RU2715081C2 - Method of alignment of ship shaft line and optical strain gauge therefor - Google Patents

Abstract

FIELD: vessels and other watercrafts.

SUBSTANCE: invention relates to shipbuilding, particularly, to installation of ship shaft lines. Disclosed is a method of aligning ship shaft line, in which prior to centring meters are installed, turn the shaft line at angle of 180° and twice (before and after turning) to measure inclinations of shaft sections, after which supports are moved according to readings of meters. Measuring devices used are an optical strain gauge with reflectors, which are installed in the specified sections of the shaft line, by means of which the angles of rotation of the sections and the actual elastic line of the shafting line are determined after deformations of the hull of the ship, and displacement of supports is carried out by value of difference between actual elastic line of shaft line and its elastic optimization along axes of main thrust bearing and deadwood shaft line. Disclosed optical strain gauge comprises a prism, an illuminator, a measuring unit and two reflectors connected to reference points on the surface of the tested shaft. At that the strain gauge is equipped with collimating lenses, two of which are installed between the prism and the reflectors, and the third one - between the prism and the measuring unit. Illuminator is installed along the axis of the triangular prism with reflecting facets, which makes it possible to divide the beam coming from the illuminator into two parts perpendicular to the axis of the prism. Reflectors are installed with possibility of beam reflection through prism on measuring unit, and measuring unit is installed in plane perpendicular to axis of prism, and is made in the form of position-sensitive matrix.

EFFECT: optimization of alignment of shaft line due to increased accuracy of determining actual elastic line of shaft line, as well as expansion of functional capabilities of strain gauge.

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Description

The invention relates to shipbuilding, in particular to the installation of ship shaft lines.

Traditionally, according to OST5R.4368-2013 [1], after alignment and assembly of the shaft line on the slipway under the action of forces arising from the movement of its supports as a result of deformations of the hull structures, the shaft line is re-centered afloat.

In [2], a method is proposed for re-centering shaft shafts and main mechanisms afloat using shaft strain gauging, which allows one to take into account the change in shaft line stresses when the ship's elastic line changes.

The essence of the method is that on the surface of the shafts in different sections along their length, four load cells are installed, included in the bridge circuit. When the curved shaft rotates, the load on the shaft changes from the reactions of the bearings (bearings) and, accordingly, the voltage of the shaft line changes. By changing the position of the supports, it is possible to achieve the absence of voltage changes (stability of the shaft loads from the reactions of the supports) or, in practice, to achieve a given level of voltage change.

The specified adjustment of the position of the supports is carried out afloat with some loading of the hull. When the vessel load changes, the shape of its elastic line will change, the mutual position of the shaft support will change, and the achieved alignment will be violated.

The accuracy of the known existing method substantially depends on the sensitivity of the strain gauges, the base between them, the length of the shaft line, the rigidity of the hull and the nature of the curve of the elastic line of the shaft line.

To optimize the alignment of the shaft line, it is necessary to know the actual elastic line at the time of centering, as well as its possible changes when the vessel load changes.

The method specified in [2], does not allow to determine the actual curve of the elastic line of the shaft line and to ensure the optimality of its shape for different ship loads.

Specified in the prototype of the method, the strain gauge is the main component of the strain gauge and is designed to measure strains. Shafting deformations are usually carried out using strain gauges [3], which make it possible to estimate the magnitude of changes in shaft stresses during rotation in the vicinity of the supports and, if necessary, to provide an acceptable level of stresses in the shafts due to the additional movement of the supports.

In the simplest case, the strain gauge [3] is an elastic structure with a strain gauge mounted on it, for example, of a wire curved in the form of a spiral (grating), glued on both sides with insulation plates made of varnish or paper film. To connect to an electrical circuit, the device is equipped with two copper lead wires. They are welded or soldered to the ends of the wire spiral and connected by a bridge electrical circuit. The strain gauge is mounted on a controlled shaft in a predetermined section with glue.

Bending stresses, measured by tensometers, are determined by the formula:

where Δn is the increment of the tensometer readings;

K is the division value of the strain gauge;

l _b - the base of the strain gauge.

The disadvantage of a wire tensometer is the inability to measure the angle of rotation of the cross sections of the shaft line and the relatively low accuracy of the measurements.

Known Martens optical tensometer [4], adopted as a prototype of the claimed invention, comprising a bar with a fixed knife at one end and a rotatable metal prism with a mirror at the other end. The knife and prism are mounted on a known base (known distance) from each other. The bar is pressed with a clamp to the test sample. Light from the illuminator is incident on the mirror. When a sample (for example, a shaft) is deformed, a prism with a mirror is rotated by an angle proportional to the deformation. At the same time, the light bunny shifts from the mirror, reflected on a remote scale, according to which a count is taken using the telescope.

Despite the fact that the rotary prism with a mirror makes it possible to ensure the accuracy of measurements of strains up to 2 μm with dimensions of the strain gauge up to 1000 mm, essentially the specified strain gauge measures only strains from tension and compression on the shaft surface. However, using the Martens tensometer, it is impossible to measure the rotation angles of the cross sections of the shaft line when it is bent, and in addition, when measuring the stresses in the ship’s shafts, their insufficient accuracy is also revealed at the dimensions acceptable in practical work.

The present invention is directed to solving the problem of developing a method for aligning a shaft shaft that meets the increased requirements of regulatory documents using a modern optical strain gauge. The technical result achieved by the implementation of the invention is to optimize the alignment of the shaft line by increasing the accuracy of determining the actual elastic line of the shaft line, as well as expanding the functionality of the strain gauge.

To solve this problem, a method for centering a ship shaft line is proposed, in which, before starting centering, reflectors are installed in predetermined sections of the shaft line, rotate the shaft line through an angle of 180 °, and the slopes of a number of sections of the shaft line are measured when it is rotated along the entire length from the main thrust bearing flange to the flange emerging from stern tube relative to the base section, located, for example, in the plane of the flange of the main thrust bearing. Based on the measurement results of the slopes of the cross sections, the shape of the actual elastic line of the shaft line is determined. Next, they optimize the shape of the elastic line and move the shaft support by the amount of the difference between the optimized and the actual elastic line. At the same time, an optical tensometer is used as measuring instruments, with the help of which the angles of rotation of the sections and the actual elastic line of the shaft line after deformations of the ship’s hull are determined.

The shape of the elastic line can be optimized according to the measurement data, for example, graphically using a flexible ruler whose ends are fixed relative to the images of the axes of the main thrust bearing and shaft shaft deadwood, or by the calculation method to minimize stresses in the shaft line (when bending it with the angles of inclination of the tangents to the elastic lines on the main thrust bearing and deadwood equal to their actual values relative to the axis of the shaft shaft). When changing the position of the supports after descent as a result of deformations of the housing according to the indicated schemes and actions, the actual elastic line of the shaft line is determined and it is centered to the state of the optimal elastic line.

Also, to solve this problem, an optical strain gauge is proposed containing a prism, a illuminator, a meter made on a known basis, and two reflectors, for example, mirrors associated with reference points on the surface of the test shaft. In addition, the strain gauge is equipped with collimating lenses, two of which are installed between the prism and the reflectors, and the third is between the prism and the meter, the illuminator is installed along the axis of the triangular prism with reflective faces, which makes it possible to divide the beam coming from the illuminator into two parts perpendicular to the axis of the prism , the reflectors are installed with the possibility of reflecting the beam through the prism on the meters, and the meter is installed in a plane perpendicular to the axis of the prism, and is made in the form of a position-sensitive matrix or inter erometra.

In the particular case of the solution of the inventive tensometer, one of its reflectors is made in the form of an angular reflector, between which a prism has a separation cube with a translucent mirror face, which makes it possible to divide the beam coming from the prism into two parts, and is also equipped with a second meter made in the form of an interferometer , and a mirror mounted on the same axis from different (two) sides of the cube in a plane perpendicular to the axis of the prism of the corner reflector.

In another particular case, the elements of the measuring unit of the strain gauge are placed in a housing equipped with a mounting unit to the test shaft.

The essence of the proposed technical solution is illustrated by drawings:

in FIG. 1 shows a diagram for determining the slopes of cross sections of a shaft line and its alignment;

In FIG. 2 is a diagram of an optical tensometer for determining rotation angles of predetermined shaft sections relative to its base section;

In FIG. 3 is a diagram for determining rotations of sections;

In FIG. 4 is a diagram of an optical tensometer for determining rotation angles of predetermined shaft sections relative to its base section, as well as shaft stresses. The right part of the measuring circuit is identical to Figure 1 and is used to measure only rotations of the shaft sections, the left part is used to measure rotations and stresses of the shaft.

In the diagram of FIG. 1 shows: 1 - centered shaft line; 2 - supports; 3 - the actual line of the shaft line; 4 - the optimal curve of the elastic line of the shaft line; 5 - the base plane (the plane of the flange of the main thrust bearing (GUP); 6 - the axis of the GUP; 7 - the plane of the flange of the stern shaft; 8 - the axis of the stern shaft; 9 - mirrors of the strain gauge (reflectors) installed in the controlled plane of the cross section of the shafting; 10 - angle strain gauge installed in a given section of the shaft line; 11 - beam of the strain gauge; 12 - beam reflected from the mirror 9; X - length; Y - deflection of the shaft axis, x _i - distance from the unitary unit to the controlled section.

From FIG. 1 it can be seen that in a number of cross sections of the shaft line 1 located on the supports 2, rotary meters of 10 sections (optical strain gauges) and their reflectors 9, for example, mirrors, are installed, including a mirror mounted on the flange of the main thrust bearing 5. The beams 11 of the 10 gauges 10 are guided on the mirrors 9. The reflected rays 12, carrying information about the angles of rotation of the mirrors 9 (and, therefore, on the rotation of the cross-sections of a curved shaft), are fed to the meters 10.

The strain gauge shown in FIG. 2, contains: 1 - shaft shaft; 21 - matrix position-sensitive element (bending meter). 9 - two reflectors (mirrors) installed in a controlled section of the shaft; 10 - meter of angular deformations, 13 - meter body 10, installed in the base section of the shaft; 14 - two hinge bars of known length (base), positioning mirrors 9 relative to the measuring unit (after positioning and measurements are deleted, or executed with the possibility of free movement of the mirrors relative to the meter); 15 - belt mounting the measuring unit on the shaft; 16 - belt mounting mirrors on the shaft; 17 - glass prism of the measuring unit; 18 - collimating lens; 19 - collimating lens; 20 - illuminator (LED).

The laser beam from the LED 20 enters the prism 17 and is divided into two parts, perpendicular to the axis of the LED and the prism. Further, these two rays are collimated by the lenses 18 and fed to the mirrors 9. After reflection from the mirrors 9, the rays are returned to the measuring unit and, after reflection from the prism 17, passing through the collimating lens 19, they enter the matrix 21 of the position-sensitive element generating the measuring signal. When you rotate the mirrors 9, the reflected rays change their position on the matrix 21 and give a signal proportional to the rotation of the mirrors and, therefore, after calibration, measure the angle of rotation of the controlled sections of the shaft relative to the base section.

In FIG. 3 is a diagram for determining rotations of cross sections relative to a GUP cross section after a 180 ° rotation of a shaft line. Here 9 is a reflector (mirror); 10 - a meter of angular deformations; βi1 - angles in sections i - at the position of the measuring-mirror system on top of the shaft, βi2 - angles in sections i - at the position of the measuring-mirror system after turning the shaft through 180 °.

Section I rotation:

Section II rotation:

Section III rotation:

Section i rotation:

Having obtained the values of the slope angles of the cross sections relative to the PMU, one can obtain an equation whose coefficients are determined by the least squares approximation by the parabola equation of the third degree

β = ƒ + a x + bx ² + cx ³ ,

where β is the slope of the tangent in this section relative to the CCP, rad .;

x is the distance between the PMU and the cross section in which this mirror is located, m;

ƒ - free term characterizing the slope of the PMU relative to the X axis, rad;

ƒ, а , b, с - coefficients calculated on a PC based on the measurement results of the tilt of the mirrors relative to the meters and PMU.

The coefficients ƒ, a , b, c of the equation should be determined from the solution of the following system of equations:

where n is the number of sections (without section GUP);

β (x _i ) - the measurement results of the tilt of the mirrors relative to the PMU mirror (in the direction parallel to the DP) in this section, angular s

As a result of integration of the slope equation, the equation of the elastic line of the vessel will take the form:

V (x) = 4.848⋅10 ^-3 ƒx + 2.424⋅10 ^-3 a x ² + 1.616⋅10 ^-3 bx ³ + 1.212⋅10 ^-3 cx ⁴ ,

where V (x) is the deflection of a given section of the ship's hull, mm.

After determining the shape of the actual elastic line of the shaft line, the shape of the elastic line is optimized, for example, graphically using a flexible ruler, the ends of which are fixed relative to the images of the axes of the main thrust bearing and shaft line, or by the calculation method to minimize stresses in the shaft line according to OST5P.4368-2013.

Then, the shaft line is centered, moving its supports by the distance difference between the actual and optimized elastic shaft line lines.

When aligning the shafting with respect to voltage, the strain gauge shown in FIG. 4, and providing higher accuracy in comparison with existing strain gauges. The same strain gauge can be used to center the shaft line along the knots for turning sections, similarly to the strain gauge shown in FIG. 3.

The strain gauge shown in FIG. 4, includes: 1 - shaft; 9 - reflector (mirror); 13 - meter housing 10; 14 - hinge strip of known length (base); 15 - belt mounting the measuring unit on the shaft; 16 - belt mounting reflectors on the shaft; 17 - a prism; 18 - collimating lens; 19 - collimating lens; 20 - illuminator (LED); 21 - a matrix of a position-sensitive element (meter); 22 - a mirror; 23 - corner reflector; 24 - a cube with a translucent mirror face; 25 - interferometer.

Sources of information

1. OST5R. 4368-2013. Shafting of ship propulsion systems. Mounting. Technical requirements, acceptance rules and control methods

2. Vassilopoulos L. Static and Underway Alignment of Main Propulsion Shaft Systems. "Naval Engineers Journal", 1988

3. Meheda V.A. Strain-strain method for measuring strains ed. SSAU, Samara, 2011

4. Shaposhnikov N.A. Mechanical testing of metals, 2nd ed., M. - L., 1954.

Claims (4)

1. The method of centering the ship’s shaft line, in which meters are installed before centering, the shaft line is rotated through an angle of 180 °, and the slopes of the shaft line are measured twice (before and after the turn), and then the supports are moved according to the readings of the meters, characterized in that they use as meters an optical strain gauge with reflectors that are installed in predetermined sections of the shaft line, with which the angles of rotation of the sections and the actual elastic line of the shaft line after deformations of the ship’s hull are determined, and eremeschenie supports carried by the difference between the actual line resilient shafting and optimization of its elastic main axis of the thrust bearing and the lower unit shafting. 2. An optical strain gauge containing a prism, a illuminator, a measuring unit and two reflectors associated with reference points on the surface of the test shaft, characterized in that the strain gauge is equipped with collimating lenses, two of which are installed between the prism and reflectors, and the third - between the prism and the measuring unit, the illuminator is mounted on the axis of a triangular prism with reflective faces, providing the possibility of dividing the beam coming from the illuminator into two parts perpendicular to the axis of the prism, reflectors are installed with the possibility the reflection of the beam through a prism to the measuring unit, and the measuring unit is installed in a plane perpendicular to the axis of the prism, and is made in the form of a position-sensitive matrix. 3. The optical strain gauge according to claim 2, characterized in that one of its reflectors is made in the form of an angular reflector, between which and a prism there is a separation cube with a translucent mirror face, which provides the possibility of dividing the beam coming from the prism into two parts, and is also equipped the second measuring unit, made in the form of an interferometer, and a mirror mounted on the same axis from different (two) sides of the cube in a plane perpendicular to the axis of the prism of the corner reflector. 4. The optical strain gauge according to claim 2 or 3, characterized in that the elements of its measuring unit are placed in a housing equipped with a mount to the test shaft.

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