RU225822U1 - Device for measuring crack opening size - Google Patents

Abstract

The utility model relates to measuring technology and is intended to measure the amount of crack opening in parts, namely in a gas pipeline during loading with internal gas pressure. The technical problem is to create a device designed to measure small values of gas pipeline crack opening in the range of 10-500 microns. The technical result is the minimization of the device error when measuring crack opening values in the range of 10-500 microns due to the possibility of calibrating the device before carrying out the measurement. The technical result is ensured by the fact that the device for measuring the magnitude of the crack opening includes a strain gauge sensor mounted on a metal bracket with control platforms made with the possibility of their fixation on the sides of the crack. Between the control areas of the bracket there is a gap corresponding to the width of the crack, with the possibility of mechanical loading of the control areas using loading elements fixed above them, and the strain gauge sensor is configured to transmit readings to the strain gauge station. According to clause 2, the loading elements are made in the form of a fastening connection of a nut and a bolt, and the strain gauge sensor is made with a bridge circuit for connecting strain gauges, 1 sp. f-ly, 5 ill.

Description

The utility model relates to measuring technology and is intended to measure the amount of crack opening in parts, namely in a gas pipeline during loading with internal gas pressure.

A device is known for determining the expansion of an object using a strain gauge in the form of a capacitor device (RU 2126535, published 02.20.1999). However, this device has a high measurement error.

There is also a known sensor for measuring the magnitude of crack opening in parts (SU 697804, publ. November 15, 1979), made in the form of a polyethylene tube with a sensitive element in the form of an elastic thread with spiral turns and a closed loop in the middle part. However, the sensor has a high error with small changes in the crack edge opening values in the range of 10-500 µm, because does not take into account the nonlinear change in voltage across the active resistance of the sensor.

No devices that perform the function of measuring with low error small values of gas pipeline crack opening (from 10 to 500 microns) under the influence of internal gas pressure have been found in open sources of information.

The technical problem is to create a device designed to measure small values of gas pipeline crack opening in the range of 10-500 microns.

The technical result is the minimization of the device error when measuring crack opening values in the range of 10-500 microns due to the possibility of calibrating the device before carrying out the measurement.

The technical result is ensured by the fact that the device for measuring the magnitude of the crack opening includes a strain gauge sensor mounted on a metal bracket with control platforms configured to be fixed on the crack sides. Between the control areas of the bracket there is a gap corresponding to the width of the crack, with the possibility of mechanical loading of the control areas using loading elements fixed above them, and the strain gauge sensor is configured to transmit readings to the strain gauge station.

According to claim 2 of the formula, the loading elements are made in the form of a fastening connection of a nut and a bolt, and the strain gauge is made with a bridge circuit for connecting strain gauges.

The design of the device in the form of a metal bracket allows it to be rigidly attached to the surface of the gas pipeline and to the crack banks, for example, by welding, which contributes to the accuracy of measuring the opening of the crack banks.

The design of the bracket with control pads makes it possible to pre-calibrate the sensor to monitor the deformation from pure bending that occurs in the working area of the sensor when the edges of a narrow crack open.

There is a gap between the control areas of the bracket that corresponds to the width of the crack, which allows you to attach the sensor to the gas pipeline for preliminary calibration without deforming the crack on the object.

The absence of crack deformation at the device calibration stage is also facilitated by the installation at the bench test site (gas pipeline surface) of loading elements in the form of fastening threaded elements - nuts and bolts. During calibration, the bolt, passing through the thread of the nut welded to the test object, exerts pressure on the loose platform of the bracket, causing bending deformation in the working area of the sensor, thereby simulating the opening of the crack edges.

The threaded connection ensures fixation of the fasteners and regulates the degree of impact on the loose control pad of the bracket. The nut and bolt must have the same thread parameters to create a complete fastening connection. The diameter and pitch of the thread can vary, but should not lead to the use of large fasteners, their dimensions do not allow measuring the opening of the microcrack edges.

The use of a bridge circuit for connecting the sensor strain gauges when they are installed on the bracket allows one to accurately measure the bending deformation of the bracket and, accordingly, the amount of opening of the crack edges. The measurement error is no more than 5 microns.

The bridge circuit also provides a standardized connection of strain gauges through a strain gauge station to the computer of a specialist who measures the opening value of the crack faces.

Figure 1 shows a diagram of the claimed device.

Fig. 2a - view A in figure 1, fig. 2b - view B in figure 1.

Figure 3 shows the placement of the micrometer during the calibration phase.

Figure 4 shows a bridge electrical circuit for connecting the sensor's strain gauges to the strain gauge station, which provided a standardized connection to a specialist's computer, which records changes in the opening value of the crack banks.

Figure 5, using a specific example, presents a table illustrating the dependence of the magnitude of the displacement of the control pads of the bracket on the magnitude of the deviation of the micrometer from the “zero” position under mechanical influence.

Figures 1, 2, 3, 4 show the following elements:

1 - metal bracket;

2 - working areas of the strain gauge;

3 - legs of the bracket;

4 - places where the bracket bends;

5 - gas pipeline;

6 - control platform;

7 - control platform;

8 - gap between platforms 6 and 7;

9 - crack banks;

10 - welding places;

11 - nut;

12 - bolt;

13 - micrometer;

14 - strain gauge R1;

15 - strain gauge R2;

16 - strain gauge R3;

17 - strain gauge R4;

18 - strain gauge;

19-24 - strain gauge station contacts;

25 - strain gauge station.

When measuring the crack opening value, the inventive device operates as follows.

During the calibration process, strain gauges 14,17 and 15,16 of sensor 18 are installed on working areas 2, as shown in Fig. 2a and 2b. Bracket 1 is secured with control platforms 6 of one of the crack banks 9 by welding. A micrometer 13 is installed under platform 7 (Fig. 3). A nut 11 is welded above the control platform 7 of the bracket 1, a bolt 12 is screwed into it and turned until it stops in the platform 7. The threaded connection ensures the fixation of the fastening elements, which allows you to adjust the degree of mechanical impact on the loose platform 7 of the bracket 1. The gap between the platforms 6 and 7 corresponds to the crack width.

Bolt 12 exerts pressure on the loose platform 7, displacing it towards the micrometer 13, creating bending deformation in the working area 2, thereby simulating the opening of the crack edges 9. This shift is made in steps of 10 µm. For each displacement step, the strain gauge station 25 records the change in the readings of the strain gauge 18 (strain gauges 14, 15, 16, 17). After this, a Table (Fig. 5) of the calibration of the sensor 18 is formed, which displays the correspondence of the displacement of the platforms 6 and 7 relative to each other, expressed as the deviation of the micrometer 13 from the “zero” position and changes in the readings of the strain gauge 18 due to bending deformation resulting from the displacement data areas, expressed in the table as readings of strain gauge 18 (strain, units).

After the calibration stage was completed, micrometer 13 was disconnected from platform 6, bolt 12 was removed from nut 11. Platform 7 was welded to the second side 9 of the crack opening. The readings of sensor 18 were reset to zero and accepted as the initial “zero”.

During bench tests of the gas pipeline when it was loaded with operating gas pressure, the readings of sensor 18 were recorded, which were then compared with the values obtained at the calibration stage (Figure 5. Table). Based on this information, the actual value of the opening value of crack banks 9 during bench tests of the pipeline was determined. The absolute measurement error was ±5 µm.

Example

Bench tests were carried out with 4 stages of increasing gas pressure inside the gas pipeline. At the zero stage, the pressure inside the pipe was equal to atmospheric pressure. At the first stage, the pressure was raised to 3 MPa, at the second – to 6 MPa, at the third – to 9 MPa, at the fourth – to 12 MPa.

At the first stage, the value was set on the strain gauge 18 - 19 units, at the second stage - 38 units, at the third stage - 57 units, at the fourth stage - 82 units. Thus, based on the linearly proportional relationship between the readings of sensor 18 and the opening value of the crack faces 9, we can conclude that the change in the readings of sensor 18 during the 4th stage of testing was 82 units, which indicates the opening value of the crack faces equal to 13 microns. Information from sensor 18 was transmitted via a USB interface from strain gauge station 25 to the operator’s personal computer (not shown).

Claims (2)

1. A device for measuring the magnitude of crack opening, including a strain gauge mounted on a metal bracket with control platforms designed to be fixed on the sides of the crack; between the control platforms of the bracket there is a gap corresponding to the width of the crack, with the possibility of mechanical loading of the control platforms using fixed above them there are loading elements, and the strain gauge sensor is configured to transmit readings to the strain gauge station. 2. A device for measuring the magnitude of crack opening according to claim 1, characterized in that the loading elements are made in the form of a fastening connection of a nut and a bolt, and the strain gauge is made with a bridge circuit for connecting strain gauges.