter drive. Resonant frequencies are determined in the process of gaining vibration frequency by the exciter. The duration of the IEE at the resonant frequency ends by indicating the drop in the current consumption of the ammeter, which is part of the technological complex for IEE.

Then the exciter 4 is rearranged in pos. 2 and attached to the skin over the nodes of intersection of the stiffeners at the side of the vessel 5 along the cross section AA and repeat the steps in pos. 1 to the ammeter readings for a drop in current consumption. Then the exciter 4 is rearranged in pos. 3 decks of the vessel and attach to the skin over the nodes of the intersection of the stiffeners of the other side of the vessel 5 of the cross section AA and repeat the same actions as in pos. 1 and pos. 2.

After conducting an IEE at all three points of the cross-section AA, we can conclude that the residual welding voltage in the zone of the cross-section AA is reduced.

Then apply the same actions for the cross-section BB in the direction of the stern of the hull, then for the cross-section BB in the direction of the bow of the hull. The distance between the cross sections should be no more than 5 m, which results in a uniform decrease in voltage throughout the ship's hull. After conducting an IEE in all cross sections of the ship's hull, the residual welding voltage throughout the hull is reduced, leading to a decrease in welding deformations of the ship's hull.

For small passenger ships and hydrofoils, to reduce welding deformations, an HBO in three cross sections is sufficient.

As a result of testing the inventive IEE method for ship hulls built in pieceboards, positive results were obtained on reducing residual welding stresses in ship hulls. To do this, measurements of deviations of the shape and size of the hulls after they were released from fastening to the stand were carried out.

According to the results of the tests, it was determined that the implementation of HBO on only one central section to reduce welding deformations of the entire hull is not enough. The maximum reduction in residual stress during an IEE reached 60%. At the same time, with the removal of the vibration exciter from the installation site, the reduction efficiency decreased. It was also noted that during vibration processing at 2-3 resonant frequencies, the decrease in residual stresses is more uniform than at a single processing frequency.

Thus, the use of this method of low-frequency vibration processing of ship hulls made in stands with circular contours will significantly reduce residual welding deformations in ship hulls before being released from fastening to the ship’s stand, increase the accuracy of the structural dimensions and shape of ship hulls, as well as reduce the cost and the complexity of the stabilization process.

Claims (1)

A method of low-frequency vibration processing of a ship’s hull made in a stand with curved contours in the form of a hull, including installing a vibration exciter on the deck sheathing over the nodes of the intersection of the stiffeners of the ship’s hull fixed in the ship’s bench, and performing low-frequency vibration processing (HBO) at a resonant frequency in cross sections ship hulls, the distance between which is not more than 5 m, at three points of each section, starting from the section passing through the center of the vessel at the intersection of the midship plane b-frame and the diametrical plane, and first, the vibration exciter is installed perpendicular to the diametrical plane in the center of the deck, then rearranged to one side, and then to the other, installing it on the skin over the nodes of intersection of the stiffeners, after which the HBO is repeated in other cross sections, initially located towards the stern, and then towards the bow.

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